Synthesis, crystal structure, electronic structure, bonding, photoluminescence and spectroscopic property investigations of a mononuclear 1,10-phenanthroline and 5-bromo-salicylate ternary indium(III) complex

The synthesis, X-ray structure, electronic structure, bonding, photoluminescence, spectroscopic property and characterization of an indium(III) complex, [In(Hbsac)₃(phen)] (1) (H₂bsac = 5-bromo-salicylic acid, and phen = 1,10-phenanthroline) are presented. Complex 1 is octacoordinate and carboxylate chelating, being novel and rarely reported for main group complexes. The electronic structure, bonding and the charge transfer properties of light excitation and light emission are discussed in detail using first-principles theory, including partial density of states (PDOSs), crystal orbital overlap population (COOP), the density functional theory (DFT/TDDFT) analysis schemes. The charge transfer is mainly π → π^∗ intraligand charge transfer transition (ILCT) for excitation, and π → π^∗ ligand-to-ligand charge transfer transition (LL′CT) for emission in nature.     

Molecular structure,vibrational spectra and HOMO,LUMO analysis of 4-piperidone by density functional theory and ab initio Hartree–Fock calculations

Vibrational frequencies and geometrical parameters of 4-piperidone (4-PID) in the ground state have been calculated by using the Hartree–Fock (HF) and density functional methods (B3LYP) with 6-311++G(d,p) and 6-311+G(3df,2p) basis sets. These methods are proposed as a tool to be applied in the structural characterisation of 4-PID (C₅H₉NO). The title molecule has C _s point group symmetry, thus providing useful support in the interpretation of experimental IR and Raman data. The DFT-B3LYP/6-311+G(3df,2p) calculations have been found more reliable than the ab initio HF/6-311++G(d,p) calculations for the vibrational study of 4-PID. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energies show that charge transfer occurs within the molecule. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.     

Fast Proton Insertion in Layered H2W2O7 via Selective Etching of an Aurivillius Phase

H₂W₂O₇, a metastable material synthesized via selective etching of the Aurivillius-related Bi₂W₂O₉, is demonstrated as an electrode for high power proton-based energy storage. Comprehensive structural characterization is performed to obtain a high-fidelity crystal structure of H₂W₂O₇ using an iterative approach that combines X-ray diffraction, neutron pair distribution function, scanning transmission electron microscopy, Raman spectroscopy, and density functional theory modeling. Electrochemical characterization shows a capacity retention of ≈80% at 1000 mV s^–1 (1.5-s charge/discharge time) as compared to 1 mV s^–1 (≈16-min charge/discharge time) with cyclability for over 100 000 cycles. Energetics from density functional theory calculations indicate that proton storage occurs at the terminal oxygen sites within the hydrated interlayer. Last, optical micrographs collected during in situ Raman spectroscopy show reversible, multicolor electrochromism, with color changes from pale yellow to blue, purple, and last, orange as a function of proton content. These results highlight the use of selective etching of layered perovskites for the synthesis of metastable transition metal oxide materials and the use of H₂W₂O₇ as an anode material for proton-based energy storage or electrochromic applications.     

Experimental and Theoretical Studies of Calcium Fructoborate

Calcium fructoborate samples of composition Ca(C₆H₁₀O₆BO)₂·3.5H₂O were characterized by chemical analysis, infrared and Raman spectroscopy, and thermoanalytical (thermogravimetric and differential thermal analysis) data. Theoretical studies, using density functional theory, were made for seven different structural models of the fructoborate moiety, and the most stable structure could be derived from these calculations. The results of the theoretical study also allow improving the assignment of the vibrational spectra of the compound.     

