Miaoli Zhu

Synthesis, structure, spectral characterization, electrochemistry and evaluation of antibacterial potentiality of a novel oxime-based palladium(II) compound.

The title monomeric Pd(II) compound, [Pd(L)(Cl)], was synthesized in moderate yield out of the reaction of equimolar proportion of Na2[PdCl4] and 3-[(5-bromo-2-hydroxy-benzylidene)-hydrazono]-butan-2-one oxime (LH) in tetrahydrofuran milieu. LH is a 1:1 Schiff-base condensate of 2,3-butanedionemonoxime monohydrazone and 5-bromosalicylaldehyde. [Pd(L)(Cl)] has been characterized by C, H and N microanalyses, (1)H and (13)C NMR, FAB-MS, FT-IR, Raman spectra, UV-Vis spectra and molar electrical conductivity measurements. [Pd(L)(Cl)] is diamagnetic. Structural elucidation reveals that the palladium center in [Pd(L)(Cl)] is nested in N2OCl coordination environment. The geometry around Pd in [Pd(L)(Cl)] is distorted square-planar. The redox behavior of [Pd(L)(Cl)] in DMF shows a reduction couple, Pd(II)/Pd(I) atxa0-0.836xa0V versus Ag/AgCl. The inxa0vitro antimicrobial activity of [Pd(L)(Cl)] was screened against both Gram-positive and Gram-negative human pathogenic bacteria. This bioactivity was substantiated with SEM study. [Pd(L)(Cl)] exhibits satisfactory bactericidal as well as bacteriostatic activity.

The crucial role of C—H...O and C=O...π interactions in the building of three-dimensional structures of dicarboxylic acid–biimidazole compounds

The supramolecular architectures of three dicarboxylic acid-biimidazole compounds, namely, 2,2-biimidazolium malonate, C(6)H(8)N(4)(2+).C(3)H(2)O(4)(2-), (I), 2,2-bi(1H-imidazole) succinic acid, C(6)H(6)N(4).C(4)H(6)O(4), (II), and 2,2-biimidazolium 2,2-iminiodiacetate chloride, C(6)H(8)N(4)(2+).C(4)H(6)NO(4)(-).Cl(-), (III), are reported. The crystal structures are assembled by the same process, namely double conventional N-H...O or O-H...N hydrogen bonds link the dicarboxylates and biimidazoles to form tapes, which are stacked in parallel through lone-pair-aromatic interactions between carbonyl O atoms and biimidazole groups and are further linked via weak C-H...O interactions. The C=O...pi interactions involved in stacking the tapes in (II) and the C-H...O interactions involved in linking the tapes in (II) and (III) demonstrate the crucial role of these interactions in the crystal packing. There is crystallographically imposed symmetry in all three structures. In (I), two independent malonate anions have their central C atoms on twofold axes and two biimidazolium dications each lie about independent inversion centres; in (II), the components lie about inversion centres, while in (III), the unique cation lies about an inversion centre and the iminiodiacetate and chloride anions lie across and on a mirror plane, respectively.

Synthesis, structure, DFT calculations, electrochemistry, fluorescence, DNA binding and molecular docking aspects of a novel oxime based ligand and its palladium(II) complex

A novel oxime based ligand, phenyl-(pyridine-2-yl-hydrazono)-acetaldehyde oxime (LH), and its palladium(II) complex (1) have been synthesised and spectroscopically characterised. The ligand crystallizes in the monoclinic space group (P21/c). The X-ray crystal structure of the ligand shows that it forms a hydrogen bonded helical network. The ligand has been characterised by C, H and N microanalyses, (1)H and (13)C NMR, ESI-MS, FT-IR and UV-Vis spectral measurements. Geometry optimizations at the level of DFT show that the Pd(II) centre is nested in a square-planar N3Cl coordination chromophore. The diamagnetic palladium complex has been characterised by C, H and N microanalyses, FAB-MS, FT-IR, UV-Vis spectra and molar electrical conductivity measurements. The observed electronic spectrum of 1 correlates with our theoretical findings as evaluated through TD-DFT. 1 displays quasi-reversible Pd(II)/Pd(III) and Pd(III)/Pd(IV) redox couples in its CV in acetonitrile. 1 is nine-fold more emissive with respect to the binding ligand. Biophysical studies have been carried out to show the DNA binding aspects of both the ligand and complex. The binding constants for the ligand and complex were found to be 3.93×10(4) and 1.38×10(3)M(-1) respectively. To have an insight into the mode of binding of LH and 1 with CT DNA a hydrodynamic study was also undertaken. The mode of binding has also been substantiated through molecular docking. A promising groove binding efficacy has been revealed for the ligand.

