1
|
Fu Z, Treacy JW, Hosier BM, Houk KN, Maynard HD. Controlling rates and reversibilities of elimination reactions of hydroxybenzylammoniums by tuning dearomatization energies. Chem Sci 2024; 15:10448-10454. [PMID: 38994402 PMCID: PMC11234877 DOI: 10.1039/d4sc02985b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Accepted: 05/23/2024] [Indexed: 07/13/2024] Open
Abstract
Hydroxybenzylammonium compounds can undergo a reversible 1,4- or 1,6-elimination to afford quinone methide intermediates after release of the amine. These molecules are useful for the reversible conjugation of payloads to amines. We hypothesized that aromaticity could be used to alter the rate of reversibility as a distinct thermodynamic driving force. We describe the use of density functional theory (DFT) calculations to determine the effect of aromaticity on the rate of release of the amine from hydroxybenzylammonium compounds. Namely, the aromatic scaffold affects the dearomatization reaction to reduce the kinetic barrier and prevent the reversibility of the amine elimination. We consequently synthesized a small library of polycyclic hydroxybenzylammoniums, which resulted in a range of release half-lives from 18 minutes to 350 hours. The novel mechanistic insight provided herein significantly expands the range of release rates amenable to hydroxybenzylammonium-containing compounds. This work provides another way to affect the rate of payload release in hydroxybenzylammoniums.
Collapse
Affiliation(s)
- Zihuan Fu
- Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California Los Angeles California 90095-1569 USA
| | - Joseph W Treacy
- Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California Los Angeles California 90095-1569 USA
| | - Brock M Hosier
- Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California Los Angeles California 90095-1569 USA
| | - K N Houk
- Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California Los Angeles California 90095-1569 USA
| | - Heather D Maynard
- Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California Los Angeles California 90095-1569 USA
| |
Collapse
|
2
|
Raczyńska ED. On Prototropy and Bond Length Alternation in Neutral and Ionized Pyrimidine Bases and Their Model Azines in Vacuo. Molecules 2023; 28:7282. [PMID: 37959699 PMCID: PMC10648772 DOI: 10.3390/molecules28217282] [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: 09/25/2023] [Revised: 10/21/2023] [Accepted: 10/22/2023] [Indexed: 11/15/2023] Open
Abstract
In this review, the complete tautomeric equilibria are derived for disubstituted pyrimidine nucleic acid bases starting from phenol, aniline, and their model compounds-monosubstituted aromatic azines. The differences in tautomeric preferences for isolated (gaseous) neutral pyrimidine bases and their model compounds are discussed in light of different functional groups, their positions within the six-membered ring, electronic effects, and intramolecular interactions. For the discussion of tautomeric preferences and for the analysis of internal effects, recent quantum-chemical results are taken into account and compared to some experimental ones. For each possible tautomer-rotamer of the title compounds, the bond length alternation, measured by means of the harmonic oscillator model of electron delocalization (HOMED) index, is examined. Significant HOMED similarities exist for mono- and disubstituted derivatives. The lack of parallelism between the geometric (HOMED) and energetic (ΔG) parameters for all possible isomers clearly shows that aromaticity is not the main factor that dictates tautomeric preferences for pyrimidine bases, particularly for uracil and thymine. The effects of one-electron loss (positive ionization) and one-electron gain (negative ionization) on prototropy and bond length alternation are also reviewed for pyrimidine bases and their models.
Collapse
Affiliation(s)
- Ewa Daniela Raczyńska
- Department of Chemistry, Warsaw University of Life Sciences (SGGW), ul. Nowoursynowska 159c, 02-776 Warszawa, Poland
| |
Collapse
|
3
|
Ieritano C, Haack A, Hopkins WS. Chemical Transformations Can Occur during DMS Separations: Lessons Learned from Beer's Bittering Compounds. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023. [PMID: 37310853 DOI: 10.1021/jasms.3c00040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
While developing a DMS-based separation method for beer's bittering compounds, we observed that the argentinated forms of humulone tautomers (i.e., [Hum + Ag]+) were partially resolvable in a N2 environment seeded with 1.5 mol % of isopropyl alcohol (IPA). Attempting to improve the separation by introducing resolving gas unexpectedly caused the peaks for the cis-keto and trans-keto tautomers of [Hum + Ag]+ to coalesce. To understand why resolution loss occurred, we first confirmed that each of the tautomeric forms (i.e., dienol, cis-keto, and trans-keto) responsible for the three peaks in the [Hum + Ag]+ ionogram were assigned to the correct species by employing collision-induced dissociation, UV photodissociation spectroscopy, and hydrogen-deuterium exchange (HDX). The observation of HDX indicated that proton transfer was stimulated by dynamic clustering processes between IPA and [Hum + Ag]+ during DMS transit. Because IPA accretion preferentially occurs at Ag+, which can form pseudocovalent bonds with a suitable electron donor, solvent clustering also facilitated the formation of exceptionally stable microsolvated ions. The exceptional stability of these microsolvated configurations disproportionately impacted the compensation voltage (CV) required to elute each tautomer when the temperature within the DMS cell was varied. The disparity in CV response caused the peaks for the cis- and trans-keto species to merge when a temperature gradient was induced by the resolving gas. Moreover, simulations showed that microsolvation with IPA mediates dienol to trans-keto tautomerization during DMS transit, which, to the best of our knowledge, is the first observation of keto/enol tautomerization occurring within an ion-mobility device.
