Carboxylate Oxygen Atoms Research Articles

Using Atomic Charges to Describe the pKa of Carboxylic Acids.

In this study, we present an accurate protocol for the fast prediction of pKa's of carboxylic acids based on the linear relationship between computed atomic charges of the anionic form of the carboxylate fragment and their experimental pKa values. Five charge descriptors, three charge models, three solvent models, gas-phase calculations, several DFT methods (a combination of eight DFT functionals and fifteen basis sets), and four different semiempirical approaches were tested. Among those, the best combination to reproduce experimental pKa's is to compute the natural population analysis atomic charge using the solvation model based on density model at the M06L/6-311G(d,p) level of theory and selecting the maximum atomic charge on the carboxylic oxygen atoms (R2 = 0.955). The applicability of the suggested protocol and its stability along geometrical changes are verified by molecular dynamics simulations performed for a set of aspartate, glutamate, and alanine peptides. By reporting the calculated atomic charge of the carboxylate form into the linear relationship derived in this work, it should be possible to accurately estimate the amino acid's pKa's in a protein environment.

Investigation of intermolecular interactions between [Ho(H2O)8]4+ based 3D metal-organic supramolecular host and bipyridyl guest through crystal structure and Hirshfeld surface analysis

A new supramolecular metal-organic complex 1, [{Ho(H2O)8}4+(TBTA)(bipy)] (where H2TBTA = tetrabromoterephthalic acid and bipy = 4,4'-bipyridyl), has been synthesized hydrothermally at 100 °C by mixing the reactants in stoichiometric ratio. The complex was characterized by single crystal X-ray diffraction (SC-XRD) along with powder X-ray diffraction (PXRD) and other spectroscopic analyses. Structural analysis reveals that 1 crystallized in the tetragonal space group I4cm and is a mononuclear complex. Ho4+ presents octa-coordinated square antiprism geometry having eight coordinated water molecules. Hydrogen bonding interactions between the coordinated water molecules and carboxylate oxygen atoms of TBTA (doubly deprotonated form of H2TBTA) anions form 3D supramolecular metal-organic host (MOSH) having 2D square grid-like supramolecular channels. Guest bipy molecules get stability within the channels through supramolecular π···π interactions between the bipy and TBTA anions. Hirshfeld surface analysis and corresponding 2D fingerprint plots correlate with the experimental findings. C···C short contact, corresponding to π···π interactions, contributes around 10.7% to the total surface.

Synthesis, characterization, in-vitro anti-inflammatory and antimicrobial screening of metal(II) mixed diclofenac and acetaminophen complexes

Mixed ligand complexes derived from diclofenac potassium salt (Kdc) and acetaminophen (ace) has been synthesized and proposed to have a general formula [MB] where M = Co2+, Ni2+, Cu2+ and Zn2+and B = (ace)(dc)(H2O)2 except for Mn2+ complex which exists as [Mn(ace)(dc)OH2]. The complexes were characterized by solubility, melting point, conductivity, elemental analyses, UV-Vis, FT-IR spectroscopy, X-ray powder diffraction (XRPD) study and magnetic susceptibility measurement. Electronic absorption spectra data are characteristic of octahedral structures for [MB]. The IR spectra revealed a bidentate coordination mode. In acetaminophen, the nitrogen and carbonyl-O atoms of the amide group were involved while the carboxylate oxygen atoms of potassium diclofenac were used; typical of a carboxylic acid derivative. The compounds were screened for in-vitro anti-inflammatory activity by inhibition of albumin denaturation assay and antimicrobial activity against bacteria strains: Bacillus subtilis, Bacillus anthrax, Escherichia coli, Salmonella typhi and a fungus Aspergillus niger. Some of the tested compounds showed moderate anti-inflammatory activity when compared to the standard drug diclofenac potassium salt. The in-vitro antimicrobial screening revealed an increased activity of the complexes against the bacteria isolates compared to the free ligands.
 