Self-assembly of lanthanide(III) coordination polymers from a bifunctional 2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylate ligand with the assistance of oxalate: syntheses, structures, luminescence, and magnetic properties

Based on a bifunctional 2-(pyridine-2-yl)-1H-4,5-imidazole-dicarboxylic acid ligand, a novel family of lanthanide coordination polymers with formulas [Ln(HPIDC)(C2O4)0.5(H2O)]n (Ln = La, 1; Ce, 2) and [Ln2(HPIDC)(C2O4)2(H2O)3]n·2nH2O (Ln = Pr, 3; Nd, 4; Sm, 5; Eu, 6; Gd, 7; Tb, 8; Dy, 9; Ho, 10; Er, 11), (H3PIDC = 2-(pyridine-2-yl)-1H-imidazole-4,5-dicarboxylic acid & H2C2O4 = oxalic acid) has been prepared under hydro-solvothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR spectroscopy, and thermogravimetric analysis. Notably, the ligands adopt the same μ3-kN,O:kO′,O′′:kO′′′ conformation in all compounds, which brings about two types of isostructural lanthanide coordination polymers. Namely, 1 and 2 crystallize in the monoclinic space group P21/n and are composed of [Ln2(COO)2] dinuclear subunits with networks having the symbol (63·82·10)2(63)2(8). Meanwhile, 3–11 crystallize in the monoclinic space group P21/c and are constructed with tetranuclear [Ln4(COO)4] subunits with networks having the symbol (103)2(104·122)(10)2. The photoluminescence measurement indicates that Eu(III) and Tb(III) coordination polymers show very strong reddish-orange and green emission bands with CIE chromaticity coordinates (0.612, 0.325) and (0.284, 0.523) and quantum yields of 54.3% & 34.7%, respectively. The magnetic properties of 3 and 7–11 are investigated, and the results indicate a ferromagnetic interaction between Gd(III) magnetic centers in complex 7 and antiferromagnetic interactions in other complexes.

A triazole Schiff base-based selective and sensitive fluorescent probe for Zn2 +: A combined experimental and theoretical study

A triazole-Schiff base, 4-(5-Chloro-2-hydroxybenzylideneamino)-1H-1,2,4-triazole-5(4H)-thione (HL), exhibits the high selectivity and sensitivity for Zn(2+) in the fluorescence spectrometry over other common metal ions, especially Cd(2+) in DMSO:H2O (1:9, v/v) solution. A 1:1 binding ratio of Zn(2+)/L for the complex has been obtained by Uv-Vis titration experiments and Jobs plot with the detection limit of 51 nmol/L. The coordination mode of the complex in solution was further confirmed by density functional theory (DFT) calculations. Time-dependent density functional theory (TD-DFT) calculations indicate that a chelation-enhanced fluorescence (CHEF) effect occurs in the process of detecting Zn ion.

The first example of rhombic dodecahedral CuBr clusters in a novel mixed-valence Cu( i , ii )– benzimidazole complex

Hydrothermal reaction of CuBr2 and 1,2-di(1H-benzoimidazol-2-yl)ethane-1,2-diol leads to the formation of a new mixed-valence copper(I,II) complex [(C7H5N2)(CuICuIIBr2)], which exhibits a two-dimensional layer structure, containing the first example of a rhombic dodecahedral CuBr [4,3] polyhedral column. The synthesis, crystal structure, electronic property, thermal stability and electrochemical characterization of this complex are investigated.

Spectroscopic and molecular docking studies on the interaction of human serum albumin with copper(II) complexes

Two osazone based ligands, butane-2,3-dione bis(2-pyridylhydrazone) (BDBPH) and hexane-3,4-dione bis(2-pyridylhydrazone) (HDBPH), were synthesized out of the 2:1M Schiff base condensation of 2-hydrazino pyridine respectively with 2,3-butanedione and 3,4-hexanedione. The X-ray crystal structures of both the ligands have been determined. The copper(II) complex of HDBPH has also been synthesized and structurally characterized. HDBPH and its copper(II) complex have thoroughly been characterized through various spectroscopic and analytical techniques. The X-ray crystal structure of the copper complex of HDBPH shows that it is a monomeric Cu(II) complex having N4O2 co-ordination chromophore. Interaction of human serum albumin (HSA) with these ligands and their monomeric copper(II) complexes have been studied by various spectroscopic means. The experimental findings show that the ligands as well as their copper complexes are good HSA binders. Molecular docking investigations have also been done to unravel the mode of binding of the species with HSA.

