Octahedral Geometry Research Articles

A New Azide-Bridged Polymeric Manganese (III) Schiff Base Complex with an Allylamine-Derived Ligand: Structural Characterization and Activity Spectra

This paper reports the synthesis and structural characterization of a novel azide-bridged polymeric manganese (III) Schiff base complex, using 2-((allylimino)methyl)-6-ethoxyphenol as a ligand. The crystal structure of the synthesized compound, elucidated by single-crystal X-ray diffraction analysis, indicates that it crystallizes in the monoclinic space group P21/c. The complex is found to display an octahedral geometry in which the central manganese Mn(III) coordinates with two bidentate donor Schiff base ligands via oxygen and nitrogen atoms. In addition, the metallic centers are linked together to form a one-dimensional chain bridged by end-to-end azide ligands. To offer a more thorough characterization of the synthesized compound, the study incorporates experimental data from FT-IR, UV-Vis, and cyclic voltammetry, alongside computational results from Hirshfeld surface analysis and DFT calculations conducted for both the ligand and complex. The computational analyses provided valuable insights into the intrachain and interchain interactions within the crystal structure, clarified the conformational characteristics of the isolated ligand molecule, and aided in the interpretation of the experimental IR spectra. Furthermore, an assessment of the compound’s drug-like properties was conducted using activity spectra for substances (PASS) predictions, revealing potential pharmacological activities.

Fabrication, Preparation, Physicochemical Characterization, and Theoretical Studies of Some Novel Schiff Base Ciprofloxacin Metal Complexes: DNA Interaction and Biomedical Applications

ABSTRACTNovel compounds with pharmacological activity were synthesized from Pd(II), Fe(III), Cr(III), Ni(II), and Cu(II) ions with 1‐cyclopropyl‐6‐fluoro‐4‐(2‐hydroxy‐phenylimino)‐7‐piperazin‐1‐yl‐1,4‐dihydro‐quinoline‐3‐carboxylic acid (CFAP). The ligand's NH and OH groups allowed it to interact with the metals as a neutral tridentate. The investigated novel compounds were described using 1H and 13C NMR spectra, FT‐IR spectrums, TGA and UV–Vis (conductance of molecules), and CHN‐analysis. Additionally, the pH profile of the CFAP complexes indicated great stability, and the complexes' stability constant was discovered in the solution. To extract important properties for CFAP and its complexes, computational research was used, CFAPCu, CFAPCr, CFAPNi, and CFAPFe have octahedral geometry, while CFAPPd has square planar geometry. To investigate the molecular geometry, density functional theory calculations (DFT) were carried out. The molar ratio and continuous fluctuation data confirmed that the (M:L) ratio was (1:1). In vitro tests were conducted to evaluate Schiff base's antimicrobial action ligand and its metal chelates against fungal and bacterial infections. The findings showed that the antimicrobial efficacy is as follows: When CFAPPd is compared to fluconazol and ofloxacin as reference medications, it is the highly inhibitor complex. The novel CFAP ligand and its complexes were investigated for In vitro carcinogenic potential against Hep‐G2, MCF‐7, and HCT‐116 cell lines. As compared to the medication vinblastine, the results once again demonstrated that CFAPPd is the most active agent. Moreover, the complexes demnstrated strong reactivity in capturing free radicals when their antioxidant activity was investigated. Viscosity, spectral investigations, and gel electrophoreses were used to identify the interaction between metal chelates and DNA. Every examined compound is shown to be an enthusiastic DNA binder by viscosity and spectrophotometric titration investigations. The heightened hydrophobic and electrostatic interactions between aromatic rings could be the cause of this. Ultimately, these compounds could be regarded as promising bioactive substances.

