Premium
Raman spectra and phase transitions of (5‐dimethylaminopenta‐2, 4‐dienylidene)‐dimethylammonium perchlorate
Author(s) -
Sano Norimichi,
Shimizu Masaaki,
Tanaka Jiro
Publication year - 1989
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250200609
Subject(s) - raman spectroscopy , differential scanning calorimetry , phase transition , chemistry , perchlorate , endothermic process , crystal (programming language) , analytical chemistry (journal) , crystallography , ion , condensed matter physics , thermodynamics , optics , organic chemistry , physics , adsorption , computer science , programming language
Lattice vibrational Raman spectra of (5‐dimethylaminopenta‐2, 4‐dienylidene)dimethylammonium perchlorate were measured for two crystal modifications at various temperatures. The phonon frequencies below 200 cm −1 were different for the two crystal forms. A phase transition was found by means of Raman spectra and differential scanning calorimetry (DSC). With increase in temperature of the crystal, the orange form is converted to the yellow form at ca. 370 K, and this transition is irreversible. Near the transition temperature, the Raman bands of both forms were observed simultaneously. This observation and an endothermic peak in the DSC curve show that two forms are correlated by a first‐order phase transition.