Jean M. McKenzie

Polymer–protein conjugates from ω-aldehyde endfunctional poly(N-vinylpyrrolidone) synthesised via xanthate-mediated living radical polymerisation

Aldehyde omega-endfunctional poly(N-vinylpyrrolidone) was synthesised via quantitative conversion of a xanthate endfunctional precursor obtained via RAFT-mediated polymerisation.

Tetrazolyl and tetrazolylidene complexes of gold: a synthetic and structural study

Lithiation of 1-benzyl-1H-tetrazole followed by transmetallation with [AuCl(PPh3)], [Au(C6F5)(tht)] or [AuCl(tht)] (tht = tetrahydrothiophene) and subsequent alkylation afforded cationic 1-benzyl-4-methyl-4,5-dihydro-1H-1,2,3,4-tetrazol-5-ylidene(triphenylphosphine)gold(I), 1, neutral 1-benzyl-4-methyl-4,5-dihydro-1H-1,2,3,4-tetrazol-5-ylidene(pentafluorophenyl)gold(I), 2, and a cationic biscarbene complex, bis(1-benzyl-4-methyl-4,5-dihydro-1H-1,2,3,4-tetrazol-5-ylidene)gold(I), 3. The first complex underwent a homoleptic rearrangement in solution to form 3. Reaction of [Au(N3)PPh3] with the three isocyanides (CH3)2C6H3NC, tBuNC and CyNC, respectively, yielded the corresponding neutral tetrazolyl(phosphine) complexes of gold, [1-(2,6-dimethylphenyl)-1H-tetrazol-5-yl](triphenylphosphine)gold(I), 4, [1-(tert-butyl)-1H-tetrazol-5-yl](triphenylphosphine)gold(I), 6, and [1-(cyclohexyl)-1H-tetrazol-5-yl](triphenylphosphine)gold(I), 7. Alkylation of 4 with methyl triflate on N4 allowed isolation of the crystalline carbene complex 1-(2,6-dimethylphenyl)-4-methyl-4,5-dihydro-1H-1,2,3,4-tetrazol-5-ylidene)(triphenylphosphine)gold(I), 5. Complex 7 was not isolable in pure form but converts by isocyanide substitution of triphenylphosphine into [1-cyclohexylisocyanide][1-(cyclohexyl)-1H-tetrazol-5-yl]gold(I), 8. From a product mixture of 7 and 8 the transformed molecules [(cyclohexylamino)(ethoxy)carbene](1-cyclohexyl-1H-tetrazol-5-yl)gold(I), 9, and [bis(cyclohexylamino)carbene](1-cyclohexyltetrazol-5-yl)gold(I), 10, co-crystallised spontaneously after a long time at −20 °C.

Investigation into the Initialization Behaviour of RAFT-Mediated Styrene-Maleic Anhydride Copolymerizations

The living radical alternating copolymerization of styrene and maleic anhydride mediated by the reversible addition–fragmentation chain transfer (RAFT) polymerization process has been studied at short chain lengths using two different dithiobenzoate RAFT agents. The results indicate specificity of addition of the RAFT-agent leaving groups for either styrene or maleic anhydride. The addition rate of the monomers and the fact that monomers are added individually favour the penultimate unit model of polymer propagation.

The osmotic stress tolerance of basidiomycetous yeasts

The growth and accumulation of intracellular polyols at reduced water activity (a(w)) were studied in 40 basidiomycetous yeast strains. The growth of most strains showed greater tolerance to NaCl than sorbitol at the same a(w). No strain was able to grow below 0.90a(w). (13)C nuclear magnetic resonance spectroscopy revealed that glycerol was the major solute accumulated intracellularly by all the yeasts when grown to 0.96a(w) (NaCl). Arabitol or mannitol was also accumulated in some yeasts, whereas a few only accumulated glycerol. Analysis of six yeasts in detail revealed that the intracellular glycerol concentrations of five yeasts increased significantly when grown at 0.96a(w) (NaCl or sorbitol) compared with growth at 0.998a(w). Arabitol and mannitol concentrations also increased, but not to the same degree. Intracellular potassium concentrations decreased when grown at 0.96a(w) (NaCl or sorbitol) and sodium increased, but only when grown at 0.96a(w) (NaCl). The survival of nine strains was evaluated in soil cultures and it was found that all grew at 100% field capacity, whereas at lower field capacity, only some strains grew or survived. The growth of basidiomycetous yeasts appears to be more sensitive to reduced a(w) than ascomycetous yeasts.

