Synthesis and Crystal Structures of Two Novel Anionic Aluminophosphates: A One-Dimensional Chain, UT-7 ([Al(3)P(5)O(20)H](5-)[C(7)H(13)NH(3)(+)](5)), and a Layer Containing Two Cyclic Amines, UT-8 ([Al(3)P(4)O(16)](3-)[C(4)H(7)NH(3)(+)](2)[C(5)H(10)NH(2)(+)])

UT-7 and UT-8 (University of Toronto, structure numbers 7 and 8) are two novel aluminophosphate materials prepared under non-aqueous conditions. Their structures, extended in one and two dimensions, respectively, have been solved by single-crystal X-ray diffraction and characterized by a variety of methods including powder X-ray diffraction (PXRD), insitu high-temperature PXRD, thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), and scanning electron microscopy (SEM). UT-7 ([Al(3)P(5)O(20)H](5)(-)[C(7)H(13)NH(3)(+)](5), triclinic space group P&onemacr;, Z = 2, a = 10.118(3) ?, b = 15.691(4) ?, c = 18.117(3) ?, alpha = 72.91(2) degrees, beta = 85.18(2) degrees, gamma = 79.49(2) degrees ) is built of polymeric one-dimensional chain units, hydrogen-bonded into anionic layers that are charge-compensated by interlamellar cycloheptylammonium cations. UT-7 is isostructural to our previously discovered UT-3 chain structure, isolated in the analogous cyclopentylamine system. UT-8 ([Al(3)P(4)O(16)](3-)[C(4)H(7)NH(3)(+)](2)[C(5)H(10)NH(2)(+)], monoclinic space group P2(1), Z = 2, a = 8.993(4) ?, b = 14.884(8) ?, c = 9.799(9) ?, beta = 103.52(3) degrees ) is a two-dimensional net isostructural to several previously reported [Al(3)P(4)O(16)](3)(-) layers. The interlayer region of UT-8 is occupied by two different cyclic organic amine species, namely piperidinium and cyclobutylammonium. To our knowledge, this is the first report of the crystal structure of an aluminophosphate material containing cyclobutylammonium or a mixture of cyclic amines. Interestingly, UT-7 is observed to thermally transform in the solid state to an as yet unknown layered material that can be independently synthesized in a similar synthetic system. In the same way as UT-3 transforms to the UT-4 layered phase, we believe UT-7 transforms to a layered material by means of a chain to layer transformation.     

The proton affinity of proline analogs using the kinetic method with full entropy analysis

The proton affinity of proline analogs, L-azetidine-2-carboxylic acid (Aze), L-proline (Pro), and L-pipecolic acid (Pip), have been measured using the Armentrout modification of the extended kinetic method in a quadrupole ion trap instrument. Experimental values of 223.0 +/- 1.5, 224.9 +/- 1.6, and 225.6 +/- 1.6 kcal/mol have been determined for the 298K proton affinities of Aze, Pro, and Pip respectively. High level theoretical calculations using both MP2 and B3LYP methods at a variety of basis sets were carried out in order to give theoretical predictions for the 298 K proton affinity and gas phase basicity of all three analogs. Recommended values for the gas phase basicity and proton affinity for proline based on our work and other recent determinations are 216 +/- 2 and 224 +/- 2 kcal/mol.     

Protonation and methylation of η-2,3,5,6-tetramethyl-1,4-benzoquinone(η-pentamethylcyclopentadienyl)cobalt

The preparation of the η⁴-4-2,3,5,6-tetramethyl-1,4-benzoquinonecomplex [CO(C₅Me₅)(C₁₀H₁₂O₂)] (I) is reported. Complex I undergoesreversible protonation to yield the 2-6-η-4-hydroxy-1-oxo-2,3,5,6-tetramethylcyclohexadienyl complex [Co(C₅Me₅)(C₁₀H₁₃O₂)BF₄ (II) and diprotonation to yield the η⁶-6-1,4-dihydroxy-2,3,5,6-tetramethylbenzene complex [Co(C₅Me₅)(C₁₀H₁₄O₂)] (BF₄)₂ (III). Methylation of complex I with MeI/AgPF₆ gives the 2---6-η-4-methoxy-1-oxo-2,3,5,6-tetramethylcyclohexadienyl complex [Co(C₅Me₅)(C₁₁H₁₅O₂])PF₆ (IV). In trifluoroacetic acid solution complex IV is protonated to form the η⁶-1-hydroxy-4-methoxy-2,3,5,6-tetramethylbenzene cation [Co(C₅Me₅)-(C₁₁H₁₆O₂)]²⁺     

