Studies on Effects of Alkyl Substitutions on Crystal Structures of Organic Colorants Focusing on Two Dye Systems

Effects of alkyl substitutions on the crystal structures of some bisazomethine dyes and quinacridone dyes were systematically investigated. The molecular geometries and the low-dimensional arrangements of the molecules in their crystal structures were characterized using some geometric parameters. Lattice energy calculations were also carried out to interpret the effects of the alkyl substituents on important low-dimensional arrangements of the molecules stabilizing the total lattice energies by strong intermolecular interactions. The alkyl substituents on the terminal amino groups of the bisazomethine dyes were found to affect the slip angles between the π-π stacked molecules forming one-dimensional arrangements. In the alkoxylated-bisaomethine dyes, the methyl and ethyl substituents on the terminal amino groups were found to be a key in determining the two-dimensional arrangement of the π-π stacked molecules. The alkyl substituents on the amino groups of the quinacridone dyes played a role in determining the one-dimensional arrangements of the molecules giving the strongest energetic contribution to the total lattice energies.