Co-crystals of 9-(2-Methoxyphenyl)-9H-xanthen-9-ol with Caffeine and Theophylline

Abstract

The host compound 9-(2-methoxyphenyl)-9H-xanthen-9-ol (H) forms a 2:1 co-crystal with caffeine (2H·CAF). The structure was solved successfully in the triclinic space group P-1 with unit cell dimensions: a = 9.1747(8) Å, b = 13.7910(12) Å, c = 16.7207(14) Å, α = 107.036(2)°, β = 99.213(2)° and γ = 95.812(2)°. The structure of the apohost was also solved in P-1 with unit cell dimensions: a = 11.402(2) Å, b = 11.993(2) Å, c = 12.994(3) Å, α = 64.96(3)°, β = 73.29(3)° and γ = 74.89(3)°. The co-crystal hydrate of H with theophylline, 2H·THEO·½H 2 O, crystallised in the space group P21/c, unit cell dimensions: a = 13.8121(12) Å, b = 14.7391(13) Å, c = 20.4630(18) Å, β = 106.759(2)°.

Graphical Abstract A co-crystal of 9-(2-methoxyphenyl)-9H-xanthen-9-ol and caffeine (2H·CAF) is stabilized by hydrogen bonding to the imidazole nitrogen and the amide oxygen of caffeine.