Blends of starch with ethylene vinyl alcohol copolymers: effect of water,glycerol, and amino acids as plasticizers

Blends of thermoplastic starch with poly(ethylene‐co‐vinyl alcohol) copolymer (EVOH) were melt extruded with water/glycerol as plasticizer and a series of amino acid additives. The biggest factor in end‐use mechanical properties proved to be the relative humidity (RH) during storage. Plasticized starch‐EVOH blends stored at 0 and 50% RH changed significantly over time, with, for example, the tensile strength (TS) of the glycerol‐plasticized blend increasing from 4.7 to 26.3 MPa over 8 weeks when maintained at 0% RH. In contrast, the TS of this same sample stored at 75% RH remained unchanged for 8 weeks. Amino acids provided relatively minor, but significant changes in mechanical properties with time. Based on TS, elongation‐to‐break, and modulus, it may be concluded that β‐alanine, sarcosine, and L ‐proline were more effective than glycerol at maintaining strong flexible blends. Increases in crystallinity and changes in morphology with time, as described by modulated DSC were correlated to these changes in mechanical properties. Published in 2007 by John Wiley & Sons, Ltd.     

Molecular rectification: self-assembled monolayers in which donor-(pi-bridge)-acceptor moieties are centrally located and symmetrically coupled to both gold electrodes

Self-assembled monolayers (SAMs) obtained from 1-(10-acetylsulfanyldecyl)-4-[2-(4-dimethylaminophenyl)vinyl]quinolinium iodide exhibit asymmetric current-voltage (I-V) characteristics. The rectification may be reversibly switched: it is suppressed when the film is exposed to HCl vapor, the intramolecular charge-transfer axis being inhibited by protonation, but restored when exposed to NH(3). The behavior is intrinsic to the donor-(pi-bridge)-acceptor moiety, and ambiguity in the assignment has been excluded by matching the alkyl tails on the substrate and contacting STM tip to locate the chromophore midway between the electrodes: Au-S-C(10)H(21)//D-pi-A-C(10)H(20)-S-Au. Films contacted by gold tips exhibit rectification ratios of ca. 18 at +/-1 V, whereas those contacted by pentanethiolate (Au-S-C(5)H(11))- and decanethiolate (Au-S-C(10)H(21))-coated tips have corresponding ratios of ca. 11 and 5, respectively. The I-V curves are different, but when adjusted for thickness the current versus electric field dependence is indistinguishable. Seven dyes are reported: SAMs with sterically hindered D-pi-A moieties, in which the donor and acceptor are twisted out of plane, exhibit rectification, whereas those that are planar or have a weak donor-acceptor combination do not.     

Percolation in half-spaces: equality of critical densities and continuity of the percolation probability

Renormalization arguments are developed and applied to independent nearest-neighbor percolation on various subsets of ^d ,d2, yielding:

,-Difluoroketone inhibitors of HMG CoA reductase

The rationale for a new class of HMG CoA reductase inhibitors, represented by ,ga-difluoroketones 3 and 4, is described. The syntheses of 3, 4, and their nonfluorinated analogue 5 are presented.     

Metallation effects on the thermal interconversion of atropisomers of di(orthomethylarene)-substituted porphyrins

A new series of meso-substituted diaryl free-base and metalloporphyrins have been prepared. Each arene has been substituted with both a methyl group in the ortho position and a formyl group in the meta position. Rotation of the arene units is prevented at room temperature due to the steric restrictions imposed by the flanking methyl groups at the porphyrin beta-pyrrolic positions on the methyl groups at the ortho position on the meso-substituted arene unit. This allowed the alpha alpha and alpha beta atropisomers of this porphyrin to be separated and characterised. X-Ray crystallographic determination of the structure of the free-base porphyrin revealed a very flat porphyrin core. Metallation resulted in the isolation and characterisation of the nickel, zinc and copper derivatives. The assignments of the alpha alpha and alpha beta isomers are confirmed by X-ray crystallographic determination of the structures of the Cu(II) analogues. The copper alpha alpha structure exhibits a very twisted porphyrin core, the copper alpha beta structure is also distorted, but to a lesser degree. The activation energy for rotation has been calculated for each of the 2H, Ni and Zn derivatives. The energy required to rotate the arene ring increases in the order Ni < Zn approximately 2H. No significant difference in the free energy of rotation was observed between experiments carried out with the alpha alpha and small alpha beta isomers.     

The direct photo-oxidative decarboxylation of α-oxo-carboxylic acids

α-Oxo-carboxylic acids undergo photo-oxidative decarboxylation from both C-1 and C-2 positions, and reaction does not involve singlet oxygen: a mechanism involving an electron transfer reaction is postulated.