1
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Mishra S, Vilas-Varela M, Fatayer S, Albrecht F, Peña D, Gross L. Observation of SOMO-HOMO Inversion in a Neutral Polycyclic Conjugated Hydrocarbon. ACS NANO 2024; 18:15898-15904. [PMID: 38833667 PMCID: PMC11191738 DOI: 10.1021/acsnano.4c03257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 05/17/2024] [Accepted: 05/24/2024] [Indexed: 06/06/2024]
Abstract
We report the generation of a nonbenzenoid polycyclic conjugated hydrocarbon, which consists of a biphenyl moiety substituted by indenyl units at the 4,4' positions, on ultrathin sodium chloride films by tip-induced chemistry. Single-molecule characterization by scanning tunneling and atomic force microscopy reveals an open-shell biradical ground state with a peculiar electronic configuration wherein the singly occupied molecular orbitals (SOMOs) are lower in energy than the highest occupied molecular orbital (HOMO).
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Affiliation(s)
| | - Manuel Vilas-Varela
- Center
for Research in Biological Chemistry and Molecular Materials (CiQUS)
and Department of Organic Chemistry, University
of Santiago de Compostela, Santiago de Compostela 15782, Spain
| | - Shadi Fatayer
- Applied
Physics Program, Physical Science and Engineering Division, King Abdullah University of Science and Technology
(KAUST), Thuwal 23955-6900, Kingdom
of Saudi Arabia
| | | | - Diego Peña
- Center
for Research in Biological Chemistry and Molecular Materials (CiQUS)
and Department of Organic Chemistry, University
of Santiago de Compostela, Santiago de Compostela 15782, Spain
- Oportunius, Galician
Innovation Agency (GAIN), Santiago
de Compostela 15702, Spain
| | - Leo Gross
- IBM
Research Europe − Zurich, Rüschlikon 8803, Switzerland
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2
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Guo H, Lovell JB, Shu C, Pink M, Morton M, Rajca S, Rajca A. Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State. J Am Chem Soc 2024; 146:9422-9433. [PMID: 38501228 DOI: 10.1021/jacs.4c02057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
We report a neutral high-spin diradical of chiral C2-symmetric bis[5]diazahelicene with ΔEST ≈ 0.4 kcal mol-1, as determined by EPR spectroscopy/SQUID magnetometry. The diradical is the most persistent among all high-spin aminyl radicals reported to date by a factor of 20, with a half-life of up to 6 days in 2-MeTHF at room temperature. Its triplet ground state and excellent persistence may be associated with the unique spin density distribution within the dihydrophenazine moiety, which characterizes two effective 3-electron C-N bonds analogous to the N-O bond of a nitroxide radical. The enantiomerically enriched (ee ≥ 94%) (MM)- and (PP)-enantiomers of the precursors to the diradicals are obtained by either preparative chiral supercritical fluid chromatography or resolution via functionalization with the chiral auxiliary of the C2-symmetric racemic tetraamine. The barrier for the racemization of the solid tetraamine is ΔG‡ = 43 ± 0.01 kcal mol-1 in the 483-523 K range. The experimentally estimated lower limit of the barrier for the racemization of a diradical, ΔG‡ ≥ 26 kcal mol-1 in 2-MeTHF at 293 K, is comparable to the DFT-determined barrier of ΔG‡ = 31 kcal mol-1 in the gas phase at 298 K. While the enantiomerically pure tetraamine displays strong chiroptical properties, with anisotropy factor |g| = |Δε|/ε = 0.036 at 376 nm, |g| ≈ 0.005 at 548 nm of the high-spin diradical is comparable to that recently reported triplet ground-state diradical dication. Notably, the radical anion intermediate in the generation of diradical exhibits a large SOMO-HOMO inversion, SHI = 35 kcal mol-1.
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Affiliation(s)
- Haoxin Guo
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Joshua B Lovell
- Teledyne ISCO, 4700 Superior Street, Lincoln, Nebraska 68504-1328, United States
| | - Chan Shu
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Maren Pink
- IUMSC, Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, United States
| | - Martha Morton
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
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3
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Liu X, Liang Z, Jin Z, Zhang X, Shen C. Enantiomerization of five-membered-heterocycle-embedded helicenes: A DFT study. J Comput Chem 2024; 45:454-460. [PMID: 37945374 DOI: 10.1002/jcc.27252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 10/24/2023] [Accepted: 10/26/2023] [Indexed: 11/12/2023]
Abstract
In this work, DFT theoretical calculations were employed to investigate the enantiomerization of helicenes embedded with five-membered heterocycles. The original benzene rings in the helicene backbone were replaced by heterocycles such as furan, thiophene, pyrrole, or phosphole to create [n]helicenes with n ranging from 4 to 7. The impact of the type, position, and number of heterocycles on the enantiomerization barrier was systematically evaluated. Notably, the enantiomerization barrier was found to be significantly dependent on the rotatory angle and the position of the heterocycles, particularly for [4, 5]helicenes. With less rotatory angle of heterocycle, the enantiomerization barrier of helicenes was revealed to be lower, while when the heterocycle was close to the central part of the helicene chain, the barrier was also lower. Furthermore, the number of thiophene rings also had a marked effect on enantiomerization, showing a decrease of the barrier with more thiophene rings placed on the helicenes backbone. We expect this work would deliver new perspective on the relative studies for the helicene conformational conversion.
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Affiliation(s)
- Xunshan Liu
- School of Chemistry and Chemical Engineering, Zhejiang Sci-Tech University, Hangzhou, China
| | - Zhen Liang
- School of Chemistry and Chemical Engineering, Zhejiang Sci-Tech University, Hangzhou, China
| | - Zhetong Jin
- School of Chemistry and Chemical Engineering, Zhejiang Sci-Tech University, Hangzhou, China
| | - Xu Zhang
- College of Chemistry and Life Science, Chifeng University, Chifeng, China
| | - Chengshuo Shen
- School of Chemistry and Chemical Engineering, Zhejiang Sci-Tech University, Hangzhou, China
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4
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Fabri B, Funaioli T, Frédéric L, Elsner C, Bordignon E, Zinna F, Di Bari L, Pescitelli G, Lacour J. Triple para-Functionalized Cations and Neutral Radicals of Enantiopure Diaza[4]helicenes. J Am Chem Soc 2024; 146:8308-8319. [PMID: 38483324 DOI: 10.1021/jacs.3c13487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024]
Abstract
Modulation of absorbance and emission is key for the design of chiral chromophores. Accessing a series of compounds absorbing and emitting (circularly polarized) light over a wide spectral window and often toward near-infrared is of practical value in (chir)optical applications. Herein, by late-stage functionalization on derivatives bridging triaryl methyl and helicene domains, we have achieved the regioselective triple introduction of para electron-donating or electron-withdrawing substituents. Extended tuning of electronic (e.g., E1/2red -1.50 V → -0.68 V) and optical (e.g., emission covering from 550 to 850 nm) properties is achieved for the cations and neutral radicals; the latter compounds being easily prepared by mono electron reductions under electrochemical or chemical conditions. While luminescence quantum yields can be increased up to 70% in the cationic series, strong Cotton effects are obtained for certain radicals at low energies (λabs ∼ 700-900 nm) with gabs values above 10-3. The open-shell electronic nature of the radicals was further characterized by electron paramagnetic resonance revealing an important spin density delocalization that contributes to their persistence.
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Affiliation(s)
- Bibiana Fabri
- Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet 30, Geneva 4 1211, Switzerland
| | - Tiziana Funaioli
- Dipartimento di Chimica e Chimica Industriale, University of Pisa, Via G. Moruzzi 13, Pisa 56124, Italy
| | - Lucas Frédéric
- Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet 30, Geneva 4 1211, Switzerland
| | - Christina Elsner
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, Geneva 4 1211, Switzerland
| | - Enrica Bordignon
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, Geneva 4 1211, Switzerland
| | - Francesco Zinna
- Dipartimento di Chimica e Chimica Industriale, University of Pisa, Via G. Moruzzi 13, Pisa 56124, Italy
| | - Lorenzo Di Bari
- Dipartimento di Chimica e Chimica Industriale, University of Pisa, Via G. Moruzzi 13, Pisa 56124, Italy
| | - Gennaro Pescitelli
- Dipartimento di Chimica e Chimica Industriale, University of Pisa, Via G. Moruzzi 13, Pisa 56124, Italy
| | - Jérôme Lacour
- Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet 30, Geneva 4 1211, Switzerland
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5
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Tuo DH, Ao YF, Wang QQ, Wang DX. Chiral Benzene Triimide (BTI) Radical Anions for Probing the Interplay of Unpaired Electron Spin and Chirality. Chemistry 2024; 30:e202302954. [PMID: 37903731 DOI: 10.1002/chem.202302954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/26/2023] [Accepted: 10/30/2023] [Indexed: 11/01/2023]
Abstract
Herein a series of chiral BTI radical anions bearing different chiral substituents were efficiently prepared by chemical reduction. X-ray crystallography revealed finely-tuned packing and helix assemblies of the radicals by the size of chiral substituents in crystalline state. In accordance with the crystalline-state packing, the powder ESR spectra indicate that 4 a- ⋅CoCp2 + and 4 c- ⋅CoCp2 + π-dimers exhibit thermally excited triplet states arising from strong spin-spin interactions, while discrete 4 b- ⋅CoCp2 + shows a broad doublet-state signal reflecting weak spin-spin interactions. The interplay between the unpaired electron spin and chiral substituents was studied by UV-Vis-NIR spectra, electronic circular dichroism (ECD) and TD DFT calculations. Different NIR absorptions of the radicals attributing to isolated SOMO→LUMO+1 (~889 nm) transitions were recorded. The emergence of Cotton effects (CEs) at the NIR region for 4 c- ⋅CoCp2 + radical enantiomers suggest the interplay between chirality and unpaired electron spin. The origin of the different circularly polarized light absorptions regarding SOMO derived transitions (around 880 nm) was attributed to chiral substitutes regulated electric and magnetic transition dipole moments of the unpaired electron participated transition.
