1
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Greiner JE, Singh A, Röhr MIS. Functionality optimization for effective singlet fission coupling screening in the full-dimensional molecular and intermolecular coordinate space. Phys Chem Chem Phys 2024. [PMID: 38958634 DOI: 10.1039/d4cp01274g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
In computational chemistry, accurately predicting molecular configurations that exhibit specific properties remains a critical challenge. Its intricacies become especially evident in the study of molecular aggregates, where the light-induced functionality is tied to highly structure-dependent electronic couplings between molecules. Here, we present an efficient strategy for the targeted screening of the structural space employing a "functionality optimization" technique, in which a chosen descriptor, constrained by the ground state energy expression, is optimized. The chosen algorithmic differentiation (AD) framework allows one to automatically obtain gradients without its tedious implementation. We demonstrate the effectiveness of the approach by identifying perylene bisimide (PBI) dimer motifs with enhanced effective SF coupling. Our findings reveal that certain structural modifications of the PBI monomer, such as helical twisting and bending as well as slipped-rotated packing arrangements, can significantly increase the effective SF coupling.
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Affiliation(s)
- Johannes E Greiner
- Julius-Maximilians-Universität Würzburg, Center for Nanosystems Chemistry, Theodor-Boveri Weg, 97074 Würzburg, Germany.
- Julius-Maximilians-Universität Würzburg, Institute of Physical and Theoretical Chemistry, Am Hubland, 97074 Würzburg, Germany
| | - Anurag Singh
- Julius-Maximilians-Universität Würzburg, Center for Nanosystems Chemistry, Theodor-Boveri Weg, 97074 Würzburg, Germany.
- Julius-Maximilians-Universität Würzburg, Institute of Physical and Theoretical Chemistry, Am Hubland, 97074 Würzburg, Germany
| | - Merle I S Röhr
- Julius-Maximilians-Universität Würzburg, Center for Nanosystems Chemistry, Theodor-Boveri Weg, 97074 Würzburg, Germany.
- Julius-Maximilians-Universität Würzburg, Institute of Physical and Theoretical Chemistry, Am Hubland, 97074 Würzburg, Germany
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2
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Girija AV, Zeng W, Myers WK, Kilbride RC, Toolan DTW, Zhong C, Plasser F, Rao A, Bronstein H. Singlet Fission in Pechmann Dyes: Planar Chromophore Design and Understanding. J Am Chem Soc 2024. [PMID: 38918896 DOI: 10.1021/jacs.4c00288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
Singlet fission in organic chromophores holds the potential for enhancing photovoltaic efficiencies beyond the single-junction limit. The most basic requirement of a singlet fission material is that it has a large energy gap between its first singlet and triplet excited states. Identifying such compounds is not simple and has been accomplished either through computational screening or by subtle modifications of previously known fission materials. Here, we propose an approach that leverages ground and excited-state aromaticity combined with double-bond conformation to establish simple qualitative design rules for predicting fundamental optical properties without the need for computational modeling. By investigating two Pechmann dye isomers, we demonstrate that although their planarity and degree of charge transfer are similar, singlet fission is active in the isomer with a trans-conformation, while the cis-isomer exhibits greater favorability for polaronic processes, experimentally validated using ultrafast and electron spin resonance spectroscopy. Our results offer a new design perspective that provides a rational framework for tailoring optoelectronic systems to specific applications such as singlet fission or triplet-triplet annihilation.
