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

摘要

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