Collapse
Affiliation(s)
- Christian Ieritano
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Watermine Innovation, Waterloo, Ontario N0B 2T0, Canada
| | - Alexander Haack
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - W Scott Hopkins
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Watermine Innovation, Waterloo, Ontario N0B 2T0, Canada
- Centre for Eye and Vision Research, 17 W Hong Kong Science Park, Shatin, New Territories 999077, Hong Kong
| |
Collapse
|
4
|
Szymańska M, Majerz I. Prototropy, Intramolecular Interactions, Electron Delocalization, and Physicochemical Properties of 1,8-dihydroxy-9-anthrone-DFT-D3 Study of Substituent Effects. MOLECULES (BASEL, SWITZERLAND) 2023; 28:molecules28010344. [PMID: 36615539 PMCID: PMC9822037 DOI: 10.3390/molecules28010344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 12/27/2022] [Accepted: 12/28/2022] [Indexed: 01/04/2023]
Abstract
1,8-dihydroxy-9-anthrone are tricyclic compounds with a ketone group in the middle ring and two hydroxyl groups substituted in the side-aromatic rings what results in formation of two intramolecular hydrogen bonds in which the oxygen atom from the ketone group is the proton acceptor. 1,8-dihydroxy-9-anthrones in which intramolecular proton transfer between C10 and CO in the middle ring occurs, can exist in a tautomeric keto-enol equilibrium. For anthralin, the most important representative of this group, this equilibrium has been studied previously, but it has not been studied for its derivatives. Substituents in the middle ring change the geometry of 1,8-dihydroxy-9-anthrones so they are also expected to affect the keto-enol equilibrium. It is also important to study the effect of intramolecular hydrogen bonds on the structure of both tautomeric forms. It was found that the nature of the substituent in the middle ring could affect the antioxidant properties of the investigated compound.
Collapse
|
5
|
Chen K, Kang QK, Li Y, Wu WQ, Zhu H, Shi H. Catalytic Amination of Phenols with Amines. J Am Chem Soc 2022; 144:1144-1151. [PMID: 35015956 DOI: 10.1021/jacs.1c12622] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Given the wide prevalence and ready availability of both phenols and amines, aniline synthesis through direct coupling between these starting materials would be extremely attractive. Herein, we describe a rhodium-catalyzed amination of phenols, which provides concise access to diverse anilines, with water as the sole byproduct. The arenophilic rhodium catalyst facilitates the inherently difficult keto-enol tautomerization of phenols by means of π-coordination, allowing for the subsequent dehydrative condensation with amines. We demonstrate the generality of this redox-neutral catalysis by carrying out reactions of a large array of phenols with various electronic properties and a wide variety of primary and secondary amines. Several examples of late-stage functionalization of structurally complex bioactive molecules, including pharmaceuticals, further illustrate the potential broad utility of the method.
Collapse
Affiliation(s)
- Kai Chen
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, School of Science, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province. China
| | - Qi-Kai Kang
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, School of Science, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province. China
| | - Yuntong Li
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, School of Science, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province. China
| | - Wen-Qiang Wu
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, School of Science, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province. China
| | - Hui Zhu
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, School of Science, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province. China
| | - Hang Shi
- Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province, School of Science, Westlake University, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province. China.,Institute of Natural Sciences, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou 310024, Zhejiang Province, China
| |
Collapse
|
6
|
Quantum-Chemical Search for Keto Tautomers of Azulenols in Vacuo and Aqueous Solution. Symmetry (Basel) 2021. [DOI: 10.3390/sym13030497] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Keto-enol prototropic conversions for carbonyl compounds and phenols have been extensively studied, and many interesting review articles and even books appeared in the last 50 years. Quite a different situation takes place for derivatives of biologically active azulene, for which only scanty information on this phenomenon can be found in the literature. In this work, quantum-chemical studies have been undertaken for symmetrically and unsymmetrically substituted azulenols (constitutional isomers of naphthols). Stabilities of two enol (OH) rotamers and all possible keto (CH) tautomers have been analyzed in the gas phase {DFT(B3LYP)/6-311+G(d,p)} and also in aqueous solution {PCM(water)//DFT(B3LYP)/6-311+G(d,p)}. Contrary to naphthols, for which the keto forms can be neglected, at least one keto isomer (C1H, C2H, and/or C3H) contributes significantly to the tautomeric mixture of each azulenol to a higher degree in vacuo (non-polar environment) than in water (polar amphoteric solvent). The highest amounts of the CH forms have been found for 2- and 5-hydroxyazulenes, and the smallest ones for 1- and 6-hydroxy derivatives. The keto tautomer(s), together with the enol rotamers, can also participate in deprotonation reaction leading to a common anion and influence its acid-base properties. The strongest acidity in vacuo exhibits 6-hydroxyazulene, and the weakest one displays 1-hydroxyazulene, but all azulenols are stronger acids than phenol and naphthols. Bond length alternation in all DFT-optimized structures has been measured using the harmonic oscillator model of electron delocalization (HOMED) index. Generally, the HOMED values decrease for the keto tautomers, particularly for the ring containing the labile proton. Even for the keto tautomers possessing energetic parameters close to those of the enol isomers, the HOMED indices are low. However, some kind of parallelism exists for the keto forms between their relative energies and HOMEDs estimated for the entire molecules.
