Pentagonal Bipyramidal Geometry Research Articles

Tetranuclear CoII4O4 Cubane Complex: Effective Catalyst Toward Electrochemical Water Oxidation.

The reaction of Co(OAc)2·6H2O with 2,2'-[{(1E,1'E)-pyridine-2,6-diyl-bis(methaneylylidene)bis(azaneylylidene)}diphenol](LH2) a multisite coordination ligand and Et3N in a 1:2:3 stoichiometric ratio forms a tetranuclear complex Co4(L)2(μ-η1:η1-OAc)2(η2-OAc)2]· 1.5 CH3OH· 1.5 CHCl3 (1). Based on X-ray diffraction investigations, complex 1 comprises a distorted Co4O4 cubane core consisting of two completely deprotonated ligands [L]2- and four acetate ligands. Two distinct types of CoII centers exist in the complex, where the Co(2) center has a distorted octahedral geometry; alternatively, Co(1) has a distorted pentagonal-bipyramidal geometry. Analysis of magnetic data in 1 shows predominant antiferromagnetic coupling (J = -2.1 cm-1), while the magnetic anisotropy is the easy-plane type (D1 = 8.8, D2 = 0.76 cm-1). Furthermore, complex 1 demonstrates an electrochemical oxygen evolution reaction (OER) with an overpotential of 325 mV and Tafel slope of 85 mV dec-1, required to attain a current density of 10 mA cm-2 and moderate stability under alkaline conditions (pH = 14). Electrochemical impedance spectroscopy studies reveal that compound 1 has a charge transfer resistance (Rct) of 2.927 Ω, which is comparatively lower than standard Co3O4 (5.242 Ω), indicating rapid charge transfer kinetics between electrode and electrolyte solution that enhances higher catalytic activity toward OER kinetics.

A 3D coordination polymer of Cd(II) with conformationally flexible mixed ligands as an active filler for silicone elastomers

The electronic configuration of d10 metals enables for a wide range of coordination numbers and geometries which, together with the use of mixtures of ligands for their coordination, allows fine-tuning of the properties of the complexes formed. By treating Cd(ClO4)2 with 1,3-bis(carboxypropyl)tetramethyldisiloxane (H2Cx) and 4,4′-azopyridyne (AzPy) in solution, a 3D coordination polymer, [Cd(Cx)(AzPy)·1.85H2O]n (1), was mostly formed. The compound was investigated by elemental and spectral analysis, as well as by powder and single crystal X-ray diffraction. Thermal behavior of compound 1 was evaluated by TGA and DSC, while the moisture behavior was studied by dynamic vapor sorption (DVS) analysis. Compound 1 contains a five-dentate Cx2− ligand with Cd atoms in a pentagonal-bipyramidal geometry, as determined by X-ray analysis. The conformational flexibility of the ligands allows the establishment of all possible intermolecular interactions in a very dense packing, the resulting structure having an extremely low free volume (14.8%). The compound is hydrophobic, adsorbing up to 2.4 wt% water vapor, thermally stable up to 160 °C, and has a phase transition around 6 °C, which, based on analysis by polarized optical microscopy (POM), is considered as a second-order crystal-to-crystal transition, facilitated by the mobility of the siloxane fragment. Due to the constraints imposed by the covalent 3D architecture, the conformational photoisomerization of 1 is extremely limited, as indicated by UV–Vis spectroscopy studies on solutions with solvents of different polarities as well as dielectric spectroscopy studies on silicone composites in which it is in solid state with 5 and 20 wt% loading. Instead, it was found that compound 1 significantly increases the dielectric strength of the resulting materials (up to 46 V/μm compared to 18 V/μm in the empty matrix) by incorporating it as a filler, making them suitable for dielectric elastomer generators, as the results of theoretical calculations indicate. In the purification process, a 2D coordination polymer, [Cd(Cx)(AzPy)·H2Cx]n (2), was also identified in traces.

Nicotinamide, acetate and their two new complexes with Zn(II) and Cd(II)

Two new complexes of Zn(II) and Cd(II) with acetate and nicotinamide as mixed ligands were synthesized and characterized. The Zn(II) complex is mononuclear, [Zn(ac)2(NA)2] (1), while the Cd(II) is a dinuclear one, [Cd2(ac)4(NA)4].2H2O (2), where ac = acetate and NA = nicotinamide. The compounds were characterized by means of single-crystal X-ray diffraction, FTIR, 1H NMR, 13C NMR spectroscopy, thermal analysis and elemental analysis. The geometry of the metal ion is distorted tetrahedral for Zn(II) and distorted pentagonal bipyramid geometry for Cd(II). In the dinuclear complex, each metal ion is coordinated by three acetate groups, but there are two different types of coordination modes for the acetate ligands: bidentate chelating and bridging bidentate chelating.