[(B3O3H3)nM]+(n = 1, 2;M = Cu, Ag, Au): a new class of metal-cation complexes

A density functional theory (DFT) investigation into the structures and bonding characteristics of [(B₃O₃H₃)_nM]⁺(n?=?1, 2;M?=?Cu, Ag, Au) complexes was performed. DFT calculations and natural bond orbital (NBO) analyses indicate that the ΙB metal complexes of boroxine exhibit intriguing bonding characteristics, different from the typical cation–π interactions between ΙB metal-cations and benzene. The complexes of [B₃O₃H₃M]⁺ and [(B₃O₃H₃)₂?M]⁺ (M?=?Cu, Ag, and Au) favor the conformation of perfectly planar structures with the C_2v and D_2h symmetry along one of the threefold molecular axes of boroxine, respectively. Detailed natural resonance theory (NRT) and canonical molecular orbitals (CMOs) analyses show that interaction between the metal cation and the boroxine in [B₃O₃H₃M]⁺ (M?=?Cu, Ag, and Au) is mainly ionic, while the ΙB metal-cations←π donation effect is responsible for the binding site. In these complexes, boroxine serves as terminals η¹-B₃O₃H₃ with one O atom of the B₃O₃ ring. The infra-red (IR) spectra of [B₃O₃H₃M]⁺ were simulated to facilitate their future experimental characterization. The complexes all give two IR active modes at about 1,300 and 2,700 cm^?1, which are inactive in pure boroxine. Simultaneously, the B–H stretching modes of the complexes are red-shifted due to the interaction between the metal-cation and boroxine. To explore the possibility of the structural pattern developed in this work forming mesoporous materials, complexes [(B₃O₃H₃M)₆]⁶⁺ (M?=?Cu, Ag, and Au) were also studied, which appear to be unique and particular interesting: they are all true minima with D_6h symmetries and pore sizes ranging from 12.04 Å to 13.65 Å.

Structure, spectroscopic and magnetic properties of a novel 1-D coordination copper(II) polymer containing BIMAM ligand [BIMAM = bis(imidazol-2-yl)methylaminomethane] and μ-1,3 squarato bridges

This paper reports the synthesis and complete characterization (structural, spectroscopic and magnetic) of [Cu(HBIMAM)Cl(C₄O₄)]_n · (H₂O)_n [BIMAM = bis(imidazol-2-yl)methylaminomethane]. This compound is made of infinite chains - running along c axis - built from [CuCl(HBIMAM)]⁺ units bridged together by μ-O¹,O³-bis(monodentate) squarate anions. Non-covalent interactions (H-bonds and π-π) drive the build-up of an infinite three-dimensional array. The coordination polyhedron about the copper(II) ion is distorted square pyramidal. The EPR spectrum is indicative of a d_z²-y² ground state for the Cu(II) ions with significant contribution of d_z². Magnetic susceptibility measurements in the range 1.8-200 K show weak antiferromagnetic exchange interactions (2J = −3.5(1) cm⁻¹). The observed magnetic behaviour is discussed in terms of the crystal structure and compared with that observed in related copper(II) complexes containing μ-O¹,O³-squarato bridges.     

A newly synthesized 6-methyl-7H,8H,9H-[1,2,4]triazolo[4,3-b][1,2,4]triazepin-8-one for potential inhibitor of adenosine A1 receptor: a combined experimental and computational studies

Abstract

6-Methyl-7H,8H,9H-[1,2,4]triazolo[4,3-b][1,2,4]triazepin-8-onehas been synthesized, characterized by spectroscopic techniques (FT-IR, ¹H and ¹³C NMR) and finally the structure was confirmed by single crystal X-ray diffraction studies. In the title molecule, C₆H₇N₅O, the 7-membered ring adopts a bowl-like conformation. In the crystal, the molecules form stacks along the c-axis direction through offset π-stacking interactions between the 5-membered rings and C–H···N hydrogen bonds. The stacks are associated via a combination of N–H···N, C–H···O and C–H···N hydrogen bonds. Further, the Hirshfeld surface analysis reveals the nature of molecular interactions and the fingerprint plot provides information about the percentage contribution from each individual molecular contact to the surface. In addition, due to its biological interest the target molecule adenosine A1 receptor was found based on Structural Activity Relationship (SAR) analysis and, further, subjected into molecular docking and molecular dynamics analysis to understand the binding interaction and stability of the molecule in adenosine A1 receptor system. Furthermore, the Density Functional Theory (DFT) calculations were carried for free compound and the compound in active site (single point DFT), to know the internal stability.