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Affiliation(s)
- Aswathy V Girija
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Weixuan Zeng
- Yusuf Hamied Department of Chemistry, Lensfield Road, Cambridge CB2 1EW, U.K
- Zhangjiang Laboratory, Shanghai 201210, PR China
| | - William K Myers
- Inorganic Chemistry, University of Oxford, South Parks Road,Oxford OX1 3QR, U.K
| | - Rachel C Kilbride
- Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, U.K
| | - Daniel T W Toolan
- Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, U.K
| | - Cheng Zhong
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China
| | - Felix Plasser
- Department of Chemistry, Loughborough University, Loughborough LE11 3TU, U.K
| | - Akshay Rao
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Hugo Bronstein
- Yusuf Hamied Department of Chemistry, Lensfield Road, Cambridge CB2 1EW, U.K
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3
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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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4
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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 PMCID: PMC11163469 DOI: 10.1021/acs.jpca.4c02580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2024] [Revised: 05/10/2024] [Accepted: 05/10/2024] [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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5
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Salikov RF, Belyy AY, Ilyushchenko MK, Platonov DN, Sokolova AD, Tomilov YV. Antiaromaticity of Cycloheptatrienyl Anions: Structure, Acidity, and Magnetic Properties. Chemistry 2024:e202401041. [PMID: 38785416 DOI: 10.1002/chem.202401041] [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: 03/14/2024] [Revised: 05/23/2024] [Accepted: 05/24/2024] [Indexed: 05/25/2024]
Abstract
Investigations of the nature and degree of antiaromaticity of cycloheptatrienyl anion derivatives using both experimental and computational tools are presented. The ground state of cycloheptatrienyl anion in the gas phase is triplet, planar and Baird-aromatic. In DMSO, it assumes a singlet distorted allylic form with a paratropic ring current. The other derivatives in both phases assume either allylic or diallylic conformations depending on the substituent pattern. A combination of experimental and computational methods was used to determine the pKa values of 16 derivatives in DMSO, which ranged from 36 to -10.7. We revealed that the stronger stabilization of the anionic system, which correlates with acidity, does not necessarily imply a lower degree of antiaromaticity in terms of magnetic properties. Conversely, the substitution pattern first affects the geometry of the ring through the bulkiness of the substituents and their better conjugation with a more distorted system. Consequently, the distortion reduces the cyclic conjugation in the π-system and thereby decreases the paratropic current in a magnetic field, which manifests itself as a decrease in the NICS. The triplet-state geometries and magnetic properties are nearly independent on the substitution pattern, which is typical for simple aromatic systems.
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Affiliation(s)
- Rinat F Salikov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
- Department of Chemistry, Higher School of Economics National Research University, Moscow, 101000, Russian Federation
| | - Alexander Y Belyy
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
| | - Matvey K Ilyushchenko
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
| | - Dmitry N Platonov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
| | - Alena D Sokolova
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
| | - Yury V Tomilov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., Moscow, 119991, Russian Federation
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6
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Stanger A. Principal Singlet Fission Properties Of Twisted Acenes. Chemphyschem 2024:e202400128. [PMID: 38659320 DOI: 10.1002/cphc.202400128] [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: 02/21/2024] [Revised: 04/24/2024] [Accepted: 04/24/2024] [Indexed: 04/26/2024]
Abstract
Acenes, especially tetracene derivatives, are used as singlet fission materials. The recent synthesis of Dodecaphenyl tetracene (showing end-to-end twist angles of 96-98 degrees) and twisted anthracene derivatives show that the synthesis of twisted linear oligoacenes is possible. Energy calculations and NICS-X-scan studies predict that twisted acenes may be better singlet fission materials compared to their planar analogues.
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Affiliation(s)
- Amnon Stanger
- Schulich Department of Chemistry, Technion, Haifa, 3200003, Israel
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7
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Cummings E, Karadakov PB. Aromaticity in the Electronic Ground and Lowest Triplet States of Molecules with Fused Thiophene Rings. Chemistry 2024; 30:e202303724. [PMID: 38038597 DOI: 10.1002/chem.202303724] [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: 11/09/2023] [Revised: 11/30/2023] [Accepted: 12/01/2023] [Indexed: 12/02/2023]
Abstract
Analysis of the variations of the off-nucleus isotropic magnetic shielding, σiso(r), around thiophene, thienothiophenes, dithienothiophenes and sulflowers in their electronic ground (S0) and lowest triplet (T1) states reveals that some of the features of aromaticity and bonding in these molecules do not fit in with predictions based on the popular Hückel's and Baird's rules. Despite having 4n π electrons, the S0 states of the sulflowers are shown to be aromatic, due to the local aromaticities of the individual thiophene rings. To reduce its T1 antiaromaticity, the geometry of thiophene changes considerably between S0 and T1: In addition to losing planarity, the carbon-carbon two 'double' and one 'single' bonds in S0 turn into two 'single' and one 'double' bonds in T1. Well-defined Baird-style aromaticity reversals are observed between the S0 and T1 states of only three of the twelve thiophene-based compounds investigated in this work, in contrast, the sulflower with six thiophene rings which is weakly aromatic in S0 becomes more aromatic in T1. The results suggest that the change in aromaticity between the S0 and T1 states in longer chains of fused rings is likely to affect mostly the central ring (or the pair of central rings); rings sufficiently far away from the central ring(s) can retain aromatic character.
