Palladium(II) chloride complexes with 1,2,4-triazolo[1,5-a]pyrimidines: X-ray, 15N–1H NMR and 15N CP MAS studies

Abstract

The crystal structure of [Pd(dbtp) 2 Cl 2 ]ؒ0.5 C 2 H 5 OH 4c was resolved by X-ray diffraction analysis, exhibiting monomeric, nearly square-planar cis geometry and N(3) co-ordination. A small tetrahedral distortion from the co-ordination plane was observed. The Pd-Cl distances are 2.276(1) and 2.283(1) Å, and Pd-N 2.042(3) and 2.040(3) Å. Spectroscopic measurements (UV-VIS, IR, NMR) suggested analogous structures for 1, 2 and 3. Compounds 4a and 4b are most likely rotational isomers in solution and distortional isomers in the solid state. 15 N-1 H heteronuclear correlation NMR was measured for 2, 4a and 4b whereas 1 and 3 were characterized with 13 C and 15 N CP MAS. Significant shielding of the co-ordinated N(3) and adjacent C(2) or C(3a) nuclei was observed.

Spectroscopic Characterization,In VitroCytotoxicity, and Antioxidant Activity of Mixed Ligand Palladium(II) Chloride Complexes Bearing Nucleobases

“…As shown in Table 3, the NH 2 cytosine protons of cis-[PdCl 2 (Gua)(Cyt)] which are directly adjacent to the coordinating N3 ring nitrogen show a downfield shift from 7.06 to 7.70 ppm in the complex. Similarly, the NH 2 protons of guanine observed in the free ligand at 5.57 ppm was shifted to 5.95 ppm showing that these protons experienced strong deshielding effects upon complexation [37]. Similar chemical shifts were observed for the remaining protons as shown in Table 3.…”

“…respectively [37]. These transitions confirm the square planar (D 4h ) geometry of the Pd(II) ion [31].…”

Synthesis, characterization, crystal structures and in vitro antistaphylococcal activity of organotin(IV) derivatives with 5,7-disubstituted-1,2,4-triazolo[1,5-a]pyrimidine

“…The IR spectra of the complexes have been examined in comparison with the spectra of the free ligands [33]. The two most characteristic bands in the IR spectra of dbtp and dptp, assigned to an overall triazolopyrimidine and pyrimidine ring mode vibrations, ν tp (1615 and 1612 cm − 1 ) and ν py (1530 and 1543 cm − 1 ), are generally moved to higher frequencies in transition metal complexes [34,35].…”

Synthesis, spectroscopic characterization and in vitro antimicrobial activity of diorganotin(IV) dichloride adducts with [1,2,4]triazolo-[1,5-a]pyrimidine and 5,7-dimethyl-[1,2,4]triazolo-[1,5-a]pyrimidine

“…1) is recognized as the main coordination behaviour of tp and dmtp [1]. It has been observed that the coordination of metal ions through N(3) results in a shift of m tp and m py bands, assigned to triazolopyrimidine and pyrimidine ring mode vibrations, respectively, usually towards higher frequencies [11][12][13][14][15][16][17][18]. The shifts observed in the spectra of our complexes, reported in Table 1, are consistent with N(3) coordination of the organotin(IV) 2 points out that this compound assumes a lower symmetry structure (see Table 2).…”