Collapse
|
7
|
Theoretical modeling of optical spectra of N(1) and N(10) substituted lumichrome derivatives. ACTA CHIMICA SLOVACA 2021. [DOI: 10.2478/acs-2020-0017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
A systematic study of (7,8-dimethylated) alloxazine, isoalloxazine, and their derivatives with substituted N(1) and N(10) positions was conducted using the density functional theory. The main aim of this work was the direct investigation of substituent effect on the molecular structure. Furthermore, HOMED aromaticity indices were calculated to describe the scope of the geometry changes. Frontier molecular orbitals of reference alloxazine, isoalloxazine and lumichrome derivatives were discussed by means of changes in their shape and energy levels. Photophysical properties were analyzed by determination of optical transition energies using the TD-DFT method. Obtained results were compared with previously published experimental data.
Collapse
|
8
|
Szymańska M, Majerz I. Effect of Substitution of Hydrogen Atoms in the Molecules of Anthrone and Anthraquinone. Molecules 2021; 26:502. [PMID: 33477805 PMCID: PMC7832899 DOI: 10.3390/molecules26020502] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 01/08/2021] [Accepted: 01/14/2021] [Indexed: 11/17/2022] Open
Abstract
The geometry of anthrone and anthraquinone-natural substances of plant origin-was investigated under the substitution of hydrogen atoms in side aromatic ring and, for anthrone, also in the central ring. A significant influence of substitution on geometry expressed by the angle between the side rings was shown. The geometry changes are connected with the changes of electron density and aromaticity of the anthrone and anthraquinone rings. The flexibility of the investigated compounds was confirmed by comparison of the optimized molecules and the molecules in the crystal state where the packing forces can influence the molecular geometry.
Collapse
Affiliation(s)
| | - Irena Majerz
- Faculty of Pharmacy, Wroclaw Medical University, Borowska 211a, 50-556 Wroclaw, Poland;
| |
Collapse
|
9
|
Michalík M, Biela M, Cagardová D, Lukeš V. Chelates of 3- and 5-hydroxyflavone: Quantum chemical study. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2020.138142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
10
|
The effect of the change in substituents’ positions on the formation of supramolecular networks and the solvent type/substituent dependence of prototropic behavior in three new o-hydroxy Schiff bases. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2019.127109] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
11
|
Tanii S, Arisawa M, Yamaguchi M. Acid-catalyzed synthesis of condensed polycyclic diaryl ethers from arenols. Chem Commun (Camb) 2019; 55:14078-14080. [PMID: 31696874 DOI: 10.1039/c9cc07172e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Diaryl ethers containing condensed polycyclic aryl groups were synthesized from arenols in the presence of a catalytic amount of p-chlorobenzenesulfonic acid. Symmetrical binaphthyl, biphenanthryl, and bipyrenyl ethers were obtained in high yields. Unsymmetrical derivatives were also synthesized from 9-phenanthrol and arenols, using combinations of reactive and unreactive substrates.
Collapse
Affiliation(s)
- Saori Tanii
- Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, 980-8578, Japan.
| | | | | |
Collapse
|
12
|
On local aromaticity of selected model aza-[n]circulenes (n = 6, 7, 8 and 9): Density functional theoretical study. ACTA CHIMICA SLOVACA 2019. [DOI: 10.2478/acs-2019-0011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Abstract
A computational study using density functional theory is reported for selected model aza[n]circulenes (n = 6, 7, 8 and 9) and their derivatives consisting of pyrrole and benzene units. Local aromaticity of central rings was discussed and analyzed using theoretical structural indices. Depending on their molecular structures, energies of the highest occupied and lowest unoccupied molecular orbitals change from –5.23 eV to –4.08 eV and from –1.97 eV to –0.41 eV, respectively. Based on B3LYP calculated optimal geometries, electronic structure of molecules and their charge transport properties resulted in the suggestion of three planar molecules containing three or four pyrrole units as potential candidates for p-type semiconductors. Hole drift mobilities for ideal stacked dimers of these potential semiconductors were calculated and they range from 0.94 cm2·V−1·s−1 to 7.33 cm2·V−1·s−1.
