Monitoring intracellular redox potential changes using SERS nanosensors.

Redox homeostasis and signaling are critically important in the regulation of cell function. There are significant challenges in quantitatively measuring intracellular redox potentials, and in this paper, we introduce a new approach. Our approach is based on the use of nanosensors which comprise molecules that sense the local redox potential, assembled on a gold nanoshell.

Gas-phase generation and cyclisation reactions of imidoyl radicals.

Some 1,2-diarylimidoyl radicals were generated in the gas-phase by intramolecular radical translocation from ortho-imino-aryloxyl radicals, in turn generated under flash vacuum pyrolysis (FVP) conditions. The imidoyls reacted with XR ortho'-substituents in the N-aryl group to give (in most cases) modest yields of cyclisation products. Depending on the nature of the bridging atom (X), the formation of these products was initiated either by a further hydrogen atom translocation (X = CH(2)), or by ipso-attack onto the aryl group (R = Ph), or by direct substitution at the heteroatom (X = S).

Specific indolo[3,2,1-jk]carbazole conducting thin-film materials production by selective substitution.

Selectively substituted indolo[3,2,1-jk] carbazole (IC) molecules have been synthesized through flash vacuum pyrolysis (FVP) and then electro-oxidized, resulting in the formation of redox-active and electronically conducting thin films consisting exclusively of three highly luminescent dimer species, the 2,2'-, 2,10'-, and 10,10'-coupled dimers. DFT calculation has enabled both the accurate calculation of monomer oxidation potentials and the prediction of the nature of the resulting dimers through consideration of the coupling of the oxidized monomer radical cations. This demonstrates that substituted ICs represent a class of molecules able to form redox-active and conducting dimer films of controlled composition upon oxidation and that DFT calculations can be used to inform the synthesis of specific IC monomers most likely to both produce electronically conducting thin-film materials and yield specific luminescent dimers with desirable materials properties.

The formation and characterisation of redox active and luminescent materials from the electrooxidation of indolizine.

Indolizine has been synthesised on the small scale with enhanced yield using a novel Flash Vacuum Pyrolysis method. Electrooxidation of indolizine results in the formation of a redox-active film on the electrode surface. Excellent agreement is found between calculated and experimental indolizine oxidation potentials; a combination of fluorescence and electrochemical studies are consistent with the computational prediction that electroxidation results in the formation of three specific and redox active indolizine dimers.

An AAAA–DDDD quadruple hydrogen-bond array.

Secondary electrostatic interactions between adjacent hydrogen bonds can have a significant effect on the stability of a supramolecular complex. In theory, the binding strength should be maximized if all the hydrogen-bond donors (D) are on one component and all the hydrogen-bond acceptors (A) are on the other. Here, we describe a readily accessible AAAA–DDDD quadruple hydrogen-bonding array that exhibits exceptionally strong binding for a small-molecule hydrogen-bonded complex in a range of different solvents (K(a) > 3 × 10(12) M(-1) in CH2Cl2, 1.

3-Hydroxypyrrolo[2,3-b]pyridine and related compounds - indoxyl analogues with fused electron deficient rings.

Flash vacuum pyrolysis (FVP) of 4-acetyltetrazolo[1,5-a]pyridine 5 at 400 °C provides 3-methyl isoxazolo[3,4-b]pyridine 6 whose structure was confirmed by X-ray crystallography. At higher pyrolysis temperatures, the unstable heteroindoxyl 8 was obtained, which exists as the keto form (1,2-dihydropyrrolo[2,3-b]pyridin-3-one) 8K in CDCl(3) solution and the enol tautomer (3-hydroxypyrrolo[2,3-b]pyridine) 8E in DMSO. The heteroindoxyl 8 oxidatively dimerises to the heteroindigotin 9, undergoes condensation reactions at the 2-position and reacts with methoxymethylene Meldrum's acid at the 1-position.

Pyrrolizine-1,3-dione.

Pyrrolizine-1,3-dione 4 was made by oxidation of the alcohol 2 using pyridinium chlorochromate. The dione 4 shows ketone properties (e.g.

Structural studies of some push-pull N-arylbenzazoles.

X-Ray crystal structures, and calculated structures (at B3LYP/6-31G level) are reported for seven N-arylbenzazoles (two carbazoles, indoles and benzimidazoles, and one indazole) bearing electron withdrawing groups in the 2-position of the N-aryl ring. The structures are markedly non-planar by rotation around the N-aryl bond, with the substituent in most cases lying s-E in relation to the N-aryl bond; intermolecular electrostatic interactions in the crystal rationalise the two examples in which an s-Z conformation is observed. A large interplanar angle between the benzazole and the N-aryl planes is associated with a small interplanar angle between the planes of the N-aryl group and the substituent and vice versa.

