Structural diversity of cocrystals formed from acridine and two isomers of hydroxybenzaldehyde: 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde

Cocrystals formed from acridine and two isomers of hydroxybenzaldehyde: 3-hydroxybenzaldehyde ( 1 ) and 4-hydroxybenzaldehyde ( 2 ) were synthesized and structurally characterized. Single-crystal X-ray diffraction measurements show that compound 1 crystallizes in the triclinic P 1&cmb.macr; space group, whereas compound 2 crystallizes in the monoclinic P 2 1 / n space group. In the crystals of title compounds, the molecules interact via O-H N and C-H O hydrogen bonds, and C-H π and π-π interactions. DCS/TG measurements indicate that compound 1 melts at a lower temperature than the separate cocrystal coformers, whereas compound 2 melts at a higher temperature than acridine but at a lower temperature than 4-hydroxybenzaldehyde. The FTIR measurements reveal that the band attributed to the stretching vibrations of the hydroxyl group of hydroxybenzaldehyde disappeared, but several bands appeared in the range of 3000-2000 cm −1 . Based on experiments carried out using SCXRD, FTIR, and TG/DSC methods, it was demonstrated that acridine forms cocrystals with two isomers of hydroxybenzaldehyde: 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde in a molar ratio of 1 : 1.