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 P1̄ space group, whereas compound 2 crystallizes in the monoclinic P2(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).