Interplay between structure and magnetism in the low-dimensional spin system $K(C_8H_{16}O_4)_2CuCl_3{*}H_2O$

TL;DR

This study synthesizes and characterizes a new low-dimensional quantum spin system based on a crown ether complex with Cu(II), revealing antiferromagnetic dimers and water's influence on magnetic exchange interactions.

Contribution

The paper reports the synthesis, structural determination, and magnetic analysis of a novel Cu(II) crown ether complex, including DFT calculations that elucidate water's role in magnetic coupling.

Findings

Complex exhibits a maximum magnetic susceptibility at 23 K.

Cu(II) ions form antiferromagnetic dimers with specific Cu-Cl distances.

Water molecules increase the singlet-triplet splitting, affecting magnetic interactions.

Abstract

Materials based on a crown ether complex together with magnetic ions, especially Cu(II), can be used to synthesize new low dimesional quantum spin systems. We have prepared the new crown ether complex Di-\mu-chloro-bis(12-crown-4)-aquqdichloro-copper(II)-potassium, $K(C_8H_{16}O_4)_2CuCl_3{*}H_2O$ (1), determined its structure, and analyzed its magnetic properties. Complex (1) has a monoclinic structure and crystallizes in space group $P2_1/n$ with the lattice parameters of $a=9.5976(5)\r{A}$, $b=11.9814\r{A}, c=21.8713\r{A}$ and $\beta=100.945(4)\deg$. The magnetic properties of this compound have been investigated in the temperature range 1.8 K - 300 K. The magnetic susceptibility shows a maximum at 23 K, but no 3-D long range magnetic order down to 1.8 K. The S=1/2 Cu(II) ions form antiferromagnetically coupled dimers with Cu-Cl distances of $2.2554(8)\r{A}$ and $4.683(6)\r{A}$, and a Cu-Cl-Cu angle of $115.12(2)\deg$ with $2J_{dimer}=-2.96meV (-23.78 cm^{-1})$. The influence of $H_2O$ on the Cl-Cu-Cl exchange path is analyzed. Our results show that the values of the singlet-triplet splitting are increasing considering $H_2O$ molecules in the bridging interaction. This is supported by Density functional theory (DFT) calculations of coupling constants with Perdew and Wang (PWC), Perdew, Burke and Ernzenrhof (PBE) and strongly constrained and appropriately normed (SCAN) exchange-correlation function show excellent agreement for the studied compound.