Alan Bassindale | The Open University (original) (raw)

Papers by Alan Bassindale

Research paper thumbnail of ChemInform Abstract: AROMATISCHE REAKTIVITAET 46. MITT. DEUTUNG DES SUBSTITUENTENEFFEKTES BEI DER BASEN-KATALYSIERTEN SPALTUNG VON ARYLTRIMETHYLSILANEN UND -STANNONEN IN WASSER-DMSO-KOH

Chemischer Informationsdienst, Sep 7, 1971

ChemInform Abstract Die Kinetik der Detritiierung von 2-und 3-[T]Methyl-benzo[b]thiophen und 3-Me... more ChemInform Abstract Die Kinetik der Detritiierung von 2-und 3-[T]Methyl-benzo[b]thiophen und 3-Methyl-2-[T]methyl-benzo[b]thiophen in wasserfreier Trifluoressigsäure wird ermittelt.

Research paper thumbnail of Preparation and characterization of a type of ladder-like poly(phenyl silsesquioxane) based hybrid star-shaped copolymer of ε-caprolactone

Journal of Applied Polymer Science, May 12, 2015

ABSTRACT Combination of the organic–inorganic hybrid such as silsesquioxane with ε-caprolactone w... more ABSTRACT Combination of the organic–inorganic hybrid such as silsesquioxane with ε-caprolactone will lead to materials expected to be environmentally friendly and applicable to biomedical usages. A ladder-like poly(phenyl silsesquioxane) based hybrid star-shaped copolymer of ε-caprolactone was prepared by ring opening polymerization of ε-caprolactone catalyzed by Sn(Oct)2 with hydroxyl terminated ladder-like poly(phenyl silsesquioxane) as initiator. The copolymers were characterized by proton nuclear magnetic resonance (1H-NMR), silicon nuclear magnetic resonance (29Si-NMR), Fourier-transform infrared spectrometer (FT-IR), size exclusion chromatography (SEC), thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC) in detail. Furthermore, the enzymatic degradation property of the copolymers was also investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42335.

Research paper thumbnail of Molecular motion in cyclic siloxanes studied by 17O, 29Si, and 13C nuclear magnetic resonance spectroscopy

Journal of the Chemical Society, 1990

ABSTRACT

Research paper thumbnail of Modelling nucleophilic substitution at silicon using hypervalent silicon compounds based on urea ligands

Journal of Organometallic Chemistry, Jan 30, 2001

ABSTRACT The X-ray crystal structure of a pentacoordinate silicon compound, 3, with a urea ligand... more ABSTRACT The X-ray crystal structure of a pentacoordinate silicon compound, 3, with a urea ligand shows partial Si–O bond formation and Si–Cl cleavage. The solution NMR parameters for the related series of compounds with different leaving groups provides structural information and this can be used to model substitution at silicon. The corresponding thioureas exhibit N–Si bond formation with the silicon remaining tetracoordinate.

Research paper thumbnail of Siloxane and hydrocarbon octopus molecules with silsesquioxane cores

Journal of Materials Chemistry, 1993

... the inefficiency of the synthesis and isolation of single species. However, Aga~kar'~ ha... more ... the inefficiency of the synthesis and isolation of single species. However, Aga~kar'~ has recently revealed a reasonably high yielding synthesis of T8 hydrogen silsesquioxane. In addition to T8, the synthesis and isolation of ...

Research paper thumbnail of Aromatic reactivity. Part XXXVIII. Protodesilylation of 1,2-dihydrobenzocyclobutene, indan, and tetralin

