Aqua Molecules Research Articles

Facile fabrication of a Cu(II) 1D zig–zag coordination polymer demonstrating affinity toward DNA molecules

A Cu(II) compound [Cu2(5-nip)2(3-brpy)2·(H2O)2·(DMF)2] (1) was synthesized using 5-nitroisophthalic acid (H25-nip) and 3-bromopyridine (3-brpy) employing slow diffusion technique. Visibly distinct blue-colored crystals of compound 1 were obtained. Single crystal X-ray analysis discloses that compound 1 crystallizes in the triclinic system, having space group P1¯ with cell dimensions a = 12.4491(14) Å, b = 13.6238(15) Å, c = 14.3315(15) Å; α = 68.027(3)°, β = 69.914(3)°, γ = 87.173(3)°and V = 2108.3(4)Å3. The compound contains core metal atom Cu(II) that is hexa-coordinated to 5-nip, 3-brpy, dimethylformamide (DMF), and aqua molecule resulting in one- dimensional coordination polymer (1D CP), propagated via strands of 5-nip bridges. The pyridine-based ligand and aqua ligands are decorated as arms on both sides of Cu(II) centers. The prominence of hydrogen bonding interactions in compound 1 was found which leads to the formation of 1D double-chain strand. The combination of 5-nip and 3-brpy ligands is responsible for the strong affinity towards DNA molecules for compound1. Docking studies have been employed to examine DNA binding affinity. Hirshfeld surface analysis was carried out in order to check out the nature of intermolecular interactions and packing modes of compound 1 in the crystalline state.

Mapping the Ultrafast Mechanistic Pathways of Co Photocatalysts in Pure Water through Time-resolved X-ray Spectroscopy.

Nanosecond time-resolved X-ray (tr-XAS) and optical transient absorption spectroscopy (OTA) are applied to study 3 multimolecular photocatalytic systems with [Ru(bpy)3]2+photoabsorber, ascorbic acid electron donor and Co catalysts with methylene (1), hydroxomethylene (2) and methyl (3) amine substituents in pure water. OTA and tr-XAS of 1 and 2 show that the favored catalytic pathway involves reductive quenching of the excited photosensitizer and electron transfer to the catalyst to form a CoII square pyramidal intermediate with a bonded aqua molecule followed by a CoI square planar derivative that decays within ~8 µs. By contrast, a CoI square pyramidal intermediate with a longer decay lifetime of ~35µs is formed from an analogous CoII geometry for 3 in H2O. These results highlight the protonation of CoI to form the elusive hydride species to be the rate limiting step and show that the catalytic rate can be enhanced through hydrogen containing pendant amines that act as H-H bond formation proton relays.

Aminopolycarboxylate zinc(II) complexes with 1,10-phenanthroline and 2,2′-bipyridyl: kinetic studies in the surfactants solutions systems

Aminopolycarboxylate zinc(II) complexes with 1,10-phenanthroline and 2,2′-bipyridyl {[Zn(IDA)(H2O)2], [Zn(IDA)(bipy)(H2O)]·2H2O and [Zn(IDA)(phen)(H2O)]·2H2O} were synthesized. In order to confirm the composition and purity of the synthesized complex compounds, elemental analysis was used. Next, the kinetics of the substitution reaction of two water molecules in the zinc(II) iminodiacetate complex for 1,10-phenanthroline and 2,2′-bipyridyl in two surfactant solvents: CTAB and Triton X-100 were investigated. The kinetic studies were carried out using the stopped flow method. The kinetic research were carried out at 3 different temperatures: 288.15, 293.15 and 298.15 K and at different molar concentrations of the complex compound [Zn(IDA)(H2O)2]: 1 mM; 0.75 mM, 0.5 mM and 0.25 mM and at a constant molar concentration of ligands: i.e. 1,10-phenanthroline and 2,2′-bipyridyl, were 0.05 mM. Changes in absorbance during the kinetic run of the tested reactions were measured at a wavelength of 260 nm. Thanks to the conducted kinetic studies, the order of the reaction was determined, and the observable rate constants of the reaction rates of the substitution of two aqua molecules into the N-donor ligand were determined by the stopped—flow method using the Glint program. In the next step the thermodynamic parameters of complexes: {[Zn(IDA)(H2O)2], [Zn(IDA)(bipy)(H2O)]·2H2O and [Zn(IDA)(phen)(H2O)]·2H2O} in aqueous solutions by use potentiometric titrations were determined. The Hyperquad2018 program was used for determining of stability constants. In addition, the stoichiometry of complexes of zinc(II) with N-heterocyclic ligands in aqueous solutions was determined using the conductometric titrations.

