The energetics of complexation for model receptors and adenine derivatives are reported. The new systems feature Watson-Crick, Hoogsteen, and bifurcated hydrogen bonding as well as aryl stacking interactions. These factors can act simultaneously on adenine derivatives because the model receptors present cleftlike shapes which are complementary to the surface of adenine. The association constants vary from 50 to lo4 M-l in solvents such as CDCI, that compete poorly for hydrogen bonds. The energetics of binding are explored as a function of receptor and guest structure, solvent, and temperature.