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Highly Functionalized Dimeric Tetraethynylethenes and Expanded Radialenes: Strong Evidence for Macrocyclic Cross‐Conjugation
Author(s) -
Nielsen Mogens Brøndsted,
Schreiber Martin,
Baek Yong Gu,
Seiler Paul,
Lecomte Steve,
Boudon Corinne,
Tykwinski Rik R.,
Gisselbrecht JeanPaul,
Gramlich Volker,
Skinner Philip J.,
Bosshard Christian,
Günter Peter,
Gross Maurice,
Diederich François
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010803)7:15<3263::aid-chem3263>3.0.co;2-3
Subject(s) - intramolecular force , chromophore , chemistry , delocalized electron , acceptor , photochemistry , dimer , crystallography , dimethylaniline , fluorescence , electron donor , stereochemistry , catalysis , biochemistry , physics , organic chemistry , quantum mechanics , condensed matter physics
A selection of dimeric tetraethynylethenes (TEEs) and perethynylated expanded radialenes, containing different donor/acceptor substitution patterns, have been prepared and fully characterized. The first X‐ray crystal structure of an expanded [6]radialene, with twelve peripheral 3,5‐di( tert ‐butyl)phenyl substituents, is presented. This macrocycle, the all‐carbon core of which is isomeric with fullerene C 60 , adopts a non‐planar, “chair‐like” conformation. Also a TEE dimer, carrying N , N ‐dimethylaniline donor substituents, has been subjected to an X‐ray crystallographic analysis. The electronic properties were studied by UV/Vis spectroscopy and electrochemistry, providing fundamental insight into mechanisms of π‐electron delocalization in the acyclic and macrocyclic chromophores. Donor or donor–acceptor‐substituted dimeric TEE derivatives show very strong absorptions extending over the entire UV/Vis region; their longest wavelength absorption bands have high charge‐transfer character. Macrocyclic cross‐conjugation in the expanded radialenes becomes increasingly efficient with increasing donor–acceptor polarization. A dual, strongly solvent‐polarity‐dependent fluorescence was observed for a tetrakis( N , N ‐dimethylaniline)‐substituted dimeric TEE; this interesting emission behavior is explained by the twisted intramolecular charge‐transfer (TICT) state model. Donor‐substituted expanded radialenes display huge resonance‐enhanced third‐order nonlinear optical coefficients.