Position of substituent dependent dimensionality in Ln–Cu heterometallic coordination polymers

Abstract

The reaction of two derivatives of iminodiacetic acid, including H₂ANMA (H₂ANMA = L-alanine-N-monoacetic acid) and H₂MIDA (H₂MIDA = N-methyl-iminodiacetic acid), with Ln(NO₃)₃ (Ln = La, Pr, Nd) and Cu(NO₃)₂ generates two types of Ln–Cu coordination polymers of different dimensionality, {[Ln₂Cu₃(ANMA)₆](H₂O)₃} and {[Ln₂Cu(MIDA)₄(H₂O)₆](H₂O)₄} (Ln = La, Pr, Nd). Crystal structure analysis reveals that the position of the methyl group in the two ligands plays an important role, which can be described as follows: (1) adjusting the coordination direction of ligand via the steric hindrance; (2) serving as an electron donating group to enhance the coordination ability of the amino group, where the H₂MIDA ligand displays a new coordination mode. It is found that the position of the methyl groups in the two ligands plays a critical role in their structural differences.