A novel Ni-complex nanocatalyst for efficient electrochemical oxidation of alcohol in alkaline medium: Mechanism and DFT study

A novel catalyst based on nanoparticles of Ni(II) complex was developed to enhance the activity toward alcohol oxidation and hence its possible application in direct alcohol fuel cells (DAFCs). The [NiII(ABP)2] complex was formed in a molar ratio 1(Ni):2(ABP), where (ABP) was synthesized based on 4-(Dimethylamino)benzaldehyde (DMBA), 4-Aminoantipyrine (AAP) and 2-aminophenol (AP) through two condensation steps. Several characterization techniques were used to evaluate the structure of the synthesized compounds, such as elemental analysis, mass, FTIR, UV–Vis, 1HNMR , magnetic, molar conductance and XRD. Transmission and scanning electron microscope (TEM and SEM) images of separated [NiII(ABP)2] complex revealed particles with a size lower than 26 nm. SEM for [NiII(ABP)2]/GCE before and after ethanol oxidation was performed along with EDX and mapping techniques. The computational DFT (density functional theory) calculations supported the octahedral geometry shape of the prepared [NiII(ABP)2] chelate. Several octahedral structures involved in a purposed mechanism were studied using DFT to show the expected optimized shapes formed during ethanol oxidation. Also, the alcohol adsorption simulation was performed using Dmol3 numerical DFT modules to calculate the adsorption energy of alcohols on nickel complex surface. Additionally, the activity toward oxidation of alcohols with different sizes and stereochemistry (methanol, ethanol, propanol, and isopropanol) was investigated in an alkaline medium. The electrode activity was represented for each alcohol as a function of anodic oxidation current. Whereas the electrode achieved 14, 26, 6, and 4 mA cm−2 for methanol, ethanol, propanol, and isopropanol, respectively. Moreover, several parameters were calculated to judge the electrode performance, like diffusion coefficient, catalytic rate constant, stability, Tafel slope, and charge transfer resistance. The theoretical calculations and the experimental findings strongly correlate with each other, where Ni-complex showed the greatest catalytic activity toward ethanol oxidation.

Synthesis, Crystal Structures and Antibacterial Activity of Nickel(II), Cadmium(II) and Zinc(II) Complexes with Hydrazone Ligands.

Three mononuclear nickel(II), cadmium(II) and zinc(II) complexes, [NiL2]·2CH3OH·H2O (1), [CdI2(HL)]·CH3OH (2) and [ZnL2] (3), have been synthesized from 3-hydroxy-4-methoxy-N'-[(Z)-(pyridin-2-yl)methylidene]benzohydrazide (HL) by microwave irradiation method. All complexes were characterized by CHN elemental analyses and infrared spectra. Structures of the complexes were further studied by single crystal X-ray determination, which reveals that the Ni and Zn atoms in complexes 1 and 3 are in octahedral coordination, and the Cd atom in complex 2 is in square pyramidal coordination. The biological activity of the complexes on the bacterial strains Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli wasevaluated. As a result, the zinc complex has interesting antibacterial activities.

Deeply Reduced Chiral MoIV6-Polyoxometalates with Highly Enhanced Electronic Conductivity.

A series of deeply reduced MoIV6-polyoxometalates (POMs), [MoIV6(bpy)6MoVI2O16S2]·10H2O (1) (bpy = 2,2'-bipyridine), [MoIV6(bpy)4(L-TrA)2MoV4(bpy)2O14S4]2·36.5H2O (2), and [MoIV6(bpy)4(D-TrA)2MoV4(bpy)2O14S4]2 (3) (TrA = tartaric acid), were obtained from one-pot hydrothermal syntheses. They feature the bioxo-bridged [MoIV3O3S]4+ incomplete cuboidal cores stabilized by strong triangular metal-metal bonds and datively chelated bpy π-ligands. The two apical MoVIO4 in 12e-Mo8 (1) and two [MoV2O3STrAbpy] in 16e-Mo10 (2, 3) complete the octahedral coordination geometry of the deeply reduced MoIV, not counting the MoIV-MoIV d2-d2 bonds. The aromatic planar bpy π ligands form a two-dimensional face-to-face π stacking supramolecular structure, which are further strengthened by point-to-face C-H···π interactions in the π stacked layers. 16e-Mo10 (2, 3) has stronger intramolecular face-to-face π stacking interactions, which are interconnected by intermolecular C-H···π into a three-dimensional framework structure. These structural features account for their highly enhanced electronic conductivities (1, 6.19 × 10-8 S cm-1; 2, 2.18 × 10-7 S cm-1), providing a new way of thinking to improve electronic conductivity of POMs. 1-3 have been described by first-principles density function theory (DFT) calculations and also characterized by elemental analyses, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), solid UV-visible spectra, and circular dichroic (CD) spectra.

