Cold Crystallization of Chiral Schiff-Base Nickel(II) Complex Having Alkyl Chains and a Characteristic Methyl Group

Abstract

Molecules exhibiting cold crystallization, an exothermic phenomenon in heating following supercooling, can be used as a heat storing material. On the other hand, examples in non-polymers are still few. A chiral Schiff-base nickel(II) complex, which had a characteristic methyl group and long alkyl chains, exhibited complicated thermal behavior including cold crystallization. The methyl group was a steric barrier to dimerization and molecular stacking, leading to the supercooled state. In addition, the thermal behavior of enantiomer was different from that of racemate.

Metal Complexes of π-Expanded Ligands (8): Cold Crystallization of bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] copper(II) by Thermal Analyses, Magnetic Studies, and FT-IR

“…1 To achieve this, emerging technologies for storage, 2 exchange, 3 extraction, 4 and others are necessary. 5 The advantage of thermal storage is to eliminate the time lag between the supply and demand of heat. Recently, Saito et al proposed the combination of glass transition and cold crystallization as a protocol to improve the controllability of heat-storage/release.…”

“…Recently, Saito et al proposed the combination of glass transition and cold crystallization as a protocol to improve the controllability of heat-storage/release. 5,6 The assumed scenario is as follows. The heat-storage material melts during the first heating process.…”

“…Therefore, the heat release on cold crystallization is the key to using supercooled liquids for thermal storage with desired controllability. 5,6 The use of the change in coordination bonds, the energy of which lies in between van der Waals interaction used in thermophysical heat-storage [7][8][9][10] and covalent bonds in thermochemical storage, [11][12][13][14][15] would lower the working temperature while maintaining relatively high energy density. In this context, it is worthwhile to develop compounds exhibiting the cold crystallization accompanied by a change in the coordination mode.…”

“…In this context, it is worthwhile to develop compounds exhibiting the cold crystallization accompanied by a change in the coordination mode. Within the various materials exhibiting a cold crystallization (polymer, [16][17][18] ionic liquid, 19 organic material, 20 and metal complexes 5,6,21 ), a Schiff-base metal complex, bis[N-(2-propyl)-5,6benzosalicylideneaminato]nickel(II) reported by Wang et al 21 They reported i) a colour change, probably caused by a change in the coordination structure from square planar (green) to tetrahedral (brown), and ii) a cold-crystallization phenomenon.…”

“…Inspired by this, the author began the study on similar compounds and reported the cold crystallization in bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] copper(II) 1(Cu) with the possible molecular origin of its cold crystallization. 5,6,21 In this report, the cold crystallization of bis[2-[(octylimino)methyl]-1-pyrenolato-N,O] copper(II) is studied and discussed using the magnetic properties, the FT-IR spectra, and thermal analyses. Zero-field cooled magnetic susceptibility was measured in the temperature range of 2-300 K for the complex.…”