Three novel end-to-end single azido-bridged ferromagnetic copper(II) chains: synthesis, crystal structure, and magnetic behavior

Abstract

Three new single end‐to‐end azido‐bridged copper(II) chains [Cu(L1)(N₃)]_n(ClO₄)_n (1), [Cu(L₂)(N₃)]_n(ClO₄)_n (2), and [Cu(L₃)(N₃)]_n(ClO₄)_n (3) using three different tridentate Schiff bases L1, L2, and L3, obtained from condensation of pyridine‐2‐carbaldehyde with N,N‐dimethylethane‐1,2‐diamine, N,N‐diethylethane‐1,2‐diamine, and 4‐(2‐aminoethyl)morpholine, respectively, have been synthesized, and their crystal structures have been determined by X‐ray diffraction methods. Complex 1, C₁₀H₁₅CuN₆ClO₄, crystallizes in an orthorhombic system, space group P2₁2₁2₁, with a = 7.434(3), b = 12.047(4), c = 17.404(6) Å, and Z = 4; complex 2, C₁₂H₁₉CuN₆ClO₄, crystallizes in an orthorhombic system, space group Pna2₁, with a = 14.723(5), b = 13.829(5), c = 8.002(5) Å, and Z = 4 and complex 3, C₁₂H₁₇CuN₆ClO₅, crystallizes in an orthorhombic system, space group Pna2₁, with a = 13.837(15), b = 14.804(2), c = 8.050(4) Å, and Z = 4. Each structure consists of a single end‐to‐end azido‐bridged copper(II) 1D chain where each copper(II) center possesses a square pyramidal geometry. Magnetic susceptibility data, measured from 4 to 300 K, show weak ferromagnetic interaction through the end‐to‐end bridging azido pathway in all the complexes. The magnetic data were fitted to a high temperature series‐expansion for a one‐dimensional system with S = 1/2 local spin based on the Hamiltonian H = −JΣS_i·S_i+1 for all the complexes, giving the parameters J = +2.15 cm^-1, g = 2.23 for 1, J = +3.61 cm^-1, g = 2.16 for 2, and J = +2.06 cm^-1, g = 2.17 for 3. This unusual magnetic behavior through the end‐to‐end bridging azido pathway has been correlated to the structural parameters.