Production of Lactic Acid via Catalytic Transfer Dehydrogenation of Glycerol Catalyzed by Base Metal Salt Ferrous Chloride and Its NNN Pincer-Iron Complexes.

NNN-Bis(imino) pyridine-based pincer-Fe(II) complexes with an expected trigonal bipyramidal (TBP) geometry equilibrated to a rearranged ion pair of an octahedral dicationic Fe complex containing two bis(imino)pyridine ligands that are neutralized by a tetrahedral dianionic-[FeCl4]2-. Single-crystal X-ray diffraction (SCXRD), high-resolution mass spectrometry (HRMS), and UV-visible (UV-vis) studies suggested that the equilibrium was dictated by the sterics of the R group on the imine N, with the less-crowded groups tilting the equilibrium to the ion pair and the bulky ones favoring the TBP geometry. Electron paramagnetic resonance (EPR) and Evan's magnetic moment measurements indicated that the complexes were paramagnetic with Fe(II) in a high-spin state. In solution, over a period of 7 days, these Fe(II) complexes oxidized to a mixture of low-spin and high-spin Fe(III) species. These pincer-Fe(II) were found to be highly active toward the transformation of biodiesel waste glycerol to value-added lactic acid (LA). Particularly, (Ph2NNN)FeCl2 (0.1 mol %) gave 91% LA with a 99% selectivity at 140 °C using 1.2 equiv of NaOH. With 0.0001 mol % (Ph2NNN)FeCl2, very high turnovers (74% LA, 98% selectivity, 740 000 turnover number (TON) at 4405 turnovers per hour (TOs/h)) were obtained after 7 days. EPR indicated Fe(III) species to be the active catalyst, a few of which were detected by HRMS. Experiments with Hg are suggestive of the mostly homogeneous molecular nature of the catalyst with a minor contribution from heterogeneous Fe nanoparticles.

Neutral Adducts of Molybdenum Hexafluoride: Structure and Bonding in MoF6(NC5H5) and MoF6(NC5H5)2.

The first Lewis acid base adducts of MoF6 and an organic base have been synthesized, i. e., MoF6(NC5H5) and MoF6(NC5H5)2. These adducts are structurally characterized with X-ray crystallography, showing that both adducts adopt capped trigonal prismatic structures. The MoF6(NC5H5) and MoF6(NC5H5)2 adducts are fluxional on the NMR time scale at room temperature. Two different fluorine environments could be resolved by 19F NMR spectroscopy at -80 °C for the 1 : 2 adduct, MoF6(NC5H5)2, whereas MoF6(NC5H5) remains fluxional at that temperature. Density functional theory (DFT) calculations aide the assignment of the infrared and Raman spectra. Natural Bond Order and Molecular Electrostatic Potential analyses elucidate the structures and properties of the MoF6 pyridine adducts. Regions of significantly higher molecular electrostatic potential, i. e., σ-holes, in trigonal prismatic compared to octahedral MoF6 rationalize the capped trigonal prismatic geometry of the adducts. Whereas MoF6(NC5H5) is stable at room temperature under exclusion of moisture, MoF6(NC5H5)2 decomposes at 60 °C in pyridine solvent, and the solid slowly decomposes at room temperature after 24 h.

