Substituent effects on novel lanthanide(III) hydrazides complexes

New lanthanide (Eu3+ and Gd3+) complexes were successfully synthesized and the effect of the p-phenyl substituent on the Eu3+ luminescent properties was evaluated. In this sense, benzhydrazide, p-toluic hydrazide, 4-hydroxybenzhydrazide and 4-aminobenzoic hydrazide were used as ligands and the complexes were obtained by mixing the lanthanide salts with hydrazides in ethanol at room temperature and keeping the reaction for 2 h under mechanical stirring. Crystal of Gd-amino was obtained and its structure was elucidated by single-crystal X-ray diffraction, revealing that Gd3+ centered in a distorted tricapped trigonal-prismatic molecular geometry. IR spectroscopy and the elucidated structure confirm hydrazides acting as bidentate ligands binding to Ln(3+) ions through the oxygen of carbonyl group and the nitrogen of terminal amine, forming a five-membered ring. CHN analyses confirm the molecular formulas [Gd(amino)(4)(H2O)](NO3)(3)center dot(C2H2OH) and [Eu(toluic)(3)(H2O)](NO3)(3). Lower T-1 state energies are observed for ligands p-substituted with higher electron donating capacity groups, such as p-NH2 and p-OH. In contrast, higher lifetimes and quantum efficiencies are obtained for Eu3+ complexes with ligands p-H and p-CH3 substituted, which are not deactivator groups. (C) 2019 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.