Time-Resolved Infrared Vibrational Spectroscopy of the Photoinduced Phase Transition of Pd(dmit)2 Salts Having Different Orders of Phase Transition

• Published in: Journal of physical chemistry. C 2013-06, Vol.117 (25), p.13187-13196
• Main Authors: Fukazawa, Naoto, Tanaka, Takahiro, Ishikawa, Tadahiko, Okimoto, Yoichi, Koshihara, Shin-ya, Yamamoto, Takashi, Tamura, Masafumi, Kato, Reizo, Onda, Ken
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Physics; Specific phase transitions
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp403193a

To clarify the mechanism of the later process of photoinduced phase transition (PIPT) in organic charge-transfer complexes, we examined by time-resolved infrared vibrational spectroscopy two dimeric anion radical salts, Et2Me2Sb[Pd(dmit)2]2 (Et2Me2Sb salt) and Cs[Pd(dmit)2]2 (Cs salt) (Et, Me, and dmit are C2H5, CH3, and 1,3-dithiol-2-thione-4,5-dithiolate, respectively), having similar characteristics except for the order of their phase transitions at thermal equilibrium. The phase transition is first order for the Et2Me2Sb salt and second order for the Cs salt at thermal equilibrium. Although both salts exhibit a high-temperature phase at later delay times (>100 ps) after the photoexcitation of the low-temperature phase, the time required for the emergence of the high-temperature phase was significantly different: 70 ps for the Et2Me2Sb salt and