Synthesis, spectral characterization, crystal structure and antibacterial studies of diorganotin(IV) complexes with isonicotinoyl hydrazone derivatives

Hydrazone-containing organotin(IV) complexes: synthesis, characterization, antimicrobial, antioxidant activity and molecular-docking studies

The diorganotin(IV) complexes (5-20) were synthesized in the present research from 4-fluorophenoxyacetic hydrazide and salicylaldehyde derivatives-based hydrazone ligands (1-4) to get an effective biological agent to combat microbial and oxidant deformities. Numerous spectral techniques such as (1H, 13C, 119Sn) NMR, UV-Vis, IR, and mass spectrometry were executed to illuminate the composition of complexes. These techniques ascertained tridentate chelation of hydrazone ligands with tin metal through enolic, phenolic oxygens and imine nitrogen, revealing pentacoordinated geometry of the complexes. The single crystal XRD of complex (5) confirmed distorted trigonal bipyramidal geometry. The TGA studies showed thermal stability up to 180 °C of the complexes, whereas the low conductance observed pointed to the non-electrolytic nature of the compounds. Furthermore, serial dilution assay was implemented to uncover the microbial inhibition efficacy (against six strains) of the compounds using ciprofloxacin and fluconazole. Among the synthesized compounds, (1, 8) exhibited comparable MIC value to standard. The compound (8) was reported as four times more potent than the fluconazole against C. albicans. Using DPPH assay, the antioxidant efficiency was examined which advocates enhanced efficacy of complexes than the ligands. The potency of complex (8) against C. albicans makes it a point of interest for molecular docking investigation, so, complex (8) and its ligand (1) were studied against protein of C. albicans (5TZ1), revealing the more efficacy of complex (binding energy-11.6 kcal/mol) than ligand. Further, the compounds were analysed for ADME prediction which concluded the efficacy of compounds as orally efficient pharmaceuticals.

Research Progress on the Biological Activities of Metal Complexes Bearing Polycyclic Aromatic Hydrazones

Due to the abundant and promising biological activities of aromatic hydrazones, it is of great significance to study the biological activities of their metal complexes for the research and development of metal-based drugs. In this review, we focus on the metal complexes of polycyclic aromatic hydrazones, which still do not receive much attention, and summarize the studies related to their biological activities. Although the large number of metal complexes in phenylhydrazone prevent them all from being summarized, the significant value of polycyclic aromatic hydrocarbons themselves (such as naphthalene and anthracene) as pharmacophores are also considered. Therefore, the bioactivities of the metal complexes of naphthylhydrazone and anthrahydrazone are focused on, and the recent research progress on the metal complexes of anthrahydrazone by the authors is also included. In terms of biological activities, these complexes mainly show antibacterial and anticancer activities, along with less bioactivities. The present review demonstrates that the structural design and bioactivities of these complexes are fundamental, which also indicates a certain structure-activity relationship (SAR) in some substructural areas. However, a systematic and comprehensive conclusion of the SAR is still not available, which suggests that more attention should be paid to the bioactivities of the metal complexes of polycyclic aromatic hydrazones since their potential in structural design and biological activity remains to be explored. We hope that this review will attract more researchers to devote their interest and energy into this promising area.

Spectroscopic Determination of Dissociation Constants of Some 4- nitrobenzaldehyde-4-substituted phenyl-1-carbonylhydrazones in Sodium Hydroxide Media

Purpose:

Hydrazones are a class of azomethines with a wide spectrum of pharmacological properties which are influenced by pH of the media. The purpose of this study was investigation of acid-base properties of five 4-nitrobenzaldehyde-4-substitutedphenyl1-carbonylhydrazones in sodium hydroxide media (14>pH>7).

Method:

The dissociation process was followed by UV-Vis spectroscopy, in the ethanol-water (V/V, 1:1) solutions, at room temperature. Semiempirical methods AM1 and PM3 were applied for determination of the deprotonation enthalpies.