Copper(II) and zinc(II) complexes bridged by benzenoid aromatic oxocarbon and dicarboxylate dianions

A novel series of Cu(II) and Zn(II) complexes were constructed through the bridging croconate (C5O5)2−, squarate (C4O4)2− and 2,5-pyridine-dicarboxylate (Py2,5-dc)2− dianions. These include pent- [Cu5(epdmpy)4(C5O5)2(H2O)6](ClO4)6‧12H2O (1) and tri-nuclear [Cu3(bepza)2(Py2,5-dc)2(ClO4)2(H2O)2]‧2H2O (4), dinuclear [Zn2(MeDPA)2(C4O4)(H2O)4](ClO4)2 (7), and 1-D- coordination polymers (CPs) catena-{[Cu2(bpzpy)2(C5O5)](ClO4)2‧MeOH} (2) and catena-{[Zn(4,4′-bipy)(H2O)4](C5O5)(H2O)} (6) as well as the mononuclear [Cu(HBph2,2′-dc)(pmdien)]ClO4 (5) have been synthesized and spectroscopically characterized as well as by single crystal X-ray crystallography. The reaction of aqueous solution Cu(ClO4)2, pymeea and C5O52− resulted in the unprecedently bis(oxalato) [Cu2(Pymeea)2(C2O4)(ClO4)2(H2O)2] (3). In these complexes, (C5O5)2−, squarate (C4O4)2− and (Py2,5-dc)2− ligands display a variety of coordination bonding modes. In complexes 1 and 2 the croconato is binding as 1,2-bidentate-3-monodentate but in addition 5-mono-dentate semi-coordinate bonding was detected for 2, whereas in 6 as counter dianion. The bonding mode in the squarato 7 was achieved through the trans μ1,3-mono-dentate. In the di-carboxylato compounds, only five-membered chelate ring was formed in 5via one of the carboxylate groups, whereas in 4 bridging was conducted through a mono-carboxylate and five-membered chelate ring including the second carboxylate and pyridyl nitrogen. In complexes 1–5 and 7, hydrogen bonds of type OH⋯O and/or NH⋯O are connecting the complex cations with the perchlorate anions/ligands to generate different dimensional supramolecular network structures, whereas in 6, the 3D network was formed through hydrogen bonding between the coordinated aqua and lattice water molecules. Non-covalent ring⋯ring interactions were also observed between pyridyl rings in complexes 1, 6 and 7, and between pyrazolyl rings as well as pyridyl ring in 2.

Synthesis and Characterization of a Dysprosium(III)–Iron(III) Heterodinuclear Complex: Crystallographic, Hirshfeld Surface, Density-Functional Theory, and Luminescence Analyses

