Complexes derived from the general copper(II)/maleamic acid/N,N′,N′′-chelate reaction systems: Synthetic, reactivity, structural and spectroscopic studies

The synthetic investigation of the CuII/maleamate(−1) ion (HL−)/N,N′,N′′-chelate general reaction system has allowed access to compounds [Cu2(HL)2(bppy)2](ClO4)2·H2O (1·H2O), [Cu(HL)(bppy)(ClO4)] (2) and [Cu(HL)(terpy)(H2O)](ClO4) (4) (bppy = 2,6-bis(pyrazol-1-yl)pyridine, terpy = 2,2′;6′,2′′-terpyridine). In the absence of externally added hydroxides, compound [Cu2(L′)2(bppy)2](ClO4)2 (3) was obtained from MeOH solutions; L′− is the monomethyl maleate(−1) ligand which is formed in situ via the CuII-assisted HL− → L′− transformation. In the case of tptz-containing (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) reaction systems, the CuII-assisted hydrolysis of tptz to pyridine-2-carboxamide (L1) afforded complex [Cu(L1)2(NO3)2] (5). The crystal structures of 1–5 are stabilized by intermolecular hydrogen bonding and π–π stacking interactions. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the ligands.

Graphical abstractThe use of maleamic acid (H2L) in CuII/N,N′,N′′-chelate (bppy, terpy, tptz) reaction systems afforded mononuclear and dinuclear complexes. Interesting CuII-assisted transformation of the maleamate(−1) ion to the monomethyl maleate(−1) ligand and CuII-promoted hydrolysis of 2,4,6-tris(2-pyridyl)-1,3,5-triazine to pyridine-2-carboxamide have been observed.Figure optionsDownload full-size imageDownload as PowerPoint slide