Brian Piggott

EXAFS of the type-1 copper site of rusticyanin

Extended X‐ray absorption fine structure (EXAFS) spectra at the Cu K‐edge have been recorded of the oxidized and reduced form at pH 3.5 of rusticyanin, the type‐1 or ‘blue’‐copper protein from Thiobacillus ferrooxidans. The EXAFS of oxidized rusticyanin is well simulated with models assuming a ligand set of 2 N(His) and 1 S(Cys) at 1.99 and 2.16 Å, respectively. Upon reduction, the average Cu‐N ligand distance increases by approx. 0.08Å. For both redox states studied, the fit by the simulation is significantly improved by including a contribution of an additional sulfur ligand at approx. 2.8 Å. From comparison with structural data of other blue‐copper proteins, it is concluded that the copper coordination environment is relatively rigid, which may be a clue to its high redox potential.

Dioxomolybdenum(VI) complexes with 2α-hydroxybenzimidazoles and their 95Mo NMR spectra

Abstract Complexes of a series of 2α-hydroxybenzimidazoles (L) with Mo(VI) are reported. In most cases the complexes form readily on reaction of MoO2(AcAc)2 with L in acetone or ethanol. Electronic spectra, infra red spectra, magnetic measurements, 1H and 95Mo NMR results are reported for the complexes which have MoO2L2 or MoO2L2(Solvent)1, stoichiometry. The physical measurements are best interpreted in terms of distorted octahedral cis-dioxoMo(VI) complexes with a 4O, 2N donor set. This is confirmed for the complex with 2α-hydroxybenzylbenzimidazole (HBB) by an X-ray crystallographic study which also shows that HBB coordinates through its imino nitrogen and alkoxy oxygen atoms.

The reaction of cis dioxobis(2,4 pentanedionato)molybdenum (VI) and 2,2′ pyridylbenzoxazole (L), a novel route to β[Mo8O26]4−

MoO 2 (C 5 H 7 O 2 ) 2 , where C 5 H 7 O 2 is 2,4-pentanedione (acac), reacts with 2-2′ pyridylbenzoxazole in acetone to give a product with stoichiometry, Mo 3 C 24 H 16 N 6 O 12 . This product dissolves readily in dimethylformamide to give a brown solution which on standing for several weeks yielded crystals. An X-ray structure determination showed these crystals to contain uncoordinated 2-2′pyridylbenzoxazole and [(CH 3 ) 2 NH 2 ] 4 + [Mo 8 O 26 ] 4− .

Metal complexes of virus inhibitors. Part II. [1]. Coordination properties of 2-α-methoxybenzylbenzimidazole (= L) and x-ray crystal structure of CoL2I2·acetone·2H2O

Abstract Complexes are described of cobalt(II) and nickel(II) salts with the title ligand (=L). The X-ray crystal structure of [CoL2I2]·acetone·2H2O shows the ligand to be chelating to give distorted cis-octahedral geometry. In other complexes the ligand is monodentate through the imidazole nitrogen and an infrared spectral criterion to distinguish these modes of coordination is described. Some of the complexes bind strongly to carbonyl groups, especially of amides. It is suggested that similar binding to proteins may be important in the mode of anti-viral activity.

95Mo NMR studies of complexes containing the Mo2O52+ core and crystal structure of Mo2O5[SC6H4NHCH2C5H4N]2(C3H7NO)3

Abstract The crystal structure of Mo2O5[SC6H4NHCH2C5H4N]2(C3N7NO)3 is reported and seen to consist of a single oxo-bridged species with each Mo atom bonded to cis dioxo groups and the nitrogen atoms and thiolate group of the tridentate ligand. 95Mo NMR spectra of this and three related complexes are presented and attempts made to interpret them in terms of their crystal structures.

95Mo NMR spectra of MoO2(C8H7N2S)2 and X-ray crystal structure of Mo2O4(C8H7N2S)2(C3H7NO)2

Abstract The facile preparation of MoO2(C8H7N2S)2 is given and its complex behaviour in dimethylformamide, as revealed by 95Mo NMR spectroscopy, discussed. The X-ray crystal structure of one of the products obtained from this dimethylformamide solution is briefly described. This structure indicates that the Mo(VI) has been reduced to Mo(V) and is based on the [Mo2O4]2+ core.

Metal complexes of the virus-inhibitor 3,4-dihydro-1-phenyl-1H-[1,4]-oxazino [4,3-a] benzimidazole

Abstract Complexes of the title ligand with cobalt(II) and nickel(II) salts have been prepared and characterised. The complexes are readily formed in solvents such as ethanol and acetone, with coordination taking place through the imidazole nitrogen (N 10). Electronic and infrared spectra and magnetic properties are reported for the complexes, which are mostly tetrahedral with ML 2 X 2 stoichiometry.

Synthesis, 95Mo NMR spectra and x-ray crystal structure of MoO2(C14H11N2O)2(C2H5H)1 and Mo2O5(C14H11N2O)2(C2H5OH)1(H2O)1

Abstract The crystal structures and 95Mo NMR spectra of two complexes formed between 2-α-hydroxybenzyl- benzimidazole (C6H5·CHOH·C7H5N2=HOBB), as its sodium salt, and MoO2Cl2 are reported. [MoO2- (OBB)2]·EtOH (OBB=deprotonated HOBB) crystallizes in space group P21/n, with a=12.8441(7), b=15.917(3), c=13.314(2) A, β=97.163(8)° and Z =4. The structure was determined from 3096 observed reflections and refined to a final R value of 0.030. The complex is a six coordinate cis-dioxo species, the 95Mo spectrum of which shows a single sharp peak at 56 ppm in dimethylformamide (DMF). The second complex, [Mo2O5(OBB)2]·EtOH·H2O, crystallizes in space group Pbca, with a=22.482(4), b=16.442(3), c=18.407(3) A and Z=8. The structure was determined from 2936 observed reflections and refined to a final R value of 0.061. The complex is a binuclear doubly bridged species in which one metal atom is six coordinate while the other is five coordinate. Its 95Mo NMR spectrum in DMF shows a sharp peak at 124 ppm and a second broader much weaker peak at 51 ppm.

A bridged Mo(VI) complex containing six and five coordinate Mo: Synthesis, 95Mo N.m.r. spectroscopy and X-ray crystal structure of Mo2O5(C17H17N2O)2

Preparation, spectre RMN de 95 Mo et structure du cristal par rayons X de Mo 2 O 5 (nPOBB) 2 , ou nPOBB est la forme deprotonee du 1-n hydroxy-2α benzylbenzimidazole

Synthesis and x-ray crystal structure of Mo2(CO)6(C34H32N10)(C3H7NO)8

Abstract The synthesis of Mo2(CO)6L DMF8 and Mo2O6- L(H2O)6 where L is N,N,N′,N′-tetrakis(2-benzimidazolyl) 1,2-ethanediamine (C34H32N10) and DMF is dimethylformamide (C7H7NO) are described together with their spectroscopic properties. The X-ray structure of Mo2(CO)6L DMF8 is reported and seen to consist of two fac Mo(CO)3 units bridged by the 1 and 2 amino nitrogen atoms of L. Six coordination about each molybdenum is completed by the imino nitrogen atoms of the benzimidazole rings of L.