Design, structure and antivirus molecular docking of chloridobis(1,10-phenanthroline)-(thiocyanato)-copper(II)

The reaction of sodium thiocyanate with CuCl2·2H2O salt using 1,10-phenanthtroline as a co-ligand led to chloridobis(1,10-phenanthroline)-(thiocyanato) copper(II), [Cu(Phen)2(Cl)(NCS)] (1). The structure of 1 was characterized by single crystal X-ray crystallography, UV-Visible and fluorescence spectroscopy. 1 crystallized in the monoclinic crystal system with space group P21/n and revealed a distorted octahedral coordination geometry. Electronic properties such as HOMO and LUMO energies were derived through DFT calculations. Hirshfeld surface analysis and 2D fingerprint plot was used to analyze the intermolecular interactions within the crystal structure. To develop anti-SARS-CoV-2 and anti-HIV drugs, we performed molecular docking studies for antiviral activity against the main protease (Mpro) of the SARS-CoV-2 (PDB ID: 6LU7 and 7LKD) and HIV-1 protease (PDB ID: 8FUI) viruses. The molecular docking calculations reveal that 1 with the Mpro of SARS-CoV-2 virus and HIV-1 protease virus resulted in calculated binding energies (ΔG) of −7.6, −7.5 and −7.2 kcal/mol with inhibition constant/dissociation constant (Ki/Kd ) values of 4.567, 4.432 and 4.632 µM, respectively. The in-vitro antibacterial study was conducted to check the efficacy of 1 against some selected bacteria. Further, the in-silico antiviral efficacy analysis shows the potential of this complex as an antiviral drug. 1 may be used as anti-SARS-CoV-2 and anti-HIV-1 agents.

Synthesis of cadmium(II) complexes with polyamines: Crystal structure, theoretical calculation, photocatalytic, DNA interaction and biological studies

Three cadmium(II) complexes of N-(2-aminoethyl)-1, 2-ethanediamine (DETA) (1), N-(3-aminopropyl)-1, 3-propanediamine (DPTA) (2) and N,N'-(ethane-1,2-diyl)bis(propane-1,3-diamine) (DPETA) (3) have been synthesized and characterized by single crystal X-ray crystallography, UV–visible spectroscopy, IR and conductivity measurements. Complexes 1 and 3 show octahedral geometry while complex 2 show five coordinated square pyramidal geometry. Two molecules of DETA ligand are coordinated to the Cd(II) ion in complex 1. But one molecule each of DPTA and DPETA ligands and two bromide ions are coordinated to the Cd(II) ions to form square pyramidal (2) and octahedral structure (3). DFT results show that complex 3 is the most favoured complex thermodynamically while complex 1 is the least. The complexes exhibit good photocatalytic activity with reference to the intensity of organic dye methylene blue. The complexes were investigated for DNA interaction by absorption and fluorescence spectroscopy suggesting both hypochromism (internal contact or intercalative interaction) and hyperchromism (external contact or electrostatic binding). The cadmium (II) complexes show growth inhibitory activity against four pathogenic bacteria, two gram +ve, viz., Staphyloccus aureus, Bacillus subtilis and two gram –ve, viz., Escherichia coli, Salmonella typhi. Albumin denaturation assay and Heat Induced Haemolysis were studied for the complexes for anti-inflammatory activity.

Synthesis, photophysical characterisation, quantum-chemical study and in vitro antiproliferative activity of cyclometalated Ir(III) complexes based on 3,5-dimethyl-1-phenyl-1H-pyrazole and N,N-donor ligands.

