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Proos Vedin N, Escayola S, Radenković S, Solà M, Ottosson H. The n,π* States of Heteroaromatics: When are They the Lowest Excited States and in What Way Can They Be Aromatic or Antiaromatic? J Phys Chem A 2024; 128:4493-4506. [PMID: 38787346 DOI: 10.1021/acs.jpca.4c02580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Heteroaromatic molecules are found in areas ranging from biochemistry to photovoltaics. We analyze the n,π* excited states of 6π-electron heteroaromatics with in-plane lone pairs (nσ, herein n) and use qualitative theory and quantum chemical computations, starting at Mandado's 2n + 1 rule for aromaticity of separate spins. After excitation of an electron from n to π*, a (4n + 2)π-electron species has 2n + 2 πα-electrons and 2n + 1 πβ-electrons (or vice versa) and becomes πα-antiaromatic and πβ-aromatic. Yet, the antiaromatic πα- and aromatic πβ-components seldom cancel, leading to residuals with aromatic or antiaromatic character. We explore vertically excited triplet n,π* states (3n,π*), which are most readily analyzed, but also singlet n,π* states (1n,π*), and explain which compounds have n,π* states with aromatic residuals as their lowest excited states (e.g., pyrazine and the phenyl anion). If the πβ-electron population becomes more (less) uniformly distributed upon excitation, the system will have an (anti)aromatic residual. Among isomers, the one that has the most aromatic residual in 3n,π* is often of the lowest energy in this state. Five-membered ring heteroaromatics with one or two N, O, and/or S atoms never have n,π* states as their first excited states (T1 and S1), while this is nearly always the case for six-membered ring heteroaromatics with electropositive heteroatoms and/or highly symmetric (D2h) diheteroaromatics. For the complete compound set, there is a modest correlation between the (anti)aromatic character of the n,π* state and the energy gap between the lowest n,π* and π,π* states (R2 = 0.42), while it is stronger for monosubstituted pyrazines (R2 = 0.84).
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Affiliation(s)
- Nathalie Proos Vedin
- Department of Chemistry─Ångström Laboratory, Uppsala University, 751 20 Uppsala, Sweden
| | - Sílvia Escayola
- Institut de Quìmica Computacional i Catàlisi and Departament de Química, Universitat de Girona, C/Maria Aurèlia Capmany, 69, 17003 Girona, Catalonia, Spain
- Donostia International Physics Center (DIPC), 20018 Donostia, Euskadi, Spain
| | - Slavko Radenković
- Faculty of Science, University of Kragujevac, P.O. Box 60, 34000 Kragujevac, Serbia
| | - Miquel Solà
- Institut de Quìmica Computacional i Catàlisi and Departament de Química, Universitat de Girona, C/Maria Aurèlia Capmany, 69, 17003 Girona, Catalonia, Spain
| | - Henrik Ottosson
- Department of Chemistry─Ångström Laboratory, Uppsala University, 751 20 Uppsala, Sweden
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2
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Blasco D, Sundholm D. The aromatic nature of auracycles and diauracycles based on calculated ring-current strengths. Dalton Trans 2024. [PMID: 38819195 DOI: 10.1039/d4dt00827h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2024]
Abstract
We have calculated the magnetically induced current density susceptibility for gold-containing organometallic molecular rings using the gauge-including magnetically induced currents (GIMIC) method. The aromatic nature has been determined by calculating the strength of the magnetically induced ring current susceptibility, which is often called ring current. To our knowledge, we show here for the first time that gold-containing organometallic rings may be aromatic or antiaromatic sustaining ring currents in the presence of an external magnetic field. The calculated aromatic character of the rings agrees with the aromatic nature one expects when using Hückel's aromaticity rules. The studied auracycles and diauracycles with 4n electrons in the conjugated orbitals generally sustain a weak paratropic ring current, whereas those having 4n + 2 electrons in the conjugated orbitals sustain a diatropic ring current that is almost as strong as that of benzene. The number of electrons are obtained by assuming that each C, N and Au atom of the ring contribute one electron, and a H atom connected to a N atom in the ring increases the number of electrons by one. An electron-attracting ligand at Au removes one electron from the ring. Formation of a short Au-Au bonding diauracycles reduces the number of electrons in the ring by two.
