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Strong Ground‐ and Excited‐State Charge Transfer in C 3 ‐Symmetric Truxene‐Derived Phenothiazine‐Tetracyanobutadine and Expanded Conjugates
Author(s) -
Sharma Rekha,
Thomas Michael B.,
Misra Rajneesh,
D'Souza Francis
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201814388
Subject(s) - phenothiazine , chemistry , tetracyanoethylene , excited state , photochemistry , ground state , electron transfer , charge (physics) , electron acceptor , acceptor , ultrafast laser spectroscopy , chemical physics , atomic physics , spectroscopy , medicine , physics , quantum mechanics , pharmacology , condensed matter physics
The C 3 ‐symmetric star‐shaped phenothiazene‐substituted truxene 1 was reacted with the electron acceptors tetracyanoethylene (TCNE) and 7,7,8,8‐tetracyanoquinodimethane (TCNQ). The cycloaddition–retroelectrocyclization reaction yields the conjugates 2 and 3 . A combination of spectral, electrochemical, and photophysical investigations of 2 and 3 reveals that the functionalization of the triple bond has a pronounced effect on their ground and excited‐state interactions. Specifically, the existence of strong ground‐state interactions between phenothiazine and the electron‐accepting groups results in charge‐transfer states, while subsequent ultrafast charge separation yields electron transfer products. This is unprecedented not only in phenothiazine chemistry but also in tetracyanobutadiene‐ and dicyanoquinodimethane‐derived donor–acceptor conjugates. Additionally, by manipulating spectroelectrochemical data, a spectrum of the charge‐separated species is construed for the first time, and shown to be highly useful in interpreting the rather complex transient spectra.