Study of vibrational spectra and donacity of some sulphur-nitrogen compounds containing; thiocarbonyl grouping

Abstract

The infrared and Raman spectra of 1,3,4,6-tetrahydropyrimidine-2-thione (tpt) and -2-one (tpo) are studied. The infrared spectra of oriented polycrystalline samples of tpt and imidazolidine-2-thione (ethylenethiourea, etu) in polarized radiation are investigated. The band assignments proposed for tpt are supported by the spectra of N,N'-dideuterated and S-methylated compounds. The complexes of tpt with Cu(II), Zn(II), Cd(II) and Hg(II) chlorides and bromides are synthesized and characterized by infrared and carbon-13 spectroscopy; bonding of the ligand in all the complexes is inferred to be through the thiocarbonyl sulfur. Synthesis of pyrimidine-2-selone (pymse) is reported. It is characterized by chemical analysis, mass spectrum, infrared, proton and carbon-13 NMR spectra. Infrared spectra of pyrimidine-2-selone and the Raman and infrared spectra of pyrimidine-2-thione (pymt) have been measured. The advantage of S-methylation and N-deuteration has been taken into account. The characteristic thioureide vibrations of pymt have been assigned by comparison with the spectrum of the selenium compound. The vibrational assignments are discussed by analogies with the spectra of related molecules. The C=S and C=Se stretching frequencies of pymt and pymse are located at 750 and 665 cm?¹ respectively. The metal ion interactions of pymt with Cu(II), Zn(II), Cd(II) and Hg(II) chlorides and bromides have been investigated. The metal complexes are investigated by infrared, proton and carbon-13 NMR spectroscopy. The results are consistent with the bonding of the ligand through sulfur and the non-protonated ring nitrogen to give a four-membered chelate ring. The complexes with deprotonated pymt have also been investigated. The infrared and Raman spectra of pyridine-2-thione (2-pyt) and the infrared spectra of pyridine-4-thione (4-pyt) have been measured in the range 4000–200 cm?¹. The polarized infrared spectra of polycrystals of 2-pyt have also been obtained. The assignment of the vibrations has been further supported by Raman depolarization measurements in chloroform. The infrared spectra of 2-pyt in chloroform reveal the existence of hydrogen-bonded dimers consistent with its structure in the solid state. The characteristic thioamide and ring vibrations of 2-pyt are assigned on the basis of C? symmetry point group of the dimer and of 4-pyt according to the molecular point group C?v. The assignments are supported by N-deuterium labelling as well as S-methylation and analogies with the spectra of 2- and 4-substituted pyridines. The metal ion interaction of 2-pyt and 4-pyt with Cu(II), Zn(II), Cd(II) and Hg(II) chlorides and bromides have been investigated. The metal complexes obtained are studied by infrared, proton and carbon-13 NMR spectroscopy. The perturbation of infrared bands of the ligands on complexation is discussed on the basis of the proposed assignments. The results are consistent with the bonding of the ligands through sulfur in all the cases. The metal complexes with deprotonated 2-pyt have also been studied. Here 2-pyt acts as a bidentate chelate coordinating through nitrogen and sulfur. The infrared and Raman spectra of N-(2-pyridyl)thioformamide (NPTF) and N-(2-pyridyl)thioacetamide (NPTA) have been investigated. The characteristic thioamide and pyridine ring vibrations are assigned. The assignments are supported by means of the spectra of N-deuterated compounds and comparison with related compounds. Proton NMR studies indicate NPTF to have a cis -CSNH- grouping and NPTA a trans -CSNH- grouping at ambient temperature. The complexes of NPTF and NPTA with Cu(II), Zn(II) and Cd(II) halides have been prepared and characterized by means of infrared and proton NMR spectroscopy. The results are concordant with the bidentate chelation of the ligands to metal through pyridine nitrogen and thioamide sulfur.