Inclusion of Caffeine by a Diol Host

Abstract  

The host compound 9,9′-(ethyne-1,2-diyl)-bis(fluoren-9-ol), H, forms inclusion compounds with caffeine (H·CAF) and methanol (H·MeOH). The host and guest ratios were 1:2 and 1:1, respectively. Both of these structures were successfully solved in P-1 with unit cell dimensions for H·CAF: a = 7.2121(14) ?, b = 9.2782(19) ?, c = 15.206(3) ?, α = 73.23(3)°, β = 84.20(3)°, γ = 73.39(3)°, Z = 2 and for H·MeOH : a = 9.7592(10) ?, b = 11.2584(11) ?, c = 20.7854(19) ?, α = 97.161(2)°, β = 99.263(2)°, γ = 95.257(2) ?, Z = 2. These crystal structures were studied together with that of a mixed clathrate, H·CAF·MeOH with stoichiometry 2:1:1.5. For H·CAF·MeOH which was solved in P2₁/c : a = 12.2051(5) ?, b = 46.8023(19) ?, c = 9.0121(4) ?, β = 91.9650(10)°, Z = 4. The kinetics of desolvation of the methanol solvate (H·MeOH) yielded an activation energy of 69.6–83.9 kJ mol⁻¹.