Here, a new cyano-bridged 3d–4f compound, a Dy(III)–Fe(III) molecular assembly ([Dy(DMF)4(H2O)3(μ-CN)Fe(CN)5.H2O] (1)), having a structure consisting of neutral one-dimensional (1D) chains, as well as an unbound aqua molecule, was synthesized and characterized using single crystal X-ray diffraction (XRD), infrared (IR), and elemental analyses. We then examined its structural topologies and studied its density functional theory (DFT), Hirshfeld surface analyses, and photophysical properties. The 1D chains were further linked by H-bond interactions, generating a three-dimensional (3D) motif which stabilizes the whole molecule. The weak interactions in 1 were assessed using Hirshfeld surface analyses, as well as fingerprint plots and DFT studies. Additionally, Hirshfeld surface analysis was performed to elucidate the roles of the weak interactions, such as the H⋯H, C⋯H, C–H⋯π, and van der Waals (vdW) interactions which are pivotal to stabilizing the crystal environment. Furthermore, the DFT studies were used to elucidate the bonding structure within the complex system. Complex 1 exhibits characteristic fluorescence as the Dy(III) complex is an excellent lime green luminescent material. Thus, it is considered to be a suitable material for preparing photoluminescent material.

The syntheses, structural and biological studies of Co(II) complexes of 1,2-Bis(pyridin-4-yl)ethane with 2-aminobenzene-1,4-disulfonic acid and 2,6-pyridinedicarboxylic acid

The newly synthesized salt named 4,4′-(ethane-1,2-diyl)bis(pyridin-1-ium) 2-aminobenzene-1,4-disulfonate, (H2BPE)2+(ADSA)2− (1), was prepared from the reaction of 1,2–bis(pyridin–4–yl)ethane (BPE) and 2–amino-benzene–1,4–disulfonic acid (H2ADSA). Two new metal complexes of 4,4′-(ethane-1,2-diyl)bis(pyridin-1-ium) 2-aminobenzene-1,4-disulfonate were also synthesized: The first complex [Co(BPE)2(H2O)4](ADSA).BPE (2) has been synthesized from the obtained proton transfer salt (1). The second complex, {[Co(BPE)(H2O)4]}n[Co(DPC)2].2H2O (4), is a one–dimensional coordination polymer and was synthesized using proton transfer salt (H2BPE)2+(DPC)2- (3). Elemental analysis, Nuclear Magnetic Resonance, Infrared and Ultraviolet–Visible spectra methods were used to elucidate the structure of 1. Elemental analysis, magnetic moment measurements, spectral (UV–Vis, AAS and IR) and X–ray crystallographic analysis were applied for structural manalysis of 2 and 4. X–ray crystallographic study for 2 and 4 revealed that in both complexes the BPE coordinated the Co(II). In compound 2, the coordination periphery of the Co(II) consists of two nitrogens from two BPE, four oxygens from four H2O molecules and forms the six–coordinated octahedral geometry. X–ray crystallographic analysis of 4 showed that the complex was polymer and the metal ions were linked by BPE ligand bridges. The molecular structure of coordination polymer 4 contains both cationic and anionic complexes, each with an octahedral geometry. The coordination sphere of the cationic complex consists of two nitrogens of two BPE and four oxygens of four aqua molecules. On the other hand, the two DPC2− ligands contribute two nitrogens and four oxygens to the coordination sphere of the anionic complex. The antibacterial and antifungal capabilities of the produced compounds were further investigated, and the MIC (Minimum Inhibitory Concentration) values were compared to those of related control substances.

Димеризация фталоцианина алюминия в органической и водно-органической средах

Aluminum phthalocyanine chloride (AlClPc) is a photoactive macroheterocyclic compound, which, in its monomeric form, is used as a photosensitizer (PS) in photodynamic therapy and diagnostics. In this paper, its physicochemical properties were studied in organic (N, N-dimethylformamide, DMF) and aqua-organic (DMF-aqua) media. It has been shown that the hydrophobic properties of AlClPc prevent its widespread use in various pharmacological compositions due to its tendency to aggregate in aqueous solutions, which leads to the formation of non-fluorescent aggregates and a decrease in its photodynamic activity. The geometry and electronic structure of AlClPc in the monomeric and dimerized (H- and 
 J-aggregates) states were studied using quantum-chemical calculations with the help of the electron density functional theory (DFT) method. Different types of orientation during the dimerization of AlClPc molecules are presented: “back to back”, “head to head”, “head to back”, as well as mixed-oriented types. It has been proven that both in DMF and DMF-aqua media, the preferred orientation is “back to back”, without sacrificing the monomeric geometry of the constituent molecules in the dimer. It is shown that in an aqueous organic solvent the AlClPc molecule is easily hydrated with the formation of a coordination bond between the Al atom of the AlClPc molecule and the O atom of the aqua molecule. The bond length is 2.23 Å, and the hydration energy is 16.84 kcal/mol. Hydration promotes the formation of dimers, in which two aqua molecules play the role of "bridges" between two AlClPc molecules. In such dimer, each aqua molecule has two bonds: one coordination bond between its O atom and the Al atom of one of the AlClPc molecules and one hydrogen bond between its H atom and the N atom of another AlClPc molecule. Based on the calculated data obtained, the AlClPc dimers in the DMF medium were assigned to H-aggregates, and in the DMF-water medium, to J-aggregates, respectively.

