Desenvolvimento de filmes automontados a partir de complexos de metais de transição derivados de um ligante aroilbis(tioureia)

Abstract

The fabrication of thin films has become an increasing demand in various fields of chemistry, enabling the construction of increasingly smaller and more precise devices. Among the self-assembly methods, the Layer-by-Layer (LbL) deposition technique is one of the most powerful tools for building nanoscale films. However, this technique generally employs water-soluble ionic compounds. Aiming to develop a method for constructing nanostructured films using neutral and water-insoluble compounds, this study focused on the synthesis and characterization of Cu(II), Ni(II), Zn(II), and Pd(II) complexes containing a ligand from the aroylbisthiourea class for application in film fabrication using the LbL technique. The ligand N¹,N⁴-bis(diethylcarbamothioyl)terephthalamide (H₂TBT) was used in complexation reactions with NiCl₂∙6H₂O, ZnCl₂, and CuCl₂∙2H₂O in the presence of triethylamine, forming [{M(TBT)}₃] (M = Ni (1), Cu (2) ou Zn (3)) complexes. The reaction of H₂TBT with the precursor [PdCl₂(MeCN)₂], without the addition of a base, resulted in the [{PdCl(HTBT)}₂] (4) complex, which forms the trimeric complex [{Pd(TBT)}₃] (5) upon addition of trietilamine. The synthesized compounds were characterized by techniques such as melting point determination, infrared spectroscopy (FTIR), UV-vis spectroscopy, and cyclic voltammetry. Characterization revealed that the Ni(II), Zn(II), and Cu(II) complexes exhibit a trimeric structure, whereas the Pd(II) complex has a dimeric structure. The compounds 1, 2, 4, and 5 exhibited square-planar geometry, while compound 3 presented tetrahedral geometry. These neutral and water-insoluble compounds 1, 2 and 4 were employed in the fabrication of nanostructured films using the LbL technique, applying sequential deposition of alternating layers to produce films with PAH/PSS/complex and PAH/GO/complex architectures. The UV-vis spectroscopy monitoring of film growth confirmed the feasibility of constructing LbL films with the synthesized compounds, demonstrating the potential of the proposed method. After film fabrication, their feasibility as electrochemical sensors for resorcinol and catechol was evaluated. The films derived from the Cu(II) and Pd(II) complexes exhibited electrochemical activity when used as working electrodes in the presence of catechol, confirming that the methodology developed in this study is suitable for the fabrication of potential sensors.