Complexes R2Sn(IV)L with Tridentate O,N,O'-Donor Schiff Bases: Photophysical Properties and Biological Activity

New tin(IV) complexes (Lⁿ)SnR₂ (R = n-Bu (I, II), t-Bu (III–V), and Ph (VI)) with O,N,O'-donor Schiff bases are synthesized. The molecular structures of compounds I and IV in the crystalline state are determined by XRD (CIF files CCDC nos. 2309864 (I) and 2309422 (IV)). The photophysical properties of the complexes are studied in comparison with the previously synthesized compounds containing phenyl or ethyl hydrocarbon groups at the tin atom. All compounds luminesce in chloroform: the emission bands are observed in the range from 580 to 638 nm. Both the groups at the tin atom and nature of the substituents in Schiff bases significantly affect the relative quantum yield. The anti/prooxidant activity of (Lⁿ)SnR₂ in the reactions with the ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) radical cation and superoxide radical anion, in the oxidative DNA damage, and during lipid peroxidation in vitro is studied. A weak antibacterial activity against the bacterial strains Staphylococcus aureus ANCC 6538 and E. faecium ATCC 3576 are observed for some compounds. The in vitro antiproliferative properties for a number of the complexes are studied for the HTC-116 and А-549 cancer cell lines. The coordination of the organometallic fragment with the O,N,O'-tridentate ligands is found to induce a pronounced decrease in the cytotoxicity of the complexes.