Ligand- and metal-exchange reactions of robust nickel complexes with pentagonal bipyramidal structures.

The coordination chemistries of transition metal complexes with pentagonal bipyramidal geometries were investigated, and the highly stable nature of a cyclic pentapyridyl ligand was disclosed. A NiCl2 complex with the pentapyridyl ligand was found to be stable toward water and acidic conditions. The stable complex underwent ligand-exchange reactions with nucleophilic reagents, and a series of pentagonal bipyramidal complexes with different apical ligands was prepared. Crystallographic analyses with the aid of theoretical calculations revealed that the complexes were constructed by electrostatic threading of a divalent linear nickel complex into the ring of the neutral, cyclic pentapyridyl, which resulted in robust water- and acid-resistant complexes with unique pentagonal bipyramidal structures. A reductive metal exchange reaction was then discovered, which enabled "linear divalent metal + electrostatic ring" formulations with different metal atoms.

Two mononuclear chromophore coumarin-based Dy(III) complexes with magnetic relaxation and luminescent properties

Lanthanide luminescent single-molecule magnets (SMMs) serve as a kind of multifunctional molecular materials that have attracted extensive attention. Herein, a novel chromophore coumarin ligand 7-(diethylamino)-(2‑hydroxy-3-methoxybenzylidene)-2-oxo-2-chromene-3-carbohydrazide (Hvalcoumarin) is designed to construct the luminescent Dy(III) complexes. Two Dy complexes 1 ([Dy(valcoumarin)(DMF)2Cl2]·(CHCl3)) and 2 [Dy(valcoumarin)(DMF)2(NO3)2] were synthesized based on the luminescent chromophore coumarin ligand (Hvalcoumarin). X-ray crystallography reveals that the Dy(III) center in complex 1 adopts a hepta-coordinated arrangement by a distorted pentagonal bipyramidal geometry. In contrast, complex 2 exhibits a nine-coordinate arrangement by a spherical capped square antiprism geometry. Magnetic investigations reveal that 1 and 2 exhibit a slow magnetic relaxation phenomenon. Furthermore, the luminescent spectra of 1 and 2 display the characteristic emission profiles associated with Dy(III) spectra. Moreover, theoretical calculations also demonstrated the relaxation dynamics of 1 and 2. The results furnish a potent avenue for the acquisition of multifunctional molecular materials with magnetic and luminescent properties.

Pu(VI) Oxalate Crystal Structure and Evidence of Photoreduction to Pu(IV) Oxalate.

We report the first crystal structure of a Pu(VI)-oxalate compound. This compound, [PuO2(C2O4)(H2O)]·2(H2O) (1), crystallizes in space group P21/c with a = 5.5993(3) Å, b = 16.8797(12) Å, c = 9.3886(6) Å, and β = 98.713(6)°. It is isostructural with the previously reported U(VI) compound, [UO2(C2O4)(H2O)]·2(H2O). Each plutonyl ion (PuO22+) is coordinated in the equatorial plane by two side-on bidentate oxalates, creating an infinite chain along [001]. A coordinated water molecule and twisting of the oxalates lead to a distorted pentagonal bipyramidal geometry of the Pu. A photochemical degradation was observed for 1, which resulted in the formation of a secondary crystalline phase. The absorption spectrum of this secondary phase confirmed the presence of Pu(IV), but it did not match the spectrum of Pu(C2O4)2·6H2O, which is considered to be the primary product of Pu-oxalate precipitation. While compound 1 has previously been proposed to exist in solution, this is the first time it has been isolated via crystallization. Although redox interactions between Pu and oxalate have been documented in the literature, the present study is the first observation of a photochemical reduction of Pu(VI)-oxalate. As a result, this study has expanded on the limited understanding of the Pu(VI)-oxalate system, which is important for nuclear fuel cycle applications.

