Synthesis, crystal structure and spectroscopic characterization of a novel bis (oxo-bridged) dinuclear vanadium(V)–dipicolinic acid complex

More than a contaminant: How zinc promotes carbonate-mineralizing bacteria metabolism and adaptation by reshaping precipitation conditions

Although microbial-induced carbonate precipitation (MICP) technology is both environmentally friendly and cost-effective, its efficiency is constrained by challenges such as low bacterial activity and heavy metal stress. This study explored the enhancement of mineralization efficiency by incorporating zinc (Zn) into the cultivation system of carbonate-mineralized bacteria. All Zn salts at a concentration of 30 μmol/L significantly enhanced the density and heavy metal resistance of bacterial cells, while also promoting CO2 hydration efficiency. The activities of urease and carbonic anhydrase (CA) were significantly elevated after treatment with 30 μmol/L ZnCl2 and Zn(C3H5O3)2 (ZnL) compared to the control. The results from qRT-PCR and ELISA confirmed that ZnL exhibited a stable biological effect on CA gene expression. Through the analysis of surface chemistry of cells and the subcellular distribution pattern of cadmium (Cd), it was observed that Zn supplementation maintained the cell surface stability and strengthened the cellular barrier against Cd uptake. SEM, FTIR and XRD results further confirmed that Zn supplementation significantly increased the complexity of the mineral morphology, resulting in a more stable crystal structure of CdCO3. This study offers additional theoretical and technical backing, opening a new avenue for the practical application of MICP technology in heavy metal remediation.

Interaction with bioligands and in vitro cytotoxicity of a new dinuclear dioxido vanadium(V) complex

One centrosymmetric bis(μ-oxido)-bridged vanadium(V) dimer with molecular formula [(V^VO₂)₂(pedf)₂] (1) has been synthesized from the reaction of VOSO₄·5H₂O with a Schiff base ligand (abbreviated with pedf^-) obtained from 2-acetylpyridine and 2-furoic hydrazide in methanol. Complex 1 was characterized by elemental analysis, UV-visible (UV-Vis), Fourier-transform infrared spectra (FT-IR), cyclic voltammetry (CV), electron paramagnetic resonance spectroscopy (EPR) and electrospray ionization-mass spectrometry (ESI-MS) techniques along with single crystal X-ray diffraction (SCXRD). The FT-IR spectral data of 1 indicated the involvement of oxygen and azomethine nitrogen in coordination to the central metal ion. The crystallographic studies revealed a dinuclear oxovanadium(V) complex with the Schiff base coordinated via the ONN donor set with formation of two five-membered chelate rings resulting in a distorted octahedral geometry. The interaction of 1 with calf thymus DNA (CT-DNA) was investigated by spectroscopic measurements and results suggested that the complex binds to CT-DNA via moderate intercalative mode with a binding constant (K_b) around 10³ M^-1. In addition, the in vitro protein binding behavior was studied by fluorescence spectrophotometric method using both bovine serum albumin (BSA) and human serum albumin (HSA) and a static quenching mechanism was observed for the interaction of the complex with both albumins that occurs with a K_b in the range (5-6) × 10³ M^-1. In vitro cytotoxicity of complex 1 on lung cancer cells (A549) and human skin carcinoma cell line (A431) demonstrated that the complex had a broad-spectrum of anti-proliferative activity with IC₅₀ value of 64.2 μM and 56.2 μM.

Role of biologically important imidazole moiety on the antimicrobial and anticancer activity of Fe(III) and Mn(II) complexes

