Bipyramidal Environment Research Articles

Structures and NMR Solution Dynamics of Diorganotin Complexes with Bulky Quadridentate Salen‐ and Salphen‐Type Schiff Bases (N2O2) Incorporating Diazenylpyridyl Side Arms

AbstractA series of six complexes [n‐Bu2Sn(L1)]⋅S (S=Benzene/toluene, mixed/partial) (1), [Ph2Sn(L1)]n⋅S (S=Benzene) (2), [Bz2Sn(L1)] (3), [n‐Bu2Sn(L2)]n (4), [Ph2Sn(L2)] (5) and [Bz2Sn(L2)] (6) were synthesized using diorganotin(IV) oxide precursors and two new bis‐Schiff bases containing N2O2 donor atoms. The Schiff bases, H2L1 and H2L2, were prepared by reacting ethane‐1,2‐diamine or benzene‐1,2‐diamine with 2‐hydroxy‐5‐(pyridin‐3‐yldiazenyl)benzaldehyde in absolute ethanol. Compounds 1–6 were characterized by IR and NMR spectroscopies, as well as by solid‐state single‐crystal X‐ray diffraction (except for 3 and 6). In all the complexes the bis‐Schiff bases occupy the equatorial positions and the R groups are in axial sites. However, while 1 and 5 are discrete molecules where the tin atoms adopt distorted octahedral geometries, 2 and 4 are monoperiodic polymers with the metal cations in pentagonal bipyramidal environments. Although solid state crystallographic results revealed asymmetrical molecular configurations, solution NMR studies proved symmetric arrangements for all the compounds. Tin NMR spectroscopy confirmed that all complexes are six‐coordinate in solution, despite variations in solid‐state coordination. Further analysis using Hirshfeld surface and fingerprint plots provided insights into intermolecular interactions in compounds 1, 2, 4, and 5. This comprehensive study underscores the structural diversity and solution‐state dynamics of organotin(IV) complexes synthesized using novel Schiff bases.

Complexes of a Noncyclic Carbazole-based N5-donor Schiff base: Structures, Redox, EPR and Poor Activity as Hydrogen Evolution Electrocatalysts.

A new noncyclic pentadentate N5-donor Schiff-base ligand, HL2Etpyr (1,1'-(3,6-ditert-butyl-9H-carbazole-1,8-diyl)bis(N-(2-(pyridin-2-yl)ethyl)methanimine)), prepared from 1,8-diformyl-3,6-ditertbutyl-carbazole (HUtBu) and two equivalents of 2-(2-pyridyl)ethylamine, along with four tetrafluoroborate complexes, [MIIL2Etpyr](BF4), where M = Co, Ni, Cu, and Zn, and two [CoIIL2EtPyr]·1/2[CoIIX4] complexes where X = NCS or Cl, isolated as solvates, are reported. All six complexes were structurally characterized, revealing the cations to be isostructural, with M(II) in a trigonal bipyramidal N5-donor environment. Only the Zn(II) complex is fluorescent. Cyclic voltammograms of [MIIL2Etpyr](BF4) in MeCN reveal reversible redox processes at positive potentials: 0.61 (Zn), 0.62 (Cu), 0.57 (Ni), and 0.25 V (Co), and for the cobalt complex a second quasi-reversible process occurs at 0.92 V vs Fc+/Fc. EPR data for the first oxidation product clearly demonstrate that the Zn complex undergoes a ligand centered oxidation, and support this being the case for the Ni and Cu complexes, although this is not definitively shown. After both oxidations the EPR data shows that the Co complex is best described as a low spin Co(III)-ligand radical. In the presence of 80 mM acetic acid, controlled potential electrolysis carried out on [MIIL2Etpyr](BF4) at -1.68 V in MeCN shows some electrocatalytic hydrogen evolution reaction (HER) performance in the order Ni(II) > Cu(II) > Co(II) - but the control, Ni(II) tetrafluoroborate, is more active than all three of the complexes.