In this paper, we present the synthesis of four new complexes: the dimeric precursor [Ir(dmppz)2(μ-Cl)]2 (1) (Hdmppz - 3,5-dimethyl-1-phenyl-1H-pyrazole) and heteroleptic bis-cyclometalated complexes: [Ir(dmppz)2(Py2CO)]PF6·½CH2Cl2 (2), [Ir(dmppz)2(H2biim)]PF6·H2O (3), and [Ir(dmppz)2(PyBIm)]PF6 (4), with auxiliary N,N-donor ligands: 2-di(pyridyl)ketone (Py2CO), 2,2'-biimidazole (H2biim) and 2-(2'-pyridyl)benzimidazole (PyBIm). In the obtained complexes, SC-X-ray analysis revealed that Ir(III) has an octahedral coordination sphere with chromophores of the type {IrN2C2Cl2} (1) or {IrN4C2} (2-4). The complexes obtained, which have been fully characterised by physicochemical methods (CHN, TG, FTIR, UV-Vis, PL and 1H, 13C, 15N NMR), were used to continue our studies on the factors influencing the cytotoxic properties of potential chemotherapeutic agents (in vitro). To this end, the following studies are presented: (i) comparative analysis of the effects on the biological properties of N,N-donor ligands and C,N-donor ligands in the studied complexes, (ii) studies of the interactions of the compounds with the selected molecular target: DNA and BSA (UV-Vis, CD and PL methods), (iii) and the reactivity towards redox molecules: GSH, NADH (UV-Vis and/or ESI-MS methods), (iv) cytotoxic activity (IC50) of potential chemotherapeutics against MCF-7, K-562 and CCRF-CEM cell lines.

Stereochemistry of the cis-Tetrafluoro Complexes of Titanium with 1-Ac-2-[Ph2P(O)]-Cyclohexane (1RS,2SR) Stereoisomers in СН2Сl2

The monodentate phosphoryl-containing ligand 1-Ac-2-[Ph2P(O)]-cyclohexane (L) bearing two asymmetric carbon atoms is synthesized. The study of its crystal structure shows that L is a racemic mixture of (1R,2S) and (1S,2R) stereoisomers. The complex formation of L with TiF4 in СН2Сl2 is studied by 19F{1Н} and 31Р{1Н} NMR spectroscopy. The compositions of the complexes formed in the solution are determined. Racemic and meso-diastereomers of the octahedral complex cis-TiF4L2 are formed in the solution as found by an analysis of the 19F and 31Р NMR spectra taking into account the concept of heterotropy of organic compounds. The influence of the optical configuration of stereoisomers of the monodentate ligand coexisting in the coordination sphere of the [MF4L2] octahedral tetrafluoro complexes of transition d0 metals on the chemical shifts of the fluorine atoms arranged in the trans positions relative to each other is shown. In the meso-diastereomer of cis-TiF4L2, this results in a nonequivalence of the fluorine atoms on the F–Ti–F' ordinate of the octahedron, and the spin-spin coupling constant JFF' = 286.1 Hz is observed in the 19F{1H} NMR spectrum.

The influence of the pyridyl substituent in N-methyl-P,P-diphenyl-N-2-pyridinyl-phosphinous amide ligand on the coordination chemistry of group 6B metal carbonyl derivatives

The reaction of N-methyl-P,P-diphenyl-N-2-pyridinyl-phosphinous amide (1) with group 6B metal hexa, tetra, and tricarbonyls yielded the same octahedral complexes cis-M(CO)4[1-κ2P,Npy] (M = Cr(2), Mo(3), W(4)) in which the ligand chelates only in a bidentate fashion through its phosphorus atom and pyridyl N-atom. Compounds 1–4 were identified and characterized by multinuclear NMR spectroscopy (1H, 13C, 31P NMR), elemental analysis, IR and UV–Vis spectroscopy. Complexes 2–4 exhibited weak metal-to-ligand charge transfer transitions unaffected by solvent polarity. Crystal structure determination is carried out on complex 4.

