Development of new thiazole‐guanidine complexes as rapid and recoverable catalysts for the synthesis of 6‐piperidin‐dihydro‐thia‐hexaaza‐s‐indacene derivatives supported by DFT studies

Abstract

In this study, the focus was on synthesizing metal chelates of Fe(III), Ni(II), and Pd(II) using thiazole‐guanidine derivatives. Various spectral and analytical methods were employed to elucidate the structural characteristics and determine the molecular formulae of these metal chelates, including infrared (IR(, 1H‐NMR and 13C‐NMR, ultraviolet–visible (UV–vis), CHN, XRD data, mass spectrometry, thermal conduction, and measures of magnetism, were used to clarify the structures of these compounds. The optimized molecular structures have been scrutinized by the DFT method. Correlation between all spectroscopic methods and DFT calculation revealed an octahedral‐coordinating environment surrounding the Fe3+ ion, [Fe (BTG)2(NO3)2].NO3.2H2O and Ni2+, [Ni (BTG)2(NO3)2].H2O cation and distorted square planner surrounding Pd2+, [Pd (BTG) (COOCH3)2].2H2O cation. The examination of the stability and stoichiometry of complexes in solution using conventional techniques has been incorporated into the investigation's scope. Under mild reaction conditions, the green technique was employed to carry out a condensation reaction for aromatic aldehyde, rhodanine, pipredine, and 5‐aminotetrazol to generate derivatives of 6‐piperidin‐dihydro‐thia‐hexaaza‐s‐indacene derivatives. In comparison to our new complexes, all reaction conditions were optimized for those variable Lewis acid catalysts. In general, tests conducted under high yield, speedy, and environmentally friendly solvent (H2O/EtOH) conditions, the BTGPd catalyst showed superiority over others. Additionally, the hetero‐catalyst recovery proved successful and could be employed with the same efficiency up to six times before the efficiency started to decrease. The effectiveness of this catalytic procedure was validated through a thorough examination using density functional theory (DFT). The DFT analysis showcased the distinctive characteristics of this complex and proposed logical mechanisms that elucidated the crucial physical parameters responsible for the superior catalytic performance of the Pd(II) complex.