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Wu CC, Li EY, Chou PT. Reducing the internal reorganization energy via symmetry controlled π-electron delocalization. Chem Sci 2022; 13:7181-7189. [PMID: 35799804 PMCID: PMC9214956 DOI: 10.1039/d2sc01851a] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/24/2022] [Indexed: 12/30/2022] Open
Abstract
The magnitude of the reorganization energy is closely related to the nonradiative relaxation rate, which affects the photoemission quantum efficiency, particularly for the emission with a lower energy gap toward the near IR (NIR) region. In this study, we explore the relationship between the reorganization energy and the molecular geometry, and hence the transition density by computational methods using two popular models of NIR luminescent materials: (1) linearly conjugated cyanine dyes and (2) electron donor–acceptor (D–A) composites with various degrees of charge transfer (CT) character. We find that in some cases, reorganization energies can be significantly reduced to 50% despite slight structural modifications. Detailed analyses indicate that the reflection symmetry plays an important role in linear cyanine systems. As for electron donor–acceptor systems, both the donor strength and the substitution position affect the relative magnitude of reorganization energies. If CT is dominant and creates large spatial separation between HOMO and LUMO density distributions, the reorganization energy is effectively increased due to the large electron density variation between S0 and S1 states. Mixing a certain degree of local excitation (LE) with CT in the S1 state reduces the reorganization energy. The principles proposed in this study are also translated into various pathways of canonically equivalent π-conjugation resonances to represent intramolecular π-delocalization, the concept of which may be applicable, in a facile manner, to improve the emission efficiency especially in the NIR region. The reorganization energies may be significantly reduced by molecular symmetry effect.![]()
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Affiliation(s)
- Chi-Chi Wu
- Department of Chemistry, National Taiwan Normal University, No. 88, Section 4, Tingchow Road, Taipei 116, Taiwan
| | - Elise Y. Li
- Department of Chemistry, National Taiwan Normal University, No. 88, Section 4, Tingchow Road, Taipei 116, Taiwan
| | - Pi-Tai Chou
- Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 106, Taiwan
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Chen WC, Cheng YC. Elucidating the Magnitude of Internal Reorganization Energy of Molecular Excited States from the Perspective of Transition Density. J Phys Chem A 2020; 124:7644-7657. [PMID: 32864966 DOI: 10.1021/acs.jpca.0c06482] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Quantifying vibronic couplings in molecular excited states is crucial for the elucidation of a broad range of photophysical phenomena. In this study, we compare different theoretical approaches for the calculation of reorganization energy, a measure of vibronic coupling strength, and provide a rigorous derivation to show that molecular transition density characterizing electron-hole excitation could be used to quantify the magnitude of reorganization energy. The theory enables a descriptor based on molecular-orbital coefficients and atomic transition densities to quantify the magnitude of reorganization energies in molecular excited states. Applying the approach to low-lying excited states of polyacenes, we demonstrate that transition density distribution explains the difference in the magnitude of the reorganization energy of different excited states. Furthermore, to clarify the applicability of the transition density descriptor in molecular design for small-reorganization energy molecules, we investigate a broad range of molecular chromophores to show the effectiveness of the proposed theory. With this perspective on the relationship between reorganization energy and transition density, we successfully provide a quantitative rule to identify π-conjugated systems with small reorganization energy in the excited state, which should be useful for the development of novel optoelectronic materials.
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Affiliation(s)
- Wei-Chih Chen
- Department of Chemistry and Center for Quantum Science and Engineering, National Taiwan University, Taipei City 106, Taiwan, R.O.C
| | - Yuan-Chung Cheng
- Department of Chemistry and Center for Quantum Science and Engineering, National Taiwan University, Taipei City 106, Taiwan, R.O.C
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Langer P, Amiri S, Bodtke A, Saleh NNR, Weisz K, Görls H, Schreiner PR. 3,5,7,9-Substituted Hexaazaacridines: Toward Structures with Nearly Degenerate Singlet−Triplet Energy Separations. J Org Chem 2008; 73:5048-63. [DOI: 10.1021/jo8005123] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Peter Langer
- Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, D-18059 Rostock, Germany, Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany, Institut für Organische Chemie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany, Institut für Pharmazie, Universität Greifswald, Friedrich-Ludwig-Jahn-Str. 17, D-17487 Greifswald, Germany, Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 18, D
| | - Shadi Amiri
- Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, D-18059 Rostock, Germany, Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany, Institut für Organische Chemie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany, Institut für Pharmazie, Universität Greifswald, Friedrich-Ludwig-Jahn-Str. 17, D-17487 Greifswald, Germany, Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 18, D
| | - Anja Bodtke
- Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, D-18059 Rostock, Germany, Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany, Institut für Organische Chemie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany, Institut für Pharmazie, Universität Greifswald, Friedrich-Ludwig-Jahn-Str. 17, D-17487 Greifswald, Germany, Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 18, D
| | - Nehad N. R. Saleh
- Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, D-18059 Rostock, Germany, Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany, Institut für Organische Chemie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany, Institut für Pharmazie, Universität Greifswald, Friedrich-Ludwig-Jahn-Str. 17, D-17487 Greifswald, Germany, Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 18, D
| | - Klaus Weisz
- Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, D-18059 Rostock, Germany, Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany, Institut für Organische Chemie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany, Institut für Pharmazie, Universität Greifswald, Friedrich-Ludwig-Jahn-Str. 17, D-17487 Greifswald, Germany, Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 18, D
| | - Helmar Görls
- Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, D-18059 Rostock, Germany, Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany, Institut für Organische Chemie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany, Institut für Pharmazie, Universität Greifswald, Friedrich-Ludwig-Jahn-Str. 17, D-17487 Greifswald, Germany, Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 18, D
| | - Peter R. Schreiner
- Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, D-18059 Rostock, Germany, Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany, Institut für Organische Chemie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany, Institut für Pharmazie, Universität Greifswald, Friedrich-Ludwig-Jahn-Str. 17, D-17487 Greifswald, Germany, Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 18, D
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