Intermolecular aurophilic interactions facilitate assembly of a complex rotaxane in solution

We describe the formation of a complex [2]rotaxane both in solution and in the solid state. The rotaxane ring is composed of a cyclic trinuclear gold complex and the Au(PMe(3))(2)(+) rod is held in place by three aurophilic interactions to the ring Au atoms. The existence of the [2]rotaxane in solution is confirmed by VT-NMR and MS analysis.

Light-induced cis/trans isomerization of cis-[Pd(L-S,O)2] and cis-[Pt(L-S,O)2] complexes of chelating N,N-dialkyl-N′-acylthioureas: key to the formation and isolation of trans isomers

Irradiation cis-[M(Ln-S,O)2] complexes (M = PtII, PdII) derived from N,N-dialkyl-N′-benzoylthioureas (HLn) with various sources of intense visible polychromatic or monochromatic light with λ < 500 nm leads to light-induced cis → trans isomerization in organic solvents. In all cases, white light derived from several sources or monochromatic blue-violet laser 405 nm light, efficiently results in substantial amounts of the trans isomer appearing in solution, as shown by 1H NMR and/or reversed-phase HPLC separation in dilute solutions at room temperature. The extent and relative rates of cis/trans isomerization induced by in situ laser light (λ = 405 nm) of cis-[Pd(L2-S,O)2] was directly monitored by 1H NMR and 195Pt NMR spectroscopy of selected cis-[Pt(L-S,O)2] compounds in chloroform-d; both with and without light irradiation allows the δ(195Pt) chemical shifts cis/trans isomer pairs to be recorded. The cis/trans isomers appear to be in a photo-thermal equilibrium between the thermodynamically favored cis isomer and its trans counterpart. In the dark, the trans isomer reverts back to the cis complex in what is probably a thermal process. The light-induced cis/trans process is the key to preparing and isolating the rare trans complexes which cannot be prepared by conventional synthesis as confirmed by the first example of trans-[Pd(L-S,O)2] characterized by single-crystal X-ray diffraction, deliberately prepared after photo-induced isomerization in acetonitrile solution. Graphical Abstract The dominantly formed cis-[M(L-S,O)2] (M = PtII or PdII) complexes from N,N-dialkyl-N′-acyl-thioureas in solution undergo a facile cis → trans isomerization on irradiation with visible light at room temperature, allowing the predictable formation and isolation of the elusive trans-[Pd(L-S,O)2] complexes.

Mono- and Binuclear Gold(I) Amido Compounds of Purine Derivatives

A series of neutral dinuclear and mononuclear gold(I) complexes with phosphine and N-bonded 9H-purin-9-ate or 9H-purin-6-ylamine-9-ate have been synthesised under basic conditions and characterised by gHSQC, 1H,13C gHMQC and 1H detected 1H,15N gHMQC experiments in addition to ESI-MS and IR spectroscopy. Intermolecular aurophilic interactions are present in the structures of polymeric 1,2-bis(diphenylphosphine)ethane(9H-purin-9-ate)gold(I) 1, (3.1641(4) Å ) and 1,3- bis(diphenylphosphine)propane(9H-purin-9-ate)gold(I) 3, (3.52Å ). The N-Au-P angle in 1 is exceptionally small (166.3(1)°). Intramolecular aurophilic interaction (3.63 Å ) complemented by hydrogen bonding dictates the non-oligomeric structure of 1,3-bis(diphenylphosphine)propane(9H-purin- 6-ylamin-9-ate)gold(I) (7). Dimeric aurophilic interactions appear in the structure of (tributylphosphine)( 9H-purin-9-ate)gold(I) (11) (3.2311(7) Å ), while the structure in the other mononuclear compound, (triphenylphosphine)(9H-purin-9-ate)gold(I) (9) is organised by Au. . .N-interactions.