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Affiliation(s)
- De-Hui Tuo
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Yu-Fei Ao
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Qi-Qiang Wang
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - De-Xian Wang
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
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6
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Duan L, Xue X, Hong B, Gu Z. Conjugation-Induced Spin Delocalization in Helical Chiral Carbon Radicals via Through-Bond and Through-Space Effects. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2304563. [PMID: 37867251 DOI: 10.1002/advs.202304563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 08/25/2023] [Indexed: 10/24/2023]
Abstract
A class of highly stable hydrocarbon radicals with helical chirality are synthesized, which can be isolated and purified by routine column chromatography on silica gel. These carbon-centered radicals are stabilized by through-bond delocalization and intramolecular through-space conjugation, which is evidenced by Density Functional Theory (DFT) calculation. The high stability enables to directly modify the carbon radical via palladium-catalyzed cross-coupling with the radical being untapped. The structures and optoelectronic properties are investigated with a variety of experimental methods, including Electron Paramagnetic Resonance (EPR), Ultraviolet Visisble Near Infrared (UV-vis-NIR) measurements, Cyclic Voltammetry (CV), Thermogravimetry Analysis (TGA), Circular Dichroism (CD) spectra, High-Performance Liquid Chromatography (HPLC), and X-ray crystallographic analysis. DFT calculations indicated that the 9-anthryl helical radical is more stable than its tail-to-tail σ-dimer over 13.2 kJ mol-1 , which is consistent with experimental observations.
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Affiliation(s)
- Longhui Duan
- Hefei National Research Center for Physical Sciences at the Microscale, Department of Chemistry, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui, 230026, P. R. China
| | - Xiaoping Xue
- College of Science, Henan Agricultural University, Zhengzhou, Henan, 450002, P. R. China
| | - Biqiong Hong
- College of Materials and Chemical Engineering, Minjiang University, Fuzhou, Fujian, 350108, P. R. China
| | - Zhenhua Gu
- Hefei National Research Center for Physical Sciences at the Microscale, Department of Chemistry, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui, 230026, P. R. China
- College of Materials and Chemical Engineering, Minjiang University, Fuzhou, Fujian, 350108, P. R. China
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7
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Shu C, Yang Z, Rajca A. From Stable Radicals to Thermally Robust High-Spin Diradicals and Triradicals. Chem Rev 2023; 123:11954-12003. [PMID: 37831948 DOI: 10.1021/acs.chemrev.3c00406] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2023]
Abstract
Stable radicals and thermally robust high-spin di- and triradicals have emerged as important organic materials due to their promising applications in diverse fields. New fundamental properties, such as SOMO/HOMO inversion of orbital energies, are explored for the design of new stable radicals, including highly luminescent ones with good photostability. A relation with the singlet-triplet energy gap in the corresponding diradicals is proposed. Thermally robust high-spin di- and triradicals, with energy gaps that are comparable to or greater than a thermal energy at room temperature, are more challenging to synthesize but more rewarding. We summarize a number of high-spin di- and triradicals, based on nitronyl nitroxides that provide a relation between the experimental pairwise exchange coupling constant J/k in the high-spin species vs experimental hyperfine coupling constants in the corresponding monoradicals. This relation allows us to identify outliers, which may correspond to radicals where J/k is not measured with sufficient accuracy. Double helical high-spin diradicals, in which spin density is delocalized over the chiral π-system, have been barely explored, with the sole example of such high-spin diradical possessing alternant π-system with Kekulé resonance form. Finally, we discuss a high-spin diradical with electrical conductivity and derivatives of triangulene diradicals.
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Affiliation(s)
- Chan Shu
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Zhimin Yang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
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8
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Christensen EG, Steele RP. Structural, Thermodynamic, and Spectroscopic Evolution in the Hydration of Copper(II) Ions, Cu 2+(H 2O) 2-8. J Phys Chem A 2023; 127:6660-6676. [PMID: 37552878 DOI: 10.1021/acs.jpca.3c03719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
Gas-phase clusters of the hydrated Cu(II) cation with 2-8 water molecules were investigated using ab initio quantum chemistry. Isomer structures, energies, and vibrational spectra were computed across this size range, yielding a qualitative picture of this ion as an intact Cu2+ hydrate that also partially oxidizes the surrounding water network at equilibrium. At sufficient cluster sizes, these ion hydrates also become thermodynamically preferred over competitive Cu(II) hydroxide hydrates. Competitive coordination environments were found to exist at some cluster sizes, due to both hydrogen-bonding and d-orbital chemical effects, and the dominant coordination number was found in some cases to be temperature-dependent. Clear spectral signatures of the ion's coordination environment were computed to exist at each cluster size, which should make experimental verification of these computational predictions straightforward. Through comparison to recent studies of hydrated CuOH+, the effective charge on the metal center was shown to converge to approximately +1.5 in both cases, despite qualitatively different behavior of their radical spin densities. Therefore, nominally Cu(II) ions exhibit considerable electronic, chemical, and structural flexibility. The electronic origins of this flexibility─including key roles played by the water network itself─are investigated in this work and should provide a conceptual foundation for future studies of copper-based, water-oxidation catalysts.
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Affiliation(s)
- Elizabeth G Christensen
- Department of Chemistry and Henry Eyring Center for Theoretical Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, United States
| | - Ryan P Steele
- Department of Chemistry and Henry Eyring Center for Theoretical Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, United States
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9
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Ajaykamal T, Palaniandavar M. Mononuclear nickel(ii)-flavonolate complexes of tetradentate tripodal 4N ligands as structural and functional models for quercetin 2,4-dioxygenase: structures, spectra, redox and dioxygenase activity. RSC Adv 2023; 13:24674-24690. [PMID: 37601601 PMCID: PMC10436029 DOI: 10.1039/d3ra04834a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 08/01/2023] [Indexed: 08/22/2023] Open
Abstract
Three new nickel(ii)-flavonolate complexes of the type [Ni(L)(fla)](ClO4) 1-3, where L is the tripodal 4N ligand tris(pyrid-2-ylmethyl)amine (tpa, L1) or (pyrid-2-ylmethyl)bis(6-methylpyrid-2-ylmethyl)amine (6-Me2-tpa, L2) or tris(N-Et-benzimidazol-2-ylmethyl)amine (Et-ntb, L3), have been isolated as functional models for Ni(ii)-containing quercetin 2,4-dioxygenase. Single crystal X-ray structures of 1 and 3 reveal that Ni(ii) is involved in π-back bonding with flavonolate (fla-), as evident from enhancement in C[double bond, length as m-dash]O bond length upon coordination [H(fla), 1.232(3); 1, 1.245(7); 3, 1.262(8) Å]. More asymmetric chelation of fla- in 3 than in 1 [Δd = (Ni-Ocarbonyl - Ni-Oenolate): 1, 0.126; 3, 0.182 Å] corresponds to lower π-delocalization in 3 with electron-releasing N-Et substituent. The optimized structures of 1-3 and their geometrical isomers have been computed by DFT methods. The HOMO and LUMO, both localized on Ni(ii)-bound fla-, are highly conjugated bonding π- and antibonding π*-orbitals respectively. They are located higher in energy than the Ni(ii)-based MOs (HOMO-1, dx2-y2; HOMO-2/6, dz2), revealing that the Ni(ii)-bound fla- rather than Ni(ii) would undergo oxidation upon exposure to dioxygen. The results of computational studies, in combination with spectral and electrochemical studies, support the involvement of redox-inactive Ni(ii) in π-back bonding with fla-, tuning the π-delocalization in fla- and hence its activation. Upon exposure to dioxygen, all the flavonolate adducts in DMF solution decompose to produce CO and depside, which then is hydrolyzed to give the corresponding acids at 70 °C. The highest rate of dioxygenase reactivity of 3 (kO2: 3 (29.10 ± 0.16) > 1 (16.67 ± 0.70) > 2 (1.81 ± 0.04 × 10-1 M-1 s-1)), determined by monitoring the disappearance of the LMCT band in the range 440-450 nm, is ascribed to the electron-releasing N-Et substituent on bzim ring, which decreases the π-delocalization in fla- and enhances its activation.