Communicated by Ramaswamy H. Sarma     

Synthesis, crystal structure, hydrogen bonding and spectroscopy of Co, Mn and Ni oxalate complexes with the ligand (N,N′-bis(2-pyridylmethyl)-1,3-propanediamine)

Three new compounds are reported with the tetradentate ligand (N,N′-bis(2-Pyridylmethyl)-1,3-propanediamine) (abbreviated as pypn), two mononuclear compounds i.e. [Co(pypn)(C₂O₄)](ClO₄) (1), [Mn(pypn)(C₂O₄)](ClO₄) (2) and one dinuclear compound [Ni₂(pypn)₂(C₂O₄)](ClO₄)₂(C₂H₆O)_1/4(H₂O) (3). In the Co(III) and Mn(II) complexes the oxalate behaves as bidentate ligand, chelating the metal in the O,O′ mode, whereas in the Ni(II) compound the oxalate behaves as tetradentate ligand binding each Ni(II) ion by two oxygen atoms and bridging the two metallic centers.The synthesis, X-ray crystal structure of all three compounds and their spectroscopic properties are presented in detail. The geometry around the Co³⁺, Mn³⁺, Ni²⁺ ions is essentially octahedrally based, while the stabilization of the crystal lattice in all cases is maintained by interesting hydrogen bond systems.     

An experimental and theoretical approach to the molecular structure of 2-{4-[3-(2,5-dimethylphenyl)-3-methylcyclobutyl]thiazol-2-yl}isoindoline-1,3-dione

The title compound, 2-{4-[3-(2,5-dimethylphenyl)-3-methylcyclobutyl]thiazol-2-yl}isoindoline-1,3-dione (C₂₄H₂₂N₂O₂S), was synthesized and characterized by IR-NMR spectroscopy and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2₁/c with a?=?19.7799(13) Å, b?=?6.7473(4) Å, c?=?15.7259(9) Å and β?=?103.416(5)°. In addition, the molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) ¹H and ¹³C chemical shift values of the title compound in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (DFT/B3LYP) with 6–31G(d), 6–31 + G(d,p) and LANL2DZ basis sets, and compared with the experimental data. To determine conformational flexibility, molecular energy profile of the title compound was obtained by semi-empirical (AM1) calculations with respect to two selected degrees of torsional freedom, which were varied from ?180° to +180° in steps of 5°. Besides, molecular electrostatic potential, frontier molecular orbitals (FMO) analysis and thermodynamic properties of the title compound were investigated by theoretical calculations.     

Isolation of ergosterol peroxide and its reversion to ergosterol in the pathogenic fungus Sporothrix schenckii

Ergosterol peroxide, a presumed product of the H_{_2}O_{_2}-dependent enzymatic oxidation of ergosterol, has been isolated from yeast forms of the pathogenic fungus Sporothrix schenckii. The substance, which may have a role in fungal virulence, has been characterized mainly using spectroscopic methods (¹H and ¹³C nuclear magnetic resonance and high resolution mass spectra). The purified compound showed a molecular formula of C_{_28}H_{_44}O_{_3}, displaying characteristic features of epidioxy sterols and was reverted to ergosterol when submitted to S. schenckii enzymatic extract. This revised version was published online in June 2006 with corrections to the Cover Date.     

Crystal structure and exchange pathways of the complex l-(trypthophyl-glycinato)copper(II)

The crystal structure and the EPR characterization of the compound Cu [C₁₃H₁₃N₃O₃] is reported. It crystallizes in the P2₁2₁2₁ space group, with a=8.2829(5), b=9.347(2), c=16.499(2) Å and Z=4. The copper ion is in a distorted square planar coordination, bonded to two nitrogen and one oxygen atoms from one dipeptide and to an oxygen atom from a symmetry-related molecule. Thus, neighbor copper atoms at 5.14 Å are connected by equatorial syn–anti carboxylate bridges giving rise to a chain structure along the b-axis. The chains are connected via hydrogen bonds and cation–π interactions, the latter being provided by the ‘sandwich’ structure involving each copper atom and two tryptophan residues from neighbor molecules. The EPR spectra of polycrystalline sample imply an essentially d_x2−y2 ground state orbital for the Cu(II) ions. The g-values reflect a slightly distorted axial symmetry around the Cu(II) ions as expected from the structural results. No hyperfine interaction is observed, which is indicative of the presence of exchange interactions between the copper atoms as suggested by the X-ray results as well.     