 KEY WORDS: Metal(II) ion, NSAIDs, Anti-inflammatory activity, Diclofenac potassium salt, XRPD, Antimicrobial activity
 
 Bull. Chem. Soc. Ethiop. 2021, 35(1), 77-86.
 DOI: https://dx.doi.org/10.4314/bcse.v35i1.6

Tridentate imidazole-based Schiff base metal complexes: molecular docking, structural and biological studies

A novel Schiff base was synthesized by the condensation of imidazole-2-carboxaldehyde with l-histidine in an equimolar ratio. The prepared Schiff base was characterized by elemental analysis and spectral characterization techniques. It was then complexed with a series of 3-d metal(II) ions like manganese, iron, cobalt, nickel, copper and zinc. The coordination properties, nature of bonding and stability of the complexes were deduced from elemental analysis, IR, UV–vis, 1H NMR, mass, electronic spectra, magnetic, conductivity and thermogravimetric analysis. IR studies support the tridentate behaviour of Schiff base as well as its coordination to the central metal ion through an azomethine nitrogen, deprotonated carboxylic oxygen and imidazole ring nitrogen atoms of histidine. The electronic spectra and magnetic moment data demonstrate that the complexes have an octahedral geometry, except zinc complex, which has a tetrahedral geometry. In vitro antimicrobial activity of the synthesized compounds has been shown to exhibit excellent antibacterial and antifungal activities. The antibacterial property of the prepared Schiff base was further confirmed by conducting a docking study of target proteins involved in the antibacterial mechanism. Communicated by Ramaswamy H. Sarma

A series of multi-responsive viologen-based alkaline-earth metal coordination complexes: Thermochromism, photochromism, and vapochromism

Due to their external stimuli responsive properties, chromic materials have attracted considerable interest in various fields. In this work, a series of alkaline-earth metal based coordination complexes constructed from viologen derivative, [Mg(H2O)6·(bdpbpy)·H2O] (1), [Ca(bdpbpy)(H2O)4] (2), [Sr(bdpbpy)(H2O)4] (3), [Ba(bdpbpy)(H2O)4] (4), (H4bdpbpy·2Cl = 1,1-bis(3,5-dicarboxyphenyl)-4,4-bipyridinium chloride) have been synthesized and characterized by elemental analyses, FT-IR spectroscopy, single-crystal X-ray diffraction, and thermogravimetric analysis. Because of electron transfer between the oxygen atom of carboxylate and bipyridinium moieties, compounds 1–4 exhibit reversible thermochromic and photochromic properties upon thermo treatment or Uv-vis irradiation. Due to presence of electron-deficient bipyridinium moieties (Lewis acidic sites), these compounds can be used as potential colorimetric sensor for ethanediamine vapor detection. The multi-responsive performances of compounds 1–4 can widen their applications in some particular systems that call for color changing properties of external stimuli.

Structural Studies of Donor‐Free and Donor‐Solvated Sodium Carboxylates

AbstractFocusing mainly on sodium 2‐ethylhexanoate, this study reveals that the carboxylate exists as a dimer in MeOD solution as evidenced by Diffusion Ordered NMR SpectroscopY (DOSY). Two crystalline varieties with distinct polymeric structures have been synthesised and crystallographically characterised. A mixed 1,10‐phenanthroline–water solvate [{(C5H10)(C2H5)COONa.(H2O)[1,10‐phen]}2]∞ contains dimeric [Na(OH2)]2 subunits, which propagate through hydrogen bonds between O atoms of the carboxylate and OH water bonds. Adjacent polymeric chains interdigitate with each other through π−π interactions between 1,10‐phen rings. Solvent‐free sodium 2‐ethylhexanoate has five‐coordinate cations comprising one bidentate chelating and three monodentate carboxylate oxygen atoms. Here, the packing arrangement is different with the central hydrophilic (NaO2)∞ core surrounded by a wrapping of disordered alkyl groups. A similar polymeric structure is observed for the crystalline DMSO‐solvated sodium valproate [{(C3H7)(C4H8)COONa.(DMSO)}]∞. This adopts a layered arrangement comprising alternating sodium carboxylate hydrophilic layers and hydrophobic organic bilayers.

Luminescent lanthanide(III) complexes of DTPA-bis(amido-phenyl-terpyridine) for bioimaging and phototherapeutic applications