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Affiliation(s)
- Tamilarasan Ajaykamal
- Department of Chemistry, Bharathidasan University Tiruchirapalli 620 024 Tamil Nadu India +91-431-2407043 +91-431-2407125
| | - Mallayan Palaniandavar
- Department of Chemistry, Bharathidasan University Tiruchirapalli 620 024 Tamil Nadu India +91-431-2407043 +91-431-2407125
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10
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Yang Z, Pink M, Nowik-Boltyk EM, Lu S, Junghoefer T, Rajca S, Stoll S, Casu MB, Rajca A. Thermally Ultrarobust S = 1/2 Tetrazolinyl Radicals: Synthesis, Electronic Structure, Magnetism, and Nanoneedle Assemblies on Silicon Surface. J Am Chem Soc 2023; 145:13335-13346. [PMID: 37285418 PMCID: PMC10438971 DOI: 10.1021/jacs.3c03402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Open-shell organic molecules, including S = 1/2 radicals, may provide enhanced properties for several emerging technologies; however, relatively few synthesized to date possess robust thermal stability and processability. We report the synthesis of S = 1/2 biphenylene-fused tetrazolinyl radicals 1 and 2. Both radicals possess near-perfect planar structures based on their X-ray structures and density-functional theory (DFT) computations. Radical 1 possesses outstanding thermal stability as indicated by the onset of decomposition at 269 °C, based on thermogravimetric analysis (TGA) data. Both radicals possess very low oxidation potentials <0 V (vs. SCE) and their electrochemical energy gaps, Ecell ≈ 0.9 eV, are rather low. Magnetic properties of polycrystalline 1 are characterized by superconducting quantum interference device (SQUID) magnetometry revealing a one-dimensional S = 1/2 antiferromagnetic Heisenberg chain with exchange coupling constant J'/k ≈ -22.0 K. Radical 1 in toluene glass possesses a long electron spin coherence time, Tm ≈ 7 μs in the 40-80 K temperature range, a property advantageous for potential applications as a molecular spin qubit. Radical 1 is evaporated under ultrahigh vacuum (UHV) forming assemblies of intact radicals on a silicon substrate, as confirmed by high-resolution X-ray photoelectron spectroscopy (XPS). Scanning electron microscope (SEM) images indicate that the radical molecules form nanoneedles on the substrate. The nanoneedles are stable for at least 64 hours under air as monitored by using X-ray photoelectron spectroscopy. Electron paramagnetic resonance (EPR) studies of the thicker assemblies, prepared by UHV evaporation, indicate radical decay according to first-order kinetics with a long half-life of 50 ± 4 days at ambient conditions.
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Affiliation(s)
- Zhimin Yang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA
| | - Maren Pink
- IUMSC, Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, USA
| | | | - Shutian Lu
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Tobias Junghoefer
- Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA
| | - Stefan Stoll
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Maria Benedetta Casu
- Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA
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11
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Dey M, Ghosh D. Curious Case of Singlet Triplet Gaps in Nonlinear Polyaromatic Hydrocarbons. J Phys Chem Lett 2022; 13:11795-11800. [PMID: 36516993 DOI: 10.1021/acs.jpclett.2c03170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The singlet triplet (ST) gap of linear polyacenes decays exponentially with the system size as a result of extended conjugation and reducing highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps. These low ST gaps can ideally be leveraged toward energy applications but are hindered by the decreasing stability of the systems. Thus, there is the need to understand the ST gap of nonlinear polyacenes, which are markedly more stable than their linear counterparts. Here, we show that the ST gaps of the nonlinear polyacenes do not decrease with the system size and have no correlation with the HOMO-LUMO gaps or increased conjugation. The reason behind this is identified as the high multireference character of the triplet high-spin state. These unprecedented results are in stark contrast to the observations in linear polyacenes and are due to the combined effects of topology and geometrical factors.
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Affiliation(s)
- Mandira Dey
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata700032, India
| | - Debashree Ghosh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata700032, India
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12
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Eckhardt P, Elliot Q, Alabugin IV, Opatz T. Two Paths to Oxidative C-H Amination Under Basic Conditions: A Theoretical Case Study Reveals Hidden Opportunities Provided by Electron Upconversion. Chemistry 2022; 28:e202201637. [PMID: 35880945 PMCID: PMC9804812 DOI: 10.1002/chem.202201637] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Indexed: 01/09/2023]
Abstract
Traditionally, cross-dehydrogenative coupling (CDC) leads to C-N bond formation under basic and oxidative conditions and is proposed to proceed via a two-electron bond formation mediated by carbenium ions. However, the formation of such high-energy intermediates is only possible in the presence of strong oxidants, which may lead to undesired side reactions and poor functional group tolerance. In this work we explore if oxidation under basic conditions allows the formation of three-electron bonds (resulting in "upconverted" highly-reducing radical-anions). The benefit of this "upconversion" process is in the ability to use milder oxidants (e. g., O2 ) and to avoid high-energy intermediates. Comparison of the two- and three-electron pathways using quantum mechanical calculations reveals that not only does the absence of a strong oxidant shut down two-electron pathways in favor of a three-electron path but, paradoxically, weaker oxidants react faster with the upconverted reductants by avoiding the inverted Marcus region for electron transfer.
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Affiliation(s)
- Paul Eckhardt
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
| | - Quintin Elliot
- Department of Chemistry and BiochemistryFlorida State UniversityTallahasseeFlorida 32306USA
| | - Igor V. Alabugin
- Department of Chemistry and BiochemistryFlorida State UniversityTallahasseeFlorida 32306USA
| | - Till Opatz
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
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13
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Sabuj MA, Muoh O, Huda MM, Rai N. Non-Aufbau orbital ordering and spin density modulation in high-spin donor-acceptor conjugated polymers. Phys Chem Chem Phys 2022; 24:23699-23711. [PMID: 36148814 DOI: 10.1039/d2cp02355e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
High-spin ground-state organic materials with unique spin topology can significantly impact molecular magnetism, spintronics, and quantum computing devices. However, strategies to control the spin topology and alignment of the unpaired spins in different molecular orbitals are not well understood. Here, we report modulating spin distribution along the molecular backbone in high-spin ground-state donor-acceptor (D-A) conjugated polymers. Density functional theory calculations indicate that substitution of different heteroatoms (such as C, Si, N, and Se) alters the aromatic character in the thiadiazole unit of the benzobisthiadiazole (BBT) acceptor and modulates the oligomer length to result in high-spin triplet ground-state, orbital and spin topology. The C, Si, and Se atom substituted polymers show a localized spin density at the two opposite ends of the polymers. However, a delocalized spin distribution is observed in the N substituted polymer. We find that the hybridization (sp3vs. sp2) of the substituent atom plays an important role in controlling the electronic structure of these materials. This study shows that atomistic engineering is an efficient technique to tune the spin topologies and electronic configurations in the high-spin ground-state donor-acceptor conjugated polymers, compelling synthetic targets for room-temperature magnetic materials.
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Affiliation(s)
- Md Abdus Sabuj
- Dave C Swalm School of Chemical Engineering, and Center for Advanced Vehicular Systems, Mississippi State University, Mississippi State, Mississippi, 39762, USA.
| | - Obinna Muoh
- Dave C Swalm School of Chemical Engineering, and Center for Advanced Vehicular Systems, Mississippi State University, Mississippi State, Mississippi, 39762, USA.
| | - Md Masrul Huda
- Dave C Swalm School of Chemical Engineering, and Center for Advanced Vehicular Systems, Mississippi State University, Mississippi State, Mississippi, 39762, USA.
| | - Neeraj Rai
- Dave C Swalm School of Chemical Engineering, and Center for Advanced Vehicular Systems, Mississippi State University, Mississippi State, Mississippi, 39762, USA.
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14
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Kasemthaveechok S, Abella L, Crassous J, Autschbach J, Favereau L. Organic radicals with inversion of SOMO and HOMO energies and potential applications in optoelectronics. Chem Sci 2022; 13:9833-9847. [PMID: 36128246 PMCID: PMC9430691 DOI: 10.1039/d2sc02480b] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 07/06/2022] [Indexed: 11/21/2022] Open
Abstract
Organic radicals possessing an electronic configuration in which the energy of the singly occupied molecular orbital (SOMO) is below the highest doubly occupied molecular orbital (HOMO) level have recently attracted significant interest, both theoretically and experimentally. The peculiar orbital energetics of these SOMO-HOMO inversion (SHI) organic radicals set their electronic properties apart from the more common situation where the SOMO is the highest occupied orbital of the system. This review gives a general perspective on SHI, with key fundamental aspects regarding the electronic and structural factors that govern this particular electronic configuration in organic radicals. Selected examples of reported compounds with SHI are highlighted to establish molecular guidelines for designing this type of radical, and to showcase the potential of SHI radicals in organic spintronics as well as for the development of more stable luminescent radicals for OLED applications.
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Affiliation(s)
| | - Laura Abella
- Department of Chemistry, University at Buffalo, State University of New York Buffalo New York 14260 USA
| | | | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York Buffalo New York 14260 USA
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15
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Kasemthaveechok S, Abella L, Jean M, Cordier M, Vanthuyne N, Guizouarn T, Cador O, Autschbach J, Crassous J, Favereau L. Carbazole Isomerism in Helical Radical Cations: Spin Delocalization and SOMO-HOMO Level Inversion in the Diradical State. J Am Chem Soc 2022; 144:7253-7263. [PMID: 35413200 DOI: 10.1021/jacs.2c00331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report a new molecular design to afford persistent chiral organic open-shell systems with configurational stability and an inversion in energy of the singly occupied molecular orbital (SOMO) and the highest doubly occupied molecular orbital (HOMO) for both mono- and diradical states. The unpaired electron delocalization within the designed extended helical π-conjugated systems is a crucial factor to reach chemical stabilities, which is not obtained using the classical steric protection approach. The unique features of the obtained helical monoradicals allow an exploration of the chiral intramolecular electron transfer (IET) process in solvents of different polarity by means of optical and chiroptical spectroscopies, resulting in an unprecedented electronic circular dichroism (ECD) sign inversion for the radical transitions. We also characterized the corresponding helical diradicals, which show near-infrared electronic circular dichroism at wavelengths up to 1100 nm and an antiferromagnetic coupling between the spins, with an estimated singlet-triplet gap (ΔEST) of about -1.2 kcal mol-1. The study also revealed an intriguing double SOMO-HOMO inversion (SHI) electronic configuration for these diradicals, providing new insight regarding the peculiar energetic ordering of radical orbitals and the impact on the corresponding (chiral) optoelectronic properties.
