Synthesis of the Bacteriostatic Poly(L-Lactide) by Using Zinc (II)[(acac)(L)H2O] (L = Aminoacid-Based Chelate Ligands) as an Effective ROP Initiator

The paper presents a synthesis of poly(l-lactide) with bacteriostatic properties. This polymer was obtained by ring-opening polymerization of the lactide initiated by selected low-toxic zinc complexes, Zn[(acac)(L)H2O], where L represents N-(pyridin-4-ylmethylene) tryptophan or N-(2-pyridin-4-ylethylidene) phenylalanine. These complexes were obtained by reaction of Zn[(acac)2 H2O] and Schiff bases, , the products of the condensation of amino acids and 4-pyridinecarboxaldehyde. The composition, structure, and geometry of the synthesized complexes were determined by NMR and FTIR spectroscopy, elemental analysis, and molecular modeling. Both complexes showed the geometry of a distorted trigonal bipyramid. The antibacterial and antifungal activities of both complexes were found to be much stronger than those of the primary Schiff bases. The present study showed a higher efficiency of polymerization when initiated by the obtained zinc complexes than when initiated by the zinc(II) acetylacetonate complex. The synthesized polylactide showed antibacterial properties, especially the product obtained by polymerization initiated by a zinc(II) complex with a ligand based on l-phenylalanine. The polylactide showed a particularly strong antimicrobial effect against Pseudomonas aeruginosa, Staphylococcus aureus, and Aspergillus brasiliensis. At the same time, this polymer does not exhibit fibroblast cytotoxicity.

Crystal structure of Zn2(HTeO3)(AsO4)

Single crystals of Zn2(HTeO3)(AsO4), dizinc(II) hydroxidodioxidotellurate(IV) oxidoarsenate(V), were obtained as one of the by-products in a hydrothermal reaction between Zn(NO3)2·6H2O, TeO2, H3AsO4 and NH3 in molar ratios of 2:1:2:10 at 483 K for seven days. The asymmetric unit of Zn2(HTeO3)(AsO4) contains one Te (site symmetry m), one As (m), one Zn (1), five O (three m, two 1) and one H (m) site. The ZnII atom exhibits a coordination number of 5 and is coordinated by four oxygen atoms and a hydroxide group, forming a distorted trigonal bipyramid. The hydroxide ion is positioned at a significantly larger distance on one of the axial positions of the bipyramid. The [ZnO4OH] polyhedra are connected to each other by corner-sharing to form ∞ 2[ZnO3/2(OH)1/2O1/1] layers extending parallel to (001). The TeIV atom is coordinated by three oxygen atoms and a hydroxide group in a one-sided manner in the shape of a bisphenoid, revealing stereochemical activity of its 5s 2 electron lone pair. The AsV atom is coordinated by four oxygen atoms to form the tetrahedral oxidoarsenate(V) anion. By corner-sharing, [TeO3OH] and [AsO4] groups link adjacent ∞ 2[ZnO3/2(OH)1/2O1/1] layers along [001] into a three-dimensional framework structure.

Triphenylantimony(V) Catecholates of the Type (3-RS-4,6-DBCat)SbPh3-Catechol Thioether Derivatives: Structure, Electrochemical Properties, and Antiradical Activity

A new series of triphenylantimony(V) 3-alkylthio/arylthio-substituted 4,6-di-tert-butylcatecholates of the type (3-RS-4,6-DBCat)SbPh3, where R = n-butyl (1), n-hexyl (2), n-octyl (3), cyclopentyl (4), cyclohexyl (5), benzyl (6), phenyl (7), and naphthyl-2 (8), were synthesized from the corresponding catechol thioethers and Ph3SbBr2 in the presence of a base. The crystal structures of 1, 2, 3, and 5 were determined by single-crystal X-ray analysis. The coordination polyhedron of 1–3 is better described as a tetragonal pyramid with a different degree of distortion, while that for 5- was a distorted trigonal bipyramid (τ = 0.014, 0.177, 0.26, 0.56, respectively). Complexes demonstrated different crystal packing of molecules. The electrochemical oxidation of the complexes involved the catecholate group as well as the thioether linker. The introduction of a thioether fragment into the aromatic ring of catechol ligand led to a shift in the potential of the “catechol/o-semiquinone” redox transition to the anodic region, which indicated the electron-withdrawing nature of the RS group. The radical scavenging activity of the complexes was determined in the reaction with DPPH radical.