Novel metal graphene framework (MGF) structures for hydrogen storage

Hierarchical novel metal graphene framework (MGF) structures designed, constructed and used for hydrogen storage by adsorption. Three different amounts of pillars used for connecting carboxylate functionalized graphene layers. The three-dimensional atomistic models optimized and then the aqua molecules removed which are coordinated to metal between graphene layers as bridge. Hydrogen storage abilities of aqua free models also investigated. The aqua existence made the structures more effective to store hydrogen according to simulation results. The highest storage capacity calculated for 181C.Aq named structure that includes aqua molecules inside could store 7.745 wt percentage hydrogen at 77 K and 100 bars pressure conditions. Hydrogen storage capacity decreases almost to half by removing aqua molecules for same structure. It is clear the coordinated aqua existence around the bridging atoms provides the spaces between graphene layers. In other word, the spaces between the graphene layers collapse by aqua removal so the hydrogen storage capacities decrease dramatically. Finally, spacing between graphene layers by bridges makes them very effective for hydrogen storage.

Physico-chemical characterizations and biological evaluation of a new semiconducting metal–organic compound based on pyrimidine frameworks

A new complex with the formula (C5H8N3)2[NiCl2(C5H7N3)2(H2O)2].2Cl (1) was synthesized in good yields and fully characterized. X-ray diffraction analysis, suggests that 1 is mononuclear nickel(II) complex and exhibits distorted octahedral geometry. Each octahedron is building from nickel(II) ion presenting the center and two nitrogen atoms from two organic ligands, two chloride ions, and two oxygen coming from aqua molecules, which occupy the six vertices. The supramolecular architecture can be described essentially as an alternating distribution of nickel octahedra and pyrimidine rings, some are oriented along [011] direction and the others follow the orientation [01 1¯ ]. This network is linked by three types of hydrogen bonds, N–H…Cl, N–H…N, and OW–H…Cl. The optical properties of the crystal were studied using UV–visible spectroscopy and the gap energy value was estimated to be 3.34 eV. The docking simulation showed acceptable binding affinities (between –4.5 and –6.3 kcal/mol), which together with the druglikeness explain the possible biological activities of the compound and its promising effects. Further in vitro and/or in vivo analyses might confirm the in silico simulation results. The analysis of the magnetic properties and ab initio calculations suggest that 1 can be described as quasi-one-dimensional anisotropic S = 1 ferromagnet with zero-field splitting parameters D/kB = 6.3 K and in-chain exchange coupling J/kB = 4.3 K.

Phenylalanine Interacts with Oleic Acid-Based Vesicle Membrane. Understanding the Molecular Role of Fibril–Vesicle Interaction under the Context of Phenylketonuria