We report here a series of coordinatively-saturated and thermodynamically stable luminescent [Ln(dtntp)(H2O)] [Ln(III) = Eu (1), Tb (2), Gd (3), Sm (4) and Dy (5)] complexes using an aminophenyl-terpyridine appended-DTPA (dtntp) chelating ligand as cell imaging and photocytotoxic agents. The N,N″-bisamide derivative of H5DTPA named as dtntp is based on 4′-(4-aminophenyl)-2,2′:6′,2″-terpyridine conjugated to diethylenetriamine-N,N′,N″-pentaacetic acid. The structure, physicochemical properties, detailed photophysical aspects, interaction with DNA and serum proteins, and photocytotoxicity were studied. The intrinsic luminescence of Eu(III) and Tb(III) complexes due to f → f transitions used to evaluate their cellular uptake and distribution in cancer cells. The solid-state structure of [Eu(dtntp)(DMF)] (1·DMF) shows a discrete mononuclear molecule with nine-coordinated {EuN3O6} distorted tricapped-trigonal prism (TTP) coordination geometry around the Eu(III). The {EuN3O6} core results from three nitrogen atoms and three carboxylate oxygen atoms, and two carbonyl oxygen atoms of the amide groups of dtntp ligand. The ninth coordination site is occupied by an oxygen atom of DMF as a solvent from crystallization. The designed probes have two aromatic pendant phenyl-terpyridine (Ph-tpy) moieties as photo-sensitizing antennae to impart the desirable optical properties for cellular imaging and photocytotoxicity. The photostability, coordinative saturation, and energetically rightly poised triplet states of dtntp ligand allow the efficient energy transfer (ET) from Ph-tpy to the emissive excited states of the Eu(III)/Tb(III), makes them luminescent cellular imaging probes. The Ln(III) complexes show significant binding tendency to DNA (K ~ 104 M−1), and serum proteins (BSA and HSA) (K ~ 105 M−1). The luminescent Eu(III) (1) and Tb(III) (2) complexes were utilized for cellular internalization and cytotoxicity studies due to their optimal photophysical properties. The cellular uptake studies using fluorescence imaging displayed intracellular (cytosolic and nuclear) localization in cancer cells. The complexes 1 and 2 displayed significant photocytotoxicity in HeLa cells. These results offer a modular design strategy with further scope to utilize appended N,N,N-donor tpy moiety for developing light-responsive luminescent Ln(III) bioprobes for theranostic applications.

Preparation of cattle bone collagen peptides-calcium chelate and its structural characterization and stability

In this study, cattle bone collagen peptides (CPs) were applied to prepare peptides-calcium chelate (CPs-Ca), and the physicochemical, structural properties, and stability of the CPs-Ca were characterized. The optimized preparation conditions were determined by single factor test, and the maximum calcium-chelating capacity was 42.70 ± 1.09 μg/mg. Physicochemical analysis indicated that CPs-Ca was a new substance compared with CPs. Structural analysis demonstrated that calcium ions chelated CPs via the sites of carboxyl oxygen, hydroxyl oxygen and amino nitrogen atom. Morphology analysis showed that CPs-Ca aggregated to large particles due to the crosslinking of calcium ions. According to the stability analysis, CPs-Ca was stable in thermal processing and gastrointestinal digestion. The acid environment was the major factor of CPs-Ca dissociation. The findings put forward a scientific basis for preparing a novel calcium supplement and high-value utilization of cattle bone.

Stable Indium Pyridylcarboxylate Framework with Highly Selective Adsorption of Cationic Dyes and Effective Nitenpyram Detection.

On the basis of an undeveloped asymmetrical pyridylcarboxylate ligand, 2-(2-carboxypyridin-4-yl)terephthalic acid (H3CPTA), an indium pyridylcarboxylate framework, [(Me)2NH2]1.5[In1.5(CPTA)2]·5.5NMF·6H2O (1), is synthesized under solvent thermal conditions. 1 displays a 3D anionic framework with a large void space, which contains open square channels with a cross section of 14.6 Å and a pore surface decorated with carboxylic oxygen atoms. Depending on the anionic skeleton and high water stability, 1 exhibits high adsorption selectivity and capacity for cationic dyes in aqueous solution. Furthermore, the luminescence performance illustrates that 1 has selectivity and sensitivity to nitenpyram with good recyclability.

Tribarium dicitrate penta-hydrate, [Ba3(C6H5O7)2(H2O)4]·H2O.

The crystal structure of tribarium dicitrate penta-hydrate, [Ba3(C6H5O7)2(H2O)4]·H2O, has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. The BaO9 and BaO10 coordination polyhedra share edges and corners to form a three-dimensional network. All of the active hydrogen atoms act as donors in O-H⋯O hydrogen bonds. Most of the acceptors are carboxyl-ate oxygen atoms, but there are also water⋯water hydrogen bonds. Both of the citrate hydroxyl groups form intra-molecular O-H⋯O hydrogen bonds to terminal carboxyl groups.

Preparation of New Complexes from a Mixture of Aspirin (acetylsalicylic acid), Paracetamol and Methyldopa with Divalent Manganese , Iron, Cobalt, Nickel and Copper, With a Study of Their Physical and Chemical Properties.