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Affiliation(s)
| | - Laura Abella
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, United States
| | - Marion Jean
- Aix Marseille University, CNRS Centrale Marseille, iSm2, 13284 Marseille, France
| | - Marie Cordier
- Univ Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France
| | - Nicolas Vanthuyne
- Aix Marseille University, CNRS Centrale Marseille, iSm2, 13284 Marseille, France
| | | | - Olivier Cador
- Univ Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France
| | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, United States
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16
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Proton-induced Conversion from Non-Aufbau to Aufbau Electronic Structure of an Organic Radical with Turn-on Fluorescence. Chem Res Chin Univ 2022. [DOI: 10.1007/s40242-022-2015-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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17
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A functional model for quercetin 2,4-dioxygenase: Geometric and electronic structures and reactivity of a nickel(II) flavonolate complex. J Inorg Biochem 2021; 226:111632. [PMID: 34700128 DOI: 10.1016/j.jinorgbio.2021.111632] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 10/06/2021] [Accepted: 10/12/2021] [Indexed: 11/22/2022]
Abstract
Quercetin 2,4-dioyxgenase (QueD) has been known to catalyze the oxygenative degradation of flavonoids and quercetin. Recent crystallographic study revealed a nickel ion occupies the active site as a co-factor to support O2 activation and catalysis. Herein, we report a nickel(II) flavonolate complex bearing a tridentate macrocyclic ligand, [NiII(Me3-TACN)(Fl)(NO3)](H2O) (1, Me3-TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane, Fl = 3-hydroxyflavone) as a functional model for QueD. The flavonolatonickel(II) complex was characterized by using spectrometric analysis including UV-vis spectroscopy, electrospray ionization mass spectrometer (ESI-MS), infrared spectroscopy (FT-IR) and 1H nuclear magnetic resonance spectroscopy (NMR). The single crystal X-ray structure of 1 shows two isomers with respect to the direction of a flavonolate ligand. Two isomers commonly are in the octahedral geometry with a bidentate of flavonolate and a monodentate of nitrate as well as a tridentate binding of Me3-TACN ligand. The spin state of 1 is determined to be a triplet state based on the Evans' method. Interestingly, electronic configuration of 1 from density functional theory (DFT) calculations revealed that the two singly occupied molecular orbitals (SOMOs) lie energetically lower than the highest (doubly) occupied molecular orbital (HOMO), that is so-called the SOMO-HOMO level inversion (SHI). The HOMO shows an electron density localized in the flavonolate ligand, indicating that flavonolate ligand is oxidized first rather than the nickel center. Thermal degradation of 1 resulted in the formation of benzoic acid and salicylic acid, which is attributed to the oxygenation of flavonolate of 1.
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18
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Kimura T, Nakahodo T, Suzuki E, Nakanishi Y, Misaki Y, Ogawa S. Preparation, Structure Determination, and Electrochemical Properties of 4,5‐Dialkylbenzo[1,2‐
d
:4,5‐
d’
]bis[1,2,3]triselenoles and Their Singlet and Triplet‐State Dications. ChemistrySelect 2021. [DOI: 10.1002/slct.202102375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Takeshi Kimura
- Center for Instrumental Analysis Iwate University Morioka 020-8551 Japan
| | - Tsukasa Nakahodo
- Department of Applied Chemistry Kindai University Higashi Osaka 577-8502 Japan
| | - Eiichi Suzuki
- Department of Chemistry and Biological Sciences Faculty of Science and Engineering Iwate University Morioka 020-8551 Japan
| | - Yoshiki Nakanishi
- Department of Physical Science and Materials Engineering Faculty of Science and Engineering Iwate University Morioka 020-8551 Japan
| | - Yohji Misaki
- Department of Applied Chemistry Faculty of Engineering Ehime University Matsuyama 790-8577 Japan
| | - Satoshi Ogawa
- Department of Chemistry and Biological Sciences Faculty of Science and Engineering Iwate University Morioka 020-8551 Japan
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19
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Tu K, Liu L, Zhang X, King RB. Tetrahedral Cyclopentadienylmetal Carbonyl Clusters of Manganese and Chromium: A Theoretical Study. Inorg Chem 2021; 60:14557-14562. [PMID: 34529409 DOI: 10.1021/acs.inorgchem.1c01200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Tetranuclear Cp4M4(CO)4 clusters have been synthesized for iron and vanadium but not for the intermediate first-row transition metals manganese and chromium. All of the low-energy structures of these "missing" Cp4M4(CO)4 (M = Mn, Cr) species are shown by density functional theory to consist of a central M4 tetrahedron with each of the four faces capped by a μ3-CO group. The individual low-energy structures differ in their spin states and in their formal metal-metal bond orders along the six edges of their central M4 tetrahedra. The two low-energy Cp4Mn4(μ3-CO)4 structures are a triplet structure with all Mn-Mn single bonds and a singlet structure with one Mn≡Mn triple bond and five Mn-Mn single bonds along the six tetrahedral edges. Related low-energy Cp4Cr4(μ3-CO)4 structures include a quintet structure with all Cr-Cr single bonds and a singlet structure with two Cr≡Cr triple bonds and four Cr-Cr single bonds. However, the potential energy surface of the Cp4Cr4(CO)4 system is complicated by three other structures of comparable energies including two triplet structures and one quintet structure with various combinations of single, double, and triple chromium-chromium bonds in the central Cr4 tetrahedron.
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Affiliation(s)
- Kaipeng Tu
- Key Laboratory of Cluster Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Ling Liu
- Key Laboratory of Cluster Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Xiuhui Zhang
- Key Laboratory of Cluster Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - R Bruce King
- Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30606, United States
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20
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Bodzioch A, Pietrzak A, Kaszyński P. Axially Chiral Stable Radicals: Resolution and Characterization of Blatter Radical Atropisomers. Org Lett 2021; 23:7508-7512. [PMID: 34533961 DOI: 10.1021/acs.orglett.1c02733] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Atropisomers of three Blatter radicals were obtained by the addition of 8-substituted 1-naphthyllithiums to 3-phenyl and 3-t-butylbenzo[e][1,2,4]triazine and separated by chiral high-performance liquid chromatography. Their absolute configurations were assigned by a comparison of experimental and time-dependent density functional theory calculated electronic circular dichroism spectra. The free energy of activation, ΔG‡298, and the half life of racemization, t1/2, at 298 K were determined at ∼25 kcal mol-1 and <130 h, respectively. Intramolecular π-π interactions in radicals were evident from single-crystal X-ray diffraction, density functional theory, and electrochemical analyses.
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Affiliation(s)
- Agnieszka Bodzioch
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, 90-363 Łódź, Poland
| | - Anna Pietrzak
- Faculty of Chemistry, Łódź University of Technology, Żeromskiego 116, 90-024 Łódź, Poland
| | - Piotr Kaszyński
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, 90-363 Łódź, Poland.,Faculty of Chemistry, University of Łódź, 91-403 Łódź, Poland.,Department of Chemistry, Middle Tennessee State University, Murfreesboro, Tennessee 37132, United States
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21
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Rajca A, Shu C, Zhang H, Zhang S, Wang H, Rajca S. Thiophene-Based Double Helices: Radical Cations with SOMO-HOMO Energy Level Inversion †. Photochem Photobiol 2021; 97:1376-1390. [PMID: 34152605 DOI: 10.1111/php.13475] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 06/17/2021] [Indexed: 11/29/2022]
Abstract
We report relatively persistent, open-shell thiophene-based double helices, radical cations 1•+ -TMS12 and 2•+ -TMS8 . Closed-shell neutral double helices, 1-TMS12 and 2-TMS8 , have nearly identical first oxidation potentials, E+/0 ≈ +1.33 V, corresponding to reversible oxidation to their radical cations. The radical cations are generated, using tungsten hexachloride in dichloromethane (DCM) as an oxidant, E+/0 ≈ +1.56 V. EPR spectra consist of a relatively sharp singlet peak with an unusually low g-value of 2.001-2.002, thus suggesting exclusive delocalization of spin density over π-conjugated system consisting of carbon atoms only. DFT computations confirm these findings, as only negligible fraction of spin density is found on sulfur and silicon atoms and the spin density is delocalized over a single tetrathiophene moiety. For radical cation, 1•+ -TMS12 , energy level of the singly occupied molecular orbital (SOMO) lies below the four highest occupied molecular orbitals (HOMOs), thus indicating the SOMO-HOMO inversion (SHI) and therefore, violating the Aufbau principle. 1•+ -TMS12 has a half-life of the order of only 5 min at room temperature. EPR peak intensity of 2•+ -TMS8 , which does not show SHI, is practically unchanged over at least 2 h.
