Synthesis and structure of d-metal complexes with derivatives of 9-oxypyrido[1,2a]pyrimidine-2-one. Crystal structure of 4-methyl-9-oxypyrido[1,2a]pyrimidine-2-one

By reacting Cu(I), Cu(II), Ni(II), Co(II), and Mn(II) chlorides and Ag(I) nitrate with 4-methyl-(8-nitro)-9-oxypyrido[1,2-a]pyrimidine-2-ones (HL1, HL2), the complex compounds ML and MHLCl2 · nH2O (n = 1-3) were produced (8 compounds in all). The spectral characteristics of the neutral, anionic, and cationic forms of ligands were determined and the crystal structure of 4-methyl-9-oxypyrido[1,2-a]pyrimidine-2-one was resolved. It was found that the monovalent metal complexes contain ligands in the anionic form, while the ligands in the bivalent metal complexes are in bipolar form. Coordination is realized with the involvement of the hydroxyl oxygen atoms and the cyclic nitrogen atom