Synthesis, calf-thymus DNA interaction with trimethyl-/triphenyl-tin(IV) derivatives of ɑ-lipoic acid and their mixed ligand complexes with N-donor (1,10-phenanthroline/2,2′-bipyridyl/benzimidazole)

The mixed ligand complexes of trimethyl-/triphenyl-tin(IV) derivatives of ɑ-lipoic acid (HLA), viz. R3Sn(LA) {R = Me (1), and Ph (2)}with 1,10-phenanthroline (phen), viz. [Me3Sn(LA).phen] (3), 2,2′-bipyridyl, viz. [Ph3Sn(LA).by] (4) and benzimidazole (bz), viz. [R3Sn(LA).bz] {R = Me (5), and Ph (6)} were synthesised and satisfactorily characterized by analytical and spectroscopic techniques, especially FT-IR, NMR (1H, 13C, and 119Sn NMR) spectroscopy and ESI-MS spectrometry. The ∠C-Sn-C bond angle calculated by optimization of their gas-phase geometry revealed that complexes (1) and (2) have distorted tetrahedral geometry and complexes (3) and (4) exhibited distorted octahedral geometry while complexes (5) and (6) exhibited trigonal bipyramidal environment around the tin, which agreed with the data obtained from NMR. Spectroscopic titrations (UV–visible absorption, fluorescence titration, and circular dichroism) were performed to ascertain the binding mode of the complex with calf thymus DNA (CT-DNA). The obtained values of Kb in the order of 105 M−1 suggested partial intercalative interactions of complexes with DNA grooves/base pairs. The complexes efficiently cleaved plasmid DNA (pBR322) into supercoiled (Form I), nicked/circular (From II), and linear structure (Form III). The fascinating biophysical data suggests the potential of these complexes as anticancer agents.

Field-Induced Slow Magnetic Relaxation in Mononuclear Cobalt(II) Complexes Decorated by Macrocyclic Pentaaza Ligands.

Two cobalt(II) complexes [CoL1](OTf)2 (1, L1 = 6,6''-di(anilino)-4'-phenyl-2,2':6',2''-terpyridine) and [CoL2](OTf)2·MeOH (2, L2 = 6,6''-di(N,N-dimethylamino)-4'-phenyl-2,2':6',2''-terpyridine) were synthesized and characterized. Crystal structure analyses showed that the spin carries were coordinated by five N atoms from the neutral pentaaza ligands, forming distorted trigonal bipyramidal coordination environments. Ab initio calculations revealed large easy-axial anisotropy in complexes 1 and 2. Magnetic measurements suggest that complexes 1 and 2 are field-induced single-molecule magnets, whose relaxations are mainly predominated by Raman and direct processes.

Copper perchlorate catalyzed oxidative cyclisation of a novel bishydrazone ligand, formation of an unusual copper complex and in vitro biological implications

A novel hexadentate bishydrazone ligand, 1,10-bis(di(2-pyridyl)ketone) adipic acid dihydrazone (H2L1) is synthesized and characterized. With copper perchlorate as a catalytic oxidant, the ligand undergoes oxidative cyclisation and resulted in the formation of an unusual copper complex [Cu(L1a)2Cl]ClO4 (1), where L1a is 3-(2-pyridyl)triazolo[1,5-a]-pyridine. The Cu(II) complex was characterized physicochemically, while the molecular structure was confirmed by single crystal X- ray diffraction. In the complex cation, copper(II) is in a distorted trigonal bipyramidal coordination environment, surrounded by two triazolo nitrogen atoms and two pyridyl nitrogen atoms of L1a and a chloride atom. The relevant non covalent intermolecular interactions of the complex quantified using Hirshfeld surface analysis reveals that the O···H/ H···O (27.2%) contacts has the highest contribution. The solution phase bandgaps of the compounds were calculated using Tauc plot, whereas the solid-state band gaps were calculated by Kubelka-Munk model. DFT studies of the compounds indicate that the theoretical calculations corroborate with the experimental data. DPPH antioxidant activity assay of the synthesized compounds showed that the proligand H2L1 has a lower IC50 value (24.1 μM) than that of complex 1 (29.7 μM). The in vitro antibacterial activity was evaluated against Escherichia coli and Staphylococcus aureus, which revealed that complex 1 have excellent activity against E. coli, much as the standard ciprofloxacin. The cytotoxic efficacy investigation of the compounds against A549 (lung) adenocarcinoma cells suggested that H2L1 has more anticancer activity (IC50 value of 149.08 μM) than that of complex 1(IC50 value of 176.70 μM).