Journal of the Chemical Society, 1969

Rates of cleavage (protodesilylation) of some trimethylsilyl derivatives of reduced benzocycloalk... more Rates of cleavage (protodesilylation) of some trimethylsilyl derivatives of reduced benzocycloalkenes and o-xylene by a mixture of 10·6M-aqueous perchloric acid and methanol (2 : 5 v/v) have been measured spectrophotometrically. Values (min.–1) of the first-order rate constants (×103) at 50·0° are as follows: 3-trimethylsilyl-o-xylene, 193; 4-trimethysilyl-o-xylene, 153; 1,2-dihydro-3-trimethylsilylbenzocyclobutene, 16·1; 1,2-dihydro-4-trimethylsilylbenzocyclobutene, 154; 4-trimethylsilylindan, 77; 5-trimethylsilylindan, 210; 5-trimethylsilyltetralin, 235; 6-trimethylsilyltetralin, 181. (Ring-opening, which complicates most studies of the behaviour of 1,2-dihydrobenzocyclobutene and its derivatives towards electrophilic reagents, does not occur under the cleavage conditions.)The main features of the results are the low reactivity of the 3-(aryl α-) and the normal reactivity of the 4-(aryl β-) position of 1,2-dihydrobenzocyclobutene in comparison with the corresponding positions of o-xylene. The aryl α-position of indan shows a somewhat lower reactivity, but the aryl β-position shows a slightly enhanced reactivity, as do both the aryl α- and β-positions of tetralin. It is suggested that strain and carbon-hydridization effects of the small rings operate jointly to determine the reactivities.Use of desilylation is suggested as a possible route to 3-substituted 1,2-dihydrobenzocyclobutenes.

Research paper thumbnail of Stereochemical Nonrigidity in a Chelated Platinum(0)-Diolefin Complex

Organometallics, Feb 1, 1994

Research paper thumbnail of Substituent effects of the groups CH2M(CH3)3(M = C to Pb) and M(CH3)3(M = Si to Pb) from proton and carbon-13 chemical shift measurements on 4-substituted styrenes

Journal of the Chemical Society, 1977

ABSTRACT

Research paper thumbnail of The mechanism of the methanolysis of N-(triakylsilyl)anilines

Journal of Organometallic Chemistry, Nov 1, 1970

The rates of methanolysis of some ArNHSiR3 compounds have been measured spectrophotometrically. T... more The rates of methanolysis of some ArNHSiR3 compounds have been measured spectrophotometrically. The reactions have been shown to be inhibited by base, and the solvolysis of XC6H4N+HSi-iPr3 compounds in methanol at 50° containing an acetic acid/sodium acetate buffer and lithium perchlorate has been shown to be subject to specific oxonium ion catalysis. The mechanism proposed for neutral and acid-catalysed alcoholysis involves rate-determining nucleophilic attact of solvent on the silicon atom in the protonated species ArN+H2SiR3. For the XC6H4NHS-i-Pr3 compounds, the effects of the substituents X correlate excellently with their Hammett σ-constants (p = −2.5).

Research paper thumbnail of The detection of various opiates and benzodiazepines by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

Rapid Communications in Mass Spectrometry, Feb 15, 2009

A technique using comprehensive two‐dimensional gas chromatography/time‐of‐flight mass spectromet... more A technique using comprehensive two‐dimensional gas chromatography/time‐of‐flight mass spectrometry (GC × GC/TOFMS) is applied to qualitative and quantitative drug testing. Human serum was ‘spiked’ with known quantities of benzodiazepines and a ‘street heroin’ mixture including some of the major metabolites and impurities. The sample components were extracted from the matrix by solid‐phase extraction (SPE). Constituents containing polar hydroxyl and/or secondary amine groups were derivatised with N‐methyl‐N‐(tert‐butyldimethyl)trifluoroacetamide (MTBSTFA) to improve the chromatographic performance. An orthogonal separation of the matrix constituents was achieved by coupling a DB‐5ms (5% phenyl) to a BPX50 (50% phenyl) GC column. The eluant was focused onto the second column by a twin‐stage cryo‐modulator. Rapid 6 s modulation times were achieved by transfer from a 30 m × 0.25 mm (length × internal diameter) to a 2 m × 0.1 mm column. TOFMS with rapid spectral acquisition (≤500 spectra/s) was employed in the mass range m/z 40–650. A clean mass spectrum was obtained for each analyte using mass spectral deconvolution software. The sensitivity and repeatability of the method were evaluated by the preparation of calibration standards for two benzodiazepines, flunitrazepam and its major metabolite 7‐aminoflunitrazepam (7‐amino‐FN), in the concentration range 5–1000 ng/mL. The limits of detection (LODs) and limits of quantitation (LOQs), calculated by repeat injections (×10) of the lowest standard, were 1.6 and 5.4 ng/mL (flunitrazepam); 2.5 and 8.5 ng/mL (7‐amino‐FN), respectively. There is scope to extend this protocol to screen a large number of drugs and metabolites stored in a library database. Copyright © 2009 John Wiley & Sons, Ltd.

