First example of mixed azoheterocycles: structural studies of metallo-macrocycle Ag(I) versus tetrahedral Cd(II) complexes of pyridyl-azo-imidazole

Imidazolyl and 3′-pyridyl are linked by azo bond (–NN–) to synthesize hitherto unknown mixed heterocyclic azo molecules, 2-[(3′-pyridyl)azo]imidazole (3′-PyaiH). Alkylation in presence of NaH has synthesized 1-alkyl-2-[(3′-pyridyl)azo]imidazole (3′-PyaiR′). 3′-PyaiR′ include three types of N-donor centers: N(imidazole), N(azo) and a peripheral N(pyridine). They bind to Ag+ to form 2:2 metallo-macrocycle, [Ag(3′-PyaiR′)]22+, while the reaction with Cd2+ forms Cd(3′-PyaiR′)42+. The complexes are structurally characterized by X-ray diffraction studies.