Evaluation of the Cytotoxic Behavior of Fungal Extracellular Synthesized Ag Nanoparticles Using Confocal Laser Scanning Microscope.

Silver nanoparticles have been synthesized by subjecting a reaction medium to a Fusarium oxysporum biomass at 28 °C for 96 h. The biosynthesized Ag nanoparticles were characterized on the basis of their anticipated peak at 405 nm using UV-Vis-NIR spectroscopy. Structural confirmation was evident from the characteristic X-ray diffraction (XRD) pattern, high-resolution transmission electron Microscopy (HRTEM) and the particle size analyzer. The Ag nanoparticles were of dimension 40 ± 5 nm and spherical in shape. The study mainly focused on using the confocal laser scanning microscope (CLSM) to examine the cytotoxic activities of fungal synthesized Ag nanoparticles on a human breast carcinoma cell line MCF7 cell, which featured remarkable vacuolation, thus indicating a potent cytotoxic activity.

Biological Screening of Newly Synthesized BIAN N-Heterocyclic Gold Carbene Complexes in Zebrafish Embryos.

N-Heterocyclic carbene (NHC) metal complexes possess diverse biological activities but have yet to be extensively explored as potential chemotherapeutic agents. We have previously reported the synthesis of a new class of NHC metal complexes N-heterocyclic with acetate [IPr(BIAN)AuOAc] and chloride [IPr(BIAN)AuCl] ligands. In the experiments reported herein, the zebrafish embryos were exposed to serial dilutions of each of these complexes for 10-12 h. One hundred percent mortality was observed at concentrations≥50 µM. At sub-lethal concentrations (10-30 µM), both compounds influenced zebrafish embryonic development. However, quite diverse categories of abnormalities were found in exposed embryos with each compound. Severe brain deformation and notochord degeneration were evident in the case of [IPr(BIAN)AuOAc]. The zebrafish embryos treated with [IPr(BIAN)AuCl] exhibited stunted growth and consequently had smaller body sizes. A depletion of 30%-40% glutathione was detected in the treated embryos, which could account for one of the possible mechanism of neurotoxicity. The fact that these compounds are capable of both affecting the growth and also compromising antioxidant systems by elevating intracellular ROS production implies that they could play an important role as a new breed of therapeutic molecules.

Sterically directed functionalization of the redox-active bis(imino)acenaphthene ligand class: an experimental and theoretical investigation.

The synthesis, characterization, and theoretical study of the sterically directed functionalization of the redox-active bis(imino)acenaphthene (BIAN) ligand class has been explored. With dependence on the steric congestion encompassing the N-C-C-N fragment of the Ar-BIAN ligand, functionalization can be directed to proceed either via a radical backbone dearomatization or a nucleophilic imine C-alkylation pathway. The structures of the Ar-BIAN derivatives 14-19 were determined by means of single-crystal X-ray diffraction. The reaction pathways involved in Ar-BIAN functionalization were monitored by means of EPR spectroscopy. The experimental results and observations were examined in conjunction with DFT-D calculations in order to explain the driving forces that direct the pathways leading to Ar-BIAN functionalization.

Unique radical dearomatization and two-electron reduction of a redox-active ligand.

The syntheses and characterizations of [Li(4)][(1,2-di-(tert-butyl)-dpp-BIAN)(2)] (7), (1,2-di-(tert-butyl)-dpp-BIAN) (8), and (1-(tert-butyl)-2-OH-dpp-BIAN) (9) are described. Compound 7 was formed via a radical dearomatization, two-electron reduction pathway that was accompanied by vicinal di-tert-butylation of the BIAN ligand backbone. Oxidation of 7 afforded a dearomatized vicinal di-tert-butyl substituted BIAN ligand (8). An analogous dearomatized vicinal tert-butyl-hydroxy substituted BIAN ligand (9) was also isolated in the course of mechanistic studies related to the formation of 7.

Tetrakis(imino)pyracene complexes exhibiting multielectron redox processes.

The differences in redox behavior of the monofunctional bis(imino)acenaphthene (BIAN) and bifunctional tetrakis(imino)pyracene (TIP) ligands have been explored by treatment of the latter with PI(3), TeI(4), or BI(3). These reactions result in the formation of products involving the transfer of three or four electrons. Accompanying DFT calculations reveal that in each case the extent of electron transfer from each p-block element into the TIP ligand is dependent upon the element-TIP bonding interactions.