Collapse
|
13
|
Application of the Extended HOMED (Harmonic Oscillator Model of Aromaticity) Index to Simple and Tautomeric Five-Membered Heteroaromatic Cycles with C, N, O, P, and S Atoms. Symmetry (Basel) 2019. [DOI: 10.3390/sym11020146] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The geometry-based HOMA (Harmonic Oscillator Model of Aromaticity) descriptor, based on the reference compounds of different delocalizations of n- and π-electrons, can be applied to molecules possessing analogous bonds, e.g., only CC, only CN, only CO, etc. For compounds with different heteroatoms and a different number of CC, CX, XX, and XY bonds, its application leads to some discrepancies. For this reason, the structural descriptor was modified and the HOMED (Harmonic Oscillator Model of Electron Delocalization) index defined. In 2010, the HOMED index was parameterized for compounds with C, N and O atoms. For parametrization, the reference molecules of similar delocalizations of n- and π-electrons were employed. In this paper, the HOMED index was extended to compounds containing the CP, CS, NN, NP, PP, NO, NS, PO, and PS bonds. For geometrical optimization of all reference molecules and of all investigated heterocompounds, the same quantum–chemical method {B3LYP/6-311+G(d,p)} was used to eliminate errors of the HOMED estimation. For some tautomeric systems, the Gn methods were also employed to confirm tautomeric preferences. The extended HOMED index was applied to five-membered heterocycles, simple furan and thiophene, and their N and P derivatives as well as for tautomeric pyrrole and phosphole and their N and P derivatives. The effects of additional heteroatom(s) in the ring on the HOMED values for furan are parallel to those for thiophene. For pyrroles, aromaticity dictates the tautomeric preferences. An additional N atom in the ring only slightly affects the HOMED values for the favored and well delocalized NH tautomers. Significant changes take place for their rare CH forms. When intramolecular proton-transfer is considered for phosphole and its P derivatives, the PH tautomers seem to be favored only for 1,2,3-triphosphole/1,2,5-triphosphole and for 1,2,3,5-tetraphosphole. For other phospholes, the CH forms have smaller Gibbs energies than the PH isomers. For phosphazoles, the labile proton in the favored form is linked to the N atom. The PH forms have smaller HOMED indices than the NH tautomers but higher than the CH ones.
Collapse
|
14
|
Quantum chemical study of electron structure and charge transport properties of symmetric acenequinones. ACTA CHIMICA SLOVACA 2018. [DOI: 10.2478/acs-2018-0013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Abstract
A systematic theoretical study using density functional theory is presented to estimate the structural, electronic, and charge-transfer characteristics of a symmetric fluorination of acenequinones outer rings. The change in aromaticity of model derivatives was described by different types of aromaticity indices. By considering a hopping mechanism and using the Marcus theory in combination with the Einstein-Smoluchowski relation, electronic drift mobilities were predicted for selected dimer configurations obtained from X-ray structures of anthraquinone, 6,13-pentacenequinone and its octafluorinated derivatives. The analysis of obtained data showed that the fluorination of the outer rings of acenequinones can lower the energy of the lowest unoccupied molecular orbital to the range from −3.0 to −4.0 eV, i.e. typical for organic n-type semiconducting materials. Finally, potential electric semiconductivity of available X-ray structures relating to drift mobilities was discussed.
Collapse
|
15
|
Theoretical investigation of reaction kinetics and thermodynamics of the keto-enol tautomerism of 1, 3, 5-triazin-2, 4(1H, 3H)-dione and its substituted systems utilizing density functional theory and transition state theory methods. COMPUT THEOR CHEM 2018. [DOI: 10.1016/j.comptc.2018.08.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
16
|
Local aromaticity of linear cata-benzocoronenes and acenes: density functional study. ACTA CHIMICA SLOVACA 2018. [DOI: 10.2478/acs-2018-0006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Abstract
A computational study using density functional theory is reported for the coronene monomer and selected linear cata-benzocoronene oligomers. Local aromaticity was discussed and analysed using the theoretical Harmonic Oscillator Model of the Electron Delocalisation (HOMED) index and its geometric (GEO) and energetic (EN) contributions. The [n]acenes (n = 3, 7, 11 and 15) served as reference molecules. Local aromaticity of individual superbenzene rings has oscillating character. On the other hand, the highest HOMED parameters which are practically independent on the molecular lengths were found for the smallest molecules including condensed benzene rings in their structure. For the largest structure of [n]acenes (n = 15), the inner rings are less aromatic than the outer ones. Depending on the molecular length, the energy gaps between the B3LYP energy levels of the highest occupied and lowest unoccupied molecular orbitals vary from 2.71 eV to 4.04 eV for coronene series and from 0.61 eV to 3.59 eV for [n]acenes.