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Affiliation(s)
- Daniel Blasco
- Departamento de Química, Instituto de Investigación en Química (IQUR), Universidad de La Rioja, Madre de Dios 53, 26006, Logroño, Spain.
| | - Dage Sundholm
- Department of Chemistry, Faculty of Science, University of Helsinki, P. O. Box 55 (A. I. Virtasen aukio 1), FIN-00014, Helsinki, Finland.
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3
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Wang Q, Sundholm D, Gauss J, Nottoli T, Lipparini F, Kino S, Ukai S, Fukui N, Shinokubo H. Changing aromatic properties through stacking: the face-to-face dimer of Ni(II) bis(pentafluorophenyl)norcorrole. Phys Chem Chem Phys 2024; 26:14777-14786. [PMID: 38716819 DOI: 10.1039/d4cp00968a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2024]
Abstract
Nuclear magnetic resonance (NMR) shielding constants have been calculated for Ni(II) bis(pentafluorophenyl)norcorrole and its face-to-face stacked dimer at the Hartree-Fock (HF), second-order Møller-Plesset perturbation theory (MP2), complete-active-space self-consistent-field (CASSCF) levels as well as at density functional theory (DFT) levels using several functionals. The calculated 1H NMR shielding constants agree rather well with the experimental ones. The shielding constants of N and Ni calculated at DFT, HF, and MP2 levels differ from those obtained in the CASSCF calculations due to near-degeneracy effects at the Ni atom. The calculated magnetically induced current densities show that the monomer is antiaromatic, sustaining a strong global paratropic ring current, and the dimer is aromatic, sustaining a strong diatropic ring current. Qualitatively the same current density is obtained at the employed levels of theory. The most accurate ring-current strengths are probably obtained at the MP2 level. The aromatic dimer has a short intermolecular distance of less than 3 Å. The intermolecular interaction changes the nature of the frontier orbitals leading to a formal double bond between the norcorrole macrocycles.
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Affiliation(s)
- Qian Wang
- Department of Chemistry, Faculty of Science, University of Helsinki, P.O. Box 55 (A.I. Virtanens plats 1), FIN-00014, Finland.
| | - Dage Sundholm
- Department of Chemistry, Faculty of Science, University of Helsinki, P.O. Box 55 (A.I. Virtanens plats 1), FIN-00014, Finland.
| | - Jürgen Gauss
- Department Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany
| | - Tommaso Nottoli
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 13, I-56124 Pisa, Italy
| | - Filippo Lipparini
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 13, I-56124 Pisa, Italy
| | - Shota Kino
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering and Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
| | - Shusaku Ukai
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering and Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
| | - Norihito Fukui
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering and Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
- Graduate School of Engineering, Nagoya University, 2JST PRESTO, Japan
| | - Hiroshi Shinokubo
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering and Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
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Badri Z, Nourigheimasi F, Foroutan-Nejad C. Tetraquinolines; four linked quinoline units or porphyrinoids. Org Biomol Chem 2024; 22:2284-2291. [PMID: 38407320 DOI: 10.1039/d3ob01616a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Tetraquinolines (TEQs) have been recently synthesized and proposed to be a new member of the porphyrinoid family with highly distorted, nonplanar, geometries. In this contribution by studying several molecules, closely related to TEQs, we have suggested that the origin of the nonplanarity of TEQs and their counterparts is a combination of steric strain and the propensity of the molecules to avoid antiaromaticity. The tendency of TEQs to coordinate with doubly charged metal ions can be interpreted in terms of their transition from potential antiaromaticity to nonaromaticity. Even metal-coordinated TEQs do not sustain diatropic ring currents. Although full planarization is not possible because of steric strain, doubly oxidized TEQs and their counterparts sustain moderate global diatropic ring currents and partially planarize. The nature of current density in the molecules is studied in the light of Steiner-Fowler selection rules.
