Sky-blue Tp*WOCl₂ has been synthesized from the high-yielding reaction of Tp*WO₂Cl with boron trichloride in refluxing toluene. Dark-red Tp*WOI₂ was prepared via thermal decarbonylation followed by aerial oxidation of Tp*WI(CO)₃ in acetonitrile. From these precursors, an extensive series of mononuclear tungstenyl complexes, Tp*WOXY [X = Cl-, Y = OPh-, SPh-; X = Y = OPh-, 2-(n-propyl)phenolate (PP-), SPh-, SePh-; XY = toluene-3,4-dithiolate (tdt²−), quinoxaline-2,3-dithiolate (qdt²-), benzene-1,2-diselenolate (bds²-); Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate], was prepared by metathesis with the respective alkali-metal salt of X-/XY²- or (NHEt₃)₂(qdt). The complexes were characterized by microanalysis, mass spectrometry, electrochemistry, IR, electron paramagnetic resonance (EPR), and electronic absorption spectroscopies, and X-ray crystallography (for X = Y = OPh-, PP-, SPh-; XY = bds²-). The six-coordinate, distorted-octahedral tungsten centers are coordinated by terminal oxo [W≡O = 1.689(6)-1.704(3) Å], tridentate Tp*, and monodentate or bidentate O/S/Se-donor ligands. Spin Hamiltonian parameters derived from the simulation of fluid-solution X-band EPR spectra revealed that the soft-donor S/Se ligand complexes had larger g values and smaller 183W hyperfine coupling constants than the less covalent hard-donor O/Cl species. The former showed low-energy ligand-to-metal charge-transfer bands in the near-IR region of their electronic absorption spectra. These oxotungsten(V) complexes display lower reduction potentials than their molybdenum counterparts, underscoring the preference of tungsten for higher oxidation states. Furthermore, the protonation of the pyrazine nitrogen atoms of the qdt²- ligand has been examined by spectroelectrochemistry; the product of the one-electron reduction of [Tp*WO(qdtH)]+ revealed usually intense low-energy bands.

The reactions of TpiPrMoVIO2Cl with salicylanilides and NEt3 produce cis-TpiPrMoVIO2(2-OC6H4CONHR) (TpiPr = hydrotris(3-isopropylpyrazol-1-yl)borate, R = Ph, 4-C6H4Cl, 4-C6H4OMe). The N-methyl complex, TpiPrMoO2{2-OC6H4CON(Me)Ph}, is similarly prepared. Reduction of the amido complexes by cobaltocene produces green, EPR-active compounds, [CoCp2][TpiPrMoVO2(2-OC6H4CONHR)], that exhibit strong, low energy, ν(MoO2) IR bands at 895 and 790 cm−1 (cf. 935 and 900 cm−1 for the Mo(VI) analogues). The X-ray structures of all seven complexes have been determined. In each case, the Mo center exhibits a distorted octahedral coordination geometry defined by mutually cis oxo and phenolate ligands and a tridentate fac-TpiPr ligand. The Mo(V) anions exhibit greater Mo═O distances (av. 1.738 Å vs 1.695 Å) and O═Mo═O angles (av. 112.4° vs 102.9°) than their Mo(VI) counterparts, indicative of the presence of a three-center (MoO2), π* semioccupied molecular orbital in these d1 complexes. The amido Mo(VI) and Mo(V) complexes exhibit an intramolecular hydrogen-bond between the NH and Ophenolate atoms. Protonation of [CoCp2][TpiPrMoVO2(2-OC6H4CONHR)] by lutidinium tetrafluoroborate is quantitative and produces EPR-active, cis-(hydroxo)oxo-Mo(V) complexes, TpiPrMoVO(OH)(2-OC6H4CONHR), related to the low pH Mo(V) forms of sulfite oxidase.

A series of bis-salicylidene based N₂S₂ copper macrocycles were prepared, structurally characterised and subjected to electrochemical analysis. The aim was to investigate the effects of length of polymethylene chains between either the imine donors or the sulfur donors on redox state and potential of the metal. The complexes structurally characterised had either distorted square planar or tetrahedral geometries depending on their oxidation state (Cu²+ or Cu+, respectively), and the N–(CH₂)n–N bridge was found to be most critical moiety in determining the redox potential and oxidation state of the copper macrocycles, with relatively little change in these properties caused by lengthening the S–(CH₂)n–S bridge from two to three carbons. In fact, a weakness was observed in the complexes at the sulfur donor, as further lengthening of the S–(CH₂)n–S methylene bridge to four carbons caused fission of the carbon–sulfur bond to give dimeric rings and supramolecular assemblies. Cu+ complexes could be oxidised to Cu²+ by tert-butylhydroperoxide, with a corresponding change in the spectrophotometric properties, and likewise Cu²+ complexes could be reduced to Cu+ by treatment with β-mercaptoethylamine. However, repeated redox cycles appeared to compromise the stability of the macrocycles, most probably by a competing oxidation of the ligand. Thus the copper N₂S₂ macrocycles show potential as redox sensors, but further development is required to improve their performance in a biochemical environment.