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Affiliation(s)
- Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, NE, USA
| | - Chan Shu
- Department of Chemistry, University of Nebraska, Lincoln, NE, USA
| | - Hui Zhang
- Department of Chemistry, University of Nebraska, Lincoln, NE, USA
| | - Sheng Zhang
- Engineering Research Center for Nanomaterials, Henan University, Kaifeng, China
| | - Hua Wang
- Engineering Research Center for Nanomaterials, Henan University, Kaifeng, China
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, NE, USA
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22
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Babaei Bidmeshki N, T Azar Y, Ziaie F, Janbazi M. Unravelling the nature of the α-keratin EPR signal: an ab initio study. Phys Chem Chem Phys 2021; 23:6815-6822. [PMID: 33725043 DOI: 10.1039/d0cp05930g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fingernail as a biodosimetry material, analyzed by the EPR technique, has attracted great attention in several experimental studies. One of the most challenging issues that should be addressed is additional signals, masking the radiation-induced signals (RIS) in EPR dosimetry analyses. In this work, we conducted a theoretical study of the RIS radicals and mechanisms to propose robust methods to distinguish the original signal from the irradiated nails' unwanted noise. Also, the proposed approach includes procedures to improve the accuracy of the dosimetry measurements. In our research, three categories of cysteine, DOPA and cystine radicals were considered due to their dominant abundance during the α-keratin reduction-oxidation processes. The SOMO-HOMO inversion is observed while investigating the electronic structure in these quasi-closed-shell systems. Furthermore, we demonstrated that the SOMO-HOMO gap is proportional to the spin localization. Indeed, new peaks in the EPR signals are not observed when the amino acid sequences are different. Moreover, the studied structures' neighborhood effect merely leads to a small change in the peak broadening of the EPR signals. On-the-fly magnetic parameter calculations were used to evaluate the system dynamics' effect on the broadening of the EPR signals in a molecular dynamics simulation. Comparing the calculated parameters with computational and experimental results in other studies helps assign low dose peaks to the corresponding tyrosyl phenoxyl radical.
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Affiliation(s)
- Nadia Babaei Bidmeshki
- Radiation Application Research School, Nuclear Science and Technology Research Institute, Tehran, Iran
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23
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Medina Rivero S, Shang R, Hamada H, Yan Q, Tsuji H, Nakamura E, Casado J. Non-Aufbau Spiro-Conjugated Quinoidal & Aromatic Charged Radicals. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20200385] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Samara Medina Rivero
- Department of Physical Chemistry, Faculty of Science, University of Málaga, Campus de Teatinos, s/n, 29071 Málaga, Spain
| | - Rui Shang
- Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hiroyoshi Hamada
- Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| | - Qifan Yan
- Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hayato Tsuji
- Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
- Department of Chemistry, Faculty of Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan
| | - Eiichi Nakamura
- Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| | - Juan Casado
- Department of Physical Chemistry, Faculty of Science, University of Málaga, Campus de Teatinos, s/n, 29071 Málaga, Spain
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24
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Yanagi T, Tanaka T, Yorimitsu H. Asymmetric systematic synthesis, structures, and (chir)optical properties of a series of dihetero[8]helicenes. Chem Sci 2021; 12:2784-2793. [PMID: 34164042 PMCID: PMC8179410 DOI: 10.1039/d1sc00044f] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 01/28/2021] [Indexed: 01/22/2023] Open
Abstract
A series of dihetero[8]helicenes have been systematically synthesized in enantiomerically enriched forms by utilizing the characteristic transformations of the organosulfur functionality. The synthetic route begins with assembling a ternaphthyl common synthetic intermediate from 2-naphthol and bissulfinylnaphthalene through an extended Pummerer reaction followed by facile multi-gram-scale resolution. The subsequent cyclization reactions into dioxa- and dithia[8]helicenes take place with excellent axial-to-helical chirality conversion. Dithia[8]helicene is further transformed into the nitrogen and the carbon analogs by replacing the two endocyclic sulfur atoms via SNAr-based skeletal reconstruction. The efficient systematic synthesis has enabled comprehensive evaluation of physical properties, which has clarified the effect of the endocyclic atoms on their structures and (chir)optical properties as well as the unexpected conformational stability of the common helical framework.
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Affiliation(s)
- Tomoyuki Yanagi
- Department of Chemistry, Graduate School of Science, Kyoto University Japan
| | - Takayuki Tanaka
- Department of Chemistry, Graduate School of Science, Kyoto University Japan
| | - Hideki Yorimitsu
- Department of Chemistry, Graduate School of Science, Kyoto University Japan
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25
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Murata R, Wang Z, Abe M. Singly Occupied Molecular Orbital−Highest Occupied Molecular Orbital (SOMO−HOMO) Conversion. Aust J Chem 2021. [DOI: 10.1071/ch21186] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Singly occupied molecular orbital−highest occupied molecular orbital (SOMO−HOMO) conversion (inversion), SHC, is a phenomenon in which the SOMO is lower in energy than the doubly occupied molecular orbitals (DOMO, HOMO). A non-Aufbau electronic structure leads to unique properties such as a switch in bond dissociation energy and the generation of high-spin species on one-electron oxidation. In addition, the pronounced photostability of these species has been reported recently for application in organic light-emitting devices. In this review article, we summarise the chemistry of SOMO−HOMO converted (inverted) species reported to date.
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26
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Kasemthaveechok S, Abella L, Jean M, Cordier M, Roisnel T, Vanthuyne N, Guizouarn T, Cador O, Autschbach J, Crassous J, Favereau L. Axially and Helically Chiral Cationic Radical Bicarbazoles: SOMO-HOMO Level Inversion and Chirality Impact on the Stability of Mono- and Diradical Cations. J Am Chem Soc 2020; 142:20409-20418. [PMID: 33201694 DOI: 10.1021/jacs.0c08948] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We report persistent chiral organic mono- and diradical cations based on bicarbazole molecular design with an unprecedented stability dependence on the type of chirality, namely, axial versus helical. An unusual chemical stability was observed for sterically unprotected axial bicarbazole radical in comparison with monocarbazole and helical bicarbazole ones. Such results were experimentally and theoretically investigated, revealing an inversion in energy of the singly occupied molecular orbital (SOMO) and the highest (doubly) occupied molecular orbital (HOMO) in both axial and helical bicarbazole monoradicals along with a subtle difference of electronic coupling between the two carbazole units, which is modulated by their relative dihedral angle and related to the type of chirality. Such findings allowed us to explore in depth the SOMO-HOMO inversion (SHI) in chiral radical molecular systems and provide new insights regarding its impact on the stability of organic radicals. Finally, these specific electronic properties allowed us to prepare a persistent, intrinsically chiral, diradical which notably displayed near-infrared electronic circular dichroism responses up to 1100 nm and almost degenerate singlet-triplet ground states with weak antiferromagnetic interactions evaluated by magnetometry experiments.
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Affiliation(s)
| | - Laura Abella
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, United States
| | - Marion Jean
- Aix Marseille University, CNRS Centrale Marseille, iSm2, Marseille 13284, France
| | - Marie Cordier
- Université Rennes, CNRS, ISCR-UMR 6226, Rennes F-35000, France
| | - Thierry Roisnel
- Université Rennes, CNRS, ISCR-UMR 6226, Rennes F-35000, France
| | - Nicolas Vanthuyne
- Aix Marseille University, CNRS Centrale Marseille, iSm2, Marseille 13284, France
| | | | - Olivier Cador
- Université Rennes, CNRS, ISCR-UMR 6226, Rennes F-35000, France
| | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, United States
| | - Jeanne Crassous
- Université Rennes, CNRS, ISCR-UMR 6226, Rennes F-35000, France
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27
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Hiroto S. Helical Pitch Dependent Optical Properties of π-Extended Aza[5]helicene Radical Cations. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2020. [DOI: 10.1246/bcsj.20200181] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Satoru Hiroto
- Graduate School of Human and Environmental Studies, Kyoto University, Nihonmatsu-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
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28
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Shaikh AC, Moutet J, Veleta JM, Hossain MM, Bloch J, Astashkin AV, Gianetti TL. Persistent, highly localized, and tunable [4]helicene radicals. Chem Sci 2020; 11:11060-11067. [PMID: 34123196 PMCID: PMC8162278 DOI: 10.1039/d0sc04850j] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 09/12/2020] [Indexed: 11/21/2022] Open
Abstract
Persistent organic radicals have gained considerable attention in the fields of catalysis and materials science. In particular, helical molecules are of great interest for the development and application of novel organic radicals in optoelectronic and spintronic materials. Here we report the syntheses of easily tunable and stable neutral quinolinoacridine radicals under anaerobic conditions by chemical reduction of their quinolinoacridinium cation analogs. The structures of these [4]helicene radicals were determined by X-ray crystallography. Density functional theory (DFT) calculations, supported by electron paramagnetic resonance (EPR) measurements, indicate that over 40% of spin density is located at the central carbon of our [4]helicene radicals regardless of their structural modifications. The localization of the charge promotes a reversible oxidation to the cation upon exposure to air. This unusual reactivity toward molecular oxygen was monitored via UV-Vis spectroscopy.