Currently, most pathogens influencing a number of epidemics outline a notable warning to human health. It has pushed researchers to design new antimicrobial drugs using transition metals that are studied in proceeding fewer years for their antimicrobial properties. Henceforth, in this work, two mononuclear complexes [Imz-H][Fe(pda)₂]⋅1⋅3H₂O (1) and [Mn(Imz)₆]⋅2Cl^-⋅2H₂O (2) [Imz = imidazole and H₂pda = 2,6 pyridine dicarboxylic acid] are isolated and characterized systematically by various spectral and single-crystal XRD studies. The antimicrobial activity of the present hexadentate complexes of Fe(III) and Mn(II) against Gram-positive as well as Gram-negative bacteria is also assessed. Augmented activity against standard isolates of Staphylococcus aureus with a minimum inhibitory concentration (MIC) is observed. Similar activity was also observed toward Escherichia coli, Klebsiella pneumoniae and Listeria monocytogenes. 1 and 2 have excellent bactericidal activity, and no resistant mutant for S. aureus was seen. The compound also unveiled antibiofilm activity and was capable to disrupt significantly the pre-formed biofilms and this property was confirmed by XTT assay experiment. The MTT assay data indicate that 1 and 2 can be used as anticancer agents toward the RAW 64.7 (human macrophage/monocyte) cell line. Further, the molecular docking study reveals that the role of imidazole is very important in the biological activity of these complexes. Moreover, our results suggest that 1 and 2 with its effective anti-microbial, anti-biofilm and cytotoxicity activity can be used to treat bacterial and fungal infections and could be appraised clinically for further applications.Communicated by Ramaswamy H. Sarma.

Synthesis, crystal structures, photoluminescence, magnetic and antioxidant properties, and theoretical analysis of Zn(ii) and Cu(ii) complexes of an aminoalcohol ligand supported by benzoate counter anions

Two photoluminescent Zn(ii) and Cu(ii) complexes are designed, characterized and assessed for DNA binding and antioxidant properties.

Hydrogen-Bonded Frameworks of Mercury(II) Complexes with Pyridinedicarboxylic Acids

Three novel mercury(ii) coordination compounds, [HgCl(2,4-pydcH2)(2,4-pydcH)]·2H2O (1) and [HgCl(2,6-pydcH)(H2O)]·3H2O (2) that exhibit hydrogen-bonded 3D frameworks, and [Hg(2,6-pydcH)2]·2H2O (3), exhibiting only hydrogen-bonded 1D chains (2,4-pydcH2 = pyridine-2,4-dicarboxylic acid; 2,6-pydcH2 = pyridine-2,6-dicarboxylic acid), were prepared in the reactions of the corresponding pyridinedicarboxylic acid with mercury(ii) chloride or mercury(ii) acetate. Compounds 1–3 were prepared by conventional solution synthesis. Only the hydrogen-bonded 1D chain of 3 was robust enough to be prepared by mechanochemical synthesis. The crystal structures of 1–3 were determined by the single-crystal X-ray diffraction method. Neutral 2,4-pydcH2 and partially deprotonated 2,4-pydcH− act as N,O-bidentate ligands in the structure of 1 whereas crystal structure analysis reveals O,N,O′-tridentate 2,6-pydcH− ligand in the structures of 2 and 3. Compounds 1–3 were characterised by IR spectroscopy in the solid state, and compounds 1 and 2 were also characterised by 1H and 13C NMR spectroscopy in DMSO solution. Thermal properties of 1–3 were also investigated. NMR data support a collapse of the hydrogen-bonded frameworks of 1 and 2 in DMSO solution, and the existence of monomeric species in DMSO solutions.

Hybrid pharmacophore approach for bio-relevant di-imines based homobimetallic complexes incorporating functionalized dicarboxylates as co-ligands: Synthesis, spectral and structural activity dependent biological insights (in-vitro DNA and HSA binding, antioxidant and cytotoxicity)

