Crystal structure, fluorescence spectroscopy, and electrochemical property of two neodymium coordination polymers with phenoxy acids

Abstract

Two nine-coordination coordination polymers of neodymium, [Nd₂(p-C₈H₄O₄)(o-C₈H₄O₄)₂ • 4H₂O]_n (I), [Nd₂(C₁₀H₄O₈)(C₁₀H₂O₈) • 2H₂O]_n (II), have been prepared by hydrothermal reaction of Nd(NO₃)₃ • 6H₂O with terephthalic acid and phthalic acid, or benzenetetracarboxylic anhydride and determined by means of IR, UV, fluorescence, TG-DTA, cyclic voltammetry (CV) and X-ray single-crystal diffraction methods (CIF files CCDC nos. 1006206 (I), 979309 (II)). Yellow-green luminescence could been observed at 391 nm (λ_ex = 305 nm) for complex I and 370 nm (λ_ex = 331 nm) for the complex II. The emission of complexes I and II may be due to the π* → n transition, which may be assigned to the ligand-to-metal charge-transfer bands. Compared with complex II, the complex I exhibits a stronger fluorescence intensity for the different coordinated environment. Cyclic voltammetric measurement of the two compounds reveal that the compounds both have a couple of irreversible redox peak, indicating that the two polymers were both corresponded to the unusual Nd(III)/Nd(V).