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Affiliation(s)
- Aslam C Shaikh
- Department of Chemistry and Biochemistry, University of Arizona Tucson AZ USA
| | - Jules Moutet
- Department of Chemistry and Biochemistry, University of Arizona Tucson AZ USA
| | - José M Veleta
- Department of Chemistry and Biochemistry, University of Arizona Tucson AZ USA
| | - Md Mubarak Hossain
- Department of Chemistry and Biochemistry, University of Arizona Tucson AZ USA
| | - Jan Bloch
- Department of Chemistry and Applied Biosciences, ETH Zürich Zürich Switzerland
| | - Andrei V Astashkin
- Department of Chemistry and Biochemistry, University of Arizona Tucson AZ USA
| | - Thomas L Gianetti
- Department of Chemistry and Biochemistry, University of Arizona Tucson AZ USA
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29
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Tani F, Narita M, Murafuji T. Helicene Radicals: Molecules Bearing a Combination of Helical Chirality and Unpaired Electron Spin. Chempluschem 2020; 85:2093-2104. [DOI: 10.1002/cplu.202000452] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 08/19/2020] [Indexed: 12/25/2022]
Affiliation(s)
- Fumito Tani
- Institute for Materials Chemistry and Engineering Kyushu University Fukuoka 819-0395 Japan
| | - Masahiro Narita
- Institute for Materials Chemistry and Engineering Kyushu University Fukuoka 819-0395 Japan
| | - Toshihiro Murafuji
- Graduate School of Sciences and Technology for Innovation Yamaguchi University Yamaguchi 753-8512 Japan
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30
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Christensen EG, Steele RP. Stepwise Activation of Water by Open-Shell Interactions, Cl(H 2O) n=4–8,17. J Phys Chem A 2020; 124:3417-3437. [DOI: 10.1021/acs.jpca.0c01544] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elizabeth G. Christensen
- Department of Chemistry and Henry Eyring Center for Theoretical Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, United States
| | - Ryan P. Steele
- Department of Chemistry and Henry Eyring Center for Theoretical Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, United States
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31
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Kumar A, Adhikary A, Sevilla MD, Close DM. One-electron oxidation of ds(5'-GGG-3') and ds(5'-G(8OG)G-3') and the nature of hole distribution: a density functional theory (DFT) study. Phys Chem Chem Phys 2020; 22:5078-5089. [PMID: 32073006 PMCID: PMC7058519 DOI: 10.1039/c9cp06244k] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Of particular interest in radiation-induced charge transfer processes in DNA is the extent of hole localization immediately after ionization and subsequent relaxation. To address this, we considered double stranded oligomers containing guanine (G) and 8-oxoguanine (8OG), i.e., ds(5'-GGG-3') and ds(5'-G8OGG-3') in B-DNA conformation. Using DFT, we calculated a variety of properties, viz., vertical and adiabatic ionization potentials, spin density distributions in oxidized stacks, solvent and solute reorganization energies and one-electron oxidation potential (E0) in the aqueous phase. Calculations for the vertical state of the -GGG- cation radical showed that the spin was found mainly (67%) on the middle G. However, upon relaxation to the adiabatic -GGG- cation radical, the spin localized (96%) on the 5'-G, as observed in experiments. Hole localizations on the middle G and 3'-G were higher in energy by 0.5 kcal mol-1 and 0.4 kcal mol-1, respectively, than that of 5'-G. In the -G8OGG- cation radical, the spin localized only on the 8OG in both vertical and adiabatic states. The calculated vertical ionization potentials of -GGG- and -G8OGG- stacks were found to be lower than that of the vertical ionization potential of a single G in DNA. The calculated E0 values of -GGG- and -G8OGG- stacks are 1.15 and 0.90 V, respectively, which owing to stacking effects are substantially lower than the corresponding experimental E0 values of their monomers (1.49 and 1.18 V, respectively). SOMO to HOMO level switching is observed in these oxidized stacks. Consequently, our calculations predict that local double oxidations in DNA will form triplet diradical states, which are especially significant for high LET radiations.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, USA.
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32
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Tsuchiya T, Katsuoka Y, Yoza K, Sato H, Mazaki Y. Stereochemistry, Stereodynamics, and Redox and Complexation Behaviors of 2,2'-Diaryl-1,1'-Biazulenes. Chempluschem 2020; 84:1659-1667. [PMID: 31943874 DOI: 10.1002/cplu.201900262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 06/25/2019] [Indexed: 11/11/2022]
Abstract
2,2'-Diaryl-1,1'-biazulenes were synthesized and electronic communication between the azulene subunits was suggested based on redox measurements. The linkage of azulene at the 1-position also appeared to increase the HOMO levels. In addition, cyclic voltammetry measurements of 2-arylazulenes showed a return peak associated with the oxidation, which was not observed for azulene. The stabilization of the single-electron oxidant may be due to the SOMO-HOMO energy inversion phenomenon. X-ray crystallography of the azulene dimers revealed that this species possessed a syn-type structure in which both aryl groups in the 2-positions formed π-stacks. The twisted structure was indicated to be in the (R)- or (S)-configuration for all molecules in the unit cell. Spontaneous resolution was also shown. Furthermore, from the solid circular dichroism (CD) spectral measurements, the relationship between the absolute configuration of the molecules and the CD spectra was determined. A racemization rotational barrier of ca. 27 kcal mol-1 was calculated. Moreover, the pyridylazulene dimer cyclized upon reaction with PdCl2 to form a 3 : 3 complex, in which the biazulene units cyclized to give ratios between the (R)- and (S)-forms of either 2 : 1 or 1 : 2.
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Affiliation(s)
- Takahiro Tsuchiya
- Department of Chemistry, Graduate School of Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, 252-0373, Japan
| | - Yuka Katsuoka
- Department of Chemistry, Graduate School of Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, 252-0373, Japan
| | - Kenji Yoza
- Bruker Japan, 3-9 Moriya-cho, Kanagawa-ku, Yokohama, 221-0022, Japan
| | - Hiroyasu Sato
- Rigaku Corporation, 3-9-12 Matsubara, Akishima, Tokyo, 196-8666, Japan
| | - Yasuhiro Mazaki
- Department of Chemistry, Graduate School of Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, 252-0373, Japan
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33
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Kumar R, Maity DK. Structure, stability and spectral properties of seleno[ n]helicenes ( n = 1–10). NEW J CHEM 2020. [DOI: 10.1039/c9nj05001a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The most stable structures of seleno[n]helicenes (n = 3–10) are flexible and helical in nature. The excited state results show that many of the seleno[n]helicene radical cations have strong absorption bands in the IR region.
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Affiliation(s)
- Rahul Kumar
- Homi Bhabha National Institute
- Training School Complex
- Anushaktinagar
- Mumbai-400094
- India
| | - Dilip Kumar Maity
- Homi Bhabha National Institute
- Training School Complex
- Anushaktinagar
- Mumbai-400094
- India
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34
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Chang H, Liu H, Dmitrieva E, Chen Q, Ma J, He P, Liu P, Popov AA, Cao XY, Wang XY, Zou Y, Narita A, Müllen K, Peng H, Hu Y. Furan-containing double tetraoxa[7]helicene and its radical cation. Chem Commun (Camb) 2020; 56:15181-15184. [PMID: 33216069 DOI: 10.1039/d0cc06970a] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
An unprecedented furan-based double oxa[7]helicene 1 was achieved, featuring a stable twisted conformation with π-overlap at both helical ends. The excellent conformational stability allowed for optical resolution of 1, which provided a pair of enantiomers exhibiting pronounced mirror-imaged circular dichroism and circularly polarized luminescence activity. The radical cation of 1 was obtained by chemical oxidation as evidenced by UV-Vis-NIR absorption, electron paramagnetic resonance spectroscopy and in situ spectroelectrochemistry. The present work is the starting point for the investigation of open-shell oxahelicenes.
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Affiliation(s)
- Hao Chang
- College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083, P. R. China.
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35
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Narita M, Teraoka T, Murafuji T, Shiota Y, Yoshizawa K, Mori S, Uno H, Kanegawa S, Sato O, Goto K, Tani F. An Azulene-Based Chiral Helicene and Its Air-Stable Cation Radical. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2019. [DOI: 10.1246/bcsj.20190219] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Masahiro Narita
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Takaaki Teraoka
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Toshihiro Murafuji
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Shigeki Mori
- Advanced Research Support Center, Ehime University, Matsuyama, Ehime 790-8577, Japan
| | - Hidemitsu Uno
- Graduate School of Science and Engineering, Ehime University, Matsuyama, Ehime 790-8577, Japan
| | - Shinji Kanegawa
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Osamu Sato
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Kenta Goto
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
| | - Fumito Tani
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 819-0395, Japan
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36
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Shu C, Zhang H, Olankitwanit A, Rajca S, Rajca A. High-Spin Diradical Dication of Chiral π-Conjugated Double Helical Molecule. J Am Chem Soc 2019; 141:17287-17294. [PMID: 31596077 DOI: 10.1021/jacs.9b08711] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We report an air-stable diradical dication of chiral D2-symmetric conjoined bis[5]diazahelicene with an unprecedented high-spin (triplet) ground state, singlet triplet energy gap, ΔEST = 0.3 kcal mol-1. The diradical dication possesses closed-shell (Kekulé) resonance forms with 16 π-electron perimeters. The diradical dication is monomeric in dibutyl phthalate (DBP) matrix at low temperatures, and it has a half-life of more than 2 weeks at ambient conditions in the presence of excess oxidant. A barrier of ∼35 kcal mol-1 has been experimentally determined for inversion of configuration in the neutral conjoined bis[5]diazahelicene, while the inversion barriers in its radical cation and diradical dication were predicted by the DFT computations to be within a few kcal mol-1 of that in the neutral species. Chiral HPLC resolution provides the chiral D2-symmetric conjoined bis[5]diazahelicene, enriched in (P,P)- or (M,M)-enantiomers. The enantiomerically enriched triplet diradical dication is configurationally stable for 48 h at room temperature, thus providing the lower limit for inversion barrier of configuration of 27 kcal mol-1. The enantiomers of conjoined bis[5]diazahelicene and its diradical dication show strong chirooptical properties that are comparable to [6]helicene or carbon-sulfur [7]helicene, as determined by the anisotropy factors, |g| = |Δε|/ε = 0.007 at 348 nm (neutral) and |g| = 0.005 at 385 nm (diradical dication). DFT computations of the radical cation suggest that SOMO and HOMO energy levels are near-degenerate.