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Affiliation(s)
- Zahra Badri
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
| | - Farnoush Nourigheimasi
- Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260, USA
| | - Cina Foroutan-Nejad
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
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Miwa K, Yokota T, Wang Q, Sakurai T, Fliegl H, Sundholm D, Shinokubo H. Metallaantiaromaticity of 10-Platinacorrole Complexes. J Am Chem Soc 2024; 146:1396-1402. [PMID: 38172072 PMCID: PMC10882971 DOI: 10.1021/jacs.3c10250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
The aromaticity of cyclic π-conjugated organometallic compounds is known as metallaaromaticity. π-Conjugated metallacycles, such as metallabenzenes and metallapentalenes, have been investigated in order to understand the involvement of the d electrons from the metal center in the π-conjugated systems of the organic ligands. Here, we report the synthesis of Pd(II) 10-platinacorrole complexes with cyclooctadiene (COD) and norbornadiene (NBD) ligands. While the Pd(II) 10-platinacorrole COD complex adopts a distorted structure without showing appreciable antiaromaticity, the corresponding NBD complex exhibits a distinct antiaromatic character due to its highly planar conformation. Detailed density functional theory (DFT) calculations revealed that two d orbitals are involved in macrocyclic π-conjugation. We furthermore demonstrated that Craig-Möbius antiaromaticity is not present in the studied system. The synthesis of 10-platinacorroles enables a systematic comparison of the antiaromaticity and aromaticity of closely related porphyrin analogues, providing a better understanding of π-conjugation that involves d orbitals.
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Affiliation(s)
- Kazuki Miwa
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering and Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 Aichi, Japan
| | - Tomoya Yokota
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering and Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 Aichi, Japan
| | - Qian Wang
- Department of Chemistry, Faculty of Science, University of Helsinki, FIN-00014 Helsinki, Finland
| | - Takahiro Sakurai
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering and Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 Aichi, Japan
| | - Heike Fliegl
- FIZ Karlsruhe─Leibniz Institute for Information Infrastructure, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Dage Sundholm
- Department of Chemistry, Faculty of Science, University of Helsinki, FIN-00014 Helsinki, Finland
| | - Hiroshi Shinokubo
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering and Integrated Research Consortium on Chemical Sciences (IRCCS), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 Aichi, Japan
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Merino G, Solà M, Fernández I, Foroutan-Nejad C, Lazzeretti P, Frenking G, Anderson HL, Sundholm D, Cossío FP, Petrukhina MA, Wu J, Wu JI, Restrepo A. Aromaticity: Quo Vadis. Chem Sci 2023; 14:5569-5576. [PMID: 37265727 PMCID: PMC10231312 DOI: 10.1039/d2sc04998h] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 02/22/2023] [Indexed: 07/25/2023] Open
Abstract
Aromaticity is one of the most deeply rooted concepts in chemistry. But why, if two-thirds of existing compounds can be classified as aromatic, is there no consensus on what aromaticity is? σ-, π-, δ-, spherical, Möbius, or all-metal aromaticity… why are so many attributes needed to specify a property? Is aromaticity a dubious concept? This perspective aims to reflect where the aromaticity community is and where it is going.
