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Quintero SM, Van Nyvel L, Roig N, Casado J, Alonso M. Electron Transport through Linear-, Broken-, and Cross-Conjugated Polycyclic Compounds. J Phys Chem A 2024; 128:6140-6157. [PMID: 39041954 DOI: 10.1021/acs.jpca.4c01588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/24/2024]
Abstract
Quantum interference (QI) effects offer unique opportunities to modulate charge transport through single molecules. In recent years, several transmission selection rules have been developed to determine constructive and destructive QIs in an intuitive and simple manner, although some of these rules fail for cross-conjugated systems. In this work, we evaluate the performance of distinct transmission rules on a broad series of anthracene and fluorene derivatives with distinctive structural features including linear-, broken-, and cross-conjugation, heteroatoms, and five-membered rings as such species affords a predictive challenge for the qualitative selection rules for QI effects. The electron transport properties and local transmission plots are first evaluated by combining DFT and the nonequilibrium Green function method allowing for an equal-footing comparison of the conductance of the different polycyclic compounds. Our findings are in line with experimental observations on the influence of the type of conjugation and the connectivity to the metallic electrodes on the transport properties. Thus, cross-conjugated systems exhibit reduced conductance values as compared to the linear-conjugated ones, although the transmission is enhanced in the meta-connected junctions. Remarkably, our study reveals that aromatic cores exhibit generally larger zero-bias conductance for a given connectivity, in contrast to the negative aromaticity-conductance relationship found in literature.
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Affiliation(s)
- Sergio Moles Quintero
- Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, Málaga 29071, Spain
| | - Louis Van Nyvel
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium
| | - Nil Roig
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, United Kingdom
| | - Juan Casado
- Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, Málaga 29071, Spain
| | - Mercedes Alonso
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium
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Cui LJ, Li Y, Leyva-Parra L, Tiznado W, Pan S, Cui ZH. Revisiting the Structure and Bonding in Li 5H 6- and the Exploration of Reactivity: Planar Pentacoordinate Hydrogen. J Phys Chem A 2024; 128:4806-4813. [PMID: 38839423 DOI: 10.1021/acs.jpca.4c02684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
Recently, Guha and co-workers (Sarmah, K.; Kalita, A.; Purkayastha, S.; Guha, A. K. Pushing The Extreme of Multicentre Bonding: Planar Pentacoordinate Hydride. Angew. Chem. Int. Ed. 2024, e202318741) reported a highly intriguing bonding motif: planar pentacoordinate hydrogen (ppH) in Li5H6-, featuring C2v symmetry in the singlet state with two distinct H-Li (center-ring) bond distances. We herein revisited the potential energy surface of Li5H6- by using a target-oriented genetic algorithm. Our investigation revealed that the lowest-energy structure of Li5H6- exhibits a ppH configuration with very high D5h symmetry and a 1A1' electronic state. We did not find any electronic effect like Jahn-Teller distortion that could be responsible for lowering its symmetry. Moreover, our calculations demonstrated significant differences in the relative energies of other low-lying isomers. An energetically very competitive planar tetracoordinate hydrogen (ptH) isomer is also located, but it corresponds to a very shallow minimum on the potential energy surface depending on the used level of theory. Chemical bonding analyses, including AdNDP and EDA-NOCV, uncover that the optimal Lewis structure for Li5H6- involves H- ions stabilized by the Li5H5 crown. Surprisingly, despite the dominance of electrostatic interactions, the contribution from covalent bonding is also significant between ppH and the Li5H5 moiety, derived from H-(1s) → Li5H5 σ donation. Magnetically induced current density analysis revealed that due to minimal orbital overlap and the highly polar nature of the H-Li covalent interaction, the ppH exhibits local diatropic ring currents around the H centers, which fails to result in a global aromatic ring current. The coordination of Li5H6- with Lewis acids, BH3 and BMe3, instantly converts the ppH configuration to (quasi) ptH. These Lewis acid-bound ptH complexes show high electronic stability and high thermochemical stability against dissociation and, therefore, will be ideal candidates for the experimental realization.