Crystal growth and magnetic properties of atom K embedded in Na5Co15.5Te6O36

In this paper, we report the structural, magnetic and specific heat properties of a new compound Na2.67K1.33Pb0.67Co15.33Te6O36 (NKPCTO). The compound can be regarded as a new system charactered by the K and Pb atom embedded in the Kagome system Na5Co15.5Te6O36 (NCTO). In the new structure, we find that the disordered occupations of the Na and Co(3) atoms is irrelevant to K atom site, and Pb has same site with K. The ground state is proposed to have an effective S = 1/2 due to the 3d7 Co2+ ion in octahedral coordination and considerable spin–orbit coupling. Magnetic and specific heat data uncover that only an antiferromagnetic phase transition develops in NKPCTO at 49 K. There are also ferromagnetic correlations above the Neel temperature, as well as anomalous hysteresis loops and multiple field-induced magnetic transitions at low temperatures.

Concerning the structures of Lewis base adducts of titanium(IV) hexafluoroisopropoxide.

The reaction of titanium(IV) chloride with sodium hexafluoroisopropoxide, carried out in hexafluoroisopropanol, produces titanium(IV) hexafluoroisopropoxide, which is a liquid at room temperature. Recrystallization from coordinating solvents, such as acetonitrile or tetrahydrofuran, results in the formation of bis-solvate complexes. These compounds are of interest as possible Ziegler-Natta polymerization catalysts. The acetonitrile complex had been structurally characterized previously and adopts a distorted octahedral structure in which the nitrile ligands adopt a cis configuration, with nitrogen lone pairs coordinated to the metal. The low-melting tetrahydrofuran complex has not provided crystals suitable for single-crystal X-ray analysis. However, the structure of chloridotris(hexafluoroisopropoxido-κO)bis(tetrahydrofuran-κO)titanium(IV), [Ti(C3HF6O)3Cl(C4H8O)2], has been obtained and adopts a distorted octahedral coordination geometry, with a facial arrangement of the alkoxide ligands and adjacent tetrahydrofuran ligands, coordinated by way of metal-oxygen polar coordinate interactions.

Synthesis, crystal Structure, theoretical calculation and luminescence properties of Cu(Ⅱ), Co(Ⅱ), Ni(Ⅱ) and Zn(Ⅱ) quinolinyl benzimidazole complexes with multiple coordination number induced by proton

The innovative ligand H2L, featuring a benzimidazole structure substituted with 8-hydroxyquinoline and equipped with N,O donor sites, underwent successful synthesis and meticulous characterization. Notably, this ligand was exclusively synthesized through catalysis under protonated conditions, accompanied by an in-depth exploration of the catalytic mechanism. Employing single-crystal X-ray diffraction, we acquired and authenticated four distinct asymmetric double-decker sandwich mononuclear transition metal complexes: [Cu(HL)2]·2H2O, [Co(HL)2]·CH3OH, [Ni(HL)2] and [Zn(HL)2]·CH2Cl2. Among these, complex 1 revealed an intriguing five-coordinate Cu(II) center adopting a distorted square pyramidal geometry, whereas the central metal ions in complexes 2–4 exhibited a six-coordinate configuration, characterized by a distorted octahedral geometry. Noteworthy is the observation that the dihedral angles within the crystal structures of complexes 2–4 approached approximately 90° to a significant extent. To delve deeper into the electronic properties and transitions, meticulous DFT and TD-DFT calculations were performed on both the ligand H2L and complexes 1–4. Furthermore, a comprehensive investigation into the luminescence properties of both H2L and its complexes was conducted, revealing a pronounced luminescence quenching effect in the complexes compared to the ligand. Through thorough analysis utilizing Hirshfeld surface examination and IRI analysis, various weak intermolecular interactions within the system were elucidated.

SnF(bipy)(H2O)]2[SnF6], a mixed-valent inorganic tin(II)-tin(IV) compound.

