Metal Ion-Modulated Torsion Angle in a Ditopic Oligothiophene Ligand: Toward Supramolecular Control of -Conjugationстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 18 декабря 2013 г.
Аннотация:A p-conjugated oligomer bearing two 15-crown-5-containing
styryl moieties connected at the inner b 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 1H 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.