Research paper thumbnail of The Structure of Silylated Amides: N-Methyl-N-Trimethylsilyltrifluoroacetamide, a Reassignment of structure

Journal of Organometallic Chemistry, Aug 1, 1979

ABSTRACT

Research paper thumbnail of Nanotechnology - New advanced hybrid polymeric nanomaterials

Research paper thumbnail of Facile Synthesis of Novel Functionalized Silsesquioxane Nanostructures Containing an Encapsulated Fluoride Anion

Organometallics, Aug 13, 2012

ABSTRACT The presence of strongly electron withdrawing groups on alkoxysilanes, EWG-(CH2)n-Si(OEt... more ABSTRACT The presence of strongly electron withdrawing groups on alkoxysilanes, EWG-(CH2)n-Si(OEt)3 (where n = 1–3 and the electron-withdrawing group EWG contains an Si–C(sp3) bond), facilitates the formation and encapsulation of the fluoride anion in a silsesquioxane cage. Such species have been studied by 19F and 29Si NMR spectroscopy and X-ray crystallography together with MALDI-TOF and ESI mass spectrometry. The EWG must not be a good leaving group. Interestingly, this strategy led only to the T8 cage and excellent yields were obtained (81–95%) even without solvent. A wide range of functionalities were used. This new route offers an opportunity to build novel nanometer-sized 3-D molecular structures with a variety of functionalities which have not been accessible in the past.

Research paper thumbnail of octakis(Isobutyl)octasilsesquioxane

Research paper thumbnail of Tetra-n-butylammonium octaphenyloctasilasesquioxane fluoride clathrate

Research paper thumbnail of octakis(4-Methoxycarbonyl)-3,3-dimethyl-n-butyl)octasilsesquioxane

Research paper thumbnail of On the non-existence of trimethylsilyl tetrafluoroborate in acetone and acetonitrile : the generation of boron trifluoride in weakly coordinating solvents

Tetrahedron Letters, 1984

ABSTRACT

Research paper thumbnail of Synthesis of optically active α,β-epoxysilanes and silylaminoalcohols

Tetrahedron Letters, 1996

ABSTRACT

Research paper thumbnail of Influence of the initial chemical conditions on the rational design of silica particles

Journal of Sol-Gel Science and Technology, Sep 24, 2018

The influence of the water content in the initial composition on the size of silica particles pro... more The influence of the water content in the initial composition on the size of silica particles produced using the Stöber process is well known. We have shown that there are three morphological regimes defined by compositional boundaries. At low water levels (below stoichiometric ratio of water:tetraethoxysilane), very high surface area and aggregated structures are formed; at high water content (>40 wt%) similar structures are also seen. Between these two boundary conditions, discrete particles are formed whose size are dictated by the water content. Within the compositional regime that enables the classical Stöber silica, the structural evolution shows a more rapid attainment of final particle size than the rate of formation of silica supporting the monomer addition hypothesis. The clearer understanding of the role of the initial composition on the output of this synthesis method will be of considerable use for the establishment of reliable reproducible silica production for future industrial adoption.

Research paper thumbnail of A higher yielding route to octasilsesquioxane cages using tetrabutylammonium fluoride, Part 2: further synthetic advances, mechanistic investigations and X-ray crystal structure studies into the factors that determine cage geometry in the solid state

Journal of Organometallic Chemistry, Oct 1, 2004

Research paper thumbnail of ChemInform Abstract: AROMATISCHE REAKTIVITAET 46. MITT. DEUTUNG DES SUBSTITUENTENEFFEKTES BEI DER BASEN-KATALYSIERTEN SPALTUNG VON ARYLTRIMETHYLSILANEN UND -STANNONEN IN WASSER-DMSO-KOH

Chemischer Informationsdienst, Sep 7, 1971

ChemInform Abstract Die Kinetik der Detritiierung von 2-und 3-[T]Methyl-benzo[b]thiophen und 3-Me... more ChemInform Abstract Die Kinetik der Detritiierung von 2-und 3-[T]Methyl-benzo[b]thiophen und 3-Methyl-2-[T]methyl-benzo[b]thiophen in wasserfreier Trifluoressigsäure wird ermittelt.

