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Terthiophene Appended with Terpyridine Units as Receptors for Protons and Zn 2+ Ions: Photoinduced Energy and Electron Transfer Processes
Author(s) -
Bergamini Giacomo,
Boselli Luca,
Ceroni Paola,
Manca Paola,
Sanna Gavino,
Pilo Maria
Publication year - 2011
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.201100582
Subject(s) - chemistry , chromophore , terpyridine , photochemistry , protonation , terthiophene , photoinduced electron transfer , electron transfer , luminescence , quantum yield , acetonitrile , quenching (fluorescence) , ligand (biochemistry) , ion , metal , fluorescence , molecule , biochemistry , physics , receptor , optoelectronics , organic chemistry , quantum mechanics , chromatography
Two ligands consisting of 2,2′:6′,2″‐terpyridine (tpy) and terthiophene units (3T) connected by a methyleneoxy ( TTT ) or an alkynyl bridge ( TAT ) show different photophysical properties: in the former there is no evidence of a ground state interaction between the two constituent chromophores and the expected 3T emission is observed. On the other hand, the latter exhibits strong π‐conjugation between the two chromophores mediated by the alkynyl bridge: this results in a substantially redshifted absorption and an emission displaced toward the red with a decreased quantum yield. Both of these ligands can be diprotonated: protonation occurs at the tpy unit in two successive steps, leading finally to TTT· 2H + and TAT· 2H + . In both cases, strong changes in the absorption spectra and very efficient quenching of the luminescence takes place by a photoinduced electron transfer from 3T to the protonated tpy unit. Both TTT and TAT can also perform as Zn 2+ ligands, giving rise to complexes with 1:2 metal/ligand stoichiometry in acetonitrile solution, as demonstrated by changes in the photophysical properties. Also in this case, the resulting complex is not luminescent because of photoinduced electron transfer from 3T to the [Zn(tpy) 2 ] 2+ moieties.