Single crystals of DPPH grown from diethyl ether and carbon disulfide solutions - Crystal structures, IR, EPR and magnetization studies

TL;DR

This study characterizes two forms of DPPH crystals grown from different solvents using X-ray, IR, EPR, and magnetization techniques, revealing structural differences and magnetic interactions relevant for EPR standards.

Contribution

It provides detailed structural, spectroscopic, and magnetic characterization of DPPH crystals grown from diethyl ether and carbon disulfide, highlighting differences in dimerization and exchange interactions.

Findings

DPPH from ether is solvent-free, while from CS2 is a solvate.

Both forms exhibit antiferromagnetic dimers with different coupling strengths.

Results enhance understanding of DPPH properties as an EPR standard.

Abstract

Single crystals of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) obtained from diethyl ether (ether) and carbon disulfide (CS2) were characterized by the X-ray diffraction, IR, EPR and SQUID magnetization techniques. The X-ray structural analysis and IR spectra showed that the DPPH form crystallized from ether (DPPH1) is solvent free, whereas that one obtained from CS2 (DPPH2) is a solvate of the composition 4DPPH.CS2. Principal values of the g-tensor were estimated by the X-band EPR spectroscopy at room and low (10 K) temperatures. Magnetization studies revealed the presence of antiferromagnetically coupled dimers in both types of crystals. However, the way of dimerization as well as the strength of exchange couplings are different in the two DPPH samples, which is in accord with their crystal structures. The obtained results improved parameters accuracy and enabled better understanding of properties of DPPH as a standard sample in the EPR spectrometry.