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Affiliation(s)
- Gabriel Merino
- Departamento de Física Aplicada, Centro de Investigación y de Estudios Avanzados Unidad Mérida, km 6 Antigua Carretera a Progreso, Apdo. Postal 73, Cordemex 97310 Mérida Yucatán Mexico
| | - Miquel Solà
- Institut de Química Computacional i Catàlisi and Department de Química, Universitat de Girona C/M. Aurèlia Capmany, 69 Girona 17003 Catalonia Spain
| | - Israel Fernández
- Departamento de Química Orgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Facultad de Ciencias Químicas, Universidad Complutense de Madrid 28040 Madrid Spain
| | - Cina Foroutan-Nejad
- Institute of Organic Chemistry, Polish Academy of Sciences Kasprzaka 44/52 01-224 Warsaw Poland
| | - Paolo Lazzeretti
- Dipartimento di Chimica e Biologia "A. Zambelli", Università degli Studi di Salerno via Giovanni Paolo II 132, Fisciano 84084 SA Italy
| | - Gernot Frenking
- Fachbereich Chemie, Philipps-Universität Marburg Hans-Meerwein-Strasse 4, D-35043 Marburg Germany
| | | | - Dage Sundholm
- Department of Chemistry, Faculty of Science, University of Helsinki P.O. Box 55, A. I. Virtasen aukio 1 FIN-00014 Helsinki Finland
| | - Fernando P Cossío
- Departamento de Química Orgánica I, Instituto de Innovaciónen Química Avanzada (ORFEO-CINQA), University of the Basque Country (UPV/EHU) Paseo Manuel Lardizabal 3 20018 Donostia/San Sebastián Spain
| | - Marina A Petrukhina
- Department of Chemistry, University at Albany, State University of New York Albany New York 12222 USA
| | - Jishan Wu
- Department of Chemistry, National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore
| | - Judy I Wu
- Department of Chemistry, University of Houston Houston Texas 77204 USA
| | - Albeiro Restrepo
- Instituto de Química, Universidad de Antioquia Calle 70 No. 52-21 050010 Medellín Colombia
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Wang Q, Pyykkö J, Dimitrova M, Taubert S, Sundholm D. Current-density pathways in figure-eight-shaped octaphyrins. Phys Chem Chem Phys 2023; 25:12469-12478. [PMID: 37097103 DOI: 10.1039/d3cp01062g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2023]
Abstract
We have calculated the current density induced by an external magnetic field in a set of figure-eight-shaped expanded porphyrinoids. The studied octaphyrins can be divided into three classes (N2, N4, and N6) based on the number of the inner hydrogen atoms of the pyrrole rings. Using the Runge-Kutta method, the current density is split into diatropic and paratropic contributions that are analyzed separately. The calculations show that one common ring current consists of two rather independent pathways. Each of them follows the outer side of the molecular frame of one half of the molecule and passes to the inner side of the frame on the other half. The ring-current pathways are similar to the ones for [12]infinitene. However, the current density of the octaphyrins is more complex having many branching points and pathways. Vertical through-space current-density pathways pass in the middle of the molecules through a plane that is parallel to the figure-eight-shaped view of the molecules when the magnetic field is perpendicular to the plane. The isolectronic N2 and the N4 dication sustain a weak paratropic ring current inside the molecule, which is also observed in the 1H NMR magnetic shielding constant of the inner hydrogen atoms. The diatropic current-density contribution dominates in the studied molecules. For the N4 and N6 molecules, the global current-density pathways are only diatropic and N6 sustains the strongest global diatropic current-density flux of 13.2 nA T-1.
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Affiliation(s)
- Qian Wang
- Department of Chemistry, Faculty of Science, P.O. Box 55 (A.I. Virtanens plats 1), FIN-00014 University of Helsinki, Finland.
| | - Jaakko Pyykkö
- Department of Chemistry, Faculty of Science, P.O. Box 55 (A.I. Virtanens plats 1), FIN-00014 University of Helsinki, Finland.
| | - Maria Dimitrova
- Department of Chemistry, Faculty of Science, P.O. Box 55 (A.I. Virtanens plats 1), FIN-00014 University of Helsinki, Finland.
| | - Stefan Taubert
- Department of Chemistry, Faculty of Science, P.O. Box 55 (A.I. Virtanens plats 1), FIN-00014 University of Helsinki, Finland.
| | - Dage Sundholm
- Department of Chemistry, Faculty of Science, P.O. Box 55 (A.I. Virtanens plats 1), FIN-00014 University of Helsinki, Finland.
