An enzymatic route to a benzocarbazole framework using bacterial CotA laccase

The CotA laccase-catalysed oxidation of the meta, para-disubstituted arylamine 2,4-diaminophenyldiamine delivers, under mild reaction conditions, a benzocarbazole derivative (1) (74% yield), a key structural motif of a diverse range of applications. This work extends the scope of aromatic frameworks obtained using these enzymes and represents a new efficient and clean method to construct in one step C-C and C-N bonds

A supramolecular zigzag chain of organometallic dipoles mediated by PF6 2- anions

Complex {Fe( 5-cyclopentadienyl)(PMe3)[P(OPh)3](4–NCC6H4NO2)} [PF6] has been characterized by spectroscopic and X-ray diffraction in order to evaluate the tuning of the electron density at the metal center and the extension ofthe delocalization on the molecule due to the presence of phosphite and phosphine co-ligands. The compound crystallizes in the centrosymmetric space group P21/c which destroys the possibility of exhibiting any quadratic NLO properties. The packing shows a supramolecular zigzag chain of antiparalell dimmers connected via the PF6 anions with C—H—F −distances ranging from 2.389 (7) to 2.667 (6)°A . Each zigzag chain is composed by isomeric organometallic fragments containing either R or S molecules. These chains are connected through weak intermolecular interactions (C—H· · ·C) forming a two dimensional plane along [101]

A supramolecular zigzag chain of organometallic dipoles mediated by PF6 2- anions

Complex {Fe( 5-cyclopentadienyl)(PMe3)[P(OPh)3](4–NCC6H4NO2)} [PF6] has been characterized by spectroscopic and X-ray diffraction in order to evaluate the tuning of the electron density at the metal center and the extension ofthe delocalization on the molecule due to the presence of phosphite and phosphine co-ligands. The compound crystallizes in the centrosymmetric space group P21/c which destroys the possibility of exhibiting any quadratic NLO properties. The packing shows a supramolecular zigzag chain of antiparalell dimmers connected via the PF6 anions with C—H—F −distances ranging from 2.389 (7) to 2.667 (6)°A . Each zigzag chain is composed by isomeric organometallic fragments containing either R or S molecules. These chains are connected through weak intermolecular interactions (C—H· · ·C) forming a two dimensional plane along [101]

Synthesis of new donor/acceptor 5-cyclopentadienyl and 5-indenyliron(II) complexes with p-benzonitrile derivatives. Crystal structures of [Fe( 5-C5H5)(CO)(P(OC6H5)3)(p-NCC6H4NO2)][BF4]·CH2Cl2 and [Fe( 5-C9H7)(CO)(P(OC6H5)3)(p-NCC6H4NO2)][BF4]

New complexes of the type [Fe( 5-Cp or Ind)(L)(L )(p-NCR)][BF4] (L, L =CO, P(OC6H5)3, P(C6H5)3; R=C6H4N(CH3)2, C6H4NO2, (E)-C(H) C(H)C6H4NO2, (E)-C(H) C(H)C6H4N(CH3)2) have been synthesised and characterised. Spectroscopic data were analysed in order to evaluate the tuning of the electronic density at the metal centre and the extension of the -delocalisation on the molecule, due to the presence of coligands with different acceptor/donor abilities. The structures of two complexes [Fe( 5-C5H5)(CO)(P(OC6H5)3)(p-NCC6H4NO2)][BF4] and [Fe( 5-C9H7)(CO)(P(OC6H5)3)(p-NCC6H4NO2)][BF4] were determined by X-ray crystallographic analysis. The compounds crystallised in the centrosymmetric space groups P1 and P21/n, respectively. Bond distances within the nitrile ligand are discussed in order to evaluate the nature of iron–nitrile bonding in these complexes

Evaluation of intermolecular interactions in thioxanthone derivatives: substituent effect on crystal diversity

A family of 9H-thioxanthen-9-one derivatives and two precursors, 2-[(4-bromophenyl) sulfanyl]-5-nitrobenzoic acid and 2-[(4-aminophenyl) sulfanyl]-5-nitrobenzoic acid, were synthesized and studied in order to assess the role of the different substituent groups in determining the supramolecular motifs. From our results we can conclude that Etter's rules are obeyed: whenever present the -COOH head to head strong hydrogen bonding dimer, R-2(2)(8) synthon, prevails as the dominant interaction. As for -NH2, the best donor when present also follows the expected hierarchy, an NH center dot center dot center dot O(COOH) was formed in the acid precursor (2) and an NH center dot center dot center dot O(C=O) in the thioxanthone (4). The main role played by weaker hydrogen bonds such as CH center dot center dot center dot O, and other intermolecular interactions, pi-pi and Br center dot center dot center dot O, as well as the geometric restraints of packing patterns shows the energetic interplay governing crystal packing. A common feature is the relation between the p-p stacking and the unit cell dimensions. A new synthon notation, R`, introduced in this paper, refers to the possibility of accounting for intra- and intermolecular interactions into recognizable and recurring aggregate patterns