Synthesis, structural characterization, and DNA binding/cleavage studies of diorganotin(IV) carboxylates and their complexes with 1,10-phenanthroline: X-ray structures of [Me8Sn4(p-FC6H4CO2)4O2], [Bu2Sn(p-NO2C6H4CO2)2.phen], and DFT studies

The present study is focused on the mode of DNA-interactions with diorganotin(IV) carboxylates and their 1,10-phenanthroline (phen) complexes, and revealed that the planarity and extended π system of phen may increase the probability of DNA intercalation. Diorganotin(IV) derivatives of p-fluoro-/p-hydroxy-/p-nitro benzoic acid, viz. Bu2Sn(p-XC6H4CO2)2: X = F (1), OH (2), NO2 (3), Oct2Sn(p-NO2C6H4CO2)2 (4), and Me8Sn4(p-FC6H4CO2)4O2 (5), and their complexes with phen viz. Bu2Sn(p-XC6H4CO2)2.phen: X = F (6), OH (7), NO2 (8), Oct2Sn(p-NO2C6H4CO2)2.phen (9), and Me2Sn(p-FC6H4CO2)2.phen (10) have been synthesized and characterized by using various techniques including single crystal X-ray diffraction studies, nuclear magnetic resonance (1H, 13C, and 119Sn NMR), electrospray ionization mass spectrometry (ESI-MS), infrared (FT-IR), and elemental analysis. Based on crystal data, complexes (5) and (8) have a P-1 space group with a triclinic crystal system. In the octahedral geometry of complex (5), Sn atom has a tetranuclear Sn4O2 core, whereas complex (8) has a pentagonal bipyramidal geometry around Sn atom. The LanL2Z basis set has been employed for optimized gas-phase geometries, and the calculated ∠C-Sn-C bond angles agree with those obtained from NMR/X-ray studies. UV-visible, fluorescence and circular dichroism (CD) titrations showed interaction with Calf Thymus DNA (CT-DNA), and Kb and KSV values in the order of 103–105 M−1 indicate intercalation within the base pairs or in minor groove. Further, gel electrophoreses studies indicate that all of the complexes have efficiently cleaved plasmid pBR322 DNA into three bands; supercoiled, nicked/circular along with linear structure. The intriguing biophysical results suggest that these complexes may have anticancer potential.

Synthesis, characterization, TD‐DFT, molecular docking, biological applications, and solvatochromic studies of some new metal complexes derived from semicarbazone of pyrano[3,2‐c]quinoline‐3‐carboxaldehyde

New Zn(II), Cd(II), VO(IV), and UO2(VI) solvatochromic complexes derived from 6‐ethyl‐4‐hydroxy‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carboxaldehyde‐semicarbazone ligand (H2L) were synthesized and established by elemental analyses, spectral (IR, UV, NMR, mass spectra), molar conductivity measurements, magnetic susceptibility, and thermal gravimetric analysis (TGA). The ligand coordinates with metal ions through ONO chelating sites, forming an octahedral geometry arrangement, except UO2(VI) that showed pentagonal bipyramidal geometry. Using Coats–Redfern methodology, the kinetic parameters (Ea, A, ΔH, ΔS, and ΔG) of the thermal decomposition steps were calculated and discussed. The complexes showed solvatochromic behavior that used to estimate the ground and excited state dipole moments. Optimization and structural parameters were carried out by density function theory (DFT) at B3LYP/GENECP method at 6‐311G(d,p) basis set for C, H, N, and O atoms and SDD (Stuttgart/Dresden) basis set for the metal atoms and interrelated with the experimental results. The complexes were tested for antimicrobial efficiency against Gram‐positive bacteria, Gram‐negative bacteria, yeast, and fungi. Also, antitumor activity was investigated against HepG‐2 cell line. Finally, the new synthesized complexes upon subjecting to molecular docking and distinguishable results showed outstanding inhibition results of VEGFR‐2 via achieving a high stabilization level inside the largest pocket of 1YWN protein.

Phenol-Tethered N-Heterocyclic Benzimidazol-2-ylidene Carbene Interactions with the Early Lanthanides

The cyclization of salophan with triethyl orthoformate in the presence of HBr results in a bisphenol benzimidazolium carbene precursor 1,3-bis(2-hydroxybenzyl)-2H-benzimidazolium bromide (H3OBBIm). By reacting H3OBBIm in a one-pot synthesis with Ln(N(SiMe3)2)3 (Ln = La–Sm excl. Pm) and an excess of KN(SiMe3)2, the N-heterocyclic carbene (NHC) complexes, [Ln(OBBIm)2(N″)][K2THFx], can be prepared and isolated. These complexes were characterized by single-crystal X-ray diffraction, solution- and solid-state UV–vis–near-infrared spectroscopy, and 1H NMR. These complexes possess distorted pentagonal bipyramid geometries.

