Hexamine copper(II) coordination polymers: synthesis, structure and magnetic properties

Abstract

Four new one-dimensional (1D) polymeric complexes, {[Cu₄(L¹)₂(µ-Br)₂(µ₄-CO₃)]Br(ClO₄)₃·3H₂O}_n (1), {[Cu₂L²(µ-Cl)Cl₂] (ClO₄)₂·H₂O}_n (2), {[Cu₂L³(µ-Cl)₂](ClO₄)₂}_n (3), and {[Cu₂L⁴(µ-Cl)₂](ClO₄)₂}_n (4), have been synthesized and characterized, where L¹ = N,N,N′,N′-tetrakis(3′-aminopropyl)-1,3-propylenediamine, L² = N,N,N′,N′-tetrakis(2′-aminoethyl)-1,3-propylenediamine, L³ = N,N,N′,N′-tetrakis(2′-aminoethyl)-1,4-butylenediamine, L⁴ = N,N,N′,N′-tetrakis(2′-aminoethyl)-1, 6-hexylenediamine. X-Ray structure analysis revealed that the polymeric complexes, created by the bridging groups which are exhibited in the formula, present different 1D coordination motifs: double-stranded chains with voids of 43.5 Ų for 1, sigmoid chains for 2, zigzag chains for 3 and 4 with different coordination polyhedra. Various hydrogen bonding interactions such as N–H⋯Cl, N–H⋯O, C–H⋯Cl, N–H⋯Br and O–H⋯Br join the polymeric chains to generate two-dimensional networks with bigger voids. Magnetic susceptibility data were fitted according to the molecular structures using Hamiltonians: H = −2J₁(S₂S₃ + S₁S₄) − 2J₂(S₂S₁) − 2J₃(S₁S₃ + S₂S₄) − 2J₄(S₃S₄), which corresponds to a rectangular array of spins for 1, and H = −2JS₁S₂ corresponds to a dinuclear array of spins for 2, 3 and 4. It was found that the coupling constants of 1 are −60, −113, −54 and −11 cm⁻¹, and those of 2, 3, and 4 are −2.46, −1.56 and −0.15 cm⁻¹, respectively.