Elucidating the Excited State Behavior of Pyridyl Pyridinium Systems via Computational and Transient Absorption Studies of Tetrahedral Multichromophoric Arrays and their Model Compounds.

Autor: Ventura B; Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via P. Gobetti 101, 40129, Bologna, Italy., Veclani D; Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via P. Gobetti 101, 40129, Bologna, Italy., Venturini A; Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via P. Gobetti 101, 40129, Bologna, Italy., Armaroli N; Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via P. Gobetti 101, 40129, Bologna, Italy., Baroncini M; CLAN-Center for Light Activated Nanostructures, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via P. Gobetti 101, 40129, Bologna, Italy.; Dipartimento di Scienze e Tecnologie Agro-alimentari, Università di Bologna, Viale G. Fanin 50, 40127, Bologna, Italy., Ceroni P; Dipartimento di Chimica 'G. Ciamician', Università di Bologna, Via F. Selmi 2, 40126, Bologna, Italy., Marchini M; Dipartimento di Chimica 'G. Ciamician', Università di Bologna, Via F. Selmi 2, 40126, Bologna, Italy.
Jazyk: angličtina
Zdroj: Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2023 Nov 02; Vol. 29 (61), pp. e202301853. Date of Electronic Publication: 2023 Sep 28.
DOI: 10.1002/chem.202301853
Abstrakt: The tetrahedral shape-persistent molecule 1 4+ , containing four identical pyridyl pyridinium units connected via a sp 3 hybridized carbon atom, has been investigated in detail by means of steady-state and time resolved spectroscopy. Remarkable photophysical properties are observed, particularly in comparison with protonated and methylated analogues (1H 4 8+ , 1Me 4 8+ ), which exhibit substantially shorter excited state lifetimes and lower emission quantum yields. Theoretical studies have rationalized the behavior of the tetrameric molecules relative to the monomers, with DFT and TD-DFT calculations corroborating steady-state (absorption and emission) and transient absorption spectra. The behavior of the monomeric compounds (each consisting in one of the four identical subunits of the tetramers, i. e., 2 + , 2H 2+ and 2Me 2+ ) considerably differs from that of the tetramers, indicating a strong electronic interaction between the subunits in the tetrameric species, likely promoted by the homoconjugation through the connecting sp 3  C atom. 2 + is characterized by a peculiar S 1 -S 2 excited state inversion, whereas the short-lived emitting S 1 state of 2H 2+ and 2Me 2+ exhibits a partial charge-transfer character, as substantiated by spectro-electrochemical studies. Among the six investigated systems, only 1 4+ is a sizeable luminophore (Φ em =0.15), which is related to the peculiar features of its singlet state.
(© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)
Databáze: MEDLINE
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