Collapse
|
17
|
Angelova S, Antonov L. Molecular Insight into Inclusion Complex Formation of Curcumin and Calix[4]arene. ChemistrySelect 2017. [DOI: 10.1002/slct.201701865] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Silvia Angelova
- Institute of Organic Chemistry with Centre of Phytochemistry; Bulgarian Academy of Sciences; 1113 Sofia Bulgaria
| | - Liudmil Antonov
- Institute of Organic Chemistry with Centre of Phytochemistry; Bulgarian Academy of Sciences; 1113 Sofia Bulgaria
| |
Collapse
|
18
|
Theoretical and vibrational spectroscopic approach to keto-enol tautomerism in methyl-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)-3-oxopropanoylcarbamate. J Mol Struct 2016. [DOI: 10.1016/j.molstruc.2016.05.060] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
19
|
Tun-Rosado FJ, Mena-Rejón GJ, Carballo RM, Mirón-López G, Quijano-Quiñones RF. Chrysophanol anthrone: a theoretical study on the potential energy surface. MOLECULAR SIMULATION 2016. [DOI: 10.1080/08927022.2016.1200040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
20
|
Phillips RS, Vita A, Spivey JB, Rudloff AP, Driscoll MD, Hay S. Ground-State Destabilization by Phe-448 and Phe-449 Contributes to Tyrosine Phenol-Lyase Catalysis. ACS Catal 2016. [DOI: 10.1021/acscatal.6b01495] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Robert S. Phillips
- Department
of Chemistry, University of Georgia, Athens, Georgia 30602, United States
- Department
of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - Andrew Vita
- Department
of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - J. Blaine Spivey
- Department
of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - Alexander P. Rudloff
- Department
of Chemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Max D. Driscoll
- Manchester Institute of Biotechnology, Manchester M1 7DN, United Kingdom
| | - Sam Hay
- Manchester Institute of Biotechnology, Manchester M1 7DN, United Kingdom
| |
Collapse
|
21
|
Effects of ionization on stability of 1-methylcytosine - DFT and PCM studies. J Mol Model 2016; 22:146. [PMID: 27259531 PMCID: PMC4893064 DOI: 10.1007/s00894-016-3020-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 05/26/2016] [Indexed: 01/01/2023]
Abstract
Consequences of ionization were studied by quantum-chemical methods (DFT and PCM) for 1-methylcytosine (MC)—a model of the nucleobase cytosine (C) connected with sugar in DNA. For calculations, three prototropic tautomers (one amino and two imino forms) and two imino zwitterions were considered, including conformational or configurational isomerism of exo heterogroups. Ionization and interactions between neighboring groups affect intramolecular proton-transfers, geometric and thermodynamic parameters, and electron delocalization for individual isomers. We discovered that an imino isomer is present in the isomeric mixture in the highest amount for positively ionized MC. Its contribution in neutral and negatively ionized MC is considerably smaller. Acid-base parameters for selected radical ions were estimated in the gas phase and compared to those of neutral MC. Gas-phase acidity of radical cations is close to that of the conjugate acid of MC, and gas-phase basicity of radical anions is close to that of the conjugate base of MC. Various routes of amino-imino conversion between neutral and ionized isomers were considered. Energetic-barrier for intramolecular proton-transfer in MC is close to that in the parent system—formamidine.
Collapse
|
22
|
|
23
|
|
24
|
Krygowski TM, Szatylowicz H, Stasyuk OA, Dominikowska J, Palusiak M. Aromaticity from the viewpoint of molecular geometry: application to planar systems. Chem Rev 2014; 114:6383-422. [PMID: 24779633 DOI: 10.1021/cr400252h] [Citation(s) in RCA: 366] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Tadeusz M Krygowski
- Department of Chemistry, Warsaw University , Pasteura 1, 02-093 Warsaw, Poland
| | | | | | | | | |
Collapse
|
25
|
Ortegón-Reyna D, Garcías-Morales C, Padilla-Martínez I, García-Báez E, Aríza-Castolo A, Peraza-Campos A, Martínez-Martínez F. NMR structural study of the prototropic equilibrium in solution of Schiff bases as model compounds. Molecules 2013; 19:459-81. [PMID: 24384925 PMCID: PMC6271073 DOI: 10.3390/molecules19010459] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 12/12/2013] [Accepted: 12/13/2013] [Indexed: 11/16/2022] Open
Abstract
An NMR titration method has been used to simultaneously measure the acid dissociation constant (pKa) and the intramolecular NHO prototropic constant ΔKNHO on a set of Schiff bases. The model compounds were synthesized from benzylamine and substituted ortho-hydroxyaldehydes, appropriately substituted with electron-donating and electron-withdrawing groups to modulate the acidity of the intramolecular NHO hydrogen bond. The structure in solution was established by 1H-, 13C- and 15N-NMR spectroscopy. The physicochemical parameters of the intramolecular NHO hydrogen bond (pKa, ΔKNHO and ΔΔG°) were obtained from 1H-NMR titration data and pH measurements. The Henderson-Hasselbalch data analysis indicated that the systems are weakly acidic, and the predominant NHO equilibrium was established using Polster-Lachmann δ-diagram analysis and Perrin model data linearization.