Synthesis of bio-efficient homobimetallic complexes, [Cu₂(L¹)₂(dipic)](NO₃)₂.3H₂O (1), [Zn₂(L¹)₂(dipic)](NO₃)₂.4H₂O (2), [Cu₂(L²)₂(oxa)](NO₃)₂.4H₂O (3) and [Zn₂(L²)₂(oxa)] (NO₃)₂.5H₂O (4) was carried out using Schiff bases [(N¹E,N²E)-N¹,N²-bis(5-chlorothiophen-2-ylmethylene)-4-chlorobenzene-1,2-diamine; L¹] and [(N¹E,N²E)-N¹,N²-bis(5-chlorofuran-2-ylmethylene)-4-chlorobenzene-1,2-diamine; L²] as main ligands and dicarboxylate moieties of 2,6-pyridine dicarboxylic acid (H₂-dipic) and oxalic acid (H₂-oxa) as co-ligands, respectively in order to apprehend their structure activity relationships on the basis of pharmacophore hybrid approach. The stoichiometry, geometry, thermal stability, morphology and crystallite size of the compounds were inferred by analytical, spectral (FT-IR, ¹H NMR and ¹³C NMR and Mass), thermal (TGA/DTA), SEM and XRD studies. In-vitro DNA and HSA binding profiles of complexes were analysed by different biophysical measurements. The absorption study divulged that the observed alterations in the physico-chemical properties of complexes upon binding with DNA connoted their intercalative binding mode while fluorescence quenching mechanism was quantified by using Stern Volmer constant (K_SV)_; 1.73×10⁴ (1), 1.47×10⁴ (2), 5.65×10³ (3) and 3.60×10³M^-1 (4) which discerned that hybrid pharmacophore active metal complexes (1 and 2) exhibited efficient quenching effect with Ct-DNA in comparison to complexes (3 and 4) due to greater planarity and extent of conjugation (π-π interactions). The intercalative binding mode of complexes is further supported by competitive displacement assay by using fluorogenic dyes (EtBr and Hoechst 33258). The results of HSA fluorescence study divulged static quenching of the complexes (1-4) with K_SV values of 7.24×10⁴ (1), 6.03×10⁴ (2), 5.06×10⁴ (3) and 2.85×10⁴ (4) while K_b values; 1.16×10⁵ (1), 2.01×10⁴ (2), 5.84×10³ (3) and 8.60×10² (4) suggested them potent avid binder of HSA. Additionally, comparative estimation of scavenging properties using DPPH, superoxide(O₂^.-), hydroxyl (OH^-) and ABTS method and in-vitro cytotoxicity against different cell lines (MCF-7, HeLa and Hep G2) brought out distinct biopotency of complexes due to diverse structural features and chelation effect.

51V magic angle spinning NMR spectroscopy and quantum chemical calculations in vanadium bio-inorganic systems: current perspective

In recent years, 51V magic angle spinning (MAS) NMR spectroscopy has been widely used to characterize vanadium centers in biology, biomimetic complexes, and inorganic compounds of medicinal and industrial relevance. It has been demonstrated that 51V NMR parameters are sensitive probes of the coordination geometry and chemical environment of the metal center, beyond the first coordination sphere. To establish the relationships between NMR parameters and structure of the vanadium centers, over the past decade a large series of coordination complexes have been analyzed by MAS NMR spectroscopy. It has been demonstrated that the interpretation of the NMR parameters requires the use of theoretical methods, such as density functional (DFT) theory, whereby the experimental NMR observables are linked to the electronic and structural properties of a molecule. DFT calculations have been successfully employed to not only predict NMR parameters but to also yield valuable information regarding the structure and function of various vanadium compounds. In this report, we review the current state of the field, and present a survey of bioinorganic vanadium complexes as well as vanadium-dependent haloperoxidases analyzed using 51V MAS NMR spectroscopy and DFT calculations, to illustrate the rich information content available from such a combined approach.

Synthesis and crystal structure of 2-amino-3-hydroxypyridinium dioxido(pyridine-2,6-dicarboxylato-κ³O²,N,O⁶)vanadate(V) and its conversion to nanostructured V₂O₅

2-Amino-3-hydroxypyridinium dioxido(pyridine-2,6-dicarboxylato-κ(3)O(2),N,O(6))vanadate(V), (C5H7N2O)[V(C7H3NO4)O2] or [H(amino-3-OH-py)][VO2(dipic)], (I), was prepared by the reaction of VCl3 with dipicolinic acid (dipicH2) and 2-amino-3-hydroxypyridine (amino-3-OH-py) in water. The compound was characterized by elemental analysis, IR spectroscopy and X-ray structure analysis, and consists of an anionic [VO2(dipic)](-) complex and an H(amino-3-OH-py)(+) counter-cation. The V(V) ion is five-coordinated by one O,N,O'-tridentate dipic dianionic ligand and by two oxide ligands. Thermal decomposition of (I) in the presence of polyethylene glycol led to the formation of nanoparticles of V2O5. Powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the synthesized powder.