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Affiliation(s)
- Edward Cummings
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Peter B Karadakov
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
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8
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Pradhan E, Zeng T. The Lack of Triplet Fusion for an Intramolecular Singlet Fission Chromophore: The Expected, the Unexpected, and a Reconciliation. J Phys Chem Lett 2024; 15:43-50. [PMID: 38127796 DOI: 10.1021/acs.jpclett.3c03238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Singlet fission (SF) has the potential to play a key role in photovoltaics since it generates a larger number of longer-lived triplet excitons after photoabsorption. Intramolecular SF (iSF) is of special interest since it enables tuning of SF efficiency by adjusting interchromophore configuration through covalent interaction. However, as elaborated in the present work, iSF chromophores are doomed to dissatisfy one general thermodynamic criterion for all SF chromophores, intramolecular or not: E(T2) ≥ 2E(T1), and therefore, the fusion of two triplet excitons to one triplet exciton is thermodynamically favorable. In our nonadiabatic quantum dynamics simulation for a model iSF chromophore, this expected fusion does not occur, because of the inefficient intersystem crossing hidden under the cover of internal conversion of the triplet fusion. A reconciliation is achieved between the dissatisfaction of E(T2) ≥ 2E(T1) and the large tetraradical character for general iSF chromophores.
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Affiliation(s)
- Ekadashi Pradhan
- Department of Chemistry, York University, Toronto, Ontario M3J1P3, Canada
| | - Tao Zeng
- Department of Chemistry, York University, Toronto, Ontario M3J1P3, Canada
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9
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Báez-Grez R, Pino-Rios R. On the aromaticity and stability of benzynes in the ground and lowest-lying triplet excited states. J Comput Chem 2024; 45:6-12. [PMID: 37671655 DOI: 10.1002/jcc.27214] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 08/02/2023] [Accepted: 08/09/2023] [Indexed: 09/07/2023]
Abstract
In this work, we have revisited the aromaticity of benzyne isomers at the unrestricted density functional theory level (UDFT) using the energetic, magnetic, and delocalization criteria. In addition, this last criterion has also been analyzed employing complete active space (CASSCF) calculations. The results show conservation of aromaticity in these monocycles. Additionally it is observed that this trend is maintained in polycyclic aromatic hydrocarbon derivatives such as biradical didehydrophenanthrenes. Do these results imply a violation of Baird's rule? The answer is No, because this conservation in aromaticity is due to the loss of hydrogen atoms affects only the electronic σ skeleton and exerts a minor influence on the π cloud. Additionally, we have analyzed the relative stability of benzyne isomers and their relationship with experimental ΔES-T values. According to the literature, the stability of the benzynes in the singlet state is due to an effective interaction between the electrons of the biradical centers; however, this effect is completely reversed in the triplet state, which explains why the para isomer has the lowest ΔES-T gap.
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Affiliation(s)
- Rodrigo Báez-Grez
- Departamento de Química, Facultad de Ciencias Exactas, Universidad Andres Bello, Santiago, Chile
| | - Ricardo Pino-Rios
- Instituto de Estudios de la Salud, Universidad Arturo, Chile
- Química y Farmacia, Facultad de Ciencias de la Salud, Universidad Arturo Prat, Chile
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10
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Sadowski B, Gryko DT. Dipyrrolonaphthyridinedione - (still) a mysterious cross-conjugated chromophore. Chem Sci 2023; 14:14020-14038. [PMID: 38098709 PMCID: PMC10718078 DOI: 10.1039/d3sc05272a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 11/08/2023] [Indexed: 12/17/2023] Open
Abstract
Dipyrrolonaphthyridinediones (DPNDs) entered the chemical world in 2016. This cross-conjugated donor-acceptor skeleton can be prepared in two steps from commercially available reagents in overall yield ≈15-20% (5 mmol scale). DPNDs can be easily and regioselectively halogenated which opens an avenue to numerous derivatives as well as to π-expansion. Although certain synthetic limitations exist, the current derivatization possibilities provided impetus for numerous explorations that use DPNDs. Structural modifications enable bathochromic shift of the emission to deep-red region and reaching the optical brightness 30 000 M-1 cm-1. Intense absorption and strong emission of greenish-yellow light attracted the interest which eventually led to the discovery of their strong two-photon absorption, singlet fission in the crystalline phase and triplet sensitization. Dipyrrolonaphthyridinedione-based twistacenes broadened our knowledge on the influence of twisting angle on the fate of the molecule in the excited state. Collectively, these findings highlight the compatibility of DPNDs with various applications within organic optoelectronics.
