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Metal Ion Modulated Torsion Angle in a Ditopic Oligothiophene Ligand: Toward Supramolecular Control of π Conjugation
Author(s) -
Lukovskaya Elena,
Bobylyova Alla,
Fedorov Yuri,
Maksimov Anton,
Anisimov Alexander,
Fedorova Olga,
Jonusauskas Gediminas,
Fages Frédéric
Publication year - 2010
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201000356
Subject(s) - delocalized electron , chemistry , solvation , oligomer , supramolecular chemistry , ion , metal ions in aqueous solution , barium , conjugated system , metal , ligand (biochemistry) , photochemistry , crystallography , molecule , inorganic chemistry , polymer chemistry , polymer , organic chemistry , biochemistry , receptor
A π‐conjugated oligomer bearing two 15‐crown‐5‐containing styryl moieties connected at the inner β positions of the terminal thiophene nuclei can adopt either a U or a Z shape depending on the structures of its complexes with magnesium and barium ions. We show that barium cations lead to the formation of a mononuclear complex in solution, which causes the system to fold into the U shape. Magnesium ions lead to the same effect at low concentration, but force the ligand to adopt the Z‐shaped geometry at high concentrations favoring formation of a binuclear complex. These geometrical reorganizations in solution are accompanied by profound changes in spectroscopic properties, which can be rationalized in terms of variations in the extent of electron delocalization along the oligothiophene backbone. The effects are analyzed by mass spectrometry and 1 H NMR, UV/Vis absorption, and fluorescence spectroscopy in the steady‐state and time‐resolved regimes. The experimental results are compared to data calculated by using MOPAC2007 with the PM6 Hamiltonian including the COSMO solvation model.