Sentitized near-infrared emission in novel neodymium complexes bearing oligothiophene derivatives as antennae

A series of neodymium complexes based on (α-oligothiophen-2-yl)(2-hydroxy-3-methoxyphenyl)methanone moiety was prepared and studied by FTIR, NMR, optical spectroscopies. As a function of the thiophene ring number in the ligand, a variation of both stoichiometry and optical properties of the complex are observed. The solid-state ligand structure indicates a close packing and a stressed situation in enolate residues, i.e. non-coplanarity between thiophene and phenyl moieties. An un-precedent stoichiometry of complexes was observed, namely two metal and five ligands, according to both the synthesis conditions and the encumbrance of ligand with respect to ionic radius of Nd3+. This fact is attributed to the contribution to the coordination of the methoxy group. Luminescence and lifetime determination are discussed in the light of the above factors.