The Usefulness of Density Functional Theory To Describe the Tautomeric Equilibrium of 4,6-Dimethyl-2-mercaptopyrimidine in Solution

Abstract

The tautomeric forms of 4,6-dimethyl-2-mercaptopyrimidine in solution were examined. Experimental support for the existence of the tautomeric forms of this molecule was provided by infrared (FTIR), ultraviolet (UV), and nuclear magnetic resonance (NMR) techniques. Density functional theory (DFT) calculations allowed us to elucidate these molecular structures. The vibrational and electronic spectra, as well as the 1H and 13C chemical shifts, were satisfactorily described by DFT theoretical calculations. The potential of the DFT methodology was confirmed by prediction of a band at 2706 cm-1, associated with the stretching vibration of −SH group, which did not appear in the experimental spectrum because it was overshadowed by the symmetric and antisymmetric vibration modes of −CH3 groups. The existence of the tautomeric thiol−thione equilibrium of 4,6-dimethyl-2-mercaptopyrimidine with the thione structure dominating in polar solvents (CH3OH and DMSO-d 6) and the thiol structure in apolar media (cyclohexane) has been demonstrated.

Ruthenium(II)/4,6-dimethyl-2-mercaptopyrimidine complexes: Synthesis, characterization, X-ray structures and in vitro cytotoxicity activities on cancer cell lines

“…For both complexes their IR spectra confirm the presence of the SpymMe 2 ligand coordinated to the metal. The band attributable to the m(N-H), which appears at 3200-3100 cm À1 in free thiones is absent in the spectra of the complexes, indicating that the SpymMe 2 is coordinated in the deprotonated form [39,40]. Bands from the coordinated ligand , both of very low intensities and a third one, of higher intensity, at 1110 mV, which could correspond to the oxidation of the free NO generated in the electrochemical process [43,44].…”

Oxidation reactions catalysed by molybdenum(VI) complexes grafted on UiO‐66 metal–organic framework as an elegant nanoreactor

“…The oxidation of cyclooctene was chosen as a model reaction for checking the reusability of UiO-66-Mo(CO) 3 . At the end of the reaction, the catalyst was recovered by filtration washed with Et 2 O and dried at 100°C.…”

“…[1][2][3] However, as homogeneous catalysts, their applicability is limited due to poor catalyst separation and reusability. To solve this problem, the catalysts are 'heterogenized' by immobilization onto various organic and inorganic supports.…”

“…A heterogeneous catalyst was synthesized by immobilizing Mo(CO) 3 in a UiO-66 metal-organic framework. The benzene ring of the organic linker in UiO-66 was modified via liquid-phase deposition of molybdenum hexacarbonyl, Mo(CO) 6 , as starting precursor to form the (arene)Mo(CO) 3 species inside the framework.…”

“…The benzene ring of the organic linker in UiO-66 was modified via liquid-phase deposition of molybdenum hexacarbonyl, Mo(CO) 6 , as starting precursor to form the (arene)Mo(CO) 3 species inside the framework. The structure of this catalyst was characterized using X-ray diffraction, and chemical integrity was confirmed using Fourier transform infrared and diffuse reflectance UV-visible spectroscopic methods.…”