Abstract: New complexes with a mixture of aspirin (acetylsalicylic acid ) with methyldopa or paracetamol with methyldopa were synthesized via the reflux of reaction mixture using a basic medium to deprotonate the ligands. These new complexes of Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) with a mixture of aspirin (acetylsalicylic acid ), paracetamol and methyldopa have characterized using FTIR , UV-visible spectra, magnetic susceptibility, flame atomic absorption, C.H.N.S analysis and melting points measurements. The two mixed ligands have been found to act as bidentate chelating agents. Aspirin (acetylsalicylic acid) complexes coordinate to the metal ions through the oxygen of Aspirin's ester group and oxygen of the carboxyl group, while Methyldopa as ligand is coordinated through the oxygen of the hydroxyl group and the nitrogen of the amide groups. The Paracetamol was coordinated through the oxygen atom of carboxyl group and the nitrogen atom of the amide group. The stability of these new complexes depends on the size of the chelate rings, thus these ligands with a flexible organic backbone and their complexes contain five and six membered chelate rings, which have almost no strain. The molar conductance measurements for the metal complexes show non-electrolytic behavior in DMF solvent. The all synthesized complexes which show non-electrolytic properties, also were no conducting electrical current behaved as bi-dentate with octahedral geometrical isomers.

Synthesis, structural and DFT investigation of Zn(nba)2(meim)2 for adsorptive removal of eosin yellow dye from aqueous solution

AbstractA novel Zn(II) mixed‐ligand complex, Zn(nba)2(meim)2 (1), synthesized from Zn(NO3)2.6H2O, nitrobenzoic acid (Hnba) and 1‐methylimidazole (meim) is reported. The complex was characterized by elemental analysis, FT‐IR, powder and single crystal X‐ray crystallography and TGA/DSC. 1 exhibits a tetrahedral geometry for Zn(II), which is coordinated to two carboxylate oxygen atoms from two nba anions and two imidazole nitrogen atoms from two meim molecules. Thermal analysis shows the stability of 1 up to 260 °C. The adsorption of eosin yellow (EY) dye on 1 was investigated. The adsorption capacity of 1 for EY amounted to 65.32 mg/g, fitting best into Langmuir isotherm and pseudo second order kinetic models. From DFT studies, it was determined that adsorption is predominantly due to electrostatic, hydrogen bonding and π‐π interactions.

Supramolecular complexes of Ni (II) and Co (II) 4‐aminobenzoate with 3‐cyanopyridine: Synthesis, spectroscopic characterization, crystal structure, and enzyme inhibitory properties

Two new complexes, [M (AB)2(CP)2(H2O)2] (where M = Ni and Co AB = 4‐aminobenzoate and CP = cyanopyridine), were synthesized and characterized using different techniques (elemental analysis, FT‐IR spectrophotometer, LC/MS, single‐crystal X‐ray diffraction, and TGA/DTA analysis). As a result of X‐ray structural analysis, it was determined that complexes are isostructural. In the crystalline structures, MII ions are bridged with their carboxylate oxygen and aminopyridine nitrogen atoms and their symmetry‐related counterparts to form a two‐dimensional polymeric structure. The MII ion is octa‐coordinated with two nitrogen atoms and two oxygen atoms of the AB and two atoms of the CP anions. In this study, the effect of these molecules, containing a biologically active group, was investigated on important metabolic enzymes (carbonic anhydrase isoenzymes I and II (hCA I and II), achethylcholinesterase (AChE), and α‐glycosidase (α‐Gly) enzymes).

Isolation of a novel calcium-binding peptide from phosvitin hydrolysates and the study of its calcium chelation mechanism

A new peptide with strong calcium binding capacity was isolated from phosvitin hydrolysates. Taking calcium chelating rate as an indicator, phosvitin hydrolysates were separated gradually by anion-exchange chromatography, gel filtration chromatography and reversed-phase high performance liquid chromatography. A peptide with a molecular weight of 1106.44402 Da was identified by liquid chromatography-electrospray/mass spectrometry (LC-ESI/MS), and its amino acid sequence was DEEENDQVK, the calcium binding capacity reached 151.10 ± 3.57 mg/g. Its chelating mechanism was investigated. Results showed that, the β-sheet structure of peptide increased after adding calcium ion, and the main binding sites were carboxyl oxygen atom and amino nitrogen atom. In vitro simulated digestion experiments showed that, the solubility and dialysis rate of calcium in peptide-calcium chelate were higher than those in CaCO3 and D-calcium gluconate. This finding would promote the development of calcium supplements from food resources.