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Affiliation(s)
- Bartłomiej Sadowski
- Centre of New Technologies, University of Warsaw S. Banacha 2c 02-097 Warsaw Poland
| | - Daniel T Gryko
- Institute of Organic Chemistry, Polish Academy of Sciences Kasprzaka 44/52 01-224 Warsaw Poland
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11
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Wen J, Zhou J, Li X, Lv M, Huang J, Li Z, Zhang B, Wang M, Chen J, Zhu M. Excitation localization/delocalization induced intramolecular singlet fission in cyclopentadithiophene-based quinoidal derivatives. Phys Chem Chem Phys 2023; 25:29698-29708. [PMID: 37882726 DOI: 10.1039/d3cp02588h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2023]
Abstract
Two triplet excitons are generated through an ultrafast photophysical process, namely singlet fission (SF), providing a solution for efficient solar energy usage. In this work, we provide an effective guideline for designing SF materials by adjusting the planarity in cyclopentadithiophene (CPDT) derivatives. A practical strategy is proposed for tuning the quinoidal-biradical resonance structures by varying the electron push-pull groups of CPDTs for SF. The localized, delocalized, and intermediate charge-transfer excited configurations are predicted in the singlet excited state via computational simulations, which is further confirmed by ultrafast spectroscopy. Deduced from the potential energy surfaces in the low-lying excited states and transient absorption, the delocalized excited state is formed in 2.1 ps via postulated intramolecular SF in a polar solvent, followed by the ultrafast formation of the free triplet state with a lifetime of 6.8 ps. In comparison with different cross-conjugated chromophores, it is found that the increase in the charge separation could enhance the triplet-pair generation for iSF. We expect that by introducing symmetry-breaking modifications in the electronic configurations and adjusting the separation between the push-pull groups of CPDTs, it should be possible to prolong the duration of the free triplet state by preventing recombination within the triplet-pair excited configuration.
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Affiliation(s)
- Jin Wen
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.
| | - Jie Zhou
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Xuesi Li
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.
| | - Meng Lv
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Jun Huang
- Jiangsu Sidike New Materials Science and Technology Co., Ltd, Sihong Economic Development Area, Jiangsu 223900, China
| | - Zheng Li
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Center for Advanced Low-dimension Materials, Donghua University, Shanghai 201620, China
| | - Boyuan Zhang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.
| | - Ming Wang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Center for Advanced Low-dimension Materials, Donghua University, Shanghai 201620, China
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Meifang Zhu
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.
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12
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He G, Parenti KR, Budden PJ, Niklas J, Macdonald T, Kumarasamy E, Chen X, Yin X, McCamey DR, Poluektov OG, Campos LM, Sfeir MY. Unraveling Triplet Formation Mechanisms in Acenothiophene Chromophores. J Am Chem Soc 2023; 145:22058-22068. [PMID: 37787467 DOI: 10.1021/jacs.3c07082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
The evolution of molecular platforms for singlet fission (SF) chromophores has fueled the quest for new compounds capable of generating triplets quantitatively at fast time scales. As the exploration of molecular motifs for SF has diversified, a key challenge has emerged in identifying when the criteria for SF have been satisfied. Here, we show how covalently bound molecular dimers uniquely provide a set of characteristic optical markers that can be used to distinguish triplet pair formation from processes that generate an individual triplet. These markers are contained within (i) triplet charge-transfer excited state absorption features, (ii) kinetic signatures of triplet-triplet annihilation processes, and (iii) the modulation of triplet formation rates using bridging moieties between chromophores. Our assignments are verified by time-resolved electron paramagnetic resonance (EPR) measurements, which directly identify triplet pairs by their electron spin and polarization patterns. We apply these diagnostic criteria to dimers of acenothiophene derivatives in solution that were recently reported to undergo efficient intermolecular SF in condensed media. While the electronic structure of these heteroatom-containing chromophores can be broadly tuned, the effect of their enhanced spin-orbit coupling and low-energy nonbonding orbitals on their SF dynamics has not been fully determined. We find that SF is fast and efficient in tetracenothiophene but that anthradithiophene exhibits fast intersystem crossing due to modifications of the singlet and triplet excited state energies upon functionalization of the heterocycle. We conclude that it is not sufficient to assign SF based on comparisons of the triplet formation kinetics between monomer and multichromophore systems.