In the present contribution, on the basis of a spectroscopic and microscopic investigation, the characterization and photophysics of various assemblies of oleic acid/oleate solution at three pH values, namely, 8.28, 9.72, and 11.77, were explored. The variation in the dynamic response of aqua molecules in and around the assemblies has been interrogated by a picoseconds solvation dynamics experiment using a time-correlated single-photon counting setup employing coumarin-153 as a probe. On the one hand, the time-resolved fluorescence anisotropy measurement along with the fluorescence correlation spectroscopy experiment was executed to extract information regarding the comparison of the extent of the internal restricted confinement of these assemblies. On the other hand, an effort to investigate the cross-interaction between the self-assembled architectures of l-phenylalanine (l-Phe), responsible for phenylketonuria (PKU) disorder, and the oleic acid at the vesicle-forming pH established that the l-Phe fibrillar morphologies strongly alter the dynamic properties of the vesicle membrane formed by the oleic acid. Specifically, the interaction of the l-Phe assemblies with the oleic acid vesicle membrane is found to introduce the flexibility of the vesicle membrane and alter the hydration properties of the membrane. To track the fibril-induced alterations of the oleic acid vesicle properties, various spectroscopic and microscopic investigations were performed. The mutual reconciliation of the experimental outputs, therefore, portrays the state of the art, which accounts for the fibril-induced alterations of the properties of the oleic acid vesicle membrane, the mimicking setup of the cellular membrane, thereby informing us that alterations of such a property of the membrane should be taken into active consideration during the rational development of therapeutic modulators against disorders like PKU.

Interfacial properties and aggregates of novel redox-active surfactant to synthesize silver nanoparticles at the air/water interface

An anionic and amphiphilic molecule, AQua (AQ-NH-(CH2)10COOH; where AQ is anthraquinone), which has two stimuli responsive functional-groups, can form self-assembled interfacial aggregates at the air-water interface and, their morphologies can be controlled by changing the subphase conditions such as the pH of the subphase. These interfacial morphologies may be altered from planar structures to wormlike aggregates which is a very rare observation in the literature. Moreover, the unique functional groups of AQua give possibility to reduce metal cations and allow the formation of organic/inorganic nanocomposite structures at the interface. In this context, formation of silver nanoparticles (AgNPs) via AQua-based self-assembled structures at the interface was studied using Langmuir techniques. The kinetics of the reduction process as well as the effect of various parameters were systematically examined. This study demonstrates that interfacial configuration of the AQua molecule at the interface as well as its orientation has a vital role in the morphology of either organic or inorganic self-assemblies formed. The morphology may be adjusted and designed interfacial structures may be obtained. The interfacial properties of AQua, a novel material, may be used in a wide variety of fields such as biotechnology, medicine, energy and pharmaceuticals.

Synthesis, crystal structures, magnetic and magnetocaloric studies of heterometallic enneanuclear {Cu7Gd2} complexes

The reaction of Gd(NO3)3·6H2O and [Cu2(piv)4(pivH)2] with the polydentate Schiff base ligands o-OH-C10H6-CH = NC(R)(CH2OH)2 (R = CH3, H3L1; R = C2H5, H3L2) in MeOH afforded the enneanuclear heterometallic complexes [Cu7Gd2(L1)4(HL1)2(piv)4(H2O)(MeOH)3] (1) and [Cu7Gd2(L2)4(HL2)2(piv)4(MeOH)5] (2). Crystallographic studies revealed that both complexes are isostructural and consist of a central core {Cu7Gd2(μ3-Oalkoxo)6(μ2-Oalkoxo)4(μ2-Opivalato)2}8+. Peripheral ligation and bridging are provided by four triply and two doubly deprotonated Schiff base ligands, two μ3-pivalates, two chelate pivalates, and terminal aqua and/or MeOH molecules. Magnetic susceptibility measurements revealed the presence of dominant ferromagnetic intramolecular interactions in both complexes. The magnetocaloric effect of 1 and 2 was examined via isothermal magnetization measurements under various applied fields and the maximum entropy change was found equal to 13.3 and 12.1 Jkg-1K−1 for 1 and 2, respectively, at 2 K for ΔH = 5 T.

