Carboxylic acid-dependent assembly of neodymium–organic frameworks with attractive topologies and second-order nonlinear optical and/or magnetic properties

Abstract

Four new neodymium(III) coordination polymers, Nd(HL)₂(CH₃COO) (1), Nd(HL)₂(CH₃COO) (1′), Nd(HL)₂(C₂H₅COO) (2) and Nd(HL)₃(H₂O) · 4H₂O (3) were prepared by the hydrothermal reactions of Nd₂O₃ with 1,6-dihydro-6-oxopyridine-3-carboxylic acid (H₂L) using the modulation roles of different carboxylic acids (acetic acid, malonic acid, propionic acid and formic acid for 1, 1′, 2 and 3, respectively). Complexes 1 and 1′ are conformational polymorphs: 1 crystallizes in an acentric space group Cmc2(1) and shows a new 3D {3,6} topology (6³)₂(4²6¹⁰8³), while 1′ crystallizes in the centrosymmetric space groupPbcn, exhibiting the rutile topology. Complex 2 possesses the same space group and topology as 1′. Complex 3 exhibits a new 2D three-node network topology with the Schläfli symbol of (8³). Complex 1 is a second-order nonlinear optical molecular material, and magnet measurements indicated the magnetic coupling interaction between Nd³⁺ ions in these four complexes is weak.