Luminescence features of neodymium(III) compounds with various tetrapyrrole macrocycles

Abstract

We considered the changes in the luminescent properties in the series of neodymium(III) complexes of various coordination types with different tetrapyrrole macrocycles (porphyrins, phthalocyanines and corroles): mononuclear complexes (metal-ligand ratio 1:1), sandwich type complexes (metal-ligand ratio 1:2 or 2:3), peripheral binding (on the basis of ditopic tetrapyrrole, metal-ligand ratio 1:1). 4f-Luminescence in the near infrared region is observed in all studied Nd-complexes as a result of intramolecular transfer of excitation energy. Each kind of complexes has its unique features, which are discussed. The peripheral complexes are dual-emissive: they display both neodymium(III) 4f-emission and molecular fluorescence. The values of quantum yield of molecular fluorescence as well as 4f-luminescence are estimated. It was found that binding type plays a key role in excited state relaxation pathways in the molecule. Corroles have unusual behaviour in terms of Nd sensitization.