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Affiliation(s)
- Guiying He
- Department of Physics, Graduate Center, City University of New York, New York, New York 10016, United States
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, New York 10031, United States
| | - Kaia R Parenti
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Peter J Budden
- Department of Physics, Graduate Center, City University of New York, New York, New York 10016, United States
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, New York 10031, United States
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Thomas Macdonald
- ARC Centre of Excellence in Exciton Science, School of Physics, UNSW Sydney, Sydney, 2052 NSW, Australia
| | - Elango Kumarasamy
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Xing Chen
- Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 102488, P. R. China
| | - Xiaodong Yin
- Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 102488, P. R. China
| | - Dane R McCamey
- ARC Centre of Excellence in Exciton Science, School of Physics, UNSW Sydney, Sydney, 2052 NSW, Australia
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Luis M Campos
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Matthew Y Sfeir
- Department of Physics, Graduate Center, City University of New York, New York, New York 10016, United States
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, New York 10031, United States
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13
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Kaleta J, Dudič M, Ludvíková L, Liška A, Zaykov A, Rončević I, Mašát M, Bednárová L, Dron PI, Teat SJ, Michl J. Phenyl-Substituted Cibalackrot Derivatives: Synthesis, Structure, and Solution Photophysics. J Org Chem 2023. [PMID: 37219972 DOI: 10.1021/acs.joc.2c02706] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Three symmetrically and three unsymmetrically substituted cibalackrot (7,14-diphenyldiindolo[3,2,1-de:3',2',1'-ij][1,5]naphthyridine-6,13-dione, 1) dyes carrying two derivatized phenyl rings have been synthesized as candidates for molecular electronics and especially for singlet fission, a process of interest for solar energy conversion. Solution measurements provided singlet and triplet excitation energies and fluorescence yields and lifetimes; conformational properties were analyzed computationally. The molecular properties are close to ideal for singlet fission. However, crystal structures, obtained by single-crystal X-ray diffraction (XRD), are rather similar to those of the polymorphs of solid 1, in which the formation of a charge-separated state followed by intersystem crossing, complemented with excimer formation, outcompetes singlet fission. Results of calculations by the approximate SIMPLE method suggest which ones among the solid derivatives are the best candidates for singlet fission, but it appears difficult to change the crystal packing in a desirable direction. We also describe the preparation of three specifically deuteriated versions of 1, expected to help sort out the mechanism of fast intersystem crossing in its charge-separated state.
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Affiliation(s)
- Jiří Kaleta
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague, Czech Republic
| | - Miroslav Dudič
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague, Czech Republic
| | - Lucie Ludvíková
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague, Czech Republic
| | - Alan Liška
- J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8, Czech Republic
| | - Alexandr Zaykov
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague, Czech Republic
- University of Chemistry and Technology, Technicka 5, 16000 Prague 6, Czech Republic
| | - Igor Rončević
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague, Czech Republic
| | - Milan Mašát
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague, Czech Republic
| | - Lucie Bednárová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague, Czech Republic
| | - Paul I Dron
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague, Czech Republic
| | - Simon J Teat
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460, United States
| | - Josef Michl
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague, Czech Republic
- Department of Chemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
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14
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Purdy M, Walton JR, Fallon KJ, Toolan DTW, Budden P, Zeng W, Corpinot MK, Bučar DK, van Turnhout L, Friend R, Rao A, Bronstein H. Aza-Cibalackrot: Turning on Singlet Fission Through Crystal Engineering. J Am Chem Soc 2023; 145:10712-10720. [PMID: 37133417 DOI: 10.1021/jacs.3c00971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Singlet fission is a photophysical process that provides a pathway for more efficient harvesting of solar energy in photovoltaic devices. The design of singlet fission candidates is non-trivial and requires careful optimization of two key criteria: (1) correct energetic alignment and (2) appropriate intermolecular coupling. Meanwhile, this optimization must not come at the cost of molecular stability or feasibility for device applications. Cibalackrot is a historic and stable organic dye which, although it has been suggested to have ideal energetics, does not undergo singlet fission due to large interchromophore distances, as suggested by single crystal analysis. Thus, while the energetic alignment is satisfactory, the molecule does not have the desired intermolecular coupling. Herein, we improve this characteristic through molecular engineering with the first synthesis of an aza-cibalackrot and show, using ultrafast transient spectroscopy, that singlet fission is successfully "turned on."
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Affiliation(s)
- Michael Purdy
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge CB2 1EW, U.K
| | - Jessica R Walton
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Kealan J Fallon
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge CB2 1EW, U.K
| | - Daniel T W Toolan
- Department of Chemistry, University of Sheffield, Dainton Building, Brook Hill, Sheffield S3 7HF, U.K
| | - Peter Budden
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Weixuan Zeng
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge CB2 1EW, U.K
| | - Merina K Corpinot
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Dejan-Krešimir Bučar
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K
| | - Lars van Turnhout
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Richard Friend
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Akshay Rao
- Department of Physics, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Hugo Bronstein
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Rd, Cambridge CB2 1EW, U.K
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15
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Pradhan E, Zeng T. Triplet Separation after the Fastest Intramolecular Singlet Fission in the Smallest Chromophore. J Chem Theory Comput 2023; 19:2092-2101. [PMID: 36966419 DOI: 10.1021/acs.jctc.3c00096] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/27/2023]
Abstract
Singlet fission is of key importance in harvesting solar energy in solar cells, as it generates a pair of triplet excitons on the incidence of a photon. This phenomenon is not yet widely employed in the organic photovoltaics industry mostly because of the rarity of singlet fission chromophores. Pyrazino[2,3-g]quinoxaline-1,4,6,9-tetraoxide was recently designed as the smallest intramolecular singlet fission chromophore, and it undergoes the fastest singlet fission with a 16 fs time scale. The subsequent separation of the generated triplet-pair is of likewise importance as their efficient generation. Through quantum chemistry calculations and quantum dynamics simulations, we show that the triplet-pair separates to residing on two chromophores with an ∼80% probability on each collision between a chromophore with the triplet-pair and a ground state chromophore. Avoided crossing, instead of conical intersection, is involved in the efficient exciton separation.