Results:

The changes in the UV-Vis spectra, as well as the deprotonation enthalpies, suggested that the dissociation process for four investigated hydrazones with an amide group took place in one step. The exception with two dissociation steps was hydrazone with amide and hydroxyl group. The pH region of dissociation was from pH 10.8 to pH 11.6 for the first step and between pH 11.7 and pH 12.1 for the second step of dissociation. The influence of the ethanol on the UV-Vis spectra was eliminated by the method of Characteristic Vector Analyses (CVA). The stoichiometric dissociation constants were determined numerically (pKHA = n·pH + logI) and graphically (intercept of the dependence of logI on pH) from the absorbance data using experimental and reconstructed UV-Vis spectra, at three different ionic strengths. Thermodynamic dissociation constants were estimated graphically as an intercept of dependence of dissociation constant on the square root of the ionic strength.

Conclusion:

The obtained results demonstrated that the influence of the substituents on pKHA values was not significant, except for hydrazone with amide and hydroxyl group. Namely, the dissociation of the amide group of this hydrazone was retarded due to the influence of the phenolic group.

In vitro anti-bacterial and time kill evaluation of binuclear tricyclohexylphosphanesilver(I) dithiocarbamates, {Cy3PAg(S2CNRR')}2

Four binuclear phosphanesilver(I) dithiocarbamates, {cyclohexyl₃PAg(S₂CNRR')}₂ for R = R' = Et (1), CH₂CH₂ (2), CH₂CH₂OH (3) and R = Me, R' = CH₂CH₂OH (4) have been synthesised and characterised by spectroscopy and crystallography, and feature tri-connective, μ₂-bridging dithiocarbamate ligands and distorted tetrahedral geometries based on PS₃ donor sets. The compounds were evaluated for anti-bacterial activity against a total of 12 clinically important pathogens. Based on minimum inhibitory concentration (MIC) and cell viability tests (human embryonic kidney cells, HEK 293), 1-4 are specifically active against Gram-positive bacteria while demonstrating low toxicity; 3 and 4 are active against methicillin resistant S. aureus (MRSA). Across the series, 4 was most effective and was more active than the standard anti-biotic chloramphenicol. Time kill assays reveal 1-4 to exhibit both time- and concentration-dependent pharmacokinetics against susceptible bacteria. Compound 4 demonstrates rapid (within 2 h) bactericidal activity at 1 and 2 × MIC to reach a maximum decrease of 5.2 log₁₀ CFU/mL against S. aureus (MRSA).

N'-[1-(5-Bromo-2-hy-droxy-phen-yl)ethyl-idene]isonicotinohydrazide monohydrate: crystal structure and Hirshfeld surface analysis

In the title isonicotinohydrazide hydrate, C14H12BrN3O2·H2O {systematic name: N'-[(1E)-1-(5-bromo-2-hy-droxy-phen-yl)ethyl-idene]pyridine-4-carbohydrazide monohydrate}, the central CN2O region of the organic mol-ecule is planar and the conformation about the imine-C=N bond is E. While an intra-molecular hy-droxy-O-H⋯N(imine) hydrogen bond is evident, the dihedral angle between the central residue and the benzene rings is 48.99 (9)°. Overall, the mol-ecule is twisted, as seen in the dihedral angle of 71.79 (6)° between the outer rings. In the crystal, hydrogen-bonding inter-actions, i.e. hydrazide-N-H⋯O(water), water-O-H⋯O(carbon-yl) and water-O-H⋯N(pyrid-yl), lead to supra-molecular ribbons along the a-axis direction. Connections between these, leading to a three-dimensional architecture, are mediated by Br⋯Br halogen bonding [3.5366 (3) Å], pyridyl-C-H⋯O(carbon-yl) as well as weak π-π inter-actions [inter-centroid separation between benzene rings = 3.9315 (12) Å]. The Hirshfeld surface analysis reveals the importance of hydrogen atoms in the supra-molecular connectivity as well as the influence of the Br⋯Br halogen bonding.