Studies of the Antiproliferative Activity of Ruthenium (II) Cyclopentadienyl-Derived Complexes with Nitrogen Coordinated Ligands

Four cationic ruthenium(II) complexes with the formula [Ru(η5-C5H5)(PPh3)2]+, with L = 5-phenyl-1H-tetrazole (TzH) 1, imidazole (ImH) 2, benzo[1,2-b;4,3-b′] dithio-phen-2-carbonitrile (Bzt) 3, and [5-(2-thiophen-2-yl)-vinyl]-thiophene-2-carbonitrile] (Tvt) 4 were prepared and characterized in view to evaluate their potentialities as antitumor agents. Studies by Circular Dichroism indicated changes in the secondary structure of ct-DNA. Changes in the tertiary structure of pBR322 plasmid DNA were also observed in gel electrophoresis experiment and the images obtained by atomic force microscopy (AFM) suggest strong interaction with pBR322 plasmid DNA; the observed decreasing of the viscosity with time indicates that the complexes do not intercalate between DNA base pairs. Compounds 1, 2, and 3 showed much higher cytotoxicity than the cisplatin against human leukaemia cancer cells (HL-60 cells)

Biological activity and cellular uptake of [Ru(eta(5)-C5H5)(PPh3)(Me(2)bpy)][CF3SO3] complex

Anticancer activity of the new [Ru(eta(5)-C5H5)(PPh3)(Me(2)bpy)][CF3SO3] (Me(2)bpy = 4,4'-dimethyl-2,2'-bipyridine) complex was evaluated in vitro against several human cancer cell lines, namely A2780, A2780CisR, HT29, MCF7, MDAMB231 and PC3. Remarkably, the IC50 values, placed in the nanomolar and sub-micromolar range, largely exceeded the activity of cisplatin. Binding to human serum albumin, either HSA (human serum albumin) or HSA(faf) (fatty acid-free human serum albumin) does not affect the complex activity. Fluorescence studies revealed that the present ruthenium complex strongly quench the intrinsic fluorescence of albumin. Cell death by the [Ru(eta(5)-C5H5)(PPh3)(Me(2)bpy)][CF3SO3] complex was reduced in the presence of endocytosis modulators and at low temperature, suggesting an energy-dependent mechanism consistent with endocytosis. On the whole, the biological activity evaluated herein suggests that the complex could be a promising anticancer agent. (C) 2013 Elsevier Inc. All rights reserved

Towards the rational biosynthesis of substituted phenazines and phenoxazinones by laccases

Laccases are multi-copper oxidases that oxidise a wide range of substrates including phenol and aniline derivatives, which could be further involved in coupling reactions leading to the formation of dimeric and trimeric structures. This paper describes the enzyme-mediated dimerisation of several ortho and meta, para-disubstituted aromatic amines into phenazine ("head-to-tail" dimers) and phenoxazinone chromophores. The redox properties of substituted aromatic amines were studied by cyclic voltammetry and the kinetic constants of CotA and Trametes versicolor laccases were measured for selected aromatic amines. The structure of novel enzymatically synthesised phenazine and phenoxazinone dyes using CotA laccase was assessed by NMR and MS. Overall our data show that this enzymatic green process is an efficient alternative to the classic chemical oxidation of aromatic amines and phenols, with an impact on the broad field of applications of these heterocyclic compounds

DNA interaction and cytotoxicity studies of new ruthenium(II) cyclopentadienyl derivative complexescontaining heteroaromatic ligands

Four ruthenium(II) complexes with the formula [Ru(eta(5)-C(5)H(5))(PP)L][CF(3)SO(3)], being (PP = two triphenylphosphine molecules), L = 1-benzylimidazole, 1; (PP = two triphenylphosphine molecules), L = 2,2'bipyridine, 2; (PP = two triphenylphosphine molecules), L = 4-Methylpyridine, 3; (PP = 1,2-bis(diphenylphosphine) ethane), L = 4-Methylpyridine, 4, were prepared, in view to evaluate their potentialities as antitumor agents. The compounds were completely characterized by NMR spectroscopy and their crystal and molecular structures were determined by X-ray diffraction. Electrochemical studies were carried out giving for all the compounds quasi-reversible processes. The images obtained by atomic force microscopy (AFM) suggest interaction with pBR322 plasmid DNA. Measurements of the viscosity of solutions of free DNA and DNA incubated with different concentrations of the compounds confirmed this interaction. The cytotoxicity of compounds 1234 was much higher than that of cisplatin against human leukemia cancer cells (HL-60 cells). IC(50) values for all the compounds are in the range of submicromolar amounts. Apoptotic death percentage was also studied resulting similar than that of cisplatin. (C) 2010 Elsevier Inc. All rights reserved