• Ray J Butcher

      Articles written in Journal of Chemical Sciences

    • Model compounds for the type III site and the combined type II and type III sites in multicopper oxidases

      Ray J Butcher Ekk Sinn Garry M Mockler

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      A series of model complexes for the diamagnetic type III site in multicopper oxidases has been developed based on tridentate ligands formed from the Schiff base condensation of bifunctional primary amines with the monoximes ofβ-diketones. The complexes resulting when copper salts, CuX2, react with the resulting ligands, HL, have the general formula Cu2L2X2 and have a central core made up of the two copper atoms bridged by two oxime groups resulting in a six-membered Cu(ON)2Cu moiety. This grouping is strictly planar and has significant shortening of the N-O bond length along with lengthening of the C=N bond indicating a delocalization of theπ-electrons in the ring. The result is a copper(II) dimer which is diamagnetic at all measurable temperatures (< 400 K). Spectroscopic, magnetic and electrochemical properties of the series of compounds will be compared with those of the parent enzyme containing the type III dicopper site. A second series of model complexes for both the type III site and the newly reported structure of the joint type II and type III site in ascorbate oxidase (crystal structure reported at the 3rd International Conference on Bioinorganic Chemistry, Boston, Mass, July 24–28, 1989) is also discussed. These compounds are obtained when ligands, H3L, resulting from the condensation of derivatives of salicylaldehyde with 1,3-diamino-2-propanol, are reacted with copper carboxylates resulting in compounds of formula Cu2L (carb). The carboxylate bridging group can be displaced by other better donors, L’, such as pyrazole, or indoles to give compounds (Cu2LL’)+ which have bridging L’ groups. The properties of this series of compounds will be compared with those of the type III site. If the L’ ligand is suitably derivatized, i.e. 6-aminoindole, then by a Schiff base condensation with copper salicylaldehyde, compounds of formula (Cu2LL’)2Cu(sal)2 can be obtained, which are models for multicopper oxidases having both the type II and type III sites in the same molecule, as has been found in the recent crystal structure of ascorbate oxidase. Comparisons between these models and multicopper oxidases will be drawn.

    • Synthesis, characterization and spectrochemical studies on a few binuclear 𝜇-oxo molybdenum(V) complexes of pyrimidine derived Schiff base ligands

      Samik Gupta Somnath Roy Tarak Nath Mandal Kinsuk Das Sangita Ray Ray J Butcher Susanta Kumar Kar

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      Ten new binuclear singly oxo-bridged molybdenum complexes (complexes 1-10) were prepared using five pyrimidine derived Schiff base ligands and two Mo(V) precursors (NH4)2MoOCl5 and (NH4)2MoOBr5. The ligands are prepared by the condensation of 4,6-dimethyl 2-hydrazino pyrimidine with salicylaldehyde (for HL1), 𝑜-hydroxy acetophenone (for HL2) and substituted salicylaldehydes (for HL3, HL4 and HL5) respectively. These ligands are already reported as good donors for Mo(VI) state. The 𝜇-oxo Mo(V) complexes reported here bears a distorted octahedral geometry around each Mo atom with either N2O2Cl or N2O2Br chromophores. Fine variations in the spectroscopic behaviour of the complexes are observed in accordance with the varying electron donating properties of the ligands. All the complexes are unstable in solution and X-ray quality crystal of complex 1 could be isolated. All the complexes are characterized by IR and UV-Vis spectra.

    • Synthesis, characterization and phosphotriesterase mimetic activity of some Zn(II) and Cu(II) complexes

      Mamata Singh Ray J Butcher Jerry P Jasinski James A Golen Govindasamy Mugesh

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      We report here the synthesis and characterization of a few phenolate-based ligands bearing tertamino substituent and their Zn(II) and Cu(II) metal complexes. Three mono/binuclear Zn(II) and Cu(II) complexes [Zn(L1)(H2O)].CH3OH.H2O (1) (H2 L1 = 6,6′-(((2-dimethylamino)ethylazanediyl)bis(methylene))bis(2, 4-dimethylphenol), [Zn2(L2)2] (2) (H2L2 = 2,2′-(((2-dimethylamino)ethyl)azanediyl)bis(methylene)bis(4-methylphenol) and [Cu2(L3)2.CH2 Cl2] (3) (H2L3 = (6,6′-(((2-(diethylamino)ethyl)azanediyl)bis(methylene)) bis(methylene))bis(2,4-dimethylphenol) were synthesized by using three symmetrical tetradendate ligands containing N2O2 donor sites. These complexes are characterized by a variety of techniques including; elemental analysis, mass spectrometry, 1H, 13C NMR spectroscopic and single crystal X-ray analysis. The new complexes have been tested for the phosphotriesterase (PTE) activity with the help of 31P NMR spectroscopy. The 31P NMR studies show that mononuclear complex [Zn(L1)(H2O)].CH3OH.H2O (1) can hydrolyse the phosphotriester i.e., p-nitrophenyl diphenylphosphate (PNPDPP), more efficiently than the binuclear complexes [Zn2(L2)2] (2) and [Cu2(L3)2.CH2Cl2] (3). The mononuclear Zn(II) complex (1) having one coordinated water molecule exhibits significant PTE activity which may be due to the generation of a Zn(II)-bound hydroxide ion during the hydrolysis reactions in CHES buffer at pH 9.0.

    • Isolation and structures of some selenium and tellurium derivatives of 1, 4, 5, 8, 9, 12-hexabromododecahydrotriphenylene as co-crystals of triphenylene

      Poonam Rajesh Prasad Harkesh B Singh Ray J Butcher

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      The synthesis and characterization of low-valent organoselenium and tellurium derivatives of hexabromododecahydrotriphenylene has been attempted. The reaction of hexabromododecahydrotriphenylene with in situ generated disodium dichalcogenides (Na2E2; E = Se, Te) afforded insoluble chalcododecahydrotriphenylene derivatives, 20, 21 respectively. Attempted aromatization of 20 and 21 using DDQ (2, 3-dichloro-5, 6-dicyano-1,4-benzoquinone) as an oxidizing agent afforded the co-crystals. The hexaselenophenyl derivative, 22 and the hexaselenocyanate derivative 23 were synthesized by the reaction of in situ generated sodium arylselenolate/potassium selenocyanate with hexabromododecahydrotriphenylene, respectively. The compounds were characterized by common spectroscopic tools and a few by single crystal x-ray crystallographic studies.

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