M. Bossa et al., X-RAY STRUCTURE AND AM1 STUDIES OF THE PROTON-TRANSFER ADDUCT BETWEEN2,5-DIHYDROXY-P-QUINONE AND 4-(N,N-DIMETHYLAMINO)PYRIDINE, Journal of physical chemistry, 100(22), 1996, pp. 9302-9307
The structure of the crystalline 1:1 adduct obtained by reacting 2,5-d
ihydroxy-1-quinone (DHpQ) and 4-(N,N-dimethylamino)pyridine (DAPY) has
been determined by X-ray single-crystal diffraction. The compound con
sists of ribbons of the two components linked by proton-transfer bonds
. Each bond is due to a proton of the 4-(N,N'-dimethylamino)pyridinium
cation (r(N-H) = 1.13 Angstrom), bifurcated between two oxygen atoms
of the monoprotonated anion. Antiparallel stacks of DHpQ-DAPY adducts
are present in the solid. According to AM1 and molecular mechanics cal
culations, it has been shown that the interaction between stacked addu
cts is the prerequisite for the establishing of proton-transfer bonds
(O-...HN+) between DHpQ and DAPY. It is suggested that electrostatic i
nteractions such as the dipole-dipole coupling play a major role in es
tablishing this type of hydrogen bond within each stack.