Thermodynamic and Kinetic Studies on Novel Platinum(II) Complex Containing Bidentate N,N-Donor Ligands in Ethanol-Water Medium

Kinetic and mechanistic investigations have been made on the displacement of the two aqua molecules from the complex 1 i.e., [Pt(2,2′-bipyridine)(H2O)2]2+ represented as {Pt(bpy)} (bpy = 2,2′-bipyridine) at pH 4.0. All the substitution reactions have been monitored at 264, 284 & 317 nm respectively where the spectral difference between the reactant and product is maximum. Two consecutive reaction steps were observed for the substitution of aqua molecules with some didentate N- and N-donor ligands namely, dimethylglyoxime (L1H), 1, 2-cyclohexanedionedioxime (L2H) and α-furildioxime (L3H) in ethanol-water medium using variable-temperature and stopped-flow spectrophotometry. Among the two steps, the former is ligand dependent and the later is ligand independent, where chelation observed. All rate and activation parameters are consistent with associative substitution mechanisms. The thermodynamic parameters were also calculated, which gives a negative DG0 value at all temperatures studied, supporting the spontaneous formation of an outer sphere association complex. The products of the reaction have been characterized with the help of IR and ESI-MS spectroscopic analysis.

Crystal structure of 4-(dimethylamino)pyridin-1-ium-2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine (2:1) water undeca-solvate

The structure of the title compound, 4-(dimethylamino)pyridin-1-ium-2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine water undeca-solvate, C57H87Cl5N12O21, obtained from interaction between chloranilic acid (caH2), and dimethyl aminopyridine (DMAP) has been determined by single crystal X-ray diffraction. The title compound, (DMAPH)5(ca)2.5·(DMAP)·11H2O, crystallized in the triclinic crystal system with space group, P (no. 2), a = 13.3824(15) Å, b = 13.4515(17) Å, c = 19.048(2) Å, α = 86.014(4)°, β = 88.821(4)°, γ = 86.367(4)°, V = 3413.3(7) Å3, Z = 2, T = 100(2) K, μ(MoKα) = 0.294 mm-1, Dcalc = 1.414 g/cm3, 59413 reflections measured (3.76° ≤ 2Θ ≤ 56°), 16405 unique (Rint = 0.0517, Rsigma = 0.0589) which were used in all calculations. The final R1 was 0.0460 (I ≥ 2σ(I)) and wR2 was 0.1271 (all data). Using supramolecular chemistry principles, proton donors (chloranilic acid) and acceptor (DMAP) were combined to generate a multicomponent hydrogen-bonded system. Due to the presence of protonated bases (DMAPH+), the dominant interactions are the N+-H···O hydrogen bonds, whereas the negative charges of an acceptor from the chloranilate dianion (ca2-) are delocalized. Additionally, three sets of water clusters in the title compound were identified, namely a cyclic pentamer, a linear, and an acute-shaped trimer water cluster. It was further observed that strong hydrogen bond interactions occurred between the solvated aqua molecule(s) acting as a proton donor and the neutral DMAP acting as a proton acceptor. The crystal packing is further stabilized by O-H···Cl and C-H···Cl weak halogen interactions. The lattice metric strength is further held by observed π-π stacking interactions (centroid-centroid) with inter centroid distances between sets of the DMAPH rings of 3.624(3), 3.642(4), 3.739(3), 3.863(3) and 3.898(3) Å, respectively.

Novel coordination compounds: Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) cations with acesulfame/N,N-diethylnicotinamide ligands

Five coordination complexes with Mn2+ (1), Co2+ (2), Ni2+ (3), Cu2+ (4), and Zn2+ (5) containing acesulfame (ace) and N,N-diethylnicotinamide (dena) ligands were synthesized and structural binding properties investigated. Four compounds (1, 2, 4, and 5) were examined with single crystal X-ray diffraction methods. The structures containing Mn(II), Co(II), and Zn(II) were iso-structural. Six-coordination of metal cations were completed with two moles dena and four aqua ligands. The dena ligands were coordinated via pyridine nitrogen as neutral-monodentate. Charge stabilities of the complexes are complemented by two moles monoanionic ace ligands, located outside of the coordination unit. In the Cu(II) complex, the coordination is completed by acidic nitrogen and carbonyl oxygen atoms of two ace ligands and pyridine nitrogen of two moles dena ligands. The coordination to Cu(II) for ace ligands was monoanionic-bidentate. All metal cations in the structure are distorted octahedral. Thermal decomposition of complexes begins with removal of the aqua molecules from the structures and is completed by combustion of organic ligands. The final decomposition products of all structures have been identified as corresponding metal oxides. Some biological applications (anti-fungal/anti-bacterial) were studied using 1–5.