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Affiliation(s)
- Li-Juan Cui
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130023, China
| | - Yahui Li
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130023, China
| | - Luis Leyva-Parra
- Centro de Química Teórica & Computacional (CQT&C), Facultad de Ciencias Exactas, Departamento de Ciencias Químicas, Universidad Andrés Bello, Avenida República 275, Santiago de Chile 8370146, Chile
| | - William Tiznado
- Centro de Química Teórica & Computacional (CQT&C), Facultad de Ciencias Exactas, Departamento de Ciencias Químicas, Universidad Andrés Bello, Avenida República 275, Santiago de Chile 8370146, Chile
| | - Sudip Pan
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130023, China
| | - Zhong-Hua Cui
- Institute of Atomic and Molecular Physics, Jilin University, Changchun 130023, China
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Leyva-Parra L, Casademont-Reig I, Pino-Rios R, Ruiz L, Alonso M, Tiznado W. New Perspectives on Delocalization Pathways in Aromatic Molecular Chameleons. Chemphyschem 2024; 25:e202400271. [PMID: 38530286 DOI: 10.1002/cphc.202400271] [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: 03/15/2024] [Accepted: 03/25/2024] [Indexed: 03/27/2024]
Abstract
This study comprehensively analyzes the magnetically induced current density of polycyclic compounds labeled as "aromatic chameleons" since they can arrange their π-electrons to exhibit aromaticity in both the ground and the lowest triplet state. These compounds comprise benzenoid moieties fused to a central skeleton with 4n π-electrons and traditional magnetic descriptors are biased due to the superposition of local magnetic responses. In the S0 state, our analysis reveals that the molecular constituent fragments preserve their (anti)aromatic features in agreement with two types of resonant structures: one associated with aromatic benzenoids and the other with a central antiaromatic ring. Regarding the T1 state, a global and diatropic ring current is revealed. Our aromaticity study is complemented with advanced electronic and geometric descriptors to consider different aspects of aromaticity, particularly important in the evaluation of excited state aromaticity. Remarkably, these descriptors consistently align with the general features on the main delocalization pathways in polycyclic hydrocarbons consisting of fused 4n π-electron rings. Moreover, our study demonstrates an inverse correlation between the singlet-triplet energy difference and the antiaromatic character of the central ring in S0.
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Affiliation(s)
- Luis Leyva-Parra
- Facultad de Ingeniería y Arquitectura, Universidad Central de Chile (UCEN), Santa Isabel 1186, 8370146, Santiago, Chile
- Centro de Química Teórica & Computacional (CQT&C), Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andres Bello, Av. República 275, 8370146, Santiago, Chile
| | - Irene Casademont-Reig
- Department of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050, Brussels, Belgium
| | - Ricardo Pino-Rios
- Centro de Investigación Medicina de Altura, Universidad Arturo Prat, Iquique, 1100000, Chile
- Química y Farmacia, Facultad de Ciencias de la Salud, Universidad Arturo Prat, Casilla 121, Iquique, 1100000, Chile
| | - Lina Ruiz
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, 8910060, Chile
| | - Mercedes Alonso
- Department of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050, Brussels, Belgium
| | - William Tiznado
- Centro de Química Teórica & Computacional (CQT&C), Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andres Bello, Av. República 275, 8370146, Santiago, Chile
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Swain CK, Scheiner S. Comparison of Various Theoretical Measures of Aromaticity within Monosubstituted Benzene. Molecules 2024; 29:2260. [PMID: 38792120 PMCID: PMC11123954 DOI: 10.3390/molecules29102260] [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: 04/11/2024] [Revised: 05/08/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
The effects of monosubstitution on the aromaticity of benzene are assessed using a number of different quantitative schemes. The ability of the mobile π-electrons to respond to an external magnetic field is evaluated using several variants of the NICS scheme which calculate the shielding of points along the axis perpendicular to the molecule. Another class of measures is related to the drive toward the uniformity of C-C bond lengths and strengths. Several energetic quantities are devised to approximate an aromatic stabilization energy and the tendency of the molecule to maintain planarity. There is a lack of consistency in that the various measures of aromaticity lead to differing conclusions as to the effects of substituents on the aromaticity of the ring.
