METAL 1,10-PHENANTHROLINE-LINKED DIHYDRONICOTINAMIDES AS MODELS FOR THE NADH ALCOHOL-DEHYDROGENASE COENZYME ENZYME COUPLE

Two phenanthroline-linked dihydronicotinamides, l,4-dihydro-l-(l,10-phenanthrolin-2-ylmethyl)-3-pyridinecarboxamide (3) and l,4-dihydro-N-(l,10-phenanthrolin-2-ylmethyl)-l-(phenylmethyl)-3-pyridinecarboxamide (6), were synthesized. The phenanthroline moiety in these compounds is able to chelate metal ions into fixed positions toward the dihydronicotinamide group providing models for the NADH-alcohol dehydrogenase complex. The reactivity of 3-M2+ and 6-M2+ is investigated toward 2,4,6-trinitrobenzene sulfonate and methylene blue (M2+ = Zn2+) and toward the metallophilic substrate 2-pyridinecarboxaldehyde (PyCHO) for which a detailed kinetic analysis is given. For reaction of 3-M2+ and PyCHO the efficiency of metal ion activation is of the order Zn2+>> Mg2+, Ni2+ > Co2+ > Cd2+. It is concluded that hydride transfer proceeds in a ternary 3-M2+-PyCHO complex in an orientation in which carbonyl group and dihydropyridine are in a coplanar position with the carbonyl oxygen pointing to the ring nitrogen. © 1990, American Chemical Society. All rights reserved.