Bio-mimetic of catecholase and phosphatase activity by a tetra-iron(III) cluster

An oxido- and acetato-bridged tetranuclear iron(III) cluster, [Fe4III(µ-O)2(µ-OAc)6(phen)2(H2O)2](NO3)2·(H2O)3 (1), [OAc = acetate; phen = 1,10-phenanthroline] has been prepared in the crystalline phase. X-ray structural analysis of the compound reveals that all the Fe(III) centres in 1 adopt an octahedral coordination geometry and the tetra-iron(III) core exists in an unusual asymmetric conformation. Bond valence sum (BVS) calculations recommend the existence of all iron ions in the +3 oxidation state in the crystalline phase. The tetra-iron(III) cluster elegantly catalyzes the oxidation of 3,5-di-tert-butylcatechol (DTBC), viz. catecholase-like activity, with a good turnover number, kcat = 9.28 × 102 h−1 in acetonitrile medium. Spectrophotometric titration shows the existence of two distinct isosbestic points, which unanimously proves the rarely observed enzyme-substrate binding phenomenon in solution. Electrochemical analysis recommends the production of Fe(II)–semiquinone species in the course of the catalytic oxidation of DTBC. Furthermore, the same iron(III) cluster displays phosphoester cleavage activity towards the disodium salt of p-nitrophenylphosphate (PNPP) in aqueous-methanol medium with rate of 7.20 × 10−4 m−1. ESI-MS measurements of the tetra-iron(III) complex in the presence of PNPP indicate the formation of an organophosphorus intermediate in solution and solvent aqua molecules probably make a nucleophilic attack on the phosphorus centre, favouring the generation of the organophosphorus intermediate.

Smart Lipid Nanotubes for Easy Formation of Gold‐Lipid Hybrid Nanotubes and Tunable Gold Superstructures

AbstractOrganic‐inorganic hybrid nanotubes are highly functional and interesting materials. However, their formation generally requires reducing agents, high temperatures, special procedures, organic solvents etc. Here, using a simple concept based on engineering and materials design, we fabricated stimuli‐responsive lipid‐gold hybrid nanotubes. Self‐assembled lipid nanotubes, made from specially designed AQua molecules, are used as the nucleation sites. Well‐coated hybrid nanotubes are obtained by the in‐situ formation of gold nanoparticles on the nanotubes. The AQua molecule itself, without any other additives, reduces and stabilizes the gold nanoparticles. The nanoparticle coating degrees on the lipid nanotubes can be adjusted by varying the temperature, pH, and/or HAuCl4 concentration. In addition to hybrid nanotubes, stimuli‐responsive gold nano‐(wires, pompoms, and cubes) and polyhedrons are formed at specific conditions. Varying the pH results in a reversible change of gold nanowires to polyhedrons.

Azido-cobalt(II) coordination polymers exhibiting slow magnetic relaxation and metamagnetic transition

Two coordination polymers of mono-dimensional doubly bridged-azido-cobalt(II) complexes catena-[Co(2,6-lutidine-N-oxide)(μ1,1-N3)2] (1) and catena-{[Co(μ1,1-N3)2(H2O)2](3-picoline-N-oxide)2} (2), where 2,6-lutidine-N-oxide = 2,6-dimethylpyridine-N-oxide and 3-picoline-N-oxide = 3-methylpyridine-N-oxide, were synthesized, and structurally characterized by single crystal X-ray crystallography. The Co(II) cations in complexes 1 and 2 are penta- and hexa-coordinate, respectively with four μ1,1-bridging azido groups and a terminal 2,6-lutidine-N-oxide molecule in 1 or two trans aqua molecules in 2. Magnetic relaxations in the zero field are consistent with single chain magnetic behavior (SCM) and the ac susceptibility measurements revealed that the weak ferromagnetic exchanges in the two complexes are associated with slow relaxation of magnetization. Complex 2 exhibits metamagnetic transition with an antiferromagnetic phase transition at 12 K at the applied field of 200 Oe.