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Ketkov SY, Rychagova EA. Influence of Ionization and Spin Transitions on Electron Delocalization in the Molecules of Transition Metal Sandwich Complexes. HIGH ENERGY CHEMISTRY 2023. [DOI: 10.1134/s0018143923010071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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Wypych K, Dimitrova M, Sundholm D, Pawlicki M. Diagnosing Ring Current(s) in Figure-Eight Skeletons: A 3D Through-Space Conjugation in the Two-Loops Crossing. Org Lett 2022; 24:4876-4880. [PMID: 35796415 PMCID: PMC9348834 DOI: 10.1021/acs.orglett.2c01625] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
The macrocyclic structures
with local conjugation readily undergo
a redox-triggered change in the diatropic character, leading to a
global current–density pathway of the doubly charged systems.
The figure-eight geometry of the neutral dimer does not significantly
change upon oxidation according to the spectroscopic and computational
data. The oxidation leads to 3D cross-conjugation at the intersection
of the two ethylene bridges resulting in a global ring current.
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Affiliation(s)
- Katarzyna Wypych
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland.,Department of Chemistry, University of Wrocław, F. Joliot-Curie 14, 503833 Wrocław, Poland
| | - Maria Dimitrova
- Department of Chemistry, University of Helsinki, P.O. Box 55, A. I. Virtasen aukio 1, FIN-00014 Helsinki, Finland
| | - Dage Sundholm
- Department of Chemistry, University of Helsinki, P.O. Box 55, A. I. Virtasen aukio 1, FIN-00014 Helsinki, Finland
| | - Miłosz Pawlicki
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland
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Đorđević S, Solà M, Radenković S. Aromaticity of Singlet and Triplet Boron Disk-like Clusters: A Test for Electron Counting Aromaticity Rules. Inorg Chem 2022; 61:10116-10125. [PMID: 35737864 DOI: 10.1021/acs.inorgchem.2c01197] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Boron clusters are polyhedral boron-containing structures that have unique features and properties. The disk-like boron clusters are among the most fascinating boron cluster forms. These clusters have a molecular orbital (MO) distribution similar to the one derived from the simple particle-on-a-disk model. In this model, the MOs come in pairs except for m = 0. Disk-like boron clusters in their singlet ground state are aromatic when they reach a closed-shell structure. One could expect that disk-like aromatic boron clusters in the singlet state, when acquiring or releasing two electrons, may also be aromatic in the lowest-lying triplet state. We use magnetically induced current densities and bond current strengths to analyze the aromatic character of a series of disk-like boron clusters. Our results show that, with the exception of triplet 3B19-, the disk-like boron clusters follow Hückel and Baird's rules if one considers the different MOs grouped by their symmetry. We also found that if the lowest-lying triplet state in disk-like boron clusters is aromatic, this triplet state is the ground state for this species.
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Affiliation(s)
- Slađana Đorđević
- Faculty of Science, University of Kragujevac, P.O. Box 60, Kragujevac 34000, Serbia
| | - Miquel Solà
- Institute of Computational Chemistry and Catalysis and Department of Chemistry, University of Girona, C/M. Aurèlia Capmany, 69, Girona 17003, Catalonia, Spain
| | - Slavko Radenković
- Faculty of Science, University of Kragujevac, P.O. Box 60, Kragujevac 34000, Serbia
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Gu X, Yang L, Jin P. Planar Inorganic Five-Membered Heterocycles with σ+π Dual Aromaticity in Both S0 and T1 States. Phys Chem Chem Phys 2022; 24:22091-22101. [DOI: 10.1039/d2cp03116g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cyclic species being aromatic in both the lowest singlet and triplet electronic states (so-called adaptive aromaticity) are scarce. To date, the reported systems are mostly organometallic heterocycles with the aromaticities...
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