Understanding the Selective Extraction of the Uranyl Ion from Seawater with Amidoxime-Functionalized Materials: Uranyl Complexes of Pyrimidine-2-amidoxime

The study of small synthetic models for the highly selective removal of uranyl ions from seawater with amidoxime-containing materials is a valuable means to enhance their recovery capacity, leading to better extractants. An important issue in such efforts is to design bifunctional ligands and study their reactions with trans-{UO2}2+ in order to model the reactivity of polymeric sorbents possessing both amidoximate and another adjacent donor site on the side chains of the polymers. In this work, we present our results concerning the reactions of uranyl and pyrimidine-2-amidoxime, a ligand possessing two pyridyl nitrogens near the amidoxime group. The 1:2:2 {UO2}2+/pmadH2/external base (NaOMe, Et3N) reaction system in MeOH/MeCN provided access to complex [UO2(pmadH)2(MeOH)2] (1) in moderate yields. The structure of the complex was determined by single-crystal X-ray crystallography. The UVI atom is in a distorted hexagonal bipyramidal environment, with the two oxo groups occupying the trans positions, as expected. The equatorial plane consists of two terminal MeOH molecules at opposite positions and two N,O pairs of two deprotonated η2 oximate groups from two 1.11000 (Harris notation) pmadH− ligands; the two pyridyl nitrogen atoms and the –NH2 group remain uncoordinated. One pyridyl nitrogen of each ligand is the acceptor of one strong intramolecular H bond, with the donor being the coordinated MeOH oxygen atom. Non-classical Caromatic-H⋯X (X=O, N) intermolecular H bonds and π–π stacking interactions stabilize the crystal structure. The complex was characterized by IR and Raman spectroscopies, and the data were interpreted in terms of the known structure of 1. The solid-state structure of the complex is not retained in DMSO, as proven via 1H NMR and UV/Vis spectroscopic techniques as well as molar conductivity data, with the complex releasing neutral pmadH2 molecules. The to-date known coordination chemistry of pmadH2 is critically discussed. An attempt is also made to discuss the technological implications of this work.

Synthesis and crystal structure of a cadmium(II) coordination polymer based on 4,4′-(1H-1,2,4-triazole-3,5-diyl)dibenzoate

The asymmetric unit of the title compound, catena-poly[[[aquabis(pyridine-κN)cadmium(II)]-μ2-4,4′-(1H-1,2,4-triazole-3,5-diyl)dibenzoato-κ4 O,O′:O′′,O′′′] 4.5-hydrate], {[Cd(C16H9N3O4)(C5H5N)2(H2O)]·4.5H2O} n or {[Cd(bct)(py)2(H2O)]·4.5H2O} n (I), consists of a Cd2+ cation coordinated to one bct2– carboxylate dianion, two molecules of pyridine and a water molecule as well as four and a half water molecules of crystallization. The metal ion in I possesses a pentagonal–bipyramidal environment with the four O atoms of the two bidentately coordinated carboxylate groups and the N atom of a pyridine molecule forming the O4N equatorial plane, while the N atom of another pyridine ligand and the O atom of the water molecule occupy the axial positions. The bct2– bridging ligand connects two metal ions via its carboxylic groups, resulting in the formation of a parallel linear polymeric chain running along the [1\overline{1}1] direction. The coordinated water molecule of one chain forms a strong O—H...O hydrogen bond with the carboxylate O atom of a neighboring chain, leading to the formation of double chains with a closest distance of 5.425 (7) Å between the cadmium ions belonging to different chains. Aromatic π–π stacking interactions between the benzene fragments of the anions as well as between the coordinated pyridine molecules belonging to different chains results in the formation of sheets oriented parallel to the (\overline{1}01) plane. As a result of hydrogen-bonding interactions involving the water molecules of crystallization, the sheets are joined together in a three-dimensional network.