Structural basis for the hydrolytic dehalogenation of the fungicide chlorothalonil

Cleavage of aromatic carbon–chlorine bonds is critical for the degradation of toxic industrial compounds. Here, we solved the X-ray crystal structure of chlorothalonil dehalogenase (Chd) from Pseudomonas sp. CTN-3, with 15 of its N-terminal residues truncated (ChdT), using single-wavelength anomalous dispersion refined to 1.96 Å resolution. Chd has low sequence identity (<15%) compared with all other proteins whose structures are currently available, and to the best of our knowledge, we present the first structure of a Zn(II)-dependent aromatic dehalogenase that does not require a coenzyme. ChdT forms a “head-to-tail” homodimer, formed between two α-helices from each monomer, with three Zn(II)-binding sites, two of which occupy the active sites, whereas the third anchors a structural site at the homodimer interface. The catalytic Zn(II) ions are solvent-accessible via a large hydrophobic (8.5 × 17.8 Å) opening to bulk solvent and two hydrophilic branched channels. Each active-site Zn(II) ion resides in a distorted trigonal bipyramid geometry with His117, His257, Asp116, Asn216, and a water/hydroxide as ligands. A conserved His residue, His114, is hydrogen-bonded to the Zn(II)-bound water/hydroxide and likely functions as the general acid-base. We examined substrate binding by docking chlorothalonil (2,4,5,6-tetrachloroisophtalonitrile, TPN) into the hydrophobic channel and observed that the most energetically favorable pose includes a TPN orientation that coordinates to the active-site Zn(II) ions via a CN and that maximizes a π–π interaction with Trp227. On the basis of these results, along with previously reported kinetics data, we propose a refined catalytic mechanism for Chd-mediated TPN dehalogenation.

Crystal structure of (μ-trans-1,2-bis{2-[(2-oxidophenyl)methylidene]hydrazin-1-ylidene}ethane-1,2-diolato-κ3 O,O′,N)bis[di-tert-butyltin(IV)]

The binuclear complex, [Sn2(C4H9)4(C16H10N4O4)], contains two Sn4+ ions, connected by doubly N-deprotonated oxalylbis[(2-oxidobenzylidene)hydrazide] ligands, and each Sn4+ ion is linked to two tert-butyl groups. The coordination sphere of each Sn atom is best described as a distorted trigonal bipyramid. Each stannic ion in the complex is in a C2O2N environment. The two homologous parts of the doubly deprotonated ligand are located in trans positions with respect to the C—C bond of the oxalamide group. The oxalamide group exhibits an asymmetric coordination geometry, as seen by the slight difference between the C—O and C—N bond lengths. The three-dimensional network is a multilayer of complex molecules with no strong supramolecular interactions.

Crystal structure of μ-4-oxidobenzoato-κ2O1:O4-bis[bis(1,10-phenanthroline-κ2N,N′)copper(II)] bis(4-hydroxybenzoate) 7.5-hydrate

The title hydrated complex, [Cu2(C7H4O3)(C12H8N2)4](C7H5O3)2·7.5H2O, is composed of dinuclear CuIIcomplex cations, noncoordinating 4-hydroxybenzoate anions and water molecules of crystallization. In the dinuclear complex cation, the CuIIions are bridged by a 4-oxidobenzoate ligand and thus each metal ion is five-coordinated by two chelating 1,10-phenanthroline (phen) molecules and one anionic O atom in a distorted trigonal-bipyramid geometry. In the crystal, aromatic π–π stacking occurs between phen rings of neighbouring dinuclear CuIIcomplex cations, forming two-dimensional supramolecular systems parallel to (100).

