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.