Structural, physicochemical characterization and antimicrobial activities of a new tris(8-quinolinolato-κ2N,O)cobalt(III) ethanol solvate [Co(C9H6NO)3].(C2H6O)

We report herein the synthesis and physicochemical characterization of a new 8-hydroxyquinoline cobalt(III) complex ethanol solvate with formula [Co(C9H6NO)3].(C2H6O). This compound was been prepared by slow evaporation at room temperature and characterized by single crystal X-ray diffraction. It crystallizes in the monoclinic system, spaces group P21/n. The central cobalt ion has a slightly distorted square bipyramidal environment, coordinated by three chelating 8-hydroxyquinoline molecules. Structural cohesion is primarily established by π-π interactions between the neighboring rings of quinoline groups and intermolecular hydrogen bonds O-H…O connecting the cobalt complex entities and uncoordinated ethanol molecules.The title compound has been characterized by the infrared (IR) and the UV–Visible (UV–Vis) spectra. Intermolecular interactions in the crystal structure were quantified by Hirshfeld surface analysis. The band gap of the complex was calculated using solid-state reflectance spectra, and the results show that the complex acts as a semiconductor. Moreover, the new compound exhibits high antibacterial and antifungal activities, as detected by the well agar diffusion against various bacterial and fungal clinical strains. The superior inhibitory effect was observed against Klebsiella pneumoniae, Candida albicans and Candida glabrata with zones inhibition of about 17.5, 17.5 and 17 mm, respectively.

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na2(PuO2)(BO3).

As part of our exploration of plutonium-containing materials as potential nuclear waste forms, we report the first extended structure Pu(V) material and the first Pu(V) borate. Crystals of Na2(PuO2)(BO3) were grown out of mixed hydroxide/boric acid flux and found to crystallize in the orthorhombic space group Cmcm with lattice parameters of a = 9.9067(4) Å, b = 6.5909(2) Å, and c = 6.9724(2) Å. Na2(PuO2)(BO3) adopts a layered structure in which layers of PuO2(BO3)2- are separated by sodium cations. Plutonium is found in a pentagonal bipyramidal coordination environment, with axial Pu(V)-O plutonyl bond lengths of 1.876(3) Å and equatorial Pu-O bond lengths ranging from 2.325(5) to 2.467(3) Å. We find that the Pu(V)-O plutonyl bond lengths are approximately 0.1 Å longer than the reported Pu(VI)-O plutonyl bond lengths and shorter by approximately 0.033 Å than the corresponding U(V) uranyl bond lengths. Raman spectroscopy on single crystals was used to determine the PuO2+ plutonyl stretching and the equatorial breathing mode frequencies of the pentagonal bipyramidal coordination environment around plutonium. Density functional theory calculations were used to calculate the Raman spectrum to help identify the Raman bands at 690 and 630 cm-1 as corresponding to the plutonyl(V) ν1 stretch and the equatorial PuO5 breathing mode, respectively. UV-vis measurements on single crystals indicate semiconducting behavior with a band gap of ∼2.60 eV.

Synthesis and crystal structure of a new copper(II) complex based on 5-ethyl-3-(pyridin-2-yl)-1,2,4-triazole.