Crystal structure ofcatena-poly[N,N,N′,N′-tetramethylguanidinium [(chloridocadmate)-di-μ-chlorido]]

In the structure of the title salt, {(C5H14N3)[CdCl3]}n, the CdIIatom of the complex anion is five-coordinated by one terminal and four bridging Cl atoms. The corresponding coordination polyhedron is a distorted trigonal bipyramid, with Cd—Cl distances in the range 2.4829 (4)–2.6402 (4) Å. The bipyramids are condensed into a polyanionic zigzag chain extending parallel to [101]. The tetramethylguanidinium cations are situated between the polyanionic chains and are linked to them through N—H...Cl hydrogen bonds, forming a layered network parallel to (010).

Crystal structure of 4,8-di-tert-butyl-6,6-dichloro-13-ethyl-2,10-dimethyl-13,14-dihydro-12H-dibenzo[d,i][1,3,7,2]dioxazasilecine toluene 0.25-solvate

The coordination polyhedron at the silicon atom in the title compound, C26H37Cl2NO2Si·0.25C7H8, is typical for pentacoordinated silicon derivatives and represents a slightly distorted trigonal bipyramid with an N atom and a Cl atom in the apical positions and the two O atoms and the other Cl atom occupying the equatorial sites. There are two independent molecules in the asymmetric unit. The N–Si–Cl fragment in each is close to linear [178.24 (5) and 178.71 (5)°], in good agreement with 4e–3ctheory, as is the elongation of the apical bond lengths [Si—Cl = 2.1663 (7) and 2.1797 (7) Å] in comparison with the equatorial bonds [Si—Cl = 2.0784 (7) and 2.0748 (7) Å]. Orthogonal least-squares fitting of the two independent molecules resulted in r.m.s. deviation of 0.017 Å. The conformations of the two molecules are almost the same, with corresponding torsion angles differing by less than 5.5°. The toluene solvent molecule is disordered about an inversion centre.

Ionothermal Synthesis and Crystal Structure of a Neutral 2D Metal- Organic Framework Based on Cobalt(II) 1,2,3-Benzenetricarboxylate

A neutral metal-organic framework [CoNa3(1,2,3-Hbtb)(1,2,3-btb)] (1) has been synthesized through an ionothermal method using 1-ethyl-3-methylimidazolium bromide as solvent (1,2,3- H3btb=1,2,3-benzenetricarboxylic acid). The complex has been characterized by IR spectroscopy, elemental analysis, PXRD and single-crystal X-ray diffraction. The structure of 1 exhibits a layer network structure in which Co(II) is five-coordinated forming a distorted trigonal bipyramid. Na1 and Na3 are surrounded by seven oxygen atoms, and Na2 is six-coordinated. In the structure, the anions of 1,2,3-H3btb are embedded in two bridging μ8 coordination modes. The luminescence properties of 1 have been investigated in the solid state at room temperature.

Synthesis and Crystal Structure of the Bioinorganic Complex [Sb(Hedta)]·2H2O

The antimony(III) complex [Sb(Hedta)]·2H2O was synthesized with ethylenediaminetetraacetic acid (H4edta) and antimonous oxide as main raw materials in aqueous solution. The composition and structure of the complex were characterized by elemental analysis, infrared spectra, single crystal X-ray diffraction, X-ray powder diffraction, thermogravimetry, and differential scanning calorimetry. The crystal structure of the antimony(III) complex belongs to orthorhombic system, space group Pna2(1), with cell parameters ofa=18.4823(18) Å,b=10.9408(12) Å,c=7.3671(5) Å,V=1489.7(2) Å3,Z=4, andDc=1.993 g cm−3. The Sb(III) ion is five-coordinated by two amido N atoms and three carboxyl O atoms from a single Hedta3−ligand, forming a distorted trigonal bipyramid geometry. The thermal decomposition processes of the complex include dehydration, oxidation, and pyrolysis of the ligand, and the last residue is Sb2O3at the temperature of 570°C.