Structure and Reactivity of a Seven-Coordinate Ruthenium Iodosylbenzene Complex.

Seven-coordinate (CN7) ruthenium-oxo species have attracted much attention as highly reactive intermediates in both organic and water oxidation. Apart from metal-oxo, other metal-oxidant adducts, such as metal-iodosylarenes, have also recently emerged as active oxidants. We reported herein the first example of a CN7 Ru-iodosylbenzene complex, [RuIV(bdpm)(pic)2(O)I(Cl)Ph]+ (H2bdpm = [2,2'-bipyridine]-6,6'-diylbis(diphenylmethanol); pic = 4-picoline). The X-ray crystal structure of this complex shows that it adopts a distorted pentagonal bipyramidal geometry with Ru-O(I) and O-I distances of 2.0451(39) and 1.9946(40) Å, respectively. This complex is highly reactive, and it readily undergoes O-atom transfer (OAT) and C-H bond activation reactions with various organic substrates. This work should provide insights for the development of new highly reactive oxidizing agents based on CN7 geometry.

Structural characterization, DNA binding study, antioxidant potential and antitumor activity of diorganotin(IV) complexes against human breast cancer cell line MDA-MB-231

Five new organotin(IV) complexes, Me2SnL (1), Bu2SnL (2), t-Bu2SnL (3), Ph2SnL (4) and Oct2SnL (5), have been synthesized from the reaction of R2SnCl2 (R= Me, Bu, tert-Bu, Ph, Oct) with N'-(3-ethoxy-2-hydroxybenzylidene)formohydrazide (H2L). The structural elucidation of synthesized compounds was done by FT-IR, 1H-NMR, 13C-NMR spectroscopy and single-crystal X-ray analysis. Crystallographic data of complex (1) showed seven coordinated central tin atom with distorted pentagonal bipyramidal geometry. Where in solution the Sn atom of synthesized complexes exhibit five coordination, confirmed from 1H-NMR. The results from DNA interaction studies via UV-visible spectroscopy, viscosity, cyclic voltammetry, and differential pulse voltammetry (DPV) suggested an intercalative mode of interaction between the synthesized compounds and SS-DNA. Furthermore, the complexes interact more significantly than ligand. Electrochemical and thermodynamic parameters, including diffusion coefficient, ∆H, ∆G, and ∆S, were calculated using cyclic voltammetry data. The linear plot of peak current (I) vs. square root of the scan rate (υ1/2) indicated the electrochemical processes to be diffusion controlled. The DPPH free radical scavenging assay results showed that complex (4) is an active antioxidant. In-vitro cytotoxicity of the synthesized compounds was determined on human breast cancer cell line MDA-MB-231 using tetrazolium-based MTT assay, and complexes (2), (3) and (4) showed significant cytotoxic activity. The structure-activity relationships may be utilised to direct the optimization of the activity of agents from this class of compounds by comparing the specifics of the compound structures, their DNA binding, and toxicity.

Copper(II) pseudoatrane appended heterobimetallic 2D‐MOF: A multi‐functional material with catalytic and sensing properties

A maiden two‐dimensional atrane‐based heterobimetallic MOF (2) was constructed employing a novel tripodal ligand N{CH2COOH}2{CH2(2‐t‐Bu‐4‐CH3‐C6H2‐OH)} (1). Single‐crystal X‐ray diffraction depicted the formation of [4.3.3.01,5] pseudoatrane cage in which copper(II) ions attained trigonal bipyramidal geometry. Besides, the co‐existing sodium(I) ions acquired a pentagonal bipyramidal geometry produced by methanol molecules and free carboxylate sites of the ligand. This compound is the first of its kind where the sequential binding of copper(II) pseudoatrane cage and hepta‐coordinated sodium ion generated a heterobimetallic metal–organic framework with a sheet‐like structure. The TEM and SEM images of the MOF having stability up to 250°C revealed the formation of spherical structures (~78 nm) with flower‐like morphology. The heterobimetallic 2D‐MOF was proved to be a multifunctional material as it successfully catalysed Friedel–Craft's alkylation of Indole with beta‐nitrostyrene as well as utilised for the efficient detection of toxic brominated flame retardants through spectrophotometric and colorimetric studies. Remarkably, the best catalysis results were seen using DCM as a solvent, and the alkylation product obtained from the reaction of 2‐methylindole with 2‐Br‐β‐nitrostyrene showed an extraordinary yield of 98%. Besides, the 2D‐MOF showed a selective response with pentabromophenol, and tetrabromophthalic anhydride with quenching in peak on the addition of TBPA while shifting of the peak was observed from 457 to 402 nm with PBP. The practical application of the MOF was explored by its successful incorporation into portable silica strips for on‐the‐spot detection of BFRs.

