Richard W. McCabe

The influence of singlet oxygen in the fading of carbonless copy paper primary dyes on clays

Singlet oxygen was shown to be involved in the mechanism of fading on a clay surface of a series of the triphenylmethane (TPM) dyes used in commercial carbonless copying paper. The dyes adsorbed on clays were found to be singlet oxygen sensitisers and the singlet oxygen produced reacted with the dyes themselves. The rate of fading of a particular dye depended upon the structure of the dyes, fluorans degrading faster than phthalides.

Synthesis of novel polyurethane polyesters using the enzyme Candida antarctica lipase B

There are significant health and environmental hazards associated with the synthesis of polyurethane polymers and the diisocyanate intermediates due to their toxicity and that of the phosgene used to produce the diisocyanate. The synthesis of polyurethane polymers avoiding or minimising the requirement for diisocyanate is reported. Using the Candida antarctica lipase B to catalyse the polyesterification, a series of polyurethanes based on bis-carbamate diols were synthesised. Several polyurethane polymers have been synthesised based on diamines for which no corresponding diisocyanate exists.

The inhibition of triphenylmethane primary dye fading in carbonless copying paper systems by singlet oxygen quenching bis(dithiocarbamato)nickel(II) complexes

Abstract Several of the dyes used in commercial carbonless copying systems act as singlet oxygen sensitisers, the production of which causes fading of the dyes [1] . A series of bis-(dithiocarbamato)nickel(II) complexes were synthesised and shown to be efficient singlet oxygen quenchers in solution in the presence of the acid activated clay. On the dry clay, however, only the hydroxyl-containing complexes were effective as they bound more efficiently to the clay. Fading was retarded more efficiently with fluoran TPM dyes, which produce more singlet oxygen, than phthalide TPM dyes. In some cases, the position and intensity of the λ max of the dyes was preserved efficiently.

Examination of the structural features necessary for mesophase formation with aroylhydrazinato-nickel(II) and -copper(II) complexes

N-Methylidene complexes and a series of N-alkylidene- and N-arylalkylidene-aroylhydrazinato-nickel(II) and -copper(II) complexes were synthesized in high yield and their mesomorphic nature studied. Only the N-methylidene complexes gave mesomorphic compounds as the larger N-alkylidene or N-aralkylidene groups probably prevented mesophase formation due to increased molecular broadening effects. The nickel(II) complexes were found to be highly stable even in the isotropic phase and generally gave wide liquid-crystalline temperature ranges. This contrasted with the very narrow temperature ranges of the copper(II) complexes, which rapidly decomposed in or just before attaining the isotropic phase.

Synthesis of novel polyurethane polyesters using the enzyme Candida antarctica lipase B.

A novel enzymatic route has been used to synthesise standard and unusual polyester polyurethanes without employing the usual highly toxic isocyanate intermediates.

Mesh phases in tetramethylammonium perfluorodecanoate–water ternary systems

The evolution of the phase behaviour and lyotropic phase structures formed in the tetramethylammonium perfluorodecanoate (C10TMA)–water system upon the addition of a third component (tetramethylammonium chloride (TMACl) or 1H, 1H-perfluoro-1-decanol (C10ol)) have been studied using optical polarizing microscope, 2H NMR and small angle X-ray scattering (SAXS) in order to understand the correlated mesh phase with Rm space group. With increasing concentration of both additives, the Mh1(Rm) phase changes to a random mesh phase Mh1(0) via a two phase region. The structure of the Mh1(Rm) phase is essentially unaltered with addition of TMACl or C10ol until the phase change to Mh1(0). With higher additive concentration, the water fraction within a mesh layer of the Mh1(0) phase is decreased. It is proposed that the transition from the Mh1(0) to Mh1(Rm) phases is driven by a reduction in the electrostatic interlayer interaction enabling non-electrostatic repulsive interactions to dominate. This is because of the strong association of the TMA counter ion with the head group region, the increase of water within the mesh layers and the decrease in separation of the mesh layers in the Mh1(Rm) phase. It is also shown that the hydrophobic counter ion has to be small relative to the surfactant for both mesh and correlated mesh to occur.

Hydrophobic counter ion effects on the formation of mesh and reversed phases in the perfluorodecanoate/water system

The tetramethylammonium perfluorodecanoate (C10TMA)/water system forms both random, Mh1(0) and correlated mesh, Mh1(Rm) phases over a wide range of concentration and temperature. Whilst the random mesh phase is found in the ammonium homologue, the extensive correlated mesh phase seems to be a result of the hydrophobic nature of the tetramethylammonium (TMA) counter ion. In order to explore the reasons for the occurrence of these mesh phases and the effects of hydrophobic counter ions on phase structure the counter ion has been substituted by a series of increasing hydrophobicity namely butyltrimethylammonium (BTMA), dibutyldimethylammonium (DBDMA), and methyltributylphosphonium (MTBP). The phases and their structures were identified by small angle X-ray scattering. Increasing counter ion hydrophobicity causes a change from mesh, to lamellar, and finally to reversed phases. All the hydrophobic counter ions are strongly bound to the water/fluorocarbon interface and, in the case of those with butyl chains, there is penetration of between 50 and 60% of the total number of counter ion methyl groups into the fluorocarbon region of the lamellar phase. These bound counter ions reduce the accessibility of the head group region to solvent water. As the number of butyl chains on the counter ion increases the lamellar phase is progressively lost and is replaced by a reversed micelle phase either as a single phase or as part of an extensive two phase region.

Fulgides as ligands 1. Synthesis and photochemistry of tricarbonyl-ν6-fulgide chromium(0) complexes

Abstract Three photochromic fulgides, E-1-(3′,4′,5′-trimethoxyphenyl)ethylidene(isopropylidene)succinic anhydride (5) and a mixture of E- and Z-1-(2′,4′,6′-trimethylphenyl)methylidene(isopropylidene)succinic anhydrides (10) and (11), were synthesised and reacted with chromium hexacarbonyl to give mixtures of the corresponding tricarbonyl-ν6-fulgide chromium(0) complexes. No evidence for formation of the corresponding diene or enone complexes was obtained. Irradiation of the purified chromium arene complexes gave E Z isomerisation and decomposition of the complexes without photochromic ring closure.

Aroylhydrazinatonickel(II) and copper(II) complexes; a new class of metallomesogens

A series of aroylhydrazinato-nickel(II) and -copper(II) complexes have been synthesised in high yield and shown to form a new class of metallomesogens, which form smectic C and nematic phases; the nickel(II) complexes were found to be highly stable even in the isotropic phase, which contrasted with the rapid decomposition of the copper(II) complexes soon after entering the liquid crystalline phase.

Removal of hydrogen bonding interferences in the near infrared spectroscopic determination of dicarboxylic acids in diols

Although several NIR spectroscopic methods exist for following the synthesis of polyesters, they are all used at the reaction temperature of between 240 and 260°C where reaction still proceeds, they also employ near equimolar concentrations of diacids and diols. A poor correlation, however, is obtained when analysing dilute diacid solutions in diols, this is attributed to hydrogen bonding between the carboxyl and hydroxyl groups. The removal of hydrogen bonding by addition of chloroform to the solution gave excellent correlation of the absorbance of the second overtone carbonyl bands with acid concentration.