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Affiliation(s)
- Ekadashi Pradhan
- Department of Chemistry, York University, Toronto, Ontario M3J1P3, Canada
| | - Tao Zeng
- Department of Chemistry, York University, Toronto, Ontario M3J1P3, Canada
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16
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Pradhan E, Zeng T. Design of the Smallest Intramolecular Singlet Fission Chromophore with the Fastest Singlet Fission. J Phys Chem Lett 2022; 13:11076-11085. [PMID: 36417555 DOI: 10.1021/acs.jpclett.2c03131] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
We designed an intramolecular singlet fission (iSF) chromophore, pyrazino[2,3-g]quinoxaline-1,4,6,9-tetraoxide. Appropriate substitutions into anthracene enhance the tetraradical character, so that the molecule accommodates a pair of triplet excitons in its lowest singlet excited state. Our simulation showed a 16 fs fast iSF of the design, which is a new record. The design also sets a new record of small size iSF chromophore and high exciton density. The design can be synthesized by oxidizing the tertiary N centers of the existent pyrazino[2,3-g]quinoxaline.
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Affiliation(s)
- Ekadashi Pradhan
- Department of Chemistry, York University, Toronto, Ontario M3J1P3, Canada
| | - Tao Zeng
- Department of Chemistry, York University, Toronto, Ontario M3J1P3, Canada
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17
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Stanger A. Singlet Fission and Aromaticity. J Phys Chem A 2022; 126:8049-8057. [DOI: 10.1021/acs.jpca.2c04146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amnon Stanger
- Schulich Department of Chemistry, Technion, Haifa 3200003, Israel
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18
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Zhan X, Jin Y, Qi D, Sun T, Jiang J. General Design Strategy of Anti‐aromatic Porphyrinoids. Chemistry 2022; 28:e202201125. [DOI: 10.1002/chem.202201125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Indexed: 11/07/2022]
Affiliation(s)
- Xiaoning Zhan
- Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials Department of Chemistry University of Science and Technology Beijing 100083 Beijing (P. R. China
| | - Yucheng Jin
- Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials Department of Chemistry University of Science and Technology Beijing 100083 Beijing (P. R. China
| | - Dongdong Qi
- Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials Department of Chemistry University of Science and Technology Beijing 100083 Beijing (P. R. China
| | - Tingting Sun
- Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials Department of Chemistry University of Science and Technology Beijing 100083 Beijing (P. R. China
| | - Jianzhuang Jiang
- Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials Department of Chemistry University of Science and Technology Beijing 100083 Beijing (P. R. China
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19
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Abstract
This year marks the 50th anniversary of Baird’s rules of aromaticity — a set of perturbational molecular orbital theory analyses that has garnered considerable attention in the past ten years in light of its many real-world applications in photochemistry.
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20
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Swathi Krishna PE, Dev VV, Ramakrishnan R, Hariharan M. Retaining Hückel Aromaticity in the Triplet Excited State of Azobenzene. Chemphyschem 2022; 23:e202200045. [PMID: 35532154 DOI: 10.1002/cphc.202200045] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 03/09/2022] [Indexed: 02/04/2023]
Abstract
The implication of the potential concept of aromaticity in the relaxed lowest triplet state of azobenzene, an efficient molecular switch, using elementary aromaticity indices based on magnetic, electronic, and geometric criteria has been discussed. Azobenzene exhibits a major Hückel aromatic character retained in the diradical lowest relaxed triplet state (T1 ) by virtue of a twisted geometry with partial delocalization of unpaired electrons in the perpendicular p-orbitals of two nitrogen atoms to the corresponding phenyl rings. The computational analysis has been expanded further to stilbene and N-diphenylmethanimine for an extensive understanding of the effect of closed-shell Hückel aromaticity in double-bond-linked phenyl rings. Our analysis concluded that stilbene has Hückel aromatic character in the relaxed T1 state and N-diphenylmethanimine has a considerable Hückel aromaticity in the phenyl ring near the carbon atom while a paramount Baird aromaticity in the phenyl ring near the nitrogen atom of the C=N double bond. The results reveal the application of excited-state aromaticity as a general tool for the design of molecular switches.
