1
|
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.
Collapse
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
| |
Collapse
|
2
|
Porsev VV, Evarestov RA. Current State of Computational Modeling of Nanohelicenes. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2295. [PMID: 37630880 PMCID: PMC10458037 DOI: 10.3390/nano13162295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 08/01/2023] [Accepted: 08/03/2023] [Indexed: 08/27/2023]
Abstract
This review considers the works that focus on various aspects of the theoretical description of nanohelicenes (other equivalent names are graphene spirals, graphene helicoid, helical graphene nanoribbon, or helical graphene)-a promising class of one-dimensional nanostructures. The intrinsic helical topology and continuous π-system lead to the manifestation of unique optical, electronic, and magnetic properties that are also highly dependent on axial and torsion strains. In this paper, it was shown that the properties of nanohelicenes are mainly associated with the peripheral modification of the nanohelicene ribbon. We have proposed a nomenclature that enables the classification of all nanohelicenes as modifications of some prototype classes.
Collapse
Affiliation(s)
- Vitaly V. Porsev
- Quantum Chemistry Department, Saint-Petersburg State University, St Petersburg 199034, Russia
| | - Robert A. Evarestov
- Quantum Chemistry Department, Saint-Petersburg State University, St Petersburg 199034, Russia
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Taninaka A, Yoshida S, Sugita Y, Takeuchi O, Shigekawa H. Evolution of local conductance pathways in a single-molecule junction studied using the three-dimensional dynamic probe method. NANOSCALE 2019; 11:5951-5959. [PMID: 30869706 DOI: 10.1039/c9nr00717b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Understanding of the dynamics of the bonding states of molecules with electrodes while the molecular conformation is changed is particularly important for elucidating the details of electrochemical devices as well as molecular devices in which the reaction dynamics of the electrodes and molecules plays an important role, such as in fuel cells, catalysis and bioelectrochemical devices. However, it has been difficult to make measurements when the distance between counter electrodes is short, namely, the molecule is raised from a lying form, almost parallel and close to the electrodes, toward a standing form and vice versa. We previously have developed a method called the three-dimensional (3D) dynamic probe method, which enables conductance measurement while the conformation of a single-molecule junction is precisely controlled by scanning tunneling microscopy (STM) techniques. Here, by combining this method with density functional theory (DFT) calculations, it has become possible to simultaneously consider the effects of the dynamics of molecular structures and the bonding states at the electrodes on the local transmission pathways, local-bond contributions to conductance. Here, by performing an analysis on 1,4-benzenediamine (BDA) and 1,4-benzenedithiol (BDT) single molecule junctions, we have observed, for the first time, the effect of a change in the molecular conformations and bonding states on the local transmission pathways for a short Au electrode distance condition.
Collapse
Affiliation(s)
- Atsushi Taninaka
- Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
| | - Shoji Yoshida
- Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
| | - Yoshihiro Sugita
- Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
| | - Osamu Takeuchi
- Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
| | - Hidemi Shigekawa
- Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
| |
Collapse
|
5
|
Xu X, Liu B, Zhao W, Jiang Y, Liu L, Li W, Zhang G, Tian WQ. Mechanism of mechanically induced optoelectronic and spintronic phase transitions in 1D graphene spirals: insight into the role of interlayer coupling. NANOSCALE 2017; 9:9693-9700. [PMID: 28675220 DOI: 10.1039/c7nr03432f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Graphene spirals (GSs), an emerging carbonic nano-material with a Riemann surface, demonstrate extraordinary topological electronic signatures: interlayer coupling similar to van der Waals (vdW) heterojunctions and intralayer coupling within the spiral conformation. Based on the state-of-the-art first-principles technique, the electronic properties of the periphery-modified GSs with geometry deformation are explored under axial strain. For all GSs, there emerges a remarkable phase transition from metal to semiconductor, due to the attenuation of interlayer "σ-bonds" reducing the interlayer tunneling probability for carriers. Analogous to graphene, GSs consist of bipartite sublattices with carbonic sp2 hybridization as well. Once the balance of the bipartite sublattices is lost, there will emerge intense edge (corner) states, contributed by the pz orbitals. In contrast to isolated graphene nanoflakes, GSs realize the continuous spin-polarized edge (corner) state coupling with 1D morphology. However, the spin-polarization is blocked by the robust interlayer "σ-bonds" so that the spintronic transition takes place until this interlayer coupling is broken. More intriguingly, an indirect-direct bandgap transition is observed, revealing excellent optical on-off features. Their tunable properties provide great potential for their application in optoelectronics, spintronics and chemical or biological sensors.
Collapse
Affiliation(s)
- Xiaodong Xu
- Department of Physics, Harbin Institute of Technology, Harbin, 150001, P. R. China.
| | | | | | | | | | | | | | | |
Collapse
|
6
|
Wang Y, Zhang H, Pink M, Olankitwanit A, Rajca S, Rajca A. Radical Cation and Neutral Radical of Aza-thia[7]helicene with SOMO–HOMO Energy Level Inversion. J Am Chem Soc 2016; 138:7298-304. [DOI: 10.1021/jacs.6b01498] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Ying Wang
- 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
| | - Maren Pink
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, 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
| |
Collapse
|
7
|
Xu X, Li W, Liu L, Feng J, Jiang Y, Tian WQ. Implementation of Outstanding Electronic Transport in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour. Sci Rep 2016; 6:26389. [PMID: 27211110 PMCID: PMC4876473 DOI: 10.1038/srep26389] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 04/29/2016] [Indexed: 11/09/2022] Open
Abstract
A theoretical investigation of the unique electronic transport properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through non-equilibrium Green's function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic electronic devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the transport properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias.
Collapse
Affiliation(s)
- Xiaodong Xu
- Department of Physics, Harbin Institute of Technology, Harbin, 150001, P. R. China
| | - Weiqi Li
- Department of Physics, Harbin Institute of Technology, Harbin, 150001, P. R. China
| | - Linhua Liu
- Department of Physics, Harbin Institute of Technology, Harbin, 150001, P. R. China
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin, 150001, P. R. China
| | - Jikang Feng
- Institute of Theoretical Chemistry and College of Chemistry, Jilin University, Changchun, 130023, P. R. China
| | - Yongyuan Jiang
- Department of Physics, Harbin Institute of Technology, Harbin, 150001, P. R. China
| | - Wei Quan Tian
- College of Chemistry and Chemical Engineering, Chongqing University, Huxi Campus, Chongqing, 401331, P. R. China
| |
Collapse
|