The thermal behavior, including the cold crystallization, of alkylderivatized Sudan III (1-[4-(phenylazo)phenylazo]-2-naphthol), SD3-OCn, was investigated. Its structural flexibility due to the two azo groups caused the formation of plural crystal structures, which further resulted in complex cold crystallization. A metastable nonflat structure and a thermodynamically stable flat structure resulted in the two sets of crystallization and melting behavior during the heating process. Further, the change in the alkyl chain length caused variations in the crystallization rate and crystallinity, thus systematically changing the cold crystallization behavior. It was proven that the high mobility of the phenyl group triggered supercooling and cold crystallization and that the alkyl chain correspondingly controlled the thermal behavior.
A previously reported odd-even effect is found to invert by substituting a phenyl with a cyclohexyl group. Crystal structures of [Ni(dmit)2]− complex salts of ω-cyclohexylalkyltrimethylammonium (CncHx; n = 1–5) are revealed by X-ray crystallographic analysis. Alternant stacks are found in all complex salts, but some differences are found in each crystal structure. Terminal cyclohexyl groups adopt chair conformation in the series, and alkylene chains adopt all-trans conformation. Ion pairs found in these crystals are classified by the angle between cations and anions. In these series, odd-even effect is observed in cation length, anion length, Ni-Ni distance and the angle of cation and anion. These are different from the case of terminal methyl and phenyl groups previously reported, indicating that odd-even effect depends on the terminal substituent.
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