Crystal structure and DFT analyses of a pentacoordinated PCP pincer nickel(II) complex

The reaction of NiCl2 with 1,3-bis[(diphenylphosphanyl)methyl]hexahydropyrimidine in the presence of 2,6-dimethylphenyl isocyanide and KPF6 afforded a new pentacoordinated PCP pincer NiII complex, namely {1,3-bis[(diphenylphosphanyl)methyl]hexahydropyrimidin-2-yl-κN 2}(2,6-dimethylphenyl isocyanide-κC)nickel(II) hexafluoridophosphate 0.70-hydrate, [Ni(C9H9N)(C30H30ClN2P2)]PF6·0.7H2O or [NiCl{C(NCH2PPh2)2(CH2)3-κ3 P,C,P′}(Xylyl-NC)]PF6·0.7H2O, in very good yield. Its X-ray structure showed a distorted square-pyramidal geometry and the compound does not undergo dissociation in solution, as shown by variable-temperature NMR and UV–Vis studies. Density functional theory (DFT) calculations provided an insight into the bonding; the nickel dsp 2-hybridized orbitals form the basal plane and the nearly pure p orbital forms the axial bond. This is consistent with the NBO (natural bond orbital) analysis of analogous nickel(II) complexes.

Bis(3,5-dimethoxy-2-{[2-(pyridin-2-yl)ethylimino-κN]methyl}phenolato-κO)bis(dimethyl sulfoxide)manganese(III) perchlorate methanol 0.774-solvate

The title compound, [Mn(C16H17N2O3)2(C2H6OS)2]ClO4·0.774CH3OH, comprises a central octahedrally coordinated MnIIIcation, with two bidentate Schiff base ligands occupying the equatorial positions and two dimethyl sulfoxide (DMSO) ligands occupying the axial positions. There are two independant cations in the asymmetric unit, with the MnIIIatoms of both cations being positioned on crystallographic centers of inversion. The perchlorate anion is disordered over two equivalent conformations, with occupancies of 0.744 (3) and 0.226 (3). In addition, there is a methanol solvent molecule in the crystal lattice that is too close to the minor component of the perchlorate anion to be present simultaneously and thus it was refined to have the same occupancy as the major component of this anion. There is a Jahn–Teller distortion which results in Mn—ODMSOaxial bond lengths of 2.2365 (12) and 2.2368 (12) Å in the two cations. In the crystal, intermolecular π–π stacking between the non-coordinating pyridine rings of each cation is observed. This π–π stacking, along with extensive O—H...O hydrogen bonding and C—H...O interactions, link the components into a complex three-dimensional array.

Reductive nitrosylation of ferric carboxymethylated-cytochrome c

Horse heart carboxymethylated-cyt[Formula: see text] (CM-cyt[Formula: see text] displays myoglobin-like properties due to the cleavage of the heme-Fe-Met80 axial bond. Here, reductive nitrosylation of CM-cyt[Formula: see text](III) between pH 8.5 and 9.5, at [Formula: see text] 20.0 C, is reported. Under anaerobic conditions, the addition of NO to CM-cyt[Formula: see text](III) leads to the transient formation of CM-cyt[Formula: see text](III)-NO in equilibrium with CM-cyt[Formula: see text](II)-NO[Formula: see text]. In turn, CM-cyt[Formula: see text](II)-NO[Formula: see text] is converted to CM-cyt[Formula: see text](II) by OH[Formula: see text]-based catalysis. Then, CM-cyt[Formula: see text](II) binds NO very rapidly leading to CM-cyt[Formula: see text](II)-NO. Kinetics of NO binding to CM-cyt[Formula: see text](III) is independent of the ligand concentration, [Formula: see text] values ranging between 3.6 ± 0.4 s[Formula: see text] and 7.1 ± 0.7 s[Formula: see text]. This indicates that the formation of the CM-cytc(III)-NO complex is rate-limited by the cleavage of the weak heme-Fe(III) distal bond (likely Lys79). The conversion of CM-cyt[Formula: see text](III)-NO to CM-cyt[Formula: see text](II)-NO is rate-limited by the OH[Formula: see text]-mediated reduction of CM-cyt[Formula: see text](II)-NO[Formula: see text] ([Formula: see text] (1.2 ± 0.1) × 103 M[Formula: see text].s[Formula: see text]. Lastly, the very fast nitrosylation of CM-cyt[Formula: see text](II) takes place, values of [Formula: see text] ranging between[Formula: see text]5.3 × 106 M[Formula: see text].s[Formula: see text] and 1.4 × 107 M[Formula: see text].s[Formula: see text]. These results indicate that CM-cyt[Formula: see text] behaves as the cardiolipin-cyt[Formula: see text] complex highlighting the role of the sixth axial ligand of the heme-Fe atom in the modulation of the metal-based reactivity.