Ethyl [(2-hydroxy­phen­yl)(pyridinium-2-ylamino)meth­yl]phospho­nate methanol solvate

In the title compound, C14H17N2O4P·CH3OH, the planes of the pyridinium-2-ylamino and 2-hydroxyphenyl groups form a dihedral angle of 75.6u2005(1)°, with the pyridinium NH group and the 2-hydroxyphenyl OH group pointing in opposite directions. Three intramolecular hydrogen bonds are observed. Two phosphonate and two methanol molecules are connected by O—H⋯O hydrogen bonds as a centrosymmetric dimeric cluster, and interact further with other dimeric clusters via N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds and C—H⋯π interactions, resulting in a sheet structure.

Binuclear Mn2+ complexes of a biphenyltetracarboxylic acid with variable N-donor ligands: syntheses, structures, and magnetic properties

Four new manganese(II) metal–organic frameworks based on H4bpta (H4bpta = 3,3′,5,5′-biphenyltetracarboxylic acid) and N-donor ligands, namely [Mn2(4,4′-bipy)(bpta)]n (1), [Mn2(1,4-bib)2(bpta)]n·2n(H2O·DMF) (2), [Mn2(1,3-bimb)2(bpta)]n·2nH2O (3), and [Mn2(1,4-bimb)2(bpta)]n·2nH2O (4) (4,4′-bipy = 4,4′-bipyridine, 1,4-bib = 1,4-bis(imidazol-1-yl)benzene, 1,3-bimb = 1,3-bis((1H-imidazol-1-yl)methyl)benzene, and 1,4-bimb = 1,4-bis((1H-imidazol-1-yl)methyl)benzene), have been obtained under solvothermal conditions. In these complexes, the fully deprotonated bpta4− ligands link binuclear SBUs to construct 2D layers with (4,4)-connected topologies. Complex 1 is a 3D network with 1D zigzag chains built up from 4-connected bpta4− ligands that contain carboxylate groups bridging Mn2+ ions in a rather rare syn–syn geometry. Complex 2 exhibits a 3D porous network with syn–anti bridging dimeric subunits. Complex 3 is a (3,4)-connected 2D novel network with double helix chains formed by cis-1,3-bimb linkers. The structure of complex 4 is similar to that of 2, but it consists of tiny pores due to trans-1,4-bimb linkers. Magnetic studies reveal that 1 is perfectly fitted by the modified Fisher model to yield an effective intrachain antiferromagnetic coupling (J = −2.21(1) cm−1). Complexes 2–4 show antiferromagnetic interactions (J = −1.57(2) cm−1 for 2, and J = −0.68(2) cm−1 for 3) in dimeric units of Mn2(μ-COO)22+ related to double syn–anti and syn–syn carboxylate bridges. An important repetitive feature of all these complexes with syn–anti or syn–syn carboxylate bridges is that the antiferromagnetic coupling is very small. In addition, the gas sorption exploration of 2 exhibits relatively high sorption of CO2 but very low sorption of N2, making it a promising material for CO2/N2 separation.

Bis(2-aminopyridinium) diaquabis(malonato-κ2O,O′)cuprate(II)

The CuII ion in the title compound, (C5H7N2)2[Cu(C3H2O4)2(H2O)2], is located on an inversion centre and coordinated by four O atoms from two bidentate malonate (mal) ligands in the equatorial plane and two O atoms from two coordinated water molxadecules in the axial positions, forming an elongated octaxadhedral geometry. Each [Cu(mal)2(H2O)2]2− anion bridges two 2-aminoxadpyridinium cations via N—H⋯O hydrogen bonds and symmetry-related anions via O—H⋯O hydrogen bonds, to form an infinite one-dimensional chain. Additional O—H⋯O and C—H⋯O hydrogen bonds generate two-dimensional sheets that are joined into a three-dimensional network via N—H⋯O, C—H⋯O and interxadlayer π–π interxadactions between aminoxadpyridinium cations (symmetry code: 1-x,1-y,2-z).