Toxicological assessment of synthesized and characterized transition metal(II) complexes of eflornithine hydrochloride hydrate on albino rats

Transition metal complexes of Cu(II), Co(II) and Ni(II) with eflornithine hydrochloride hydrate (EFN), an antitrypanosomiasis drug, as ligand have been synthesized and characterized by melting point, elemental analysis, Fourier transform infrared (FTIR), electronic spectra, magnetic susceptibility and electrospray ionization mass spectrometry (ESI-MS). The FTIR spectral data suggested the coordination modes of the ligand to be bidentate, coordinated to the metal ions through its carboxylate oxygen atom and an amino nitrogen atom. From the microanalytical data, the stoichiometry of the metal complexes is 1:2 (metal to ligand). The electronic absorption and magnetic susceptibility studies generally suggested octahedral geometry for the metal complexes. Toxicological evaluation of the ligand (EFN) and complexes were carried out using albino rats. Twenty-five albino rats that were used for the experiment were randomly divided into five groups and animals in group 1 served as a control. All the animals were sacrificed twenty-four hours after completion of their doses. The results revealed a high level of toxicity of EFN than the synthesized metal complexes.
 
 KEY WORDS: Eflornithine hydrochloride hydrate, Carboxylate moiety, Antitrypanosomiasis drug, Toxicological evaluation, Albino rats
 
 Bull. Chem. Soc. Ethiop. 2020, 34(3), 489-500.
 DOI: https://dx.doi.org/10.4314/bcse.v34i3.6

Simultaneous quantitative recognition of all purines including N6-methyladenine via the host-guest interactions on a Mn-MOF

Simultaneous quantitative recognition of all purines including N6-methyladenine via the host-guest interactions on a Mn-MOF

Effect of N,N′-dimethylformamide solvent on structure and thermal properties of lanthanide(III) complexes with flexible biphenyl-4,4′-dioxydiacetic acid

The N,N′-dimethylformamide (DMF) was used in the microwave-assisted (MW) solvothermal method for the preparation of lanthanide(III) complexes with biphenyl-4,4′-dioxydiacetic acid (H2L) of the formula Ln2L3·xDMF⋅yH2O where Ln = lanthanide(III) ions from La(III) to Lu(III) with the Pm(III) exception x = 1.5–3; y = 2 for Yb and Lu or 0 for the remaining complexes and L = C14H12O2(COO) 2 2− . The obtained complexes were characterized by the elemental analysis, infrared spectroscopy (ATR-FTIR), X-ray diffraction patterns and different methods (TG-DSC and TG-FTIR) of thermal analysis. Crystalline complexes contain N,N′-dimethylformamide molecules in their structures. Additionally, water molecules are present in the structures of Yb(III) and Lu(III) complexes. Coordination of lanthanide ions occurs through carboxylate oxygen atoms from the biphenyl-4,4′-dioxydiacetate ligand and most probably carbonyl oxygen atom from N,N′-dimethylformamide. The investigated compounds exhibit different thermal stability, and removal of solvent molecules takes place in a more complex way in the group of heavy lanthanide complexes. Their desolvated forms are an unstable [except Yb(Lu)2L3 compounds], and their further heating leads to the formation of suitable lanthanide oxides (air atmosphere). Thermal stability of the investigated compounds is higher in nitrogen atmosphere. The TG-FTIR methods allowed to propose way of thermal decomposition of investigated compounds through identification of volatile products such as: DMF, H2O, CO2, CO and CH4 evolved during heating of complexes. The luminescent properties of terbium(III) and europium(III) complexes were also investigated.

Crystal Structure and Magnetic Properties of 3,5-Pyridinedicarboxylate-Bridged Re(Ii)M(Ii) Heterodinuclear Complexes (M = Cu, Ni and Co)