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Affiliation(s)
- Chan Shu
- Department of Chemistry , University of Nebraska , Lincoln , Nebraska 68588-0304 , United States
| | - Hui Zhang
- Department of Chemistry , University of Nebraska , Lincoln , Nebraska 68588-0304 , United States
| | - Arnon Olankitwanit
- Department of Chemistry , University of Nebraska , Lincoln , Nebraska 68588-0304 , United States
| | - Suchada Rajca
- Department of Chemistry , University of Nebraska , Lincoln , Nebraska 68588-0304 , United States
| | - Andrzej Rajca
- Department of Chemistry , University of Nebraska , Lincoln , Nebraska 68588-0304 , United States
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37
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Christensen EG, Steele RP. Probing the Partial Activation of Water by Open-Shell Interactions, Cl(H 2O) 1-4. J Phys Chem A 2019; 123:8657-8673. [PMID: 31513400 DOI: 10.1021/acs.jpca.9b07235] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The partial chemical activation of water by reactive radicals was examined computationally for small clusters of chlorine and water, Cl•(H2O)n=1-4. Using an automated isomer-search procedure, dozens of unique, stable structures were computed. Among the resulting structural classes were intact, hydrated-chlorine isomers, as well as hydrogen-abstracted (HCl)(OH)(H2O)n-1 configurations. The latter showed increased stability as the degree of hydration increased, until n = 4, where a new class of structures was discovered with a chloride ion bound to an oxidized water network. The electronic structure of these three structural classes was investigated, and spectral signatures of this hydration-based evolution were connected to these electronic properties. An ancillary outcome of this detailed computational analysis, including coupled-cluster benchmarks, was the calibration of cost-effective quantum chemistry methods for future studies of these radical-water complexes.
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Affiliation(s)
- Elizabeth G Christensen
- Department of Chemistry and Henry Eyring Center for Theoretical Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112 , United States
| | - Ryan P Steele
- Department of Chemistry and Henry Eyring Center for Theoretical Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112 , United States
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38
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Guo H, Peng Q, Chen XK, Gu Q, Dong S, Evans EW, Gillett AJ, Ai X, Zhang M, Credgington D, Coropceanu V, Friend RH, Brédas JL, Li F. High stability and luminescence efficiency in donor-acceptor neutral radicals not following the Aufbau principle. NATURE MATERIALS 2019; 18:977-984. [PMID: 31332338 DOI: 10.1038/s41563-019-0433-1] [Citation(s) in RCA: 107] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 06/13/2019] [Indexed: 06/10/2023]
Abstract
With their unusual electronic structures, organic radical molecules display luminescence properties potentially relevant to lighting applications; yet, their luminescence quantum yield and stability lag behind those of other organic emitters. Here, we designed donor-acceptor neutral radicals based on an electron-poor perchlorotriphenylmethyl or tris(2,4,6-trichlorophenyl)methyl radical moiety combined with different electron-rich groups. Experimental and quantum-chemical studies demonstrate that the molecules do not follow the Aufbau principle: the singly occupied molecular orbital is found to lie below the highest (doubly) occupied molecular orbital. These donor-acceptor radicals have a strong emission yield (up to 54%) and high photostability, with estimated half-lives reaching up to several months under pulsed ultraviolet laser irradiation. Organic light-emitting diodes based on such a radical emitter show deep-red/near-infrared emission with a maximal external quantum efficiency of 5.3%. Our results provide a simple molecular-design strategy for stable, highly luminescent radicals with non-Aufbau electronic structures.
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Affiliation(s)
- Haoqing Guo
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | - Qiming Peng
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
- Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), Nanjing, China
| | - Xian-Kai Chen
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Qinying Gu
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Shengzhi Dong
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | | | - Xin Ai
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | - Ming Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | - Dan Credgington
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Veaceslav Coropceanu
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | | | - Jean-Luc Brédas
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA.
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China.
- Cavendish Laboratory, University of Cambridge, Cambridge, UK.
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39
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Dhbaibi K, Favereau L, Crassous J. Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P). Chem Rev 2019; 119:8846-8953. [DOI: 10.1021/acs.chemrev.9b00033] [Citation(s) in RCA: 242] [Impact Index Per Article: 48.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Kais Dhbaibi
- ISCR (Institut des Sciences Chimiques de Rennes), UMR6226, CNRS, Université Rennes, F-35000 Rennes, France
- Faculty of Science of Gabès, University of Gabés, Zrig, 6072 Gabès Tunisia
| | - Ludovic Favereau
- ISCR (Institut des Sciences Chimiques de Rennes), UMR6226, CNRS, Université Rennes, F-35000 Rennes, France
| | - Jeanne Crassous
- ISCR (Institut des Sciences Chimiques de Rennes), UMR6226, CNRS, Université Rennes, F-35000 Rennes, France
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40
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Kim Y, Bielawski CW, Lee E. Oxygen atom transfer: a mild and efficient method for generating iminyl radicals. Chem Commun (Camb) 2019; 55:7061-7064. [PMID: 31143894 DOI: 10.1039/c9cc03521d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Treating iminoxyl species with oxygen acceptors such as PPh3 resulted in oxygen atom transfer and afforded the corresponding iminyl radicals. DFT and other calculations revealed that association between the oxygen atom acceptors and the iminoxyl species results in the formation of key intermediates during the reaction. Subsequent dissociation is accompanied with homolytic cleavage of the N-O bond and generates iminyl radicals with spin densities that are localized on exocyclic nitrogen atoms.
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Affiliation(s)
- Youngsuk Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea. and Center for Self-assembly and Complexity (CSC), Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea
| | - Christopher W Bielawski
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea and Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea and Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea. and Center for Self-assembly and Complexity (CSC), Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
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41
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Rahman MS, Yoshikai N. Synthesis and Properties of Phospha[5]helicenes Bearing an Inner-Rim Phosphorus Center. Org Lett 2019; 21:3232-3236. [PMID: 30990704 DOI: 10.1021/acs.orglett.9b00955] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
New phospha[5]helicene derivatives featuring angular fusion of phosphole and carbohelicene moieties have been synthesized using 7-hydroxybenzo[ b]phosphole oxide as a key intermediate, which can be regioselectively prepared through one-pot multicomponent coupling. The structural behavior of the present phospha[5]helicene oxide, sulfide, and gold complex in the solid and solution states, along with DFT calculations, demonstrated close correlation between the P-centered chirality and the helical chirality as well as facile helicity inversion and equilibrium between the diastereomers in solution.
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Affiliation(s)
- Md Shafiqur Rahman
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences , Nanyang Technological University , Singapore 637371 , Singapore
| | - Naohiko Yoshikai
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences , Nanyang Technological University , Singapore 637371 , Singapore
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42
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Pop F, Zigon N, Avarvari N. Main-Group-Based Electro- and Photoactive Chiral Materials. Chem Rev 2019; 119:8435-8478. [DOI: 10.1021/acs.chemrev.8b00770] [Citation(s) in RCA: 127] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Flavia Pop
- Laboratoire MOLTECH-Anjou,
UMR 6200 CNRS-Université d’Angers, UFR Sciences, Bât. K, 2 Bd. Lavoisier, 49045 Angers Cedex, France
| | - Nicolas Zigon
- Laboratoire MOLTECH-Anjou,
UMR 6200 CNRS-Université d’Angers, UFR Sciences, Bât. K, 2 Bd. Lavoisier, 49045 Angers Cedex, France
| | - Narcis Avarvari
- Laboratoire MOLTECH-Anjou,
UMR 6200 CNRS-Université d’Angers, UFR Sciences, Bât. K, 2 Bd. Lavoisier, 49045 Angers Cedex, France
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43
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Tok OL, Lang K, Růžička A, Cvačka J. Helicenes Built from Silacyclopentadienes via Ring-by-Ring Knitting of the Helical Framework. Angew Chem Int Ed Engl 2019; 58:1654-1658. [PMID: 30548911 DOI: 10.1002/anie.201811140] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 11/14/2018] [Indexed: 12/25/2022]
Abstract
Despite the apparent diversity of the protocols developed for the synthesis of helicenes, they essentially follow the same strategy: the closure of one, or several, internal rings in a key step. Herein, we report the synthesis of a new family of the heterohelicenes consisting of fused silacyclopentadiene rings formed via a facile and novel process. The treatment of oligo(alkynilydenesilylene) precursors of type H2 C=CH-(SiMe2 -C≡C)n -R (n=3-7), bearing a vinyl group on the terminal silicon atom, with 9-borabicyclononane leads first to 1,2-hydroboration of the terminal double bond which then continues with a cascade of intramolecular 1,1-carboboration reactions accompanied with the closure of a new silole ring after each step affording the target silahelicenes with, currently, up to seven condensed silole rings and with excellent yields. According XRD analysis, the seven fused silole rings of the heptacyclic compound 11 b form an almost complete turn of a helix. The presented one-pot sequence of reactions is the first example of ring-by-ring knitting of a helical framework starting from easily available linear precursors.
