Metal Ion Modulated Torsion Angle in a Ditopic Oligothiophene Ligand: Toward Supramolecular Control of π Conjugation |
| |
Authors: | Dr. Elena Lukovskaya Dr. Alla Bobylyova Dr. Yuri Fedorov Prof. Anton Maksimov Prof. Alexander Anisimov Prof. Olga Fedorova Dr. Gediminas Jonusauskas Prof. Frédéric Fages |
| |
Affiliation: | 1. Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory, 119992 Moscow (Russia);2. A. N. Nesmyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova str., 119991, Moscow (Russia);3. Centre de Physique Moléculaire Optique et Hertzienne, UMR CNRS 5798, Université Bordeaux 1, 351 Cours de la Libération, 33405 Talence (France);4. CINaM UPR 3118 CNRS, Université de la Méditerranée, Campus de Luminy, Case 913, Marseille, 13288 (France), Fax: (+33)?491418916 |
| |
Abstract: | 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 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. |
| |
Keywords: | alkaline earth metals crown compounds oligothiophenes optical spectroscopy supramolecular chemistry |
|
|