Collapse
Affiliation(s)
- David Ortegón-Reyna
- Laboratorio de Posgrado, Facultad de Ciencias Químicas, Universidad de Colima, Km 9 Carretera Colima-Coquimatlán, Colima 28400, Mexico.
| | - Cesar Garcías-Morales
- Laboratorio de Posgrado, Facultad de Ciencias Químicas, Universidad de Colima, Km 9 Carretera Colima-Coquimatlán, Colima 28400, Mexico.
| | - Itzia Padilla-Martínez
- Laboratorio de Posgrado, Facultad de Ciencias Químicas, Universidad de Colima, Km 9 Carretera Colima-Coquimatlán, Colima 28400, Mexico.
| | - Efren García-Báez
- Laboratorio de Posgrado, Facultad de Ciencias Químicas, Universidad de Colima, Km 9 Carretera Colima-Coquimatlán, Colima 28400, Mexico.
| | - Armando Aríza-Castolo
- Laboratorio de Posgrado, Facultad de Ciencias Químicas, Universidad de Colima, Km 9 Carretera Colima-Coquimatlán, Colima 28400, Mexico.
| | - Ana Peraza-Campos
- Laboratorio de Posgrado, Facultad de Ciencias Químicas, Universidad de Colima, Km 9 Carretera Colima-Coquimatlán, Colima 28400, Mexico.
| | - Francisco Martínez-Martínez
- Laboratorio de Posgrado, Facultad de Ciencias Químicas, Universidad de Colima, Km 9 Carretera Colima-Coquimatlán, Colima 28400, Mexico.
| |
Collapse
|
26
|
Korth HG, Mulder P. Anthrone and related hydroxyarenes: tautomerization and hydrogen bonding. J Org Chem 2013; 78:7674-82. [PMID: 23815684 DOI: 10.1021/jo401243b] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The keto-enolization of hydroxyl-substituted naphthols and 9-anthrols has been investigated by means of CBS-QB3 calculations. An excellent agreement between experiment and theory is found for the energetics for the anthrone (5) ⇌ anthrol (6) equilibrium, with an enthalpy of tautomerization, Δ(t)H, of 3.8 kcal mol(-1). In contrast, 1-naphthol is the preferred tautomer with a Δ(t)H = -9.0 kcal mol(-1). Substitution of the hydrogens at the adjacent carbons by hydroxyl groups leads to the formation of strong intramolecular hydrogen bonds within a six-membered ring in the enones and the enols. Due to the difference in the intramolecular hydrogen bond enthalpy, Δ(HB)H(intra), the equilibrium shifts further to the enone. Thus, for 1,8-dihydroxy-anthrone (anthralin, dithranol) Δ(t)H increases to 12.7 kcal mol(-1) with an enol/enone ratio of 10(-10). The solvent effect on the 5 ⇌ 6 equilibrium has been quantified by considering the formation of intermolecular hydrogen bond(s), leading to an acidity parameter α₂(H) for anthrol of 0.42. It is shown that the hydrogen bond donating ability of bulk methanol is greatly attenuated through the formation of cyclic oligomers. The benzylic and phenolic bond dissociation enthalpies for anthrone up to anthralin suggest some antioxidant potency but the precise (radical) mechanism of action remains uncertain.
Collapse
Affiliation(s)
- Hans-Gert Korth
- Institut für Organische Chemie, Universität Duisburg-Essen, D-45117 Essen, Germany.
| | | |
Collapse
|
27
|
Giuliano BM, Reva I, Lapinski L, Fausto R. Infrared spectra and ultraviolet-tunable laser induced photochemistry of matrix-isolated phenol and phenol-d5. J Chem Phys 2012; 136:024505. [DOI: 10.1063/1.3666018] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
28
|
Karabıyık H, Karabıyık H, Ocak İskeleli N. Hydrogen-bridged chelate ring-assisted π-stacking interactions. ACTA CRYSTALLOGRAPHICA SECTION B: STRUCTURAL SCIENCE 2012; 68:71-9. [DOI: 10.1107/s0108768111052608] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 12/06/2011] [Indexed: 11/10/2022]
Abstract
A salicylideneaniline (SA) derivative, (6Z)-6-({[2-(hydroxymethyl)phenyl]amino}methylidene)-3,5-dimethoxycyclohexa-2,4-dien-1-one monohydrate, has an increased aromaticity within its hydrogen-bridged chelate ring owing to its NH character. In the reported crystal structure, nonconventional π-stacking interactions, which are referred to as hybrid π-stacking interactions, are observed between a quasiaromatic chelate ring, formed as a result of the resonance-assisted intramolecular hydrogen bond and ordinary aromatic rings. Besides, π-stacking interactions are also seen between two hydrogen-bridged quasiaromatic chelate rings, which are referred to as pure π-stacking interactions. A CSD search has revealed that both kinds of interactions are frequently observed in molecular crystals of SA derivatives in fully or partially NH tautomeric form, and aromaticity levels of certain fragments of SA derivatives have dramatic effects on their stacking arrangements. These interactions are distinguished from the usual π...π interactions by their formation character, i.e. both σ- and π-deficient and σ-deficient character of pure interactions is more pronounced than that of the hybrid ones.