Studies on Polyoxins,Antifungal Antibiotics

Seven additional components, polyoxins C, D, E, F, G, H and I were isolated from polyoxin complex. They have molecular formulae corresponding to C₁₁H₁₅N₃O₈, C₁₇H₂₃N₅O₁₄, C₁₇H₂₃N₅O₁₃, C₂₃H₃₀N₆O₁₅, C₁₇H₂₅N₅O₁₂, C₂₃H₃₂N₆O₁₃ and C₁₉H₂₄N₄O₁₂, respectively. These polyoxins except inactive polyoxins C and I were highly active against various kinds of phytopathogenic fungi. The close structural similarity among them including polyoxins A and B is also discussed.     

X-ray crystal structure and antimony-121 Mössbauer spectrum of catecholato bis(1,10-phenanthroline)antimony(III) tetraphenylborate

The crystal structure of the title compound was solved by means of X-ray diffraction at room temperature. The salt consists of a tetrahedral tetraphenylborate anion and a complex cation containing a catecholatoantimony(III) unit chelated by two 1,10-phenanthrolines. The three bidentate ligands are essentially arranged in one half of the Sb coordination sphere, leaving ample space to accomodate the lone pair of electrons. The Mössbauer parameters of the title compound and of the complex (C₆H₄O₂)SbF·Phen were measured and their rationalization accomplished in the light of their respective molecular structures.     

Koninginin C: A Biologically Active Natural Product from Trichoderma koningii

Koninginin C, a congener of koninginins A and B, was isolated from Trichoderma koningii fermented on a shredded wheat medium. The compound inhibited the growth of etiolated wheat coleoptiles by 100% at 10^?3 M. It was a fine, white cystalline substance with a molecular formula of C₁₆H₂₈O₄ and a melting point of 70–72°C.     

B30H8, B39H9 2−, B42H10, B48H10, and B72H12: polycyclic aromatic snub hydroboron clusters analogous to polycyclic aromatic hydrocarbons

Calculations performed at the ab initio level using the recently reported planar concentric π-aromatic B₁₈H₆ ²⁺(1) [Chen Q et al. (2011) Phys Chem Chem Phys 13:20620] as a building block suggest the possible existence of a new class of B_3n H _m polycyclic aromatic hydroboron (PAHB) clusters—B₃₀H₈(2), B₃₉H₉ ^2?(3), B₄₂H₁₀(4/5), B₄₈H₁₀(6), and B₇₂H₁₂(7)—which appear to be the inorganic analogs of the corresponding C _n H _m polycyclic aromatic hydrocarbon (PAHC) molecules naphthalene C₁₀H₈, phenalenyl anion C₁₃H₉ ^?, phenanthrene/anthracene C₁₄H₁₀, pyrene C₁₆H₁₀, and coronene C₂₄H₁₂, respectively, in a universal atomic ratio of B:C?=?3:1. Detailed canonical molecular orbital (CMO), adaptive natural density partitioning (AdNDP), and electron localization function (ELF) analyses indicate that, as they are hydrogenated fragments of a boron snub sheet [Zope RR, Baruah T (2010) Chem Phys Lett 501:193], these PAHB clusters are aromatic in nature, and exhibit the formation of islands of both σ- and π-aromaticity. The predicted ionization potentials of PAHB neutrals and electron detachment energies of small PAHB monoanions should permit them to be characterized experimentally in the future. The results obtained in this work expand the domain of planar boron-based clusters to a region well beyond B₂₀, and experimental syntheses of these snub B_3n H _m clusters through partial hydrogenation of the corresponding bare B_3n may open up a new area of boron chemistry parallel to that of PAHCs in carbon chemistry.

Chemistry of Heliangine

The evidences which allow to assign the partial structures (a, b and c) for heliangine, C₂₀H₂₆O₆, are described. The chemical and spectroscopic data obtained for this compound are interpreted in terms of the structure I, which has been preliminarily proposed by the authors, as well as of the structure II established by X-ray analysis conducted by Nishikawa et al.     

