Heteronuclear multiple-quantum correlation 15N–1H, cross-polarized magic angle spinning 13C, 15N nuclear magnetic resonance and infrared spectroscopic studies of 1,2,4-triazolo-[1,5α]-pyrimidine and its Zn(II) halide and thiocyanate complexes

1,2,4-Triazolo-[1,5α]-pyrimidine (tp) was studied by gradient heteronuclear multiple-quantum correlation 15N–1H NMR and by cross-polarized magic angle spinning 13C, 15N NMR. The 15N signals were unambiguously assigned. The assignments of some IR absorption bands were proposed by comparison to purine and adenine spectra. The obtained results were used for the investigation of Zn(tp)2X2-type complexes (X=Cl, Br, I, NCS), suggesting a pseudo-tetrahedral configuration around the Zn(II) ion with unidentately N(3) bonded heterocycles and halides or thiocyanates (N bonded) in terminal positions. A slight shielding effect on the N(3) nucleus upon the formation of Zn(II)–N coordination bonding was observed.