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Affiliation(s)
| | - Steve Scheiner
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300, USA
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Báez-Grez R, Rios RP. Is azulene's local aromaticity and relative stability driven by the Glidewell-Lloyd rule? Phys Chem Chem Phys 2024; 26:12162-12167. [PMID: 38590242 DOI: 10.1039/d4cp00091a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
The local aromaticity of azulene has been studied to understand their electronic properties. For this purpose, we have used the magnetic criterion through magnetically induced current density maps, ring current strengths, NICSzz(1), and the bifurcation value of three-dimensional surfaces of NICSzz. On the other hand, the delocalization criterion was used by calculating the MCI and ELFπ. The results show that the five-membered ring (5-MR) is more aromatic than the seven-membered ring (7-MR) and more aromatic than the free C5H5- ring. The opposite case is seen for the seven-membered ring, which is less aromatic than the free C7H7+. The local aromatic rings in azulene are formed due to an intramolecular electron transfer from the 7-MR to the 5-MR. In addition, the proposed resonance structures that allow explaining the properties of azulene, such as the dipole moment or the relative stability (in comparison to other isomers), show a preference for the formation of 5-MRs; for this reason, it is possible to conclude that the aromaticity and relative stability of azulene is driven by the Glidewell-Lloyd rule.
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Affiliation(s)
- Rodrigo Báez-Grez
- Facultad de Ciencias, Universidad Arturo Prat, Casilla 121, Iquique 1100000, Chile
| | - Ricardo Pino Rios
- Centro de Investigación Medicina de Altura - CEIMA, Universidad Arturo Prat. Casilla 121, Iquique 1100000, Chile.
- Química y Farmacia, Facultad de Ciencias de la Salud, Universidad Arturo Prat, Casilla 121, Iquique 1100000, Chile
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Orozco-Ic M, Soriano-Agueda L, Escayola S, Sundholm D, Merino G, Matito E. Understanding Aromaticity in [5]Helicene-Bridged Cyclophanes: A Comprehensive Study. J Org Chem 2024; 89:2459-2466. [PMID: 38236016 DOI: 10.1021/acs.joc.3c02485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
This study explores the aromaticity of doubly [5]helicene-bridged (1,4)cyclophane and triply [5]helicene-bridged (1,3,5)cyclophane via calculations of the magnetic response and of electronic aromaticity indices. The primary objective is to assess the π-electron delocalization to determine whether they sustain global ring currents associated with π aromaticity. The molecules show local ring currents in the presence of an external magnetic field. The ring currents flow diatropically in the stacked six-membered rings and in the helicene arms. However, these π currents are not interconnected due to the discontinuity of the π delocalization at the C-C single bonds connecting the central six-membered rings to the helicene arms. Electronic indices suggest that the helicene-arm systems have significantly smaller electron delocalization than benzene. The reduction in the delocalization does not compromise their ability to exhibit ring currents in the presence of an external magnetic field. The analysis provides further evidence that the magnetic criteria yield a different degree of aromaticity for the helicene arms than obtained in the calculation of the electronic aromaticity indices. However, both approaches confirm that the studied molecules are not globally aromatic.
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Affiliation(s)
- Mesías Orozco-Ic
- Donostia International Physics Center (DIPC), Donostia, 20018 Euskadi, Spain
| | - Luis Soriano-Agueda
- Donostia International Physics Center (DIPC), Donostia, 20018 Euskadi, Spain
| | - Sílvia Escayola
- Donostia International Physics Center (DIPC), Donostia, 20018 Euskadi, Spain
- Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, C/Maria Aurèlia Capmany, 69, Girona, 17003 Catalonia, Spain
| | - Dage Sundholm
- Department of Chemistry, Faculty of Science, University of Helsinki, A. I. Virtasen aukio 1, P.O. Box 55, FIN-00014 Helsinki, Finland
| | - 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, Yuc., México
| | - Eduard Matito
- Donostia International Physics Center (DIPC), Donostia, 20018 Euskadi, Spain
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