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Engineering a Remarkably Low HOMO–LUMO Gap by Covalent Linkage of a Strong π ‐Donor and a π ‐Acceptor—Tetrathiafulvalene‐ σ ‐Polynitrofluorene Diads: Their Amphoteric Redox Behavior, Electron Transfer and Spectroscopic Properties
Author(s) -
Perepichka Dmitrii F.,
Bryce Martin R.,
Batsanov Andrei S.,
McInnes Eric J. L.,
Zhao Jing P.,
Farley Robert D.
Publication year - 2002
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(20021018)8:20<4656::aid-chem4656>3.0.co;2-1
Subject(s) - tetrathiafulvalene , chemistry , homo/lumo , electrochromism , photochemistry , acceptor , redox , intramolecular force , electron paramagnetic resonance , crystallography , electron transfer , intermolecular force , electron acceptor , molecule , stereochemistry , inorganic chemistry , organic chemistry , nuclear magnetic resonance , physics , electrode , condensed matter physics
Novel R 3 TTF–σ–A compounds 14, 16 and 19 (R 3 TTF=trialkyltetrathiafulvalene, σ=saturated spacer, A=polynitrofluoren‐9‐dicyanomethylene acceptor) incorporating very strong donor and acceptor moieties have been synthesized by condensation of the corresponding R 3 TTF–σ‐fluoren‐9‐one diads with malononitrile. Reversible five‐step amphoteric redox behavior has been observed with an extremely low HOMO–LUMO gap (≈0.3 eV). For compound 14 a strong EPR signal is observed in the solid state, ascribed to intermolecular complexation: a less intense signal is seen in solution, corresponding to ca. 2 % of the molecules existing in a radical form at room temperature. Intramolecular charge transfer in diads 14 and 16 is manifested in strong absorption bands in the near‐IR region of their electronic spectra. Spectroelectrochemical data reveal marked electrochromic behavior in the visible and near‐IR region of both compounds. The first X‐ray crystal structure of a fluorene radical‐anion salt is reported, namely the copper salt of 2,4,5,7‐tetranitro‐9‐dicyanomethylenefluorene (1:1 stoichiometry).