New Gd(I)/Cs(III) complexes of benzil‐based thiocarbohydrazone macrocyclic ligand: Chemical synthesis, characterization, and study their biological effectiveness as antibacterial, antioxidant, and antiviral additives for polyurethane surface coating

Abstract

Germs are transmitted in different ways and remain viable or infectious on metal, glass, wood, fabrics, and plastic surfaces for prolonged periods of time. Thus, sterilizing commonly handled everyday objects and public places with high contamination potential is a major global strategy to combat the spread of pathogenic microorganisms. Consequently, our response is development of durable surface‐active coating embedded with new Gd(I)/Cs(III) complexes that derived from condensation of thiocarbohydrazide and benzil precursors. Chemical structures of these complexes were elucidated by Fourier transform infrared (FTIR), electron impact ionization (EI‐MS), 1H nuclear magnetic resonance (NMR), elemental analysis, and scanning electron microscopy (SEM). Next, the well‐established complexes were physically mixed with wide‐range applicable polyurethane (PU) varnish as potential biocide agents. With laboratory scale, coating material was loaded into stainless steel and wood panels to evaluate the physical and mechanical properties. In comparison with the blank formulation, our additives enhanced the gloss levels of the developed PU from 75 to 80 gloss unit (GU), and the scratch hardness was increased to reach >2 kg. Meanwhile, all the coated films passed the flexibility bend test and showed none flaking in mechanical adhesion test. Consequently, Gd(I) and Cs(III) metal complexes did not show any undesirable side effects on PU coating performance. Concerning biological screening, macrocyclic Gd(I) and Cs(III) complexes as well as the reformulated PU varnish were assayed for their antibacterial, antioxidant, and antiviral activities. Antibacterial activity of the developed PU was slightly increased than the individual treatments of Gd(I)/Cs(III) complexes by 1–2 mm, although the blank PU showed no obvious activity against all the tested bacterial strains. Antiviral overall results indicated that the Gd(I) and Cs(III) complexes demonstrated higher activity than the developed PU samples against ADeno‐7, CV‐B4, and HSV‐1 viruses in all modes of action, and hence these coordinated compounds could be promising virucidal agents with good biocompatibility.