Two Zn(II) mononuclear coordination compounds with pyridinedicarboxylate and auxiliary N-(pyridin-4-ylmethylidene)hydroxylamine ligands

Two new mononuclear coordination compounds, bis{4-[(hydroxyimino)methyl]pyridinium} diaquabis(pyridine-2,5-dicarboxylato-κ(2)N,O(2))zincate(II), (C6H7N2O)2[Zn(C7H3NO4)2(H2O)2], (1), and (pyridine-2,6-dicarboxylato-κ(3)O(2),N,O(6))bis[N-(pyridin-4-ylmethylidene-κN)hydroxylamine]zinc(II), [Zn(C7H3NO4)(C6H6N2O)2], (2), have been synthesized and characterized by single-crystal X-ray diffractometry. The centrosymmetric Zn(II) cation in (1) is octahedrally coordinated by two chelating pyridine-2,5-dicarboxylate ligands and by two water molecules in a distorted octahedral geometry. In (2), the Zn(II) cation is coordinated by a tridentate pyridine-2,6-dicarboxylate dianion and by two N-(pyridin-4-ylmethylidene)hydroxylamine molecules in a distorted C2-symmetric trigonal bipyramidal coordination geometry.

Spectroscopic characterization, X-ray structure, antimicrobial activity and DFT calculations of novel dipicolinate copper(II) complex with 2,6-pyridinedimethanol

Novel dipicolinate complex of copper(II) ion, [Cu(dmp)(dpc)]·0.8H(2)O [dmp: 2,6-pyridinedimethanol; dpc: dipicolinate or pyridine-2,6-dicarboxylate], has been prepared and fully characterized by single crystal X-ray structure determination. The central copper(II) ion is bonded to dpc and dmp ligands through pyridine nitrogen atom together with two oxygen atom, forming the distorted octahedral geometry. The complex molecules, connected via O-H···O hydrogen bonds, form a supramolecular structure. H(2)dpc, [Cu(dpc)(H(2)O)(3)] and [Cu(dmp)(dpc)]·0.8H(2)O were screened for antimicrobial activity against Gram-positive, Gram-negative bacteria and yeast. H(2)dpc and [Cu(dpc)(H(2)O)(3)] exhibited antibacterial and antifungal activity, while [Cu(dmp)(dpc)]·0.8H(2)O exhibited activity only for Gram-positive bacteria. The geometry optimization and EPR parameters were carried out using the following unrestricted hybrid density functionals: LSDA, BPV86, B3LYP, B3PW91, MPW1PW91, PBEPBE and HCTH. Although the supramolecular interactions have some influences on the molecular geometry in solid state phase, calculated data show that the predicted geometries can reproduce the structural parameters. The electronic station in the frontier orbitals of the copper complex calculated from the experimental data is compared to the results of time-depended DFT calculations with the polarizable continuum model. Calculated vibrational frequencies are consistent with the experimental IR data.

Synthesis and characterization of transition metal 2,6-pyridinedicarboxylic acid derivatives, interactions of Cu(II) and Ni(II) complexes with DNA in vitro

Mononuclear complexes M(L)Cl(2) where M=Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) and (L=N,N-diethylpiperazinyl,2,6-pyridinedicarboxylate), have been synthesized and characterized by elemental analysis, FT-IR, (1)H NMR spectroscopy, UV-vis, magnetic moment, TGA/DSC, cyclic voltammetry and conductivity measurement data. The spectral data suggests that the dipicolinic acid acts as a bidentate ligand and is coordinated to the metal ion through the carboxylate oxygen. The cyclic voltammogram for Cu(L)Cl(2) complex was found to display two reversible Cu(II)/Cu(I) and Cu(II)/Cu(III) redox couple. The ligand exhibits a two-step thermolytic pattern while the complexes decompose in three stages respectively. An octahedral geometry has been proposed for both the complexes. The investigation of the interaction of the complexes with calf thymus DNA has been performed with absorption spectroscopy and fluorescence quenching experiments, which showed that the complexes are avid binders of calf thymus DNA. Also the interaction of the Cu(II) and Ni(II) complexes with plasmid DNA (pUC 19) was studied using agarose gel electrophoresis. The results revealed that these complexes can act as effective DNA cleaving agents resulting in the nicked form of DNA (pUC 19) under physiological conditions. The gel was run both in the absence and presence of an oxidizing agent (H(2)O(2)). The ligand and its complexes have also been screened against microbes in order to study their antibacterial action. The results revealed that the Cu(II) complex has activity comparable with the reference drugs gentamycin and flucanzole.