New copper(II), nickel(II) and zinc(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidines and the chelating ligand 1,3-propanediamine: An unexpected coordination behavior for the 7-amine-derivative

Five new metal complexes with the metal ions Cu(II), Ni(II) and Zn(II) and containing 1,2,4-triazolo[1,5-a]pyrimidine derivatives and 1,3-propanediamine (tn) are described. The structural morphology of these coordination compounds depends on the triazolopyrimidine derivative used, being mononuclear for 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp) and 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO), and 1D-polymeric for 7-amine-1,2,4-triazolo[1,5-a]pyrimidine (7atp). In the 7atp case, this ligand does not coordinate through N3 atom, as expected, but through N1, N4 and N71 in a bridging fashion. This unexpected coordination mode seems to be induced by the stability of the polynuclear metal complex in presence of tn ligand. All isolated metal complexes have been characterized by single-crystal X-ray diffraction, IR and UV–Vis spectroscopies, and EPR measurements. Moreover, luminescence measurements have been carried out for 7atp ligand and its polynuclear complex with Zn(II).

Graphical abstractFive transition metal complexes containing 1,2,4-triazolo[1,5-a]pyrimidine derivatives and the chelating ligand 1,3-propanediamine (tn) have been synthesized and fully characterized. The structural morphology of these coordination compounds depends on the triazolopyrimidine derivative used being their coordination mode affected by the presence of tn. These results support the use of several auxiliary ligands to try modulating the 1,2,4-triazolo[1,5-a]pyrimidines coordination with several metal ions in order to obtain new metal–organic systems which show striking structural features and physical properties.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Transition metal complexes with some nucleobase-analogs: 5 and/or 7-substituted-1,2,4-triazolo[1,5-a]pyrimidines. ► Auxiliary ligand influence in the bridging mode of 1,2,4-triazolo[1,5-a]pyrimidines. ► Rare bridging action of 7-amine-1,2,4-triazolo[1,5-a]pyrimidine. ► Firstly studied NMR spectra and luminescent properties of 7atp and their complexes.