One-dimensional magnetism in a facile spin 1/2 Heisenberg antiferromagnet with a low saturation field

Abstract

This work reports the synthesis, structure and magnetic properties of a facile spin 1/2 one dimensional Heisenberg antiferromagnet bis(4-aminopyridinium) bis(oxalato)cuprate(II) dihydrate, (C₅H₇N₂)₂[Cu(C₂O₄)₂]·2H₂O. Single crystals of large sizes of the title compound were obtained using the technique liquid–liquid diffusion or layer diffusion with 100% yield. Single crystal X-ray diffraction measurements revealed the very good quality of the grown single crystals with a small value of goodness of fit R obtained (1.058). Powder X-ray diffraction showed the presence of peaks of the main phase with no impurity peaks, confirming the good quality of the crystals. The structure comprises corner sharing CuO₆ octahedra resulting in Cu–Cu chains in the a-direction that are very well isolated in the b and c directions. Density functional theory (DFT) calculations with three different basis sets (B3LYP/6-311++G(d,p); B3LYP/LanL2DZ and B3LYP/6-311++G(d,p), B3LYP/LanL2DZ) generated the optimized geometry of a monomeric unit as well as its vibrational spectra. A vibrational frequency corresponding to the CuO₆ octahedron was found in the experimentally obtained FTIR spectrum that matched very well with the theoretically obtained IR spectra incorporating the mixed basis. Temperature dependent dc magnetic susceptibility measurements revealed a low temperature peak, suggesting the presence of low dimensional magnetism in the system. Bonner–Fisher fit confirmed the one dimensional nature of the magnetic interaction with an exchange coupling constant of 1.23 K. Magnetisation measurements along with quantum Monte Carlo simulations confirm this metal–organic crystal to be a very good spin-1/2 Heisenberg antiferromagnet with a low saturation field H_s of 1.75 T.