Collapse
|
29
|
|
30
|
Raczyńska E, Kolczyńska K, Stępniewski T. Tautomeric preferences and π-electron delocalization for redox forms of phenol. COMPUT THEOR CHEM 2011. [DOI: 10.1016/j.comptc.2010.10.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
31
|
Gut IG, Scheibler LC, Wirz J. Flash photolytic generation of two keto tautomers of 1-naphthol in aqueous solution: kinetics and equilibria of enolization. Photochem Photobiol Sci 2010; 9:901-7. [PMID: 20383354 DOI: 10.1039/c0pp00034e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Benzo[b]cyclohexa-2,4-dien-1-one (4) and benzo[b]cyclohexa-2,5-dien-1-one (5), the two most stable keto tautomers of 1-naphthol (1), were generated in aqueous solution by Norrish Type II fission of 4- and 2-phenacyl-1-tetralone, respectively, and the pH-rate profiles of their enolization were measured by flash photolysis. Several isotopic exchange rates of 1 were measured in aqueous acid to determine the corresponding rate constants of ketonization. The resulting equilibrium constants for enolization are pKE(4) = -7.1 and pKE(5) = -6.2. The acidity constants of the carbon acids 4 and 5, pKa(4) = 2.1 and pKa(5) = 3.0, were then obtained from a thermodynamic cycle using pKa(1) = 9.25.
Collapse
Affiliation(s)
- Ivo Glynne Gut
- Centro Nacional de Analisis Genomico, Parc Cientific de Barcelona, C/Baldiri Reixac 4, 08028, Barcelona, Spain.
| | | | | |
Collapse
|
32
|
On the Harmonic Oscillator Model of Electron Delocalization (HOMED) Index and its Application to Heteroatomic π-Electron Systems. Symmetry (Basel) 2010. [DOI: 10.3390/sym2031485] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
|
33
|
Raczyńska ED, Zientara K, Stępniewski TM, Kolczyńska K. Stability, polarity, intramolecular interactions and π-electron delocalization for all eighteen tautomers rotamers of uracil. DFT studies in the gas phase. ACTA ACUST UNITED AC 2009. [DOI: 10.1135/cccc2008149] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Complete tautomeric equilibria were investigated for uracil at the DFT(B3LYP)/6-311+G(d,p) level to establish the stability order of all possible 18 tautomers-rotamers in the gas phase and to characterize their internal effects, polarity and aromatic character. Although the di-NH form strongly predominates (100%) in the mixture, the NH–OH, di-OH and CH–NH forms can be also considered. The favored tautomer is moderately stabilized by intramolecular interactions (attractions of the NH and C=O groups); it is also moderately polar and moderately delocalized. Stability of the functional groups (both amide functions) seems to be more important than intramolecular interactions, polarity and aromaticity. This is probably the main factor that dictates the tautomeric preferences in the uracil molecule.
Collapse
|
34
|
Raczyńska ED, Makowski M, Hallmann M, Duczmal K. Computational (MP2 and DFT) modeling of the substrate/inhibitor interaction with the LDH active pocket in the gas phase and aqueous solution: bimolecular charged (pyruvate/oxamate-guanidinium cation) and neutral adducts (pyruvic/oxamic acids-guanidine). J PHYS ORG CHEM 2009. [DOI: 10.1002/poc.1430] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
35
|
Raczyńska E, Zientara K, Kolczyńska K, Stępniewski T. Change of tautomeric equilibria, intramolecular interactions and π-electron delocalization when going from phenol to uracil. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.theochem.2008.10.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
36
|
Alkorta I, Elguero J. How Aromaticity Affects the Chemical and Physicochemical Properties of Heterocycles: A Computational Approach. TOPICS IN HETEROCYCLIC CHEMISTRY 2008. [DOI: 10.1007/978-3-540-68343-8_4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
|
37
|
Huang L, Huang Y, Chi Y, Lin J, Yu L, Xu L, Chen G. Study on the kinetics of keto-enol tautomerism of p-hydroxyphenylpyruvic acid using capillary electrophoresis. J Chromatogr A 2007; 1175:283-8. [PMID: 18021791 DOI: 10.1016/j.chroma.2007.10.078] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2007] [Revised: 10/18/2007] [Accepted: 10/19/2007] [Indexed: 11/24/2022]
Abstract
The kinetics of keto-enol tautomerism of p-hydroxyphenylpyruvic acid (pHPP) as a model of alpha-carbonyl compounds in aqueous solution at room temperature (25 degrees C) was first investigated by capillary electrophoresis with UV detection at 200 nm. The two tautomers could be separated and detected within 3 min. Since the ketonization of enolic pHPP varied with the buffer composition and buffer pH, the kinetics of pHPP was studied under different conditions, and relevant distributing fractions of enolic pHPP, ketonization rate constants and half-life were determined. In addition, beta-CD played an important part in the separation of the two tautomers, thus, the interaction between pHPP and beta-CD was also investigated by electrochemical techniques.
