Synthesis, Structural Elucidation, Biocidal and Preliminary DNA Interaction Studies of Organotin(IV) Complexes with [O,O] and [O,N,O] Donor Ligands

Abstract

In the present study, thirteen novel [O,O] and [O,N,O] potential donor ligands were synthesized by reaction of salicylaldehyde and substituted salicylaldehyde with tranexamic acid, hydrazides and dihydrazides in ethanol. The di- and triorganotin(IV) derivatives of these compounds have also been obtained in good yields by refluxing the compound or its sodium/triethylammonium salt and the respective organotin(IV) chlorides/oxides/dihydroxidechloride in dry toluene for 8-10 hours. The ligands were 4-((5-bromo-2-hydroxybenzylideneamino)methyl)cyclohexanecarboxylic acid (H2La) 4-((1-(2-hydroxyphenyl)ethylideneamino)methyl)cyclohexanecarboxylic acid (H2Lb), 4-((1-(5-bromo-2-hydroxyphenyl)ethylideneamino)methyl)cyclohexanecarboxylic acid (H2Lc), N′-(2-hydroxybenzylidene)formohydrazide (H2Ld), N′-(5-bromo-2- hydroxybenzylidene)formohydrazide (H2Le), N′-(2-hydroxy-3-methoxybenzylid- f ene)formohydrazide (H2L ), N′-(4-(diethylamino)-2-hydroxybenzylidene)formohyd- razide (H2Lg), N′-(2-hydroxynaphthalen-1-yl)methylene)formohydrazide (H2Lh), N′- (1-(5-bromo-2-hydroxyphenyl)ethylidene)formohydrazide (H2Li), N′-(2-hydroxyben- zylidene)-4-tert-butylbenzohydrazide (H2Lj), N1′, N6′-bis(2-hydroxyben-zylidene)- adipohydrazide (H4Lk), N1′, N6′-bis(5-bromo-2-hydroxybenzylidene)adipohydrazide (H4Ll), N1′, N6′-bis(2-hydroxy-3-methoxybenzylidene)adipohydrazide (H4Lm) and N1′, N4′-bis(2-hydroxybenzylidene)succinohydrazide (H4Ln). A variety of spectroscopic techniques like FT-IR, multinuclear NMR spectroscopy (1H, 13 C and 119 Sn) and mass spectrometry were used to ascertain the structure, coordination mode of ligands and geometry of tin in the synthesized complexes. The solid state structures were also studied by performing single crystal X-ray analyses. The results revealed that in case of [O,O] donor ligands, the coordination to the tin atom is through the COO moiety. The triorganotin(IV) derivatives demonstrate trigonal bipyramidal geometry in the solid and tetrahedral in the solution state with few exceptions. All diorganotin(IV) derivatives with [O,N,O] donor ligands retain their geometry as trigonal bipyramid in solid as well as in solution. The complexes were screened for cytotoxicity, antifungal, antibacterial, antiurease, and leishmanicidal activities. The triorganotin(IV) derivatives of [O,O] donor ligands and dibutyl(IV) complexes in case of [O,N,O] donor ligands exhibit iii reasonable biocidal activities. Most complexes were more active than the corresponding free ligands. The interaction of R2SnLd (R = −CH3, n−C4H9, and −C6H5) with DNA were investigated by cyclic voltammetry (CV) and UV-Vis spectroscopy. The diffusion coefficient of the free and DNA bound complexes were determined by the Randles-Sevcik equation. The positive peak potential shift in CV suggests an intercalative mode of interaction for these complexes with DNA. The CV results revealed the following decreasing order of binding strengths: (C4H9)2SnLd (1.69 x 104) > (C6H5)2SnLd (1.10 x 104) > (CH3)2SnLd (9.61 x 103) M-1. The results are also supported by the UV-Vis spectroscopic data. The negative values of ∆G indicate the spontaneous nature of this interaction.