Luminescent Silk Fibroin with Organotin Compounds from Amino Acid Schiff Bases – Microwave‐Assisted Synthesis, Chemo‐Optical Characterization, Cytotoxicity, and Confocal Microscopy

In this work we report the microwave-assisted synthesis of six new pentacoordinate and chiral organotin compounds 1-6 derived from amino acid based Schiff bases. The syntheses were carried out by multicomponent reactions (MCRs) from L-amino acids (tryptophan, tyrosine, and phenylalanine), 2-hydroxy-1-naphthaldehyde and the corresponding diorganotin oxide (R2SnO, R = nBu or Ph). These compounds were characterized by using NMR (1H, 13C, and 119Sn), HRMS, UV-Vis, and fluorescence spectroscopy. All compounds exhibited in solution fluorescence with quantum yields (Φ) in the range of 0.08 to 0.21. Cytotoxicity activity shows that the compounds 1-6 at 0.1 µg mL-1 are practically harmless to melanoma B16F10 cells. The fluorescent staining ability of organotin compounds toward the silk fibroin was carried out by immersion method and analysed by confocal microscopy which showed the efficient and uniform integration of the luminescent compounds. Also, DFT calculations of truncated organotin-fibroin complex interactions are reported.