The title compound, bis-[μ-3-ethyl-5-(pyridin-2-yl)-1H-1,2,4-triazol-1-ido]bis[acetato-(di-methyl-formamide)-copper(II)], [Cu2(C9H9N4)2(C2H3O2)2(C3H7NO)2] or [Cu2(L Et)2(OAc)2(dmf)2], is a triazolate complex, which contains two 3-(2-pyrid-yl)-5-ethyl-triazolates (L Et)- in bidentate-bridged coordination modes. Both copper atoms are involved in the formation of a planar six-membered metallocycle Cu-[N-N]2-Cu. The inversion center of the complex is located at the mid-point of the Cu⋯Cu vector. Each CuII atom has a distorted trigonal-bipyramidal environment formed by the three nitro-gen atoms of the deprotonated bridging 3-(2-pyrid-yl)-5-ethyl-triazolate unit, oxygen atoms of the OAc- group and dmf mol-ecule. In the crystal, C-H⋯O hydrogen bonds link the mol-ecules into chains running along the c-axis direction.

Carbonyl-bis-{6,6'-[(3,3'-di-tert-butyl-5,5'-dimeth-oxy-1,1'-biphenyl-2,2'-di-yl)bis(oxy)]bis-(dibenzo[d,f][1,3,2]-dioxaphosphepine)}hydridorhodium(I) toluene-d 8 2.25-solvate.

The crystal-structure determination of the title compound, [RhH(C46H44O8P2)2(CO)]·2.25C7D8, is reported. The bis-phosphite ligand, C46H44O8P2, is well known as Biphephos. One specific characteristic of this hydrido rhodium(I) monocarbonyl complex is that one bis-phosphite ligand is coordinated in the expected bidentate mode and the other is coordinated in a monodentate mode. Thus, one phosphite moiety remains non-coordinating. All three coordinating phospho-rus atoms occupy the equatorial positions in the trigonal-bipyramidal environment around the rhodium atom. The crystals of the hydrido rhodium(I) monocarbonyl complex contains deuterated solvent mol-ecules (toluene-d 8). Most of them are included in the model, but the contributions of about 0.84 toluene per unit cell were removed from the diffraction data, using the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18].

Non-Antibiotic Antimony-Based Antimicrobials.

A series of the eight novel organoantimony(V) cyanoximates of Sb(C6H5)4L composition was synthesized using the high-yield heterogeneous metathesis reaction between solid AgL (or TlL) and Sb(C6H5)4Br in CH3CN at room temperature. Cyanoximes L were specially selected from a large group of 48 known compounds of this subclass of oximes on the basis of their water solubility and history of prior biological activity. The synthesized compounds are well soluble in organic solvents and were studied using a variety of conventional spectroscopic and physical methods. The crystal structures of all reported organometallic compounds were determined and revealed the formation of the distorted trigonal bipyramidal environment of the Sb atom and monodentate axial binding of acido-ligands via the O atom of the oxime group. The compounds are thermally stable in the solid state and in solution molecular compounds. For the first time, this specially designed series of organoantimony(V) compounds is investigated as potential non-antibiotic antimicrobial agents against three bacterial and two fungal human pathogens known for their increasing antimicrobial resistance. Bacterial pathogens included Gram-negative Escherichia coli and Pseudomonas aeruginosa, and Gram-positive Staphylococcus aureus. Fungal pathogens included Cryptococcus neoformans and Candida albicans. The cyanoximates alone showed no antimicrobial impact, and the incorporation of the SbPh4 group enabled the antimicrobial effect. Overall, the new antimony compounds showed a strong potential as both broad- and narrow-spectrum antimicrobials against selected bacterial and fundal pathogens and provide insights for further synthetic modifications of the compounds to increase their activities.

Synthesis, Coordination Chemistry, and Mechanistic Studies of P,N-Type Phosphaalkene-Based Rh(I) Complexes.

