title: Alkyl group as entropy reservoir in an MMX chain complex, Pt2(n-PenCS2)4I.
abstract: Heat capacity of halogen-bridged one-dimensional binuclear metal complex (so-called MMX chain) having four n-pentyl groups, Pt2(n-PenCS2)4I, was measured by adiabatic calorimetry. A first-order phase transition was observed at 207.4 K when measurement was made after cooling from room temperature. The enthalpy and entropy of transition were determined to be 10.19 kJ mol(-1) and 49.1 J K(-1) mol(-1), respectively. A monotropic phase transition was observed at 324 K on heating, and the entropy of transition was essentially null. The sample once heated above 324 K never returned to the initial phase at room temperature and underwent a higher-order phase transition at 173 K and a first-order phase transition at 220.5 K. The enthalpy and entropy of the first-order phase transition were estimated to be 11.6 kJ mol(-1) and 52.4 J K(-1) mol(-1), respectively. The magnitude of the entropy gain at the phase transition from the initial room-temperature phase to the high-temperature phase at 324 K shows that in Pt2(n-PenCS2)4I a large amount of entropy reserved in alkyl chain is transferred to dithiocarboxylato groups upon the phase transition, as in the cases of Pt2(n-PrCS2)4I and Pt2(n-BuCS2)4I.
authors.affiliation: Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. kazuya@chem.tsukuba.ac.jp
authors.forename: Kazuya
authors.initials: K
authors.lastname: Saito
authors.forename: Satoaki
authors.initials: S
authors.lastname: Ikeuchi
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Nakazawa
authors.forename: Akane
authors.initials: A
authors.lastname: Sato
authors.forename: Minoru
authors.initials: M
authors.lastname: Mitsumi
authors.forename: Takami
authors.initials: T
authors.lastname: Yamashita
authors.forename: Koshiro
authors.initials: K
authors.lastname: Toriumi
authors.forename: Michio
authors.initials: M
authors.lastname: Sorai