Uranyl(VI) Mixed-ligand complex synthesis and characterization using 4-acylhydrazone-5-pyrazolone and 4-acylpyrazolone: Covalency, crystal assay, DFT study and Hirshfeld analysis

Newly prepared bidentate HLA and tridentate Bz-HLA ligands were used to synthesize the novel uranyl mixed ligand [UO2(HLA)(Bz-HLA)] complex with pentagonal bipyramidal geometry. HLA ligand was prepared via the common acylation method, and the Bz-HLA ligand was prepared using the Schiff base reaction of HLA with a benzohydrazide molecule. FTIR, 1H and 13C NMR, SCXRD, molar conductance, and TG-DTA were mainly implemented to examine the structure of produced compounds. The combined covalency effect of complex due to both ligands has been studied, which was discovered to be influenced by the average bond length values on the pentagonal plane, uranyl axial bond lengths, ligand coordination, and donor ability of various atoms. To demonstrate that solvents have no impact on the covalency of the synthesised complex, Sinha's covalency parameters were computed using UV–vis data. DFT calculations were performed in order to validate experimental findings in comparison to theoretical findings, and theoretical bond characteristics were also investigated through the recognition of global index values. Hirshfeld surface analysis was used to examine the crystal strength, energy characteristics and non-covalent surface interactions. Analysis using cyclic voltammetry(CV) shows that the complex is irreversibly reducing. Understanding the Schiff base of acylpyrazolones and their covalency in uranyl complexes allow for the investigation of a wide range of chemical properties and applications.

New supramolecular architectures of 4′-(4-quinolinyl)-2,2′:6′,2″-terpyridine based on tin complexes: Design, structural variations and thermal properties

The reactions of 4′-(4-quinolinyl)-2,2′:6′,2″-terpyridine (qtpy) with SnMe2Cl2 and SnMe2(NCS)2 have been investigated. The reaction of SnMe2Cl2 with qtpy resulted in the formation of the new complex [SnMe2Cl(qtpy)]+[SnMe2Cl3]− (1) while the reaction of SnMe2(NCS)2 with qtpy affords the complex [SnMe2(NCS)2(qtpy)] (2). The resulting products have been characterized using elemental analysis, IR and multinuclear NMR (1H, 13C, 119Sn) spectroscopy. The new complex [SnCl2(qtpy)] (3) was characterized by X-ray crystallography from an acetone/n-hexane solution of 1 which reveals that 1 dissociates in solution. The new complex 2[SnMe2(NCS)2(qtpy)]·CH2Cl2·H2O (2.CH2Cl2·H2O) was characterized by X-ray crystallography from a dichloromethane/n-hexane solution of 2. Interestingly, the crystal structure of 3 reveals that the Sn(II) center is penta-coordinated as a slightly distorted square pyramid, as suggested by the index of the trigonality (τ) parameter. However, Sn(IV) is hepta-coordinated in 2.CH2Cl2·H2O which adopts a pentagonal bipyramidal geometry. The intermolecular hydrogen bond interactions and π…π stacking interactions establish to form the supramolecular assembly. The Hirshfeld surfaces analysis confirms that H…H and π…π interactions play major roles to stabilize the crystal architectures. The crystal structure of 2.CH2Cl2·H2O reveals the formation of porous material containing voids which have been occupied by the solvents. The volume of voids is 370 and 17 Å3, occupied by dichloromethane and water, respectively. Analysis of Sn-N bond lengths of complex 2.CH2Cl2·H2O shows that Sn-N bond lengths are greater than 2.39 Å for active organotin(IV) complexes, suggesting it as a good candidate for anti‐tumor activity. The thermal properties of the complexes indicate that 1 is stable up to 120 °C while 2 decomposes at 147 °C.

A seven-coordinate Mn(II) complex with a pyridine-based 15-membered macrocyclic ligand containing one acetate pendant arm: structure, stability and relaxation properties.