The synthesis of P,N-phosphaalkene ligands, py-CH═PMes* (1, py = 2-pyridyl, Mes* = 2,4,6-tBu-C6H2) and the novel quin-CH═PMes* (2, quin = 2-quinolinyl) is described. The reaction with [Rh(μ-Cl)cod]2 produces Rh(I) bis(phosphaalkene) chlorido complexes 3 and 4 with distorted trigonal bipyramidal coordination environments. Complexes 3 and 4 show a pronounced metal-to-ligand charge transfer (MLCT) from Rh into the ligand P═C π* orbitals. Upon heating, quinoline-based complex 4 undergoes twofold C-H bond activation at the o-tBu groups of the Mes* substituents to yield the cationic bis(phosphaindane) Rh(I) complex 5, which could not be observed for the pyridine-based analogue 3. Using sub- or superstoichiometric amounts of AgOTf the C-H bond activation at an o-tBu group of one or at both Mes* was detected, respectively. Density functional theory (DFT) studies suggest an oxidative proton shift pathway as an alternative to a previously reported high-barrier oxidative addition at Rh(I). The Rh(I) mono- and bis(phosphaindane) triflate complexes 6 and 7, respectively, undergo deprotonation at the benzylic CH2 group of the phosphaindane unit in the presence of KOtBu to furnish neutral, distorted square-planar Rh(I) complexes 8 and 9, respectively, with one of the P,N ligands being dearomatized. All complexes were fully characterized, including multinuclear NMR, vibrational, and ultraviolet-visible (UV-vis) spectroscopy, as well as single-crystal X-ray and elemental analysis.

Homogeneous {Ti2Ni} Heterotrinuclear Catalyst for Ethylene Polymerization and Copolymerization

We synthesized and spectroscopically characterized a new heterotrimetallic {Ti2Ni} ethylene (co)polymerization precatalyst containing one (α-diimine)NiBr2 and two (phenoxy-imine)TiCl4 scaffolds. Its calculated structure was investigated at the DFT B3LYP/LACVP** level. Our calculations showed that the titanium(IV) centers were in a slightly distorted trigonal bipyramidal environment, and the average Ti···Ni distance was 8.76 Å. The precatalyst was used for synthesizing polyethylene and ethylene copolymers. The results of GPC analyses showed that the obtained polyethylenes had the desired bimodal molecular weight distributions. The FTIR spectra revealed that polydispersity decreased as the vinyl end-group content increased. These results suggested that high mechanical resistance can increase the mechanical energy needed for processing the material. All 13C NMR signals were assigned to short-chain branches with specific spatial arrangements along the polymer backbone. The chain walking mechanism of branch formation controls the spacing and conformational arrangements between these short chains.

Exploiting the Multifunctionality of M2+/Imidazole-Etidronates for Proton Conductivity (Zn2+) and Electrocatalysis (Co2+, Ni2+) toward the HER, OER, and ORR.

This work deals with the synthesis and characterization of one-dimensional (1D) imidazole-containing etidronates, [M2(ETID)(Im)3]·nH2O (M = Co2+ and Ni2+; n = 0, 1, 3) and [Zn2(ETID)2(H2O)2](Im)2, as well as the corresponding Co2+/Ni2+ solid solutions, to evaluate their properties as multipurpose materials for energy conversion processes. Depending on the water content, metal ions in the isostructural Co2+ and Ni2+ derivatives are octahedrally coordinated (n = 3) or consist of octahedral together with dimeric trigonal bipyramidal (n = 1) or square pyramidal (n = 0) environments. The imidazole molecule acts as a ligand (Co2+, Ni2+ derivatives) or charge-compensating protonated species (Zn2+ derivative). For the latter, the proton conductivity is determined to be ∼6 × 10–4 S·cm–1 at 80 °C and 95% relative humidity (RH). By pyrolyzing in 5%H2–Ar at 700–850 °C, core–shell electrocatalysts consisting of Co2+-, Ni2+-phosphides or Co2+/Ni2+-phosphide solid solution particles embedded in a N-doped carbon graphitic matrix are obtained, which exhibit improved catalytic performances compared to the non-N-doped carbon materials. Co2+ phosphides consist of CoP and Co2P in variable proportions according to the used precursor and pyrolytic conditions. However, the Ni2+ phosphide is composed of Ni2P exclusively at high temperatures. Exploration of the electrochemical activity of these metal phosphides toward the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) reveals that the anhydrous Co2(ETID)(Im)3 pyrolyzed at 800 °C (CoP/Co2P = 80/20 wt %) is the most active trifunctional electrocatalyst, with good integrated capabilities as an anode for overall water splitting (cell voltage of 1.61 V) and potential application in Zn–air batteries. This solid also displays a moderate activity for the HER with an overpotential of 156 mV and a Tafel slope of 79.7 mV·dec–1 in 0.5 M H2SO4. Ni2+- and Co2+/Ni2+-phosphide solid solutions show lower electrochemical performances, which are correlated with the formation of less active crystalline phases.