Synthesis and antimicrobial activity of tetradentate ligands bearing hydrazone and/or thiosemicarbazone motifs and their diorganotin(IV) complexes

Four novel ligands derived from 2,3-butanedione have been synthesized, two dissymmetric thiosemicarbazone/3-hydroxy-2-naphthohydrazone ligands, H₂L¹ (bearing 4-isopropyl-3-thiosemicarbazone) and H₂L² (containing 4-cyclohexyl-3-thiosemicarbazone) and the symmetric H₂L³, diacetyl bis(3-hydroxy-2-naphthohydrazone), and H₂L⁴, diacetyl bis(4-cyclohexyl-3-thiosemicarbazone). Their reactivity with SnR₂Cl₂ (R=methyl, n-butyl and phenyl) was explored and the resulting complexes were characterized by elemental analysis, molar conductivity, mass spectrometry, IR, ¹H, ¹³C and ¹¹⁹Sn NMR and seven of them also by single crystal X-ray diffraction. The results showed that the reactivity of the dissymmetric ligands is strongly different and while the cyclohexyl derivative is very stable, with isopropyl easily undergoes a symmetrization reaction to yield the corresponding symmetric ligands. The antimicrobial activity of the ligands and the corresponding diorganotin(IV) complexes was investigated in vitro against seven species of microorganisms and minimum inhibitory concentrations (MICs) were determined. The results showed that the ligand H₂L² and several of its derivatives, together with methyl and phenyl complexes of H₂L¹, have the ability of inhibiting the growth of tested bacteria and fungi to different extents. Bacillus subtilis and Staphylococcus aureus Gram positive strains were the most sensitive microorganisms.

Crystal structures of (E)-N'-(2-hy-droxy-5-methyl-benzyl-idene)isonicotinohydrazide and (E)-N'-(5-fluoro-2-hy-droxy-benzyl-idene)isonicotinohydrazide

Two derivatives of the well-known iron chelator, (E)-N'-(2-hy-droxy-benzyl-idene)isonicotinohydrazide (SIH), substituted in the 5-position of the 2-hy-droxy-benzene ring by a methyl and a fluorine group viz. (E)-N'-(2-hy-droxy-5-methyl-benzyl-idene)isonicotinohydrazide, C14H13N3O2, (I), and (E)-N'-(5-fluoro-2-hy-droxy-benzyl-idene)isonicotinohydrazide, C13H10FN3O2, (II), have been prepared and characterized by single-crystal X-ray diffraction, (1)H NMR and mass spectrometry. The mol-ecules of both compounds deviate slightly from planarity [r.m.s. deviations are 0.145 and 0.110 Å for (I) and (II), respectively] and adopt an E conformation with respect to the double bond of the hydrazone bridge. In each mol-ecule, there is an intra-molecular O-H⋯N hydrogen bond forming an S(6) ring motif. The dihedral angles between the mean planes of the isonicotinoyl ring and the cresol ring in (I) or the fluoro-phenol ring in (II) are 10.49 (6) and 9.43 (6)°, respectively. In the crystals of both compounds, zigzag chains are formed via N-H⋯N hydrogen bonds, in the [10-1] direction for (I) and [010] for (II). In (I), the chains are linked by weak C-H⋯π and π-π stacking inter-actions [centroid-to-centroid distances = 3.6783 (8) Å; inter-planar angle = 10.94 (5)°], leading to the formation of a three-dimensional supra-molecular architecture. In (II), adjacent chains are connected through C-H⋯O hydrogen bonds to form sheets parallel to (100), which enclose R 4 (4)(30) ring motifs. The sheets are linked by weak C-H⋯π and π-π [centroid-to-centroid distance = 3.7147 (8) Å; inter-planar angle = 10.94 (5)°] inter-actions, forming a three-dimensional supra-molecular architecture.

Synthesis and spectroscopic characterization of diorganotin(iv) complexes of N′-(4-hydroxypent-3-en-2-ylidene)isonicotinohydrazide: chemotherapeutic potential validation by in vitro interaction studies with DNA/HSA, DFT, molecular docking and cytotoxic activity

A diorganotin(iv) hydrazide complex as a potential cancer chemotherapeutic agent targeting DNA using the carrier protein HSA.