Synthesis and characterization of a p-type boron arsenide photoelectrode.

A p-type boron arsenide photoelectrode was prepared from a material consisting of a thin layer of boron arsenide on a boron substrate. The structure of the material was identified using X-ray diffraction and scanning electron microscopy, and the surface composition was determined by means of X-ray photoelectron spectroscopy. The electrode was found to be photoactive under both visible light and UV-vis irradiation and displayed a photocurrent of ~0.1 mA/cm(2) under UV-vis irradiation at an applied potential of -0.25 V vs Ag/AgCl. Mott-Schottky plots for this boron arsenide electrode displayed an estimated flat-band potential near the onset photopotential. The estimated indirect band gap, as determined from incident photon-to-electron conversion efficiency plots, is 1.46 ± 0.02 eV.

A recyclable, self-supported organocatalyst based on a poly(N-heterocyclic carbene).

We report the synthesis and catalytic activity of a polymeric imidazolium salt. In contrast to the well-known resin-supported N-heterocyclic carbenes (NHCs), the material described herein affords a polymer with NHCs orthogonally positioned along a main chain upon generation in situ. The unique structural characteristics of the corresponding poly(NHC)s enabled the materials to display catalytic activities that were similar or superior to those displayed by monomeric analogues. Moreover, the new catalyst was successfully recovered and reused with minimal loss of performance over several cycles.

Lanthanide-based coordination polymers assembled from derivatives of 3,5-dihydroxy benzoates: syntheses, crystal structures, and photophysical properties.

Two new aromatic carboxylic acids, namely, 3,5-bis(benzyloxy)benzoic acid (HL1) and 3,5-bis(pyridine-2-ylmethoxy)benzoic acid (HL2), have been prepared by replacing the hydroxyl hydrogens of 3,5-dihydroxy benzoic acid with benzyl and pyridyl moieties, respectively. The anions derived from HL1 and HL2 have been used for the support of a series of lanthanide coordination compounds [Eu(3+) = 1-2; Tb(3+) = 3-4; Gd(3+) = 5-6]. The new lanthanide complexes have been characterized on the basis of a variety of spectroscopic techniques in conjunction with an assessment of their photophysical properties. Lanthanide complexes 2, 4, and 6, which were synthesized from 3,5-bis(pyridine-2-ylmethoxy)benzoic acid, were structurally authenticated by single-crystal X-ray diffraction. All three complexes were found to exist as infinite one-dimensional (1-D) coordination polymers with the general formula {[Ln(L2)(3)(H(2)O)(2)]·xH(2)O}(n). Scrutiny of the packing diagrams for 2, 4, and 6 revealed the existence of interesting two-dimensional molecular arrays held together by intermolecular hydrogen-bonding interactions. Furthermore, the coordinated benzoate ligands serve as efficient light harvesting chromophores. In the cases of 1-4, the lowest energy maxima fall in the range 280-340 nm [molar absorption coefficient (ε) = (0.39-1.01) × 10(4) M(-1) cm(-1)]. Moreover, the Tb(3+) complexes 3 and 4 exhibit bright green luminescence efficiencies in the solid state (Φ(overall) = 60% for 3; 27% for 4) and possess longer excited state lifetimes than the other complexes (τ = 1.16 ms for 3; 1.38 ms for 4). In contrast to the foregoing, the Eu(3+) complexes 1 and 2 feature poor luminescence efficiencies.

Syntheses, structures and antimicrobial activities of bis(imino)acenaphthene (BIAN) imidazolium salts.

The syntheses of four new bis(imino)acenaphthene (BIAN) imidazolium chlorides are reported, three of which have been structurally characterized. The synthesis of a new, structurally authenticated BIAN ligand is also described. We report the results of the use of these BIAN imidazolium salts as antimicrobials against the pathogens S. aureus, B. subtilis, E. coli and P. aeruginosa. The antimicrobial efficacies were particularly high for the N-(2,6-diisopropylphenyl)- and N-(mesityl)-substituted BIAN imidazolium salts (MIC values < 0.6 µg/mL).

Antimicrobial properties of some bis(iminoacenaphthene (BIAN)-supported N-heterocyclic carbene complexes of silver and gold.

