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Gon M, Yaegashi M, Tanaka K, Chujo Y. Near-Infrared Emissive Hypervalent Compounds with Germanium(IV)-Fused Azobenzene π-Conjugated Systems. Chemistry 2023; 29:e202203423. [PMID: 36441133 DOI: 10.1002/chem.202203423] [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: 11/04/2022] [Revised: 11/28/2022] [Accepted: 11/28/2022] [Indexed: 11/30/2022]
Abstract
A novel molecular design for showing near-infrared (NIR) emission is still required for satisfying growing demands for NIR-light technology. In this research, hypervalent compounds with germanium (Ge)-fused azobenzene (GAz) scaffolds were discovered that can exhibit NIR emission (λPL =690∼721 nm, ΦPL =0.03∼0.04) despite compact π-conjugated systems. The unique optical properties are derived from the trigonal bipyramidal geometry of the hypervalent compounds constructed by combination of Ge and azobenzene-based tridentate ligands. Experimental and theoretical calculation results disclosed that the germanium-nitrogen (Ge-N) coordination at the equatorial position strongly reduces the energy level of the LUMO (lowest unoccupied molecular orbital), and the three-center four-electron (3 c-4 e) bond in the apical position effectively rises the energy level of the HOMO (highest occupied molecular orbital). It is emphasized that large narrowing of the HOMO-LUMO energy gap is achieved just by forming the hypervalent bond. In addition, the narrow-energy-gap property can be enhanced by extension of π-conjugation. The obtained π-conjugated polymer shows efficient NIR emission both in solution (λPL =770 nm and ΦPL =0.10) and film (λPL =807 nm and ΦPL =0.04). These results suggest that collaboration of a hypervalent bond and a π-conjugated system is a novel and effective strategy for tuning electronic properties even in the NIR region.
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Affiliation(s)
- Masayuki Gon
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Misao Yaegashi
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Kazuo Tanaka
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Yoshiki Chujo
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan
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Recent progresses in the mechanistic studies of aggregation-induced emission-active boron complexes and clusters. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214779] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Tanaka K, Chujo Y. Frustrated element-blocks: A new platform for constructing unique stimuli-responsive luminescent materials. Polym J 2022. [DOI: 10.1038/s41428-022-00709-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Wang X, Wang G, Li J, Li X, Zhang K. A simple and straightforward polymer post-modification method for wearable difluoroboron β-diketonate luminescent sensors. POLYMER 2022. [DOI: 10.1016/j.polymer.2021.124449] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Nakamura M, Gon M, Natsuda SI, Tamai Y, Ohkita H, Tanaka K, Chujo Y. Development of NIR emissive fully-fused bisboron complexes with π-conjugated systems including multiple azo groups. Dalton Trans 2021; 51:74-84. [PMID: 34881749 DOI: 10.1039/d1dt03652a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Development of novel near-infrared (NIR) emitters is essential for satisfying the growing demands of advancing optical telecommunication and medical technology. We synthesized elemental skeletons composed of robust π-conjugated systems including two boron-fused azo groups, which showed an intense emission in the red or near-infrared (NIR) region both in solution and solid states. Two types of bisboron complexes with different aromatic linkers showed emission properties with larger bathochromic shifts and emission efficiencies in solution than the corresponding monoboron complex. Transient absorption spectroscopy disclosed that the inferior optical properties of the monoboron complex can be attributed to fast nonradiative deactivation accompanied by a large structural relaxation after photoexcitation. The expanded π-conjugated system through multiple boron-fused azo groups can contribute to rigid molecular skeletons followed by improved emission properties. Moreover, the anti-form of the bisboron complex with fluorine groups in the opposite directions to the π-plane exhibited crystallization-induced emission enhancement in the NIR region. The molecular design by using multiple boron-fused azo groups is expected to be a critical strategy for creating novel NIR emitters.
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Affiliation(s)
- Masashi Nakamura
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
| | - Masayuki Gon
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
| | - Shin-Ichiro Natsuda
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
| | - Yasunari Tamai
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan. .,Japan Science and Technology Agency (JST), PRESTO, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - Hideo Ohkita
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
| | - Kazuo Tanaka
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
| | - Yoshiki Chujo
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
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Ito S, Gon M, Tanaka K, Chujo Y. Recent developments in stimuli-responsive luminescent polymers composed of boron compounds. Polym Chem 2021. [DOI: 10.1039/d1py01170g] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
This review summarizes recent developments in stimuli-responsive luminescent polymers with boron chromophores, including three- and four-coordinated compounds. Sensing mechanisms based on the features of boron and polymer structures are described.
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Affiliation(s)
- Shunichiro Ito
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Masayuki Gon
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Kazuo Tanaka
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Yoshiki Chujo
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
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