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Affiliation(s)
- P E Swathi Krishna
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, Kerala 695551, India
| | - Vivek V Dev
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, Kerala 695551, India
| | - Remya Ramakrishnan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, Kerala 695551, India
| | - Mahesh Hariharan
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, Kerala 695551, India
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21
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Mathew CM, Varghese A, Sugunan SK, Thomas VI. Rapid Computational Approach Towards Designing Singlet-Fission Chromophores by Tuning the Diradical Character of Heteroatom-Doped Polycyclic Aromatic Hydrocarbons Using the Atom-Specific Fukui Function. J Phys Chem A 2022; 126:1579-1590. [PMID: 35258970 DOI: 10.1021/acs.jpca.1c08094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Singlet fission (SF) is proposed as a promising method to circumvent the Shockley-Queisser threshold of single junction photovoltaics. Progress towards realizing efficient SF-based devices has been impeded by the fact that only a handful of molecules and their derivatives practically exhibit efficient SF. In the present work, we demonstrate a TDDFT-based rapid and cost-effective computational approach for designing SF chromophores by doping various atomic sites (substituting carbon atoms) of polycyclic aromatic hydrocarbons with nitrogen, phosphorus, and silicon. We establish a hitherto unexplored, direct correlation between the atom-specific chemical reactivity parameter─Fukui function─of these molecules with their frontier molecular orbital energies, diradical characters, and vertical singlet and triplet excitation energies. These quantitative correlations show exactly opposite trends for nitrogen-doped molecules and phosphorus- or silicon-doped molecules. The doped derivatives that have the Fukui function falling in a range of 0.03-0.14 possess the required intermediate diradical character and suitable singlet-triplet energies to qualify for SF candidature. Our findings enable one, at reasonable computational times and cost, to easily assess the doping criteria and to develop design rules for SF molecules in particular and for diradicaloids in general.
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Affiliation(s)
- Christina Mariam Mathew
- Department of Chemistry, CMS College Kottayam (Autonomous) (Mahatma Gandhi University), Kottayam 686001, Kerala, India.,Department of Chemistry, Baselius College Kottayam (Mahatma Gandhi University), Kottayam 686001, Kerala, India
| | - Ann Varghese
- Department of Chemistry, CMS College Kottayam (Autonomous) (Mahatma Gandhi University), Kottayam 686001, Kerala, India
| | - Sunish K Sugunan
- Department of Chemistry, CMS College Kottayam (Autonomous) (Mahatma Gandhi University), Kottayam 686001, Kerala, India
| | - Vibin Ipe Thomas
- Department of Chemistry, CMS College Kottayam (Autonomous) (Mahatma Gandhi University), Kottayam 686001, Kerala, India.,Institute for Integrated Programmes and Research in Basic Sciences (IIRBS), Mahatma Gandhi University, Priyadarshini Hills, Kottayam 686560, Kerala, India
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22
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Kim J, Kim H, Oh J, Kim D. Ligand‐to‐metal charge transfer driven by excited‐state antiaromaticity in metallohexaphyrins. B KOREAN CHEM SOC 2022. [DOI: 10.1002/bkcs.12483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Jinseok Kim
- Department of Chemistry Yonsei University Seoul Korea
| | - Hyeonwoo Kim
- Department of Chemistry Soonchunhyang University Asan Korea
| | - Juwon Oh
- Department of Chemistry Soonchunhyang University Asan Korea
| | - Dongho Kim
- Department of Chemistry Yonsei University Seoul Korea
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23
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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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24
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Baranac-Stojanović M, Stojanović M, Aleksić J. Revival of Hückel Aromatic (Poly)benzenoid Subunits in Triplet State Polycyclic Aromatic Hydrocarbons by Silicon Substitution. Chem Asian J 2021; 17:e202101261. [PMID: 34964285 DOI: 10.1002/asia.202101261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/22/2021] [Indexed: 11/08/2022]
Abstract
By employing density functional theory (DFT) calculations we show that mono- and disilicon substitution in polycyclic aromatic hydrocarbons, having two to four benzene units, quenches their triplet state antiaromaticity by creating Hückel aromatic (poly)benzenoid subunit(s) and weakly antiaromatic, or almost nonaromatic silacycle. Therefore, such systems are predicted to be globally aromatic in both the ground state and the first excited triplet state. Putting the silicon atom(s) into various positions of a hydrocarbon provides an opportunity to tune the singlet-triplet energy gaps. They depend on the global aromaticity degree which, in turn, depends on the type of aromatic carbocyclic subunit(s) and the extent of their aromaticity. On the basis of the set of studied compounds, some preliminary rules on how to regulate the extent of global, semiglobal and local aromaticity are proposed. The results of this work extend the importance of Hückel aromaticity concept to excited triplet states which are usually characterized by the Baird type of (anti)aromaticity.