The AgCl, AgOAc, AuCl, and AuOAc complexes of the new bis(imino)acenaphthene(BIAN)-supported N-heterocyclic carbene ligand and the precursor imidazolium salt have been investigated with respect to their antimicrobial activities against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Psudomonas aeruginosa. The most active antimicrobial is the precursor imidazolium salt, which has a minimum inhibitory concentration (MIC) value of <40 µg/mL. The MIC values for the silver complexes IPr(BIAN)AgCl and IPr(BIAN)AgOAc against Gram-positive S. aureus are comparable to that for AgNO3, while those against Gram-negative E. coli and P.aeroginosa are significantly larger. Similar behavior was evident for the gold acetate complex IPr(BIAN)AuOAc. However, in the case of the gold chloride analogue, the MIC values are virtually identical for both the Gram-positive and the Gram-negative bacteria.

Design, synthesis, and study of main chain poly(n-heterocyclic carbene) complexes: applications in electrochromic devices.

A series of poly(N-heterocyclic carbene) complexes in which the carbene functionalities are orthogonally connected to the main chains of the respective polymers have been synthesized via oxidative electropolymerization of various bis(bithiophene)-substituted monomers with appended transition metal or main group entities (M = Ir, Au, Ag, or S). The polymers were characterized using a range of electrochemical, X-ray photoelectron spectroscopy, UV-vis spectroscopy, profilometry, and four-point probe conductivity measurements. Most of the polymers exhibited an intense absorbance wave at 700 nm under oxidative conditions which was attributable to the formation of polarons along the main chains. The iridium-containing thin film poly(8) was found to possess a significant NIR absorbance at 1100 nm in which the metal moiety effectively functioned as an electron sink. Electrochemical analyses of the polymer thin films revealed that they exhibited highly reversible electrochromic phenomena.

Synthesis, crystal structure, and photoluminescence of homodinuclear lanthanide 4-(dibenzylamino)benzoate complexes.

Three new binuclear lanthanide complexes of general formula [Ln(2)(L)(6)(H(2)O)(4)] (Ln = Tb (1), Eu (2), and Gd (3)) supported by the novel aromatic carboxylate ligand 4-(dibenzylamino)benzoic acid (HL) have been synthesized. Complexes 1 and 2 were structurally characterized by single-crystal X-ray diffraction. Both 1 and 2 crystallize in the triclinic space group P(1), and their molecular structures consist of homodinuclear species that are bridged by two oxygen atoms from two carboxylate ligands via different coordination modes. The discrete bridged dimer of 1 is centrosymmetric and features 8-coordinate terbium atoms, each of which adopts a distorted square-antiprismatic geometry. Both coordination spheres comprise two eta(2)-chelating benzoates, two mu-eta(1):eta(1)-carboxylate interactions from the bridging benzoates, and two water molecules. By contrast, in complex 2, the Eu(3+) ion coordination environment is best described as a distorted tricapped-trigonal prism, each europium ion being coordinated to three eta(2)-chelating benzoate ligands and two water molecules. One of the eta(2)-carboxylate ligands is involved in a further interaction with an adjacent metal, thus rendering the overall binding mode bridging tridentate, mu-eta(2):eta(1). Scrutiny of the packing diagrams for 1 and 2 revealed the existence of a one-dimensional molecular array that is held together by intermolecular hydrogen-bonding interactions. The Tb(3+) complex 1 exhibits high green luminescence efficiency in the solid state with a quantum yield of 82%. On the other hand, poor luminescence efficiency has been noted for the Eu(3+)-4-(dibenzylamino)benzoate complex.

Highly luminescent poly(methyl methacrylate)-incorporated europium complex supported by a carbazole-based fluorinated ß-diketonate ligand and a 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene oxide co-ligand.

A novel efficient antenna complex of Eu(3+) [Eu(CPFHP)(3)(DDXPO)] supported by a highly fluorinated carbazole-substituted ß-diketonate ligand, namely, 1-(9H-carbazol-2-yl)-4,4,5,5,5-pentafluoro-3-hydroxypent-2-en-1-one (CPFHP) and the 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene oxide (DDXPO) ancillary ligand, has been synthesized, structurally characterized, and its photoluminescent behavior examined. The single-crystal X-ray diffraction analysis of Eu(CPFHP)(3)(DDXPO) revealed that this complex is mononuclear, and that the central Eu(3+) ion is surrounded by eight oxygen atoms, six of which are provided by the three bidentate ß-diketonate ligands. The remaining two oxygen atoms are furnished by the chelating phosphine oxide ligand. The coordination polyhedron is best described as that of a distorted square antiprism. The photophysical properties of Eu(CPFHP)(3)(DDXPO) benefit from adequate protection of the metal by the ligands with respect to non-radiative deactivation as well as an efficient ligand-to-metal energy transfer process which exceeds 66% in chloroform solution with a quantum yield of 47%. As an integral part of this work, the synthesis, characterization, and luminescent properties of poly(methyl methacrylate) (PMMA) polymer films doped with Eu(CPFHP)(3)(DDXPO) are also reported. The luminescent efficiencies of the doped films (photoluminescence quantum yields 79-84%) are dramatically enhanced in comparison with that of the precursor complex. The new luminescent PMMA-doped Eu(CPFHP)(3)(DDXPO) complex therefore shows considerable promise for polymer light-emitting diode and active polymer optical fiber applications.

