Table 1.

Characteristics of the most stable bimolecular hetero-molecular complexes formed by caffeine in analyzed solutions. Primes in the geometry parameters denote atoms of solvent molecules. The values of Gibbs free energy of reaction represent the concentration-independent quantity derived using activities at 25 °C.

caffeine–DMF	caffeine–DMSO
dH⋯O’ = 2.149 Å, αC-H⋯O’ = 176.3° ΔGr(AB) = −5.7 kcal/mol	dH⋯O’= 2.105 Å, αC-H⋯O’= 179.1° ΔGr(AB) = −6.5 kcal/mol		+0.01e2/Å2 −0.01e2/Å2
caffeine–1,4-dioxane	caffeine–acetone
dH⋯O’ = 2.192 Å, αC-H⋯O’ = 176.5° ΔGr(AB) = −5.0 kcal/mol	dH⋯O’ = 2.283 Å, αC-H⋯O’ = 175.5° ΔGr(AB) = −4.2 kcal/mol
caffeine–acetonitrile	caffeine–water
dH⋯O’ = 2.388 Å, αC-H⋯O’ = 175.5° ΔGr(AB) = −3.5 kcal/mol	dN⋯H’ = 1.852 Å, αC-H⋯O’ = 177.3° ΔGr(AB) = −6.4 kcal/mol