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Affiliation(s)
- Oleg L Tok
- Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, 25068, Řež, Czech Republic
| | - Kamil Lang
- Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, 25068, Řež, Czech Republic
| | - Aleš Růžička
- Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 53210, Pardubice, Czech Republic
| | - Josef Cvačka
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nam. 2, 16610, Prague 6, Czech Republic
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44
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Tok OL, Lang K, Růžička A, Cvačka J. Helicenes Built from Silacyclopentadienes via Ring‐by‐Ring Knitting of the Helical Framework. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201811140] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Oleg L. Tok
- Institute of Inorganic ChemistryAcademy of Sciences of the Czech Republic 25068 Řež Czech Republic
| | - Kamil Lang
- Institute of Inorganic ChemistryAcademy of Sciences of the Czech Republic 25068 Řež Czech Republic
| | - Aleš Růžička
- Department of General and Inorganic ChemistryFaculty of Chemical TechnologyUniversity of Pardubice Studentská 573 53210 Pardubice Czech Republic
| | - Josef Cvačka
- Institute of Organic Chemistry and BiochemistryAcademy of Sciences of the Czech Republic Flemingovo nam. 2 16610 Prague 6 Czech Republic
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45
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Huang S, Zhang H, Paletta JT, Rajca S, Rajca A. Reduction kinetics and electrochemistry of tetracarboxylate nitroxides. Free Radic Res 2018; 52:327-334. [PMID: 29402129 DOI: 10.1080/10715762.2018.1437268] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Tetracarboxylate pyrroline nitroxides undergo very fast reduction with ascorbate/glutathione (GSH), with second-order rate constants that are five orders of magnitude greater than those for gem-diethyl pyrroline nitroxides. For tetracarboxylate nitroxides, the electrochemical reduction potentials, measured by square wave voltammetry, are much less negative (by about 0.8 V), compared with the corresponding gem-diethyl nitroxides, while the oxidation potentials become more positive (by about 0.7 V). Electrochemical potentials correlate well via simple regressions with field/inductive parameters such as Swain/Lupton F-parameters (and/or Charton σI-parameters). Rates of reduction with ascorbate/GSH similarly correlate well for four pyrroline nitroxides, except for the slowest reducing gem-diethyl nitroxide. These results suggest that the electron withdrawing groups adjacent to the nitroxide moiety have a strong accelerating impact on the reduction rates, and thus they are not suitable for the design of hydrophilic nitroxides for in vivo applications.
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Affiliation(s)
- Shengdian Huang
- a Department of Chemistry , University of Nebraska , Lincoln , NE , USA
| | - Hui Zhang
- a Department of Chemistry , University of Nebraska , Lincoln , NE , USA
| | - Joseph T Paletta
- a Department of Chemistry , University of Nebraska , Lincoln , NE , USA
| | - Suchada Rajca
- a Department of Chemistry , University of Nebraska , Lincoln , NE , USA
| | - Andrzej Rajca
- a Department of Chemistry , University of Nebraska , Lincoln , NE , USA
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46
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Abstract
![]()
Conventionally, the
singly occupied molecular orbital (SOMO) of
a radical species is considered to be the highest occupied molecular
orbital (HOMO), but this is not the case always. In this study, we
considered a number of radicals from smallest diatomic anion radicals
such as superoxide anion radical to one-electron oxidized DNA related
base radicals that show the SOMO is energetically lower than one or
more doubly occupied molecular orbitals (MOs) (SOMO–HOMO level
inversion). The electronic configurations are calculated employing
the B3LYP/6-31++G** method, with the inclusion of aqueous phase via
the integral equation formalism of the polarized continuum model solvation
model. From the extensive study of the electronic configurations of
radicals produced by one-electron oxidation or reduction of natural-DNA
bases, bromine-, sulfur-, selenium-, and aza-substituted DNA bases,
as well as 20 diatomic molecules, we highlight the following important
findings: (i) SOMO–HOMO level inversion is a common phenomenon
in radical species. (ii) The more localized spin density in σ-orbital
on a single atom (carbon, nitrogen, oxygen, sulfur, or selenium),
the greater the gap between HOMO and SOMO. (iii) In species with SOMO–HOMO
level inversion, one-electron oxidation takes place from HOMO not
from the SOMO, which produces a molecule in its triplet ground state.
Oxidation of aqueous superoxide anion producing triplet molecular
oxygen is one example of many. (iv) These results are for conventional
radicals and in contrast with those reported for distonic radical
anions in which SOMO–HOMO gaps are smaller for more localized
radicals and the orbital inversions vanish in water. Our findings
yield new insights into the properties of free radical systems.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
| | - Michael D Sevilla
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
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47
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Kato K, Furukawa K, Mori T, Osuka A. Porphyrin-Based Air-Stable Helical Radicals. Chemistry 2017; 24:572-575. [DOI: 10.1002/chem.201705291] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Kenichi Kato
- Department of Chemistry, Graduate School of Science; Kyoto University; Sakyo-ku Kyoto 606-8502 Japan
| | - Ko Furukawa
- Center for Instrumental Analysis; Niigata University; Nishi-ku, Niigata 950-2181 Japan
| | - Tadashi Mori
- Department of Applied Chemistry, Graduate School of Engineering; Osaka University; Suita, Osaka 565-871 Japan
| | - Atsuhiro Osuka
- Department of Chemistry, Graduate School of Science; Kyoto University; Sakyo-ku Kyoto 606-8502 Japan
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48
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Mukhopadhyay A, Hossen T, Ghosh I, Koner AL, Nau WM, Sahu K, Moorthy JN. Helicity-Dependent Regiodifferentiation in the Excited-State Quenching and Chiroptical Properties of Inward/Outward Helical Coumarins. Chemistry 2017; 23:14797-14805. [PMID: 28792106 DOI: 10.1002/chem.201701787] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Indexed: 01/30/2023]
Abstract
Influence of helicity on the excited-state as well as chiroptical properties of two sets of regiohelical coumarins that are differentiated by "inward" and "outward" disposition of the pyran-2-one ring has been investigated. A subtle difference in the helicities manifests in divergent excited-state properties and significant differences in the dipole moments. The latter permit heretofore unprecedented regiodifferentiation in the O-H⋅⋅⋅O hydrogen-bond assisted electron-transfer quenching by phenols. Furthermore, the enantiopure hexahelical coumarins exhibit strong Cotton effects and lend themselves to a very high differentiation in the specific rotations and anisotropic dissymmetry factors. The specific rotation observed for 6-in turns out being the highest of the values reported for all hexahelicenes reported so far.
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Affiliation(s)
| | - Tousif Hossen
- Department of Chemistry, Indian Institute of Technology, Guwahati, 781039, India
| | - Indrajit Ghosh
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany
| | - Apurba Lal Koner
- Department of Chemistry, Indian Institute of Science Education and Research, Bhopal, 462066, India
| | - Werner M Nau
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany
| | - Kalyanasis Sahu
- Department of Chemistry, Indian Institute of Technology, Guwahati, 781039, India
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49
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Shimizu D, Furukawa K, Osuka A. Stable Subporphyrin meso
-Aminyl Radicals without Resonance Stabilization by a Neighboring Heteroatom. Angew Chem Int Ed Engl 2017; 56:7435-7439. [DOI: 10.1002/anie.201703097] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Indexed: 12/12/2022]
Affiliation(s)
- Daiki Shimizu
- Department of Chemistry; Graduate School of Science; Kyoto University, Sakyo-ku; Kyoto 606-8502 Japan
| | - Ko Furukawa
- Center for Instrumental Analysis; Niigata University, Nishi-ku; Niigata 950-2181 Japan
| | - Atsuhiro Osuka
- Department of Chemistry; Graduate School of Science; Kyoto University, Sakyo-ku; Kyoto 606-8502 Japan
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50
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Shimizu D, Furukawa K, Osuka A. Stable Subporphyrin meso
-Aminyl Radicals without Resonance Stabilization by a Neighboring Heteroatom. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201703097] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Daiki Shimizu
- Department of Chemistry; Graduate School of Science; Kyoto University, Sakyo-ku; Kyoto 606-8502 Japan
| | - Ko Furukawa
- Center for Instrumental Analysis; Niigata University, Nishi-ku; Niigata 950-2181 Japan
| | - Atsuhiro Osuka
- Department of Chemistry; Graduate School of Science; Kyoto University, Sakyo-ku; Kyoto 606-8502 Japan
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