A new 15-membered pyridine-based macrocyclic ligand containing one acetate pendant arm (N-carboxymethyl-3,12,18-triaza-6,9-dioxabicyclo[12.3.1]octadeca-1(18),14,16-triene, L1) was synthesized and its Mn(II) complex MnL1 was investigated in the context of MRI contrast agent development. The X-ray molecular structure of MnL1 confirmed a coordination number of seven with an axially compressed pentagonal bipyramidal geometry and one coordination site available for an inner-sphere water molecule. The protonation constants of L1 and the stability constants of Mn(II), Zn(II), Cu(II) and Ca(II) complexes were determined by potentiometry, and revealed higher thermodynamic stabilities in comparison with complexes of 15-pyN3O2, the parent macrocycle without an acetate pendant arm. The MnL1 complex is fully formed at physiological pH 7.4, but it shows fast dissociation kinetics, as followed by relaxometry in the presence of an excess of Zn(II). The short dissociation half-life estimated for physiological pH (ca. 3 minutes) is related to fast spontaneous dissociation of the non-protonated complex. At lower pH values, the proton-assisted dissociation pathway becomes important, while the Zn(II) concentration has no effect on the dissociation rate. 17O NMR and 1H NMRD data indicated the presence of one inner-sphere water molecule with a rather slow exchange (k298ex = 4.5 × 106 s-1) and provided information about other microscopic parameters governing relaxation. The relaxivity (r1 = 2.45 mM-1 s-1 at 20 MHz, 25 °C) corresponds to typical values for monohydrated Mn(II) chelates. Overall, the acetate pendant arm in L1 has a beneficial effect with respect to 15-pyN3O2 in increasing the thermodynamic stability and kinetic inertness of its Mn(II) complex, but leads to a reduced number of inner-sphere water molecules and thus lower relaxivity.

A pentagonal bipyramidal Co(II) single-ion magnet based on an asymmetric tetradentate ligand with easy plane anisotropy

High-coordinate 3d single-ion magnets(SIMs) especially with pentagonal bipyramidal geometry as an emerging class of representative molecular magnets have received considerable concern. Whereas, it is not easy to construct and obtain 3d SIMs with high coordination numbers (CN = 7 or 8). Herein, a mononuclear Co(II) complex ([Co(pypzbeyz)(NCS)2(DMF)], pypzbeyz = N-((6-(1H-pyrazol-1-yl)pyridin-2-yl)methylene)benzohydrazide) based on a tetradentate ligand has been synthesized and structurally and magnetically characterized. Single-crystal X-ray diffraction analysis reveals that the Co(II) complex adopts a seven-coordinate distorted pentagonal bipyramidal geometry. Magnetic investigations show that the Co(II) complex has large easy plane anisotropy with a positive D value (D = +36.8 cm−1) and a small E value, and exhibits slow magnetic relaxation behavior under a dc field. Theoretical calculations show a positive zero-field splitting of 33.5 cm−1, which is in excellent agreement with the experiment. The results support that the 3d high-coordinate SIMs could be effectively achieved by using a suitable multi-dentate ligand with a certain ligand field.

Competent DNA binder pentagonal bipyramidal Fe(II) complex executed as a proficient catalyst for primary carbamates production from alcohols and urea

The iron (II) complex, [Fe(H2L)(H2O)2](ClO4)2(H2O) (1) of Schiff base ligand H2L [5-Methyl-1-H-pyrazole-3-carboxylic acid (1-pyridin-2-yl-ethylidene)-hydrazide] was prepared and structurally determined by X-ray crystal analysis. The complex 1 is being hepta-coordinated mononuclear system that adopts pentagonal bipyramidal geometry. Moreover, the calf thymus DNA (CT-DNA) interaction with 1 was carried out by proper bio-physical methods. The complex 1 was observed to interact with CT-DNA by intercalation binding mode and the binding constant of this interaction was calculated as (1.5 ± 0.06) × 106 M−1 and that was obtained from fluorimetric spectral titration. Again the complex 1 is very much effective in the catalytic reaction of primary carbamate synthesis. In this procedure alcohols and eco-friendly sustainable carbonylation source urea were used for the synthesis of desired product. Both aromatic alcohols as well as aliphatic alcohols were efficiently proceeded through the catalytic reaction and produced medium to high yield (up to 94%) of carbamate products under mild reaction conditions. The catalytic mechanism was also supported by DFT studies.

