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Effect of Ethynyl and 2‐Thienyl Substituents on the Complexation of 4′‐Substituted 2,2′:6′,2″‐Terpyridines with Zn 2+ and Fe 2+ Ions, and the Spectroscopic Properties of the Ligands and Formed Complex Species
Author(s) -
Vitvarová Tereza,
Zedník Jiří,
Bláha Michal,
Vohlídal Jiří,
Svoboda Jan
Publication year - 2012
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201200256
Subject(s) - chemistry , ion , terpyridine , ligand (biochemistry) , acetonitrile , metal ions in aqueous solution , fluorescence , chelation , conjugated system , spectroscopy , crystallography , luminescence , nuclear magnetic resonance spectroscopy , stereochemistry , metal , inorganic chemistry , polymer , organic chemistry , biochemistry , physics , receptor , quantum mechanics , optoelectronics
Abstract The complexation of terpyridine ( tpy ) and its 4′‐ethynyl (E) and 4′‐(2‐thienyl) (T) derivatives, as promising chelate end groups for oligomeric components of conjugated metallosupramolecular polymers, with Zn 2+ and Fe 2+ ions as ion couplers was investigated in acetonitrile using NMR and UV/Vis spectroscopy. The binding of these ligands with Zn 2+ ions shows two distinct steps with comparable binding constants in the range of 10 6 dm 3 mol –1 , whereas their binding with Fe 2+ ions shows a strong tendency to form [FeL 2 ] 2+ species, which almost do not dissociate to monoligand species [FeL] 2+ even at a twofold excess of Fe 2+ ions. The ligand exchange dynamics between [ZnL 2 ] 2+ species in solution was studied by NMR spectroscopy and the related parameters were determined. UV/Vis spectra taken during complexation show an apparent isosbestic point at 310 ± 10 nm, and those of the systems with Fe 2+ ions also show a metal‐to‐ligand charge‐transfer band at 550–580 nm. 4′‐Substituents strongly enhance the luminescence of tpy (ca. 400 times). Additional enhancement is provided by binding the ligands to Zn 2+ ions, whereas their binding to Fe 2+ ions quenches the fluorescence.