Collapse
Affiliation(s)
- Lu Huang
- Ministry of Education Key Laboratory of Analysis and Detection Technology for Food Safety (Fuzhou University), Fuzhou, Fujian 350002, China
| | | | | | | | | | | | | |
Collapse
|
38
|
Wang Q, Newton MD. Structure, Energetics, and Electronic Coupling in the (TCNE2)-• Encounter Complex in Solution: A Polarizable Continuum Study. J Phys Chem B 2007; 112:568-76. [DOI: 10.1021/jp0753528] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Qian Wang
- Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973
| | - Marshall D. Newton
- Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973
| |
Collapse
|
39
|
Rosokha SV, Kochi JK. The question of aromaticity in open-shell cations and anions as ion-radical offsprings of polycyclic aromatic and antiaromatic hydrocarbons. J Org Chem 2007; 71:9357-65. [PMID: 17137362 DOI: 10.1021/jo061695a] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Arene cation-radicals and anion-radicals result directly from the one-electron oxidation and reduction of many aromatic hydrocarbons, yet virtually nothing is known of their intrinsic (thermodynamic) stability and hence "aromatic character". Since such paramagnetic ion radicals lie intermediate between aromatic (Hückel) hydrocarbons with 4n + 2-electrons and antiaromatic analogues with 4n-electrons, we can now address the question of pi-delocalization in these odd-electron counterparts. Application of the structure-based "harmonic oscillator model of aromaticity" or the HOMA method leads to the surprising conclusion that the aromaticity of these rather reactive, kinetically unstable arene cation and anion radicals (as measured by the HOMA index) is actually higher than that of their (diamagnetic) parent-contrary to conventional expectations.
Collapse
Affiliation(s)
- Sergiy V Rosokha
- Department of Chemistry, University of Houston, Houston, Texas 77204, USA
| | | |
Collapse
|
40
|
La JQH, Michaelides AA, Manderville RA. Tautomeric equilibria in phenolic A-ring derivatives of prodigiosin natural products. J Phys Chem B 2007; 111:11803-11. [PMID: 17867672 DOI: 10.1021/jp074620z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The prodigiosin natural products contain a common 4-methoxy-pyrromethene chromophore that is attached to a pyrrole A-ring that has its lone-pair nitrogen electrons in conjugation with the pyrromethene entity. This feature is known to play a key role in the biological activities (anticancer, antimicrobial, and immunosuppressive) of the prodigiosins. In an attempt to alter or improve upon the therapeutic potential of the prodigiosins, we have synthesized two new isomeric analogues that contain phenolic A-ring systems (a para (p)-phenol; an ortho (o)-phenol with respect to the pyrromethene) with lone-pair oxygen electrons in conjugation with the pyrromethene chromophore of the natural product. Herein, we report on the optical properties of the phenolic prodigiosin analogues that have been measured using absorbance and steady-state emission spectroscopy. For both analogues absorption measurements in aprotic solvents show that the neutral (L) ligands exist as the enol tautomers with lambda(max) ~ 460 nm, as noted for the parent prodigiosin natural product. However, in polar protic solvents the phenolic derivatives undergo ground-state prototropic tautomerization to generate keto tautomers with lambda(max) ~ 530 nm. This unique feature for a prodigiosin analogue involves proton transfer from the phenolic OH to the pyrromethene N1 proton acceptor atom. Tautomeric equilibrium constants (KT) of 1.4 in 1:4 MeCN/H2O (v/v) have been determined from examination of the absorption spectra. Titration of the o-phenolic derivative with Zn(II) in methanol yielded a 40-fold increase in fluorescence intensity (lambda(max) 542 nm) and generated a new 1:1 complex with Zn(II) with a log K of 5.29, suggesting the potential utility of this analogue to act as a fluorescence probe in a biological matrix to monitor Zn(II) concentrations. Our results demonstrate that phenolic A-ring derivatives of prodigiosins possess some unique properties that may act to enhance the biological properties of the prodigiosin natural products.
Collapse
Affiliation(s)
- Jamie Q-H La
- Department of Chemistry, University of Guelph, Guelph, Ontario, Canada
| | | | | |
Collapse
|