(C$_{4}$H$_{12}$N$_{2}$)[CoCl$_{4}$] -tetrahedrally coordinated Co$^{2+}$ without the orbital degeneracy

TL;DR

This paper reports the synthesis and characterization of a new tetrahedral Co$^{2+}$ compound with an S=3/2 ground state, showing no orbital degeneracy or spin-orbit coupling, contrasting with similar compounds.

Contribution

It introduces a novel Co$^{2+}$ compound with tetrahedral coordination exhibiting an orbital singlet ground state, expanding understanding of Co$^{2+}$ magnetic properties in different environments.

Findings

No magnetic ordering above 2 K.

Absence of spin-orbit coupling in the ground state.

Comparison with hydrated analogue shows structural influence.

Abstract

We report on the synthesis, crystal structure, and magnetic properties of a previously unreported Co$^{2+}$ $S={3 \over 2}$ compound, (C$_{4}$H$_{12}$N$_{2}$)[CoCl$_{4}$], based upon a tetrahedral crystalline environment. The $S={3 \over 2}$ magnetic ground state of Co$^{2+}$, measured with magnetization, implies an absence of spin-orbit coupling and orbital degeneracy. This contrasts with compounds based upon an octrahedral and even known tetrahedral Co$^{2+}$ based systems where a sizable spin-orbit coupling is measured. The compound is characterized with single crystal x-ray diffraction, magnetic susceptibility, infrared, and ultraviolet/visible spectroscopy. Magnetic susceptibility measurements find no magnetic ordering above 2 K. The results are also compared with the previously known monoclinic hydrated analogue.