In the title compound, bis-[aqua-(2,2'-bi-pyridine)-fluorido-tin(II)] hexa-fluorido-tin(IV), [SnF(C10H8N2)(H2O)]2[SnF6], an ionic mixed-valent tin(II)-tin(IV) compound, the bivalent tin atom is the center atom of the cation and the tetra-valent tin atom is the center atom of the anion. With respect to the first coordination sphere, the cation is monomeric, with the tin(II) atom having a fourfold seesaw coordination with a fluorine atom in an equatorial position, a water mol-ecule in an axial position and the two nitro-gen atoms of the chelating 2,2'-bi-pyridine ligand in the remaining axial and equatorial positions. The bond lengths and angles of this hypervalent first coordination sphere are described by 2c-2e and 3c-4e bonds, respectively, all of which are based on the orthogonal 5p orbitals of the tin atom. In the second coordination sphere, which is based on an additional, very long tin-fluorine bond that leads to dimerization of the cation, the tin atom is trapezoidal-pyramidally coordinated. The tetra-valent tin atom of the centrosymmetric anion has an octa-hedral coordination. The differences in its tin-fluorine bond lengths are attributed to hydrogen bonding, as the two of the four fluorine atoms are each involved in two hydrogen bonds, linking anions and cations together to form strands.

Mer-[Ni(dien)2]Cl2.H2O and mer-[Ni(dien)2](NO3)2 complexes (dien= diethylenetriamine): Synthesis, physical, computational studies, antioxidant activity, and their use as precursors for Ni/NiO nanoparticles’ preparation

Two new Ni(II) complexes, mer-[Ni(dien)2]Cl2.H2O (I) and mer-[Ni(dien)2](NO3)2 (II), where dien= diethylenetriamine and mer refers to meridional coordination, have been prepared under ambient conditions. Complex (I) crystallizes in the P21/c space group of the monoclinic system, with a = 13.5000(4) Å, b = 8.7170(3) Å, c = 13.9430(4) Å, β = 102.091(2)° and V = 1604.41 Å3, whereas complex (II) crystallizes in the Pbca space group of the orthorhombic system, with a = 8.8117(6) Å, b = 14.0023(8) Å, c = 26.7603(17)Å and V = 3301.79 Å3. Both structures contain the [Ni(C4H13N3)2]2+ cation, together with two chloride anions and a water molecule for (I) and two nitrate anions for (II). The metal centre is coordinated to six nitrogens of the neutral dien ligands in a slightly distorted octahedral geometry. The two compounds have been characterised by FTIR and UV-Vis spectroscopy. Their morphology and size were studied by scanning electron microscopy (SEM). The thermal behaviour of the title compounds was also investigated. Calcination of the two complexes in air yielded Ni/NiO nanoparticles. The structures of both complexes were optimised and their simulated geometric parameters and vibrational modes were discussed and correlated with the experimental data. The antioxidant potential of both complexes was evaluated using DPPH, ferric reducing power tests and phosphomolybdenum assay.

Synthesis, characterization, in vitro and in silico biological studies of 3d transition metal(II) chelates of a Schiff base derived from sulfamethazine and 3,5-diiodosalicylaldehyde

A Schiff base (imine) ligand, (E)-4-((2-hydroxy-3,5-diiodobenzylidene)amino)-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide (HL), was synthesized by condensation of 3,5-diiodosalicylaldehyde with sulfamethazine. The ligand was then complexed with Zn(II), Cu(II), Ni(II), Co(II) and Fe(II) employing a metal to ligand ratio of 1:2 to form chelates (1-5), [M(L)2(H2O)2]. Characterization was done by UV-visible, FTIR, 1H and 13C NMR spectroscopy, elemental analysis, magnetic moments, thermogravimetric analyses (TGA) and conductance studies. The Schiff base behaved as a bidentate ligand and metal chelates assumed octahedral geometry. MOE-docking was employed to assess binding of the Schiff base (HL) and its chelates (1-5) with 1T2P, 1VVQ, 2W61, 3U2D, 4H8E and 5K18 proteins. Results indicated that Zn(II) chelate (1) and Fe(II) chelate (5) are the most potent compounds. Antibacterial and antibiofilm activities were executed against Enterococcus faecalis, Staphylococcus aureus, Proteus mirabilis and Klebsiella pneumoniae. Antifungal activities were performed against Candida albicans and Aspergillus niger. The Schiff base exhibited moderate antibacterial/antifungal activities that were enhanced on chelation with metal ions. Zinc(II) chelate (1) and Fe(II) chelate (5) show excellent antibacterial/antifungal activities. Complex 2 exhibited good antibiofilm activity.

