Theoretical study on the supramolecular complexes of 12-crown-4 with adrenaline

Conformations of adrenaline (Ad) and protonated adrenaline (PAd+) were studied by performing B3LYP/6-31G(d) full geometry optimization calculations. The B3LYP/6-31G(d) optimized geometries for the most stable conformations of Ad, PAd+, and 12-crown-4 (12C4) are reported. Supramolecular complexes (containing one or two hydrogen bonds) of a 12-crown-4 molecule with one adrenaline molecule or one protonated adrenaline were carefully studied by performing B3LYP/6-31G(d) full geometry optimization calculations. The calculations indicate that the P1-complex (containing one hydrogen bond at one of the hydroxy-hydrogen atoms of catechol in Ad) is the most stable Ad-12C4 complex and that the N2A+-complex (containing two hydrogen bonds at the hydrogen atoms at the alcohol-oxygen atom and at the nitrogen atom in PAd+) is the most stable PAd+-12C4 complex. The accurate calculation results for the model systems will be useful for experimental researchers working in this field.