Phenoxazinone synthase and antimicrobial activity by a bis(1,3-diamino-2-propanolate) cobalt(III) complex

In this work, we have synthesised and structurally characterized a mononuclear cobalt(III) complex, $$[\hbox {Co(2-O-pn)}_{2}]\hbox {Cl}^{.} \hbox {2H}_{2} \hbox {O}$$ (1), (2-O-pn = 1,3-diamino-2-propanolate). From the X-ray structure of the cobalt complex, it is revealed that Co(III) ion in 1 adopts an octahedral geometry and crystallizes in the monoclinic system with C2 / c space group. The lattice aqua molecule in combination with chloride ion in 1 forms a water-chloride cluster, $$(\hbox {H}_{2} \hbox {O})_{2}{}^{\cdots } \, \hbox {(Cl)}_{2}$$ through strong H-bonding interaction mediated via cobalt(III) complex in a unique binding motif. This cobalt(III) complex has been tested as an effective catalytic system towards the oxidative coupling of 2-aminophenol (2-AP) in the MeCN medium. In situ mass spectral analysis confirms that 2-AP forms an adduct with cobalt ion and the course of catalysis proceeds through catalyst-substrate binding followed by oxidative coupling of 2-AP with iminobenzoquinone. This cobalt(III) catalyst affords exclusively aminophenoxazinone species with a significant turnover number, $$k_{\mathrm{cat}}: \, 6.37 \times 10^{2} \, \hbox {h}^{-1}$$ in the MeCN medium. This cobalt(III) complex is able to screen out the growth of some bacteria and fungi species. Quantum chemical calculations employing density functional theory is used to model structural parameters and spectroscopic behaviour. The theoretical findings corroborate well with the experimental results. SYNOPSIS A mononuclear cobalt(III) complex exhibits significant catalytic efficacy towards oxidative coupling of 2-aminphenol (2-AP) in MeCN medium and predominantly produces aminophenoxazinone species with a significant turn over number, $$k_{\mathrm{cat}}: \, 6.37 \times 10^{2} \, \hbox {h}^{-1}$$ in presence of molecular oxygen.

Synthetic and structural investigations of Cd(II) complexes of tetradentate pyrimidine based Schiff base ligand: Insight through non-covalent interactions, TDDFT calculation and Hirshfeld surface analysis

Two new Cd(II) complexes [Cd(L) (H2O)2]·(ClO4)2 (1) and [Cd(L) (SCN)2]·(H2O) (2) involving pyrimidine based tetradentate schiff base ligand 2,2'-((2E, 2′E)-2,2'-(butane-2,3-diylidene)bis (hydrazin-1-yl-2-ylidene))bis (4,6-dimethylpyrimidine) (L) are reported in this work. Both the complexes 1 and 2 are synthesized and characterized by elemental analyses, UV, IR, single crystal X-ray diffraction studies accordingly. Both of them are pseudooctahedral in geometry. In this report we want to highlight the variation of supramolecular non-covalent interactions in the solid state as a consequence of both apical ligand substitution (replacement of neutral aqua molecules by thiocyanate ion) and substitution of noncoordinating anionic counterions by coordinating anions. Complex 1 exhibits H-bonding, π … π stacking, CH … π and anion … π interaction whereas complex 2 displays π … π stacking and CH … π interaction only. The electronic transitions of both 1 and 2 were recorded and the electronic distribution of HOMO - LUMO can be rationalized theoretically (through time-dependent density functional theory (TDDFT)).