Formation of dibenzofurans by flash vacuum pyrolysis of aryl 2-(allyloxy)benzoates and related reactions.

Flash vacuum pyrolysis (FVP) of aryl 2-(allyloxy)benzoates 5 and of the corresponding aryl 2-(allylthio)benzoates 6 at 650 degrees C, gives dibenzofurans 19 and dibenzothiophenes 20, respectively. The mechanism involves generation of phenoxyl (or thiophenoxyl) radicals by homolysis of the O-allyl (or S-allyl) bond, followed by ipso attack at the ester group, loss of CO2 and cyclisation of the resulting aryl radical. Synthetically, the procedure works well for p-substituted substrates, which lead to 2-substituted dibenzofurans 19b-f (73-90%) and dibenzothiophenes 20b-c (90-94%).

Reactions of 2-(pyrrol-1-yl)benzyl radicals and related species under flash vacuum pyrolysis conditions.

2-(Pyrrol-1-yl)phenoxyl, aminyl, thiophenoxyl and benzyl radicals 2a-2d, respectively, were generated in the gas-phase under flash vacuum pyrolysis conditions. In all cases except the phenoxyl, cyclisation took place providing acceptable synthetic routes to the fused heterocycles 11, 14 and 15, respectively. Only sigmatropic rearrangement products were isolated, in low yields, from the phenoxyl 2a.

Synthetic routes to pyrrolizine-1,5-dione derivatives by flash vacuum pyrolysis of amidomethylene derivatives of Meldrum's acid.

Methoxymethylene Meldrum's acid 1 reacts with 5- and 6-membered lactams in refluxing acetonitrile to give the N-substituted products 9-15. If the reactions are continued for extended times, the Meldrum's acid derivatives decompose to provide enamidoesters e.g.

Hydrogenation of pyrrolizin-3-ones; new routes to pyrrolizidines.

Pyrrolizin-3-ones (e.g. 1) can be easily hydrogenated to their hexahydro (pyrrolizidin-3-one) derivatives in the presence of heterogeneous catalysts.

AAA-DDD triple hydrogen bond complexes.

Experiment and theory both suggest that the AAA-DDD pattern of hydrogen bond acceptors (A) and donors (D) is the arrangement of three contiguous hydrogen bonding centers that results in the strongest association between two species. Murray and Zimmerman prepared the first example of such a system (complex 3*2) and determined the lower limit of its association constant (K(a)) in CDCl(3) to be 10(5) M(-1) by (1)H NMR spectroscopy (Murray, T. J.

1-Methoxycarbonylpyrrolizin-3-one and related compounds.

Flash vacuum pyrolysis (FVP) of dimethyl E- or Z-pyrrol-2-ylbut-2-enedioate at 700 degrees C gave 1-methoxycarbonylpyrrolizin-3-one 1. The sequence involves E- to Z-isomerisation (if necessary), elimination of methanol and cyclisation; the elimination step is rate determining. The pyrrolizinone 1 is stable at low temperatures, but at room temperature dimerises spontaneously across the 1,2-bond to give a mixture of trans- and cis- cyclobutanes 2 and 3, respectively.

Synthesis and chemistry of 4,5-dihydrothieno[3,2-b]pyrrol-6-one--a heteroindoxyl.

Flash vacuum pyrolysis (FVP) of 2-acetyl-3-azidothiophene gives 3-methylthieno[3,2-c]isoxazole as the major product at a furnace temperature of 350 degrees C whereas at temperatures above 550 degrees C the new heteroindoxyl 4,5-dihydrothieno[3,2-b]pyrrol-6-one is exclusively formed. The heteroindoxyl exists predominantly as the keto tautomer. It is O-protonated by TFA, N-acetylated by acetic anhydride, N-nitrosated by nitrous acid, and provides an N-methylene Meldrum's acid derivative on treatment with methoxymethylene Meldrum's acid.

The production and characterisation of novel conducting redox-active oligomeric thin films from electrooxidised indolo[3,2,1-jk]carbazole.

Indolo[3,2,1-jk]carbazole (IC) has been synthesised on a gram scale by flash vacuum pyrolysis. In contrast to a previous suggestion, IC is planar and it is also highly fluorescent, with a solution quantum yield of 0.41.

Thermal ring contraction of dibenz[b,f]azepin-5-yl radicals: new routes to pyrrolo[3,2,1-jk]carbazoles.

Flash vacuum pyrolysis (FVP) of N-allyl- or N-benzyldibenz[b,f]azepine at temperatures from 750 to 950 degrees C gives pyrrolo[3,2,1-jk]carbazole as the major product. The mechanism of the ring contraction involves dibenzazepin-1-yl radical formation, followed by transannular attack and formation of a 2-(indol-1-yl)phenyl radical which cyclizes. The mechanism is supported by independent generation of 2-(indol-1-yl)phenyl radicals by two different methods, and the use of 1-(2-nitrophenyl)indole as a radical generator gives an optimized synthetic route to pyrrolo[3,2,1-jk]carbazole (54% overall yield in two steps from indole).