Synthesis, Spectral Characterization, Crystal Structure and Antibacterial Activity of dichloro-{2-[(4-fluorophenyl)iminomethyl]pyridine-κ2N,N'}mercury(II)

The title complex has been prepared using (4-Fluoro-phenyl)-pyridin-2-ylmethylene-amine bidentate Schiff base ligand (L) and HgCl2. The Hg(II) center in the title compound, [HgCl2(C12H9FN2)], is covalently bonded to three Cl atoms and two N atoms of the diimine ligand. Mercury ion mononuclear fragment that forms a polymeric structure due to bridging chloride ligands is in a distorted trigonal–bipyramidal coordination environment formed by the bis-chelating N-heterocyclic ligand, two bridging Cl ligands and one terminal Cl ligand. One of the bridging Hg—Cl bonds is significantly longer than the other. In the crystal, weak C—H.....Cl hydrogen bonds are observed in addition to π-π stacking interactions. It crystallizes in the Orthorhombic space group P212121 with a = 7.2248 (3) Å, b = 8.7713 (3) Å, c = 20.0217 (7) Å, α = 90.00°, β = 90.00, γ = 90.00°, V = 1268.79(8) Å3, R1 = 0.023 and wR2= 0.062 [I > 2σ(I)] respectively. The antibacterial activities of the complex, ligand and metal salt were tested against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli studied by disk diffusion method.

Slow magnetic relaxation for cobalt(II) complexes in axial bipyramidal environment: an S = 1/2 spin case.

A new family of magnetically mononuclear cobalt(II) complexes with formula [{NiII(L)CoII(H2O)2(MeOH)}{NiII(L)}2](ClO4)2 where H2L1 = bis(N,N'-bis(3-methoxysalicylidene)ethylene-1,2-diamine) (1), H2L2 = bis(N,N'-bis(3-methoxysalicylidene)propane-1,2-diamine) (2) and [{CuII(L4)}2CoII](ClO4)2 (3) where H2L4 = bis(N,N'-bis(3-ethoxysalicylidene)cyclohexane-1,2-diamine) have been obtained employing non chiral or enantiomerically pure Schiff bases. The structural studies have been carried out by single crystal X-ray and powder diffraction. Dynamic magnetic studies indicate that some members of this family present field induced slow relaxation of the magnetization and its response has been compared with the magnetically diluted [Zn0.9Co0.1] complex 1D. Ultra-low frequency Raman spectroscopy has been used to relate the slow relaxation with lattice vibrations.

