Hexacyanometalate Molecular Chemistry : Trinuclear CrNi2 Complexes; MicroSQUID Magnetisation Studies of Intermolecular Interactions

TL;DR

This study synthesizes three CrNi2 complexes with different ligands and counterions, and investigates their magnetic properties and intermolecular interactions using microSQUID magnetization measurements at very low temperatures.

Contribution

It provides new insights into how ligand and crystal structure influence magnetic interactions in CrNi2 complexes.

Findings

All complexes exhibit a ground state spin of 7/2.

They show three-dimensional magnetic ordering at low temperatures.

Intermolecular coupling correlates with ligand sterics and crystal symmetry.

Abstract

Three different CrNi2 complexes were synthesized. They differ from each other by the nature of the terminal ligand and of the counter anion : [Cr(CN)4[CN-Ni(tetren)]2]Cl, that crystallizes in two different crystallographic systems and [Cr(CN)4[CN-Ni(dienpy2)]2](ClO4). The ground state spin value is 7/2 for the three systems (ferromagnetic interaction between chromium(III) and nickel(II) ions). The magnetisation of the three CrNi2 complexes was measured using an array of micro-SQUIDs in a temperature range between 0.04 K and 7 K, under a magnetic field up to 1 T. The three samples present a three dimensional magnetic ordering. The correlation between the structure and the intermolecular coupling is analysed in terms of steric hindrances of the terminal ligand, orientation of the molecules in the unit cell (canted structure) and crystal symmetry.