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Affiliation(s)
- Marija Baranac-Stojanović
- Faculty of Chemistry, University of Belgrade, Organic Chemistry, Studentski trg 16, 11000, Belgrade, SERBIA
| | - Milovan Stojanović
- Institute of Chemistry Technology and Metallurgy: Institut za hemiju tehnologiju i metalurgiju, Center for Chemistry, SERBIA
| | - Jovana Aleksić
- Institute of Chemistry Technology and Metallurgy: Institut za hemiju tehnologiju i metalurgiju, Center for Chemistry, SERBIA
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25
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Kim J, Oh J, Osuka A, Kim D. Porphyrinoids, a unique platform for exploring excited-state aromaticity. Chem Soc Rev 2021; 51:268-292. [PMID: 34879124 DOI: 10.1039/d1cs00742d] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Recently, Baird (anti)aromaticity has been referred to as a description of excited-state (anti)aromaticity. With the term of Baird's rule, recent studies have intensively verified that the Hückel aromatic [4n + 2]π (or antiaromatic [4n]π) molecules in the ground state are reversed to give Baird aromatic [4n]π (or Baird antiaromatic [4n + 2]π) molecules in the excited states. Since the Hückel (anti)aromaticity has great influence on the molecular properties and reaction mechanisms, the Baird (anti)aromaticity has been expected to act as a dominant factor in governing excited-state properties and processes, which has attracted intensive scientific investigations for the verification of the concept of reversed aromaticity in the excited states. In this scientific endeavor, porphyrinoids have recently played leading roles in the demonstration of the aromaticity reversal in the excited states and its conceptual development. The distinct structural and electronic nature of porphyhrinoids depending on their (anti)aromaticity allow the direct observation of excited-state aromaticity reversal, Baird's rule. The explicit experimental demonstration with porphyrinoids has contributed greatly to its conceptual development and application in novel functional organic materials. Based on the significant role of porphyrinoids in the field of excited-state aromaticity, this review provides an overview of the experimental verification of the reversal concept of excited-state aromaticity by porphyrinoids and the recent progress on its conceptual application in novel functional molecules.
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Affiliation(s)
- Jinseok Kim
- Department of Chemistry, Yonsei University, Seoul 03722, Korea.
| | - Juwon Oh
- Department of Chemistry, Soonchunhyang University, Asan-si 31538, Korea.
| | - Atsuhiro Osuka
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| | - Dongho Kim
- Department of Chemistry, Yonsei University, Seoul 03722, Korea.
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26
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Pino-Rios R, Báez-Grez R, Solà M. Acenes and phenacenes in their lowest-lying triplet states. Does kinked remain more stable than straight? Phys Chem Chem Phys 2021; 23:13574-13582. [PMID: 34109330 DOI: 10.1039/d1cp01441b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The larger stability of phenacenes compared to their acene isomers in their ground states is attributed to the larger aromaticity of the former. To our knowledge the relative stability of acenes and phenacenes in their lowest-lying triplet states (T1) has not been discussed yet. Using unrestricted density functional theory calculations, our results show that for the smallest members of the series, acenes in their T1 states are more stable than the corresponding phenacenes. However, when the number of the rings (n) involved increases, the energy difference is reduced and for n > 12, phenacenes become more stable than acenes in their T1 states. To rationalize this trend, we analyze the aromaticity of acenes and phenacenes using a set of aromaticity descriptors. We find that in the T1 states of both acenes and phenacenes, the outer rings form aromatic Clar π-sextets. In acenes, delocalization of spin density in the central rings leads to the preferred formation of the largest antiaromatic diradical. Resonant structures in the form of antiaromatic diradical Baird π-octadectets and π-tetradectets are the major contributors, while the smaller ones, such as π-doublets and π-sextets, contribute the least. In phenacenes, structures with diradical antiaromatic Baird π-sextets in some of the central rings contribute the most. These results are relevant to understand the (anti)aromaticity of larger polycyclic aromatic hydrocarbons in their triplet states.
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Affiliation(s)
- Ricardo Pino-Rios
- Laboratorio de Química Teórica, Facultad de Química y Biología, Universidad de Santiago de Chile (USACH), Región Metropolitana, Chile.
| | - Rodrigo Báez-Grez
- Computational and Theoretical Chemistry Group, Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andres Bello, República 498, Santiago, Chile
| | - Miquel Solà
- Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, 17003 Girona, Catalonia, Spain.
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