Crystal structure of (2-formylphenolato-κ2O,O′)oxido(2-{[(2-oxidoethyl)imino]methyl}phenolato-κ3O,N,O′)vanadium(V)

In the unsymmetrical title vanadyl complex, [V(C9H9NO2)(C7H5O2)O], one of the ligands (2-formylphenol) is disordered over two sets of sites, with an occupancy ratio of 0.55 (2):0.45 (2). The metal atom is hexacoordinated, with a distorted octahedral geometry. The vanadyl O atom (which subtends the shortest V—O bond) occupies one of the apical positions and the remaining axial bond (the longest in the polyhedron) is provided by the (disordered) formyl O atoms. The basal plane is defined by the two phenoxide O atoms, the iminoalcoholic O and the imino N atom. The planes of the two benzene rings are almost perpendicular to each other, subtending an interplanar angle of 84.1 (2)° between the major parts. The crystal structure features weak C—H...O and C—H...π interactions, forming a lateral arrangement of adjacent molecules.

Study on Indoor Detecting Methods and Performance of Shotcrete

Using self-designed indoor detecting methods, the performance test of shotcrete doped compound admixture and crude fiber were carried out. The results showed that compound admixture and crude fiber can improve the compressive strength, flexural toughness and crack resistance of shotcrete. Axial bond strengths of shotcrete with rock were more than 1.0MPa, and that can be increased by combined-doped compound admixture and crude fiber. Rebound rates of shotcrete were 23% and 20%, layer thickness in one shot cycle were 22cm and 25cm, and combined-doped compound admixture and fiber can increase the cohesiveness and reduce rebound rate. Self-designed methods can be used to compare construction performance of different shotcretes.

Thermodynamic and spectroscopic study on the binding of interaction anionic phthalocyanine with calf thymus DNA

The interaction between anionic form of copper (II) N,N',N",N'"-tetrasulfonated phthalocyanine Cu (tspc) and to calf thymus deoxyribonucleic acid (ct-DNA) is investigated by measuring UV-vis absorption and fluorescence spectroscopy in phosphate buffer. The binding constant and stoichiometry were determined by analysis of optical absorption spectra of phthalocyanine at various ct-DNA concentrations using SQUAD software. The static mode of fluorescence quenching of phthalocyanine by calf thymus deoxyribonucleic acid indicates the formation of a ground-state complex. The formation of ground-state complex is a spontaneous molecular interaction procedure in which outside groove binding through the formation of an axial bond between the base pairs of nucleotide and Cu in the central core of phthalocyanine.

Structural Changes in CuII Complexes of Potential Octadentate Ligands by Coordination with Carboxylate/Carboxylic Acid: DFT, TD-DFT, and Experimental Studies

The structural and spectroscopic studies of N,N,N′,N′,N′-pentakis-(benzimidazol-2-yl-methyl)diethylenetriamine (L1) and N,N,N′,N′-tetrakis-(benzimidazol-2-yl-methyl)-N′-(carboxylmethyl)diethylenetriamine (L2H) and [CuL1]2+, [CuL2H]2+, and [CuL2]+ were carried out by density functional theory (DFT) and time-dependant (TD)-DFT techniques. The results show that a geometrical change occurs when carboxylate/carboxylic acid coordinates with the metal ion. For example, the ligand L2H forms an octahedral geometry with CuII and in the structure, four nitrogens (N3, N13, N44, N47) are equatorially coordinated with the metal ion, and atoms O50 (–COOH) and N41, which are weakly bonded at the axial positions, are in competition in the formation of an axial bond with CuII; however, for the ligand L2, only a square pyramidal (SP) geometry results with CuII because of the formation of a strong axial bond by O50 (–COO–) with CuII, which dictates non-bonding at its trans position. Molecular orbital analysis proves that both HOMO and HOMO – 1 are localized over the carboxylate ion that favours a strong axial bond with the metal ion; thus, the SP geometry results in the X-ray structure of [CuL2]ClO4. Furthermore, for the complexes, since the electronic spectroscopic bands were unseparated in the spectra, the TD-DFT was used to identify the bands.