Isoindolo[2,1-a]indol-6-one--a new pyrolytic synthesis and some unexpected chemical properties.

Isoindolo[2,1-a]indol-6-one 1 is formed by a sigmatropic shift-elimination-cyclisation cascade by flash vacuum pyrolysis (FVP) of methyl 2-(indol-1-yl)benzoate 7 at 950 degrees C. The dihydro compound 16 is easily obtained by catalytic reduction of 1, but the reaction is very sensitive to steric effects at the 11-position. Attempted ring-opening of 1 in basic methanol provides an equilibrium of isoindolo[2,1-a]indol-6-one 1 and the ester 19.

A thermal cascade route to pyrroloisoindolone and pyrroloimidazolones.

Flash vacuum pyrolysis (FVP) of indol-1-ylacrylate derivatives 11 and 15 or the isomeric indol-3-ylacrylates 21, 22, and 24 at 925 degrees C (0.05 Torr) provides pyrrolo[1,2-a]indol-3-ones 2, 18, 28, and 29 in 53-90% yield by a cascade mechanism that involves a sigmatropic migration, elimination, electrocyclization sequence. Pyrrolo[1,2-a]imidazol-5-ones 3 and pyrrolo[1,2-c]imidazol-5-ones 4 were similarly obtained by FVP of corresponding 2,5-unsubstituted imidazol-1-ylacrylates (e.

Generation and contrasting gas-phase reactivity of 2-(2-alkenylpyrrol-1-yl)phenoxyl and thiophenoxyl radicals.

The pyrrolylacrylates 9 and 10 were synthesised and subjected to flash vacuum pyrolysis (FVP) at 650-700 degrees C to generate the radicals 11 and 18, respectively. The phenoxyl 11 underwent hydrogen capture to give a mixture of the phenol 12 and the pyrrolobenzoxazine 13 in low yields, which were also obtained by a Wittig reaction of the 2-formylpyrrole 14. The thiophenoxyl 18 gave a single major product in 41% yield which was identified as the pyrrolo[1,2-a]quinoline 17 by a sequence of NMR experiments.

The assembly of rotaxane-like dye/cyclodextrin/surface complexes on aluminium trihydroxide or goethite.

Simple azo-dyes carrying phosphonic acid and arsonic acid substituents such as 4-(4-hydroxyphenyl azo)phenylphosphonic acid (5) and 4-(4-hydroxyphenylazo)phenylarsonic acid (6) bind more strongly to high surface area oxides such as aluminium trihydroxide and goethite than their carboxylic and sulfonic acid analogues and the phosphonate-functionalized dyes have been shown to have greater humidity fastness when printed onto commercial alumina-coated papers. Adsorption isotherm measurements provide evidence for the formation of ternary dye/cyclodextrin/surface complexes. Dyes which form such ternary complexes show higher light fastness when printed onto alumina coated papers in an ink formulation containing alpha-cyclodextrin.

Design of base metal extractants. Part 1. Inter-ligand hydrogen bonding in the assembly of pseudo-macrocyclic bis(aminosulfonamidato)M(II) complexes.

Monosulfonyl derivatives of simple 1,2- and 1,3-diamines (R2HN-R-NHSO2R1 = L) have been shown to be easily deprotonated to give neutral 2:1 complexes, [M(L - H)(2)], with Co(II), Ni(II), Cu(II) or Zn(II). The Ni(II) and Cu(II) complexes with deprotonated N-tosyl-1,2-diaminoethane have a planar N4(2-) donor set and a 14-membered pseudo-macrocyclic structure based on head-to-tail S=O..

Negative ion electrospray mass spectrometry of neoflavonoids.

The electrospray ionisation mass spectra of the neoflavanoids brazilin and hematoxylin are reported in both their reduced (1 and 2, respectively) and their oxidised forms (3 and 4, respectively). In the reduced forms, breakdown pathways under collision induced decomposition (CID) conditions produce fragments characteristic of rings A and C; in their oxidised forms, the fragments are characteristic of rings B and D. The structural assignments of the fragments are substantiated by recording the spectra after deuterium exchange at the hydroxyl groups.

An empirical study of the effect of the variables in a flash vacuum pyrolysis (FVP) experiment.

The effect of the variation of the experimental parameters on the conversion of precursor to products in a typical flash vacuum pyrolysis (FVP) experiment was investigated empirically. Temperature-conversion plots can be used to optimise FVP conditions and their mechanistic significance is exemplified. At a given temperature, the conversion can be increased by an increase in the background pressure, or by packing a section of the furnace tube with inert material (particularly when placed at the trap end of the furnace tube) or by employing a catalyst.