Electropolymerization of an N-heterocyclic carbene-gold(I) complex.

We report the first example of a polymer in which each monomer contains an N-heterocyclic carbene (NHC) orthogonally connected to its main chain. A polymerizable imidazolylidene-AuCl complex containing pendant bithiophene moieties was prepared in a high-yield multistep procedure. Oxidative electropolymerization of this monomer afforded the desired polymer, (Au[NHC]Cl)(n), which was characterized via electrochemical studies as well as X-ray photoelectron and UV-vis spectroscopy.

A beta-diketiminato hydroxyphosphenium cation: phosphinous acid-secondary phosphine oxide tautomerism revisited.

The first example of a beta-diketiminato-supported hydroxyphosphenium cation has been prepared, structurally characterized, and modeled by DFT calculations.

Synthesis and reactivity of tetrakis(imino)pyracene (TIP) ligands; bifunctional analogues of the BIAN ligand class.

The first two examples of a new class of bifunctional BIAN-type ligand have been prepared, and the reactions of one such ligand with CuBr(2) and BCl(3) have been explored.

1D molecular ladder of the ionic complex of terbium-4-sebacoylbis(1-phenyl-3-methyl-5-pyrazolonate) and sodium dibenzo-18-crown-6: synthesis, crystal structure, and photophysical properties.

On the basis of the novel heterocyclic beta-diketone, 4-sebacoylbis(1-phenyl-3-methyl-5-pyrazolone (H 2SbBP), three new lanthanide complexes Tb 2(SbBP) 3(H 2O) 2 ( 1), Gd 2(SbBP) 3(H 2O) 2 ( 2), and [Tb(SbBP) 2] [Na(DB18C6)H 2O] ( 3) have been synthesized and characterized by various spectroscopic techniques. The single-crystal X-ray diffraction analysis of 3 reveals that the complex crystallizes in the monoclinic space group C2/ c with a = 25.300(6) A, b = 19.204(7) A, c = 15.391(3) A, beta = 93.17(3) degrees , and V = 7466(4) A (3). The crystal structure of 3 is heterodinuclear and features a Tb (3+) center surrounded by two tetradentate bispyrazolone ligands in a somewhat distorted square-antiprismatic geometry. The Na (+) coordination environment is distorted hexagonal pyramidal and involves six oxygen atoms furnished by DB18C6 and one oxygen atom from a water molecule. The X-ray diffraction study of 3 also revealed an interesting 1D molecular ladder structure based on C-H/pi, intra- and intermolecular hydrogen-bonding interactions. The photophysical properties of 1 and 3 in solid state have been investigated, and the quantum yields and (5)D 4 lifetimes were found to be 4.82 +/- 0.01% and 18.13 +/- 0.82% and 1.11 +/- 0.01 and 2.82 +/- 0.02 ms, respectively.

Valence isomer of a beta-diketiminate-supported phosphinidene: a case of C-H activation and ring contraction.

A valence isomer of a beta-diketiminate-supported phosphinidene has been prepared by potassium metal reduction of the corresponding chlorophosphenium cation.

Synthesis and structures of 1,2-bis(imino)acenaphthene (BIAN) lanthanide complexes that involve the transfer of zero, one, or two electrons.

The syntheses and X-ray crystal structures of the first 1,2-bis(imino)acenaphthene (BIAN) complexes of the lanthanides are described.

Controlling the oxidation state of arsenic in cyclic arsenic cations.

Reduction of AsCl3 with SnCl2, followed by treatment of the "AsCl" with a 1,4-diimine results in electron transfer and formation of an arsenic(III) salt, while treatment of this arsenic(I) reagent or AsI3 with an alpha,alpha'-diiminopyridine ligand forms an arsenic(I) salt.