Impact of SnO2 doping on spectroscopic characteristics of the SnO2-Na2O-CoO-B2O3 borate glass matrix

The role of tin oxide (SnO2) on the structure-optical features of borate glasses containing low cobalt oxide impurities was studied. The study was carried out on a glass system [x SnO2 – (80-x) B2O3 – 19.5 Na2O – 0.5 CoO]; x = 0.0, 0.5, 1.0, 2.0 and 3.0 mol%. Glass synthesis was carried out by the melt-quench technique. Structure and optical absorption spectroscopy were carried out to explore the optical transitions of Co cations inside the present glass matrix. The obtained results indicate that, with the further addition of SnO2 content, the molar volume decreased from 31.675 cm3/mol to 29.147 cm3/mol. FTIR studies indicated the basic structural units of trigonal BO3 units and BO4 tetrahedra. Herein also, additional contents of tin oxide increased the nonbridging oxygen contents. The reason behind such increment is attributed to the existence of Sn4+ ions in octahedral coordination acting as network modifiers. Optical absorption spectra indicated the existence of Co ions in both Co2+ and Co3+ oxidation states. Moreover, the existence of significant SnO2 concurred with the significant blue shift in the visible absorption bands and red shift in near infrared absorption bands. The positions absorption bands of Co ions were analyzed in the context of ligand field parameters determinations. The obtained data of the crystal field splitting parameter (10Dqt) showed decreased values from 3451 cm−1 to 3364 cm−1 with more SnO2 addition. While Racah parameter B values were also, attained showing increased values from 967 cm−1 to 985 cm−1 when additional SnO2 is added. Further, the impacted role of SnO2 addition on the structural and optical properties of the present glasses was finally estimated.

Porphyrin films as discrete elements for nucleoside identification: Experimental and DFT study

In this work, the interaction of metal-free octaethylporphyrin (P) and a Mn(III) octaethylporphyrin chloride (MnP) films with various RNA nucleoside molecules (adenosine [A], cytidine [C], guanosine [G] and uridine [U]) was investigated to elucidate a possible molecular recognition. The porphyrin film-nucleoside interaction took place in solution, which was analyzed to quantify the nucleoside adsorption. The films were investigated by using microscopy and spectroscopic techniques (SEM, AFM, UV-Vis and IR), in addition to the in-plane film conductivity. Experimental results were correlated with DFT calculations to investigate binding energies, separation distances, and adsorption sites, among others. From these results, it was observed that purine bases were preferably adsorbed by the metal-free porphyrin film, while pyrimidine bases were adsorbed on the manganese porphyrin surface. Conductivity results exhibited the highest resistance for the bare metal-free film, but its conductivity increases after nucleoside adsorption, being the purine molecules the most resistive and the pyrimidine molecules the most conductive. In contrast, the Mn porphyrin film showed the highest conductivity, but after nucleoside adsorption, the resistivity increased for purine and pyrimidine bases, being pyrimidines the less conductive. DFT calculations showed binding energies PG>PA>PC>PU and MnPC>MnPG>MnPA>MnPU, which were consistent with experimental findings. In general, the main interactions took place between the porphyrin core and the pentose of the nucleoside, while MnP formed Mn porphyrin-nucleoside arrangements with octahedral geometry. The calculated UV-Vis spectra were in agreement with the experimental plots. From these results, changes in nucleoside adsorption can lead to a selective recognition of nucleoside molecules.