Fluorescent selective angiotensin AT₁ receptor antagonists (sartans) that contain naphthalene (6, 7, 10, and 11), anthracene (12 and 14), acenaphthene (13 and 15), and coumarin (8 and 9) substituents have been prepared and their preliminary pharmacology evaluated in Chinese hamster ovary (CHO) cell based assays. Compounds 6-15 proved to be effective sartans with pKB estimates in the range of 6.7-10.5; their potential as cellular imaging agents is also discussed.

The study reports an advance in designing copper-based redox sensing MRI contrast agents. Although the data demonstrate that copper(II) complexes are not able to compete with lanthanoids species in terms of contrast, the redox-dependent switch between diamagnetic copper(I) and paramagnetic copper(II) yields a novel redox-sensitive contrast moiety with potential for reversibility.

The supramolecular structure of the title molecule, [Ca(C7H4ClO4S)(H2O)6](C7H4ClO4S)·H2O, contains alternating organic and inorganic layers along the b direction. The sulfonate group on one of the aryl units is coordinated to Ca, while the other does not form any interaction with a Ca atom.

The synthesis of tri- and tetrasubstituted cyclopropanes from 3-aryl-substituted levoglucosenones (LGO) has been developed. In contrast to the unstabilised ylide dimethylsulfonium methylide which gives epoxides from LGO via 1,2-addition, we have found that the soft nucleophile dimethylsulfoxonium methylide affords cyclopropanes in moderate yields from LGO and in excellent yields and stereoselectivity with 3-aryl LGO derivatives. The use of 1,1,3,3-tetramethylguanidine as base in DMSO to generate the ylide provided the best yields and shortest reaction times. Ester stabilised sulfonium ylides could also be used to generate tetrasubstituted cyclopropane derivatives. One of the products was converted into a cyclopropyl lactone via Baeyer-Villiger oxidation to demonstrate the utility of applying cyclopropanation chemistry to LGO.

The X-ray crystal structures of (N,N'-bis-(o-amidobenzilidene)-1,3-diaminopropane)nickel (Niambpr), (N,N'-bis-(o-amidobenzilidene)-1,4-diaminobutane)nickel (Niambut), (N,N'-bis-(o-thiobenzilidene)-1,4-diaminobutane)nickel(II) (Nitsalbut), {bis-acetonitrile-(N,N'-bis-(o-aminobenzyl)-1,2-diaminoethane)}nickel(II) tetrafluoroborate [Ni(H₄amben)(MeCN)₂] [BF₄]₂, {bis-O-acetato-(N,N'-bis-(o-aminobenzyl)-1,2-diaminoethane)}nickel(II) [Ni(H₄amben)(OAc)₂ · H₂O] and {bis-O-acetato-(N,N'-bis-(o-aminobenzyl)-1,3-diaminopropane)}nickel(II) [Ni(H₄ambpr)(OAc)₂] are presented. These structures complete the structural characterisation of the simple unsubstituted Schiff's base complexes with N₄ and N₂S₂ donor sets and allow us to assess the effects of donor groups and polymethylene chain length on the coordination geometries of nickel(II). The hydrogenated N4 complexes offer an insight into the effects of increased flexibility and character of the internal nitrogen donors. Unlike the parent N4 imine species the hydrogenated amine species do not deprotonate at the peripheral nitrogen donors and do not seem to be restricted to the meridial plane of the nickel.

Benzothiophene and benzoselenophene analogues of the thiophene-containing antihypertensives milfasartan and eprosartan were prepared and tested for AT1 receptor antagonist properties. While the sulfur-containing systems were prepared following existing methodology, the selenium-containing analogues required the development of novel, tandem free-radical chemistry involving addition of aryl radicals to alkynes, followed by intramolecular homolytic substitution at the higher heteroatom. All four compounds prepared proved to be excellent AT₁ receptor antagonists, with pKв estimates of 7.2-9.5.

The title tetradentate Schiff base complex (systematic name: {2,2'-[propane-1,3-diylbis(nitrilomethylidyne)]benzenethiolato- κ⁴S,N,N',S'}nickel(II) 1,4-dioxane solvate), [Ni(C₁₇H₁₆-N₂S₂)]·C₄H₈O₂, contains an Ni atom coordinated within a tetrahedrally distorted planar N₂S₂ environment, with average Ni-N and N-S bond lengths of 1.922 (1) and 2.167 (1) Å, respectively.