Green and efficient removal of sulfides using oxo-peroxo tungsten(VI)-MIL-101(Cr) nanoreactor as heterogeneous recyclable catalyst

Efficient removal of sulfide using a modified MIL-101(Cr) nanoreactor by Schiff base complex has been investigated using H2O2 as a green oxidant. In addition, a new oxo-peroxo tungsten(VI) complex has been synthesized successfully by treating WO3 with a tridentate ONO donor Schiff base ligand in the presence of H2O2. Different techniques have been used to characterize the complex, while the crystal structure was investigated using an X-ray crystallographic approach. A seven-coordinated tungsten ion with a deformed pentagonal–bipyramidal geometry was explored using single-crystal X-ray diffraction analysis. The [WO(O2)(L)(CH3OH)] (L: (E)-N'-(5-chloro-2-hydroxybenzylidene) iso nicotinohydrazide) complex has been screened for the sulfoxidation of aryl and alkyl sulfides with H2O2 as a homogeneous catalyst. Furthermore, Chloromethylated MIL-101(Cr) having a mesoporous structure has been used as a support for the immobilization of [WO(O2)(L)(CH3OH)] complex to produce a heterogeneous and recyclable catalyst. This heterogeneous catalyst is novel in its efficiency, as illustrated by its improved activity with reference to the homogeneous catalyst under the same reaction conditions. The heterogeneous structure displayed excellent reusability several times without losing activity due to covalent grafting between –CH2Cl and W(VI) Schiff base, which introduces high stable nanostructure without leaching the complex during the reaction.

Synthesis and Characterization of a Calcium‐Pyrazolonato Complex. Observation of In‐Situ Desolvation During Micro‐Electron Diffraction

AbstractThe synthesis and characterization of a calcium pyrazolonato complex is reported. X‐ray diffraction (XRD) of single crystals revealed an octahedral geometry with two axial solvent ligands. Analysis of the bulk sample by means of microcrystal electron diffraction (micro‐ED) measurement revealed a polymeric pentagonal bipyramidal coordination geometry joined via a central Ca2O2 ring with axial water ligands. During the micro‐ED measurement, loss of water was observed resulting in a secondary structure with a polymeric distorted octahedral coordination geometry joined via a central Ca2O2 ring. These findings demonstrate that XRD and micro‐ED methods can provide complementary data during structural determination, and that even electrophilic metals are susceptible to desolvation under micro‐ED measurements.

Di-Pyridine-Containing Macrocyclic Triamide Fe(II) and Ni(II) Complexes as ParaCEST Agents.

Fe(II) and Ni(II) paraCEST contrast agents containing the di-pyridine macrocyclic ligand 2,2',2″-(3,7,10-triaza-1,5(2,6)-dipyridinacycloundecaphane-3,7,10-triyl)triacetamide (DETA) are reported here. Both [Fe(DETA)]2+ and [Ni(DETA)]2+ complexes were structurally characterized. Crystallographic data revealed the seven-coordinated distorted pentagonal bipyramidal geometry of the [Fe(DETA)]·(BF4)2·MeCN complex with five coordinated nitrogen atoms from the macrocyclic ring and two coordinated oxygen atoms from two amide pendant arms. The [Ni(DETA)]·Cl2·2H2O complex was six-coordinated in nature with a distorted octahedral geometry. Four coordinated nitrogen atoms were from the macrocyclic ring, and two coordinated oxygen atoms were from two amide pendant arms. [Fe(DETA)]2+ exhibited well-resolved sharp proton resonances, whereas very broad proton resonances were observed in the case of [Ni(DETA)]2+ due to the long electronic relaxation times. The CEST peaks for the [Fe(DETA)]2+ complex showed one highly downfield-shifted and intense peak at 84 ppm with another shifted but less intense peak at 28 ppm with good CEST contrast efficiency at body temperature, whereas [Ni(DETA)]2+ showed only one highly shifted intense peak at 78 ppm from the bulk water protons. Potentiometric titrations were performed to determine the protonation constants of the ligand and the thermodynamic stability constant of the [M(DETA)]2+ (M = Fe, Co, Ni, Cu, Zn) species at 25.0 °C and I = 0.15 mol·L-1 NaClO4. Metal exchange studies confirmed the stability of the complexes in acidic medium in the presence of physiologically relevant anions and an equimolar concentration of Zn(II) ions.