Enzymatic and spectroscopic properties of a thermostable [NiFe]‑hydrogenase performing H2-driven NAD+-reduction in the presence of O2

Biocatalysts that mediate the H₂-dependent reduction of NAD⁺ to NADH are attractive from both a fundamental and applied perspective. Here we present the first biochemical and spectroscopic characterization of an NAD⁺-reducing [NiFe]?hydrogenase that sustains catalytic activity at high temperatures and in the presence of O₂, which usually acts as an inhibitor. We isolated and sequenced the four structural genes, hoxFUYH, encoding the soluble NAD⁺-reducing [NiFe]?hydrogenase (SH) from the thermophilic betaproteobacterium, Hydrogenophilus thermoluteolus TH-1^T (Ht). The HtSH was recombinantly overproduced in a hydrogenase-free mutant of the well-studied, H₂-oxidizing betaproteobacterium Ralstonia eutropha H16 (Re). The enzyme was purified and characterized with various biochemical and spectroscopic techniques. Highest H₂-mediated NAD⁺ reduction activity was observed at 80 °C and pH 6.5, and catalytic activity was found to be sustained at low O₂ concentrations. Infrared spectroscopic analyses revealed a spectral pattern for as-isolated HtSH that is remarkably different from those of the closely related ReSH and other [NiFe]?hydrogenases. This indicates an unusual configuration of the oxidized catalytic center in HtSH. Complementary electron paramagnetic resonance spectroscopic analyses revealed spectral signatures similar to related NAD⁺-reducing [NiFe]?hydrogenases. This study lays the groundwork for structural and functional analyses of the HtSH as well as application of this enzyme for H₂-driven cofactor recycling under oxic conditions at elevated temperatures.     

Spectroscopic properties of ironthiosemicarbazone compounds. Structure of [Fe(C7H7N4S)2]·1.25H2O

The reaction of FeCl₃ and HL, where HL=C₇H₈N₄S, pyridine-2-carbaldehyde thiosemicarbazone, at physiological pH values in air gives rise to a powder of composition C₁₄H₁₆Cl_0.3FeN₈O_1.2S₂ which contains iron(II)- and iron(III)-thiosemicarbazone species. This fact confirms the reducing character of the ligand in neutral and basic media. The [Fe(C₇H₇N₄S)₂]·1.25H₂O compound has been isolated. The crystal structure consists of discrete monomeric cationic entities containing low-spin iron(II) ions in a distorted octahedral environment. The metal ion is bonded to one sulfur and two nitrogen atoms of each thiosemicarbazone molecule. The powdered X-band EPR spectra of C₁₄H₁₆Cl_0.3FeN₈O_1.2S₂ show a significant variation with temperature which can be explained considering an ‘exchange narrowing’ phenomenon, in good accordance with the presence of antiferromagnetic interactions. The Mössbauer measurements are in good agreement with the existence of one iron(II) and two iron(III) low-spin species, with relative areas of 69, 17 and 14%, respectively.     

Experimental and DFT computational studies on 5-benzyl-4-(3,4-dimethoxyphenethyl)-2H-1,2,4-triazol-3(4H)-one

The triazole compound, 5-benzyl-4-(3,4-dimethoxyphenethyl)-2H-1,2,4-triazol-3(4H)-one, has been synthesized and characterized by ¹H-NMR, ¹³C-NMR, IR, and X-ray single-crystal determination. The compound crystallizes in the monoclinic space group P2₁ with a?=?11.8844(3) Å, b?=?17.5087(4) Å, c?=?17.3648(6) Å, β?=?99.990(2)? and Z?=?8. In addition to the molecular geometry from X-ray experiment, the molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) ¹H- and ¹³C-NMR chemical shift values of the title compound in the ground state have been calculated using the density functional method (B3LYP) with 6-31G(d,p) basis set. The calculated results show that the optimized geometries can well reproduce the crystal structure and the theoretical vibrational frequencies and chemical shift values show good agreement with experimental ones. Besides, molecular electrostatic potential (MEP), natural bond orbital (NBO), and frontier molecular orbitals (FMO) analysis of the title compound were performed by the B3LYP/6-31G(d,p) method.