The use of the mononuclear rhenium(II) precursor NBu 4 [Re(NO)Br 4 (H 2 pydc)]· i -PrOH ( 1 ) (H 2 pydc = 3,5-pyridinedicarboxylic acid) as a metalloligand towards Cu(II), Ni(II) and Co(II) afforded three new heterobimetallic complexes [Re(NO)Br 4 (μ-Hpydc)Cu(4,4’-dmbipy) 2 ]·(CH 3 ) 2 CO·0.25MeCN ( 2 ), [Re(NO)Br 4 (μ-Hpydc)Ni(dmphen) 2 ]·MeCN ( 3 ) and [Re(NO)Br 4 (μ-Hpydc)Co(dmphen) 2 ]·2H 2 O ( 4 ), respectively [4,4’-dmbipy = 4,4’-dimethyl-2,2’-bipyridine, dmphen = 2,9-dimethyl-1,10-phenanthroline and n -Bu 4 N + = tetra- n -butylammonium]. The crystal structures of 1 and 2 are reported herein together with the cryomagnetic investigation of 1 - 4 in the temperature range of 2.0-300 K. 1 is a mononuclear compound whose structure is made of [Re(NO)Br 4 (H 2 pydc)] - complex anions, tetra- n -butylammonium cations and isopropanol molecules of crystallization. Each rhenium(II) ion in 1 is six-coordinate with four bromide ligands in the equatorial positions and a nitrosyl group and one pyridyl-nitrogen atom from an H 2 pydc ligand filling the axial sites. 2 is a neutral heterobimetallic compound where the [Re(NO)Br 4 (Hpydc)] 2- complex anion acts as a monodentate ligand towards the [Cu(dmphen) 2 ] 2+ complex cation through one carboxylate-oxygen atom. The rhenium(II) ion is six-coordinate in a somewhat distorted octahedral surrounding similar to that in 1 . The copper(II) ion in 2 is five-coordinate with four nitrogen atoms from two bidentate 4,4’-dmbipy ligands and one carboxylate-oxygen atom, describing a surrounding intermediate between square pyramidal and trigonal bipyramidal. Compound 1 behaves as a quasi-magnetically isolated spin doublet with weak antiferromagnetic interactions through space Br⋯Br contacts, ligand field, spin-orbit coupling, tetragonal distortion, and covalence effects considered as variable parameters in a successful simulation of the magnetic data . Compounds 2 – 4 exhibit also weak intramolecular antiferromagnetic interactions ( J ) covering the range -0.60(1) to -1.50(1) cm -1 with the Hamiltonian being defined as H = - J S Re S M , M = Cu ( 2 ), Ni ( 3 ) and Co ( 4 ).

Dispersion-corrected density functional theory studies on glycolic acid-metal complexes

The structure and metal complexation studies using dispersion-corrected density functional theory methods are performed for four stable glycolic acid conformers named SSC, GAC, SAC, and AAT. The condensed Fukui functions are calculated to study the favourable reactive site for metal binding on the glycolic acid conformers. The interaction of alkali metal ions (Na+, K+) with different binding sites (carboxyl, hydroxyl oxygen) of the glycolic acid conformers in the gas phase is investigated at the same level of theory. Our calculations show that the order of stability changes into SSC > AAT > GAC = SAC due to the binding of the metal ion. The relative energy values indicate that the AAT conformer is more stable than the GAC and SAC conformers. This occurs when a metal ion (Na+, K+) is bound with the carboxyl oxygen atom of glycolic acid. The QTAIM, RDG, NCI, ELF, LOL, and NBO analysis are employed in this work to understand the strength of intra- and intermolecular interactions in the glycolic acid metal complexes.

Mixed-ligand complexes of ampicillin derived Schiff base ligand and Nicotinamide: Synthesis, physico-chemical studies, DFT calculation, antibacterial study and molecular docking analysis

A novel series of mixed-ligand complexes of the type, [ML1(L2)3]Clx [M= Cr(III), Fe(III), Co(II),Ni(II), Cu(II), Cd(II) and Hg(II), n = 2, 3], was synthesized using Schiff base (HL1) as main ligand, nicotinamide (L2) as secondary ligand, and the corresponding metal ions in 1:3:1 molar ratio. The main ligand, HL1 was prepared by the interaction of ampicillin drug and 4-chlorobenzophenone. The synthesized mixed ligand complexes were characterized by elemental analysis, UV-Vis, FT-IR,1H-NMR,13C-NMR and TG/DTG studies. In the mixed-ligand complexes, the Schiff base ligand, HL1 showed coordination to the central metal ion in tridentate manner via azomethine nitrogen, β-lactam ring oxygen and deprotonated carboxylic oxygen atoms, whereas the secondary ligand L2 (nicotinamide, Nam) coordinated through pyridine nitrogen atoms. The synthesized complexes exhibited significant antimicrobial activity when evaluated against P. pseudomonas, E. coli, S. aureus and B. subtilis microbes. The DFT calculations were also carried out to ascertain the bonding insights into the structure. In addition, molecular docking analysis was performed carried out to know the interactions between complexes and their probable binding sites in penicillin binding protein (PBP2). Moreover, drug-likeness and toxicity of the compounds were also performed to predict the suitability of the complexes as drugs.