The Crystal Structures of 6-N-Heptylmercaptopurine at 123 K and 6-N-Hexylaminopurine at 295 K

Abstract

6-N-Heptylmercaptopurine, C₁₂H₁₈N₄S, (I), is monoclinic, P2₁c, Z = 4, with cell dimensions at 123 K [295 K] of a = 15.527(7) [15.219(7)], b = 7.140(3) [7.275(3)], c = 11.979(6) [12.414(7)] Å, β = 101.21(4) [100.15(4)]° 6-N-Hexylaminopurine, C₁₁H17 N₅, (11), is triclinic, P1, Z = 2, with cell dimensions a = 5.210(10), b = 8.466(13), c = 13.932(10) Å, α = 97.03(16), β = 92.03(7), γ = 104.43(17)°.

In the crystal structure of I the molecular packing is head-to-head bilayer with double stacks of purine moieties and interdigitating alkyl chains. This structure is isostructural with the long-chain alkyl pyranosides. In II, the hydrogen-bonded purine residues are packed in imbricated layer structure with antiparallel twisted alkyl chains which are not intercalated. Only structure II shows evidence of thermotropic crystal-to-crystal phase transitions in both heating and cooling cycles; neither crystal forms a liquid crystal phase and both melt directly to an isotropic liquid.