Co(II) Amide, Pyrrolate, and Aminopyridinate Complexes: Assessment of their Manifold Structural Chemistry and Thermal Properties**

AbstractA series of cobalt(II) (silyl)amides, pyrrolates and aminopyridinates were synthesized. Inspired by the dimeric bis(trimethylsilylamido)cobalt(II) complex ([Co(TMSA)2]2), facile salt metathesis employing the ligand 2,2,5,5‐tetramethyl‐1,2,5‐azadisilolidinyl (TMADS) yielded its congener [Co(TMADS)2]2. Novel, heteroleptic Lewis adducts of the former resulted in unusual three‐ to four‐fold coordination geometry around the metal center. Similarily, the salt [Li(DAD)2][Co(TMADS)3] was isolated which demonstrates an ion separated Co(II) anion with silylamide ligation and Li+ counter cation. Transpyrrolylation using [Co(TMSA)2]2 was established for the synthesis of bis[N,N’‐2‐(dimethylaminomethyl)pyrrolyl]cobalt(II), and bis(N‐2‐(tert‐butyliminomethyl)pyrrolyl)cobalt(II). Treatment of CoCl2 with two equivalents of lithiated N,N‐dimethyl(N’‐tert‐butyl)ethane‐1‐amino‐2‐amide and N,N‐dimethyl(N’‐trimethylsilyl)ethane‐1‐amino‐2‐amide resulted in the respective Co(II) amido‐amines. Reaction of CoCl2 with lithium 4‐methyl‐N‐(trimethylsilyl)pyridine‐2‐amide yielded the first binuclear, homoleptic Co(II) aminopyridinate complex with a distorted trigonal bipyramidal coordination environment (τ5=0.533) for one central Co(II) ion and a weakly distorted tetrahedral coordination geometry (τ4=0.845) for the other. All of the new compounds were thoroughly characterized in terms of composition and structure. Finally, the key thermal characteristics of volatility and thermal stability were assessed using a combination of thermogravimetric analysis and complementary bulk sublimation experiments.

Exploring different equatorial donors in a series of five-coordinate Cu(II) complexes supported by rigid tetradentate ligands

A series of tetradentate mixed-donor ligands has been synthesized containing an amine, thioether, or phosphine donor at the 8-position of a 2-(1,1-di(pyridin-2-yl)ethyl)quinoline backbone. Upon metalation with CuCl2, the preorganized N4, N3P, and N3S donor ligands enforce distorted trigonal bipyramidal coordination environments around the copper metal center, in which a chlorido donor occupies the remaining axial coordination site. The complexes were characterized by elemental analysis, high-resolution mass spectrometry, and X-ray crystallography. The non-pyridyl equatorial donor was the sole difference from among the tetradentate ligands, and is responsible for the structural and electronic variations across the series. Indeed, more intermediate geometries between the ideal trigonal bipyramidal and square pyramidal extremes are observed with the larger phosphorus and sulfur donors. Relative to the N4 derivative, the N3P and N3S systems have greater chemical stability upon redox cycling as observed in spectroelectrochemical experiments and lower inner-sphere reorganization energies for the CuII/I redox couples based on density functional theory calculations.

Rare cis‐Dioxido Uranyl Framework Crystalline Complexes: Synthesis, Structure, Characterization and Properties

AbstractThe trans‐dioxido uranyl frameworks named as [(UO2)(Aip)(DMA)] (1), H[(UO2)(Aib)3] (2) and rare cis‐dioxido [(UO2)Co(Suc)2(H2O)4] (3), and [(UO2)Ni(Suc)2(H2O)4] (4) have been synthesized, which based on 5‐aminoisophthalic acid (H2Aip), 3‐aminobenzoic acid (HAib), and succinic acid (H2Suc) as ligands. They were characterized by Fourier Transform Infrared spectra, UV‐vis absorption spectra, single‐crystal X‐ray diffraction, powder X‐ray diffraction and thermogravimetry analysis. It was found that uranium ion of the complex 1 is in the pentagonal bipyramidal coordination environment, while those of the complexes 2–4 are in the hexagonal bipyramidal coordination environment. Complexes 1, 3, and 4 are 3D network structures, 2 is a discrete structure. In particular, geometry of O=U=O for 1 and 2 are trans, ones for 3 and 4 are cis. The highest removal rate of methylene blue was almost to 96 % by complex 1 as an adsorbent, which illustrates that potential application on dye adsorption.