Research paper thumbnail of Preparation and characterization of a type of ladder-like poly(phenyl silsesquioxane) based hybrid star-shaped copolymer of ε-caprolactone

Journal of Applied Polymer Science, May 12, 2015

ABSTRACT Combination of the organic–inorganic hybrid such as silsesquioxane with ε-caprolactone w... more ABSTRACT Combination of the organic–inorganic hybrid such as silsesquioxane with ε-caprolactone will lead to materials expected to be environmentally friendly and applicable to biomedical usages. A ladder-like poly(phenyl silsesquioxane) based hybrid star-shaped copolymer of ε-caprolactone was prepared by ring opening polymerization of ε-caprolactone catalyzed by Sn(Oct)2 with hydroxyl terminated ladder-like poly(phenyl silsesquioxane) as initiator. The copolymers were characterized by proton nuclear magnetic resonance (1H-NMR), silicon nuclear magnetic resonance (29Si-NMR), Fourier-transform infrared spectrometer (FT-IR), size exclusion chromatography (SEC), thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC) in detail. Furthermore, the enzymatic degradation property of the copolymers was also investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42335.

Research paper thumbnail of Molecular motion in cyclic siloxanes studied by 17O, 29Si, and 13C nuclear magnetic resonance spectroscopy

Journal of the Chemical Society, 1990

ABSTRACT

Research paper thumbnail of Modelling nucleophilic substitution at silicon using hypervalent silicon compounds based on urea ligands

Journal of Organometallic Chemistry, Jan 30, 2001

ABSTRACT The X-ray crystal structure of a pentacoordinate silicon compound, 3, with a urea ligand... more ABSTRACT The X-ray crystal structure of a pentacoordinate silicon compound, 3, with a urea ligand shows partial Si–O bond formation and Si–Cl cleavage. The solution NMR parameters for the related series of compounds with different leaving groups provides structural information and this can be used to model substitution at silicon. The corresponding thioureas exhibit N–Si bond formation with the silicon remaining tetracoordinate.

Research paper thumbnail of Siloxane and hydrocarbon octopus molecules with silsesquioxane cores

Journal of Materials Chemistry, 1993

... the inefficiency of the synthesis and isolation of single species. However, Aga~kar'~ ha... more ... the inefficiency of the synthesis and isolation of single species. However, Aga~kar'~ has recently revealed a reasonably high yielding synthesis of T8 hydrogen silsesquioxane. In addition to T8, the synthesis and isolation of ...

Research paper thumbnail of Aromatic reactivity. Part XXXVIII. Protodesilylation of 1,2-dihydrobenzocyclobutene, indan, and tetralin

Journal of the Chemical Society, 1969

Rates of cleavage (protodesilylation) of some trimethylsilyl derivatives of reduced benzocycloalk... more Rates of cleavage (protodesilylation) of some trimethylsilyl derivatives of reduced benzocycloalkenes and o-xylene by a mixture of 10·6M-aqueous perchloric acid and methanol (2 : 5 v/v) have been measured spectrophotometrically. Values (min.–1) of the first-order rate constants (×103) at 50·0° are as follows: 3-trimethylsilyl-o-xylene, 193; 4-trimethysilyl-o-xylene, 153; 1,2-dihydro-3-trimethylsilylbenzocyclobutene, 16·1; 1,2-dihydro-4-trimethylsilylbenzocyclobutene, 154; 4-trimethylsilylindan, 77; 5-trimethylsilylindan, 210; 5-trimethylsilyltetralin, 235; 6-trimethylsilyltetralin, 181. (Ring-opening, which complicates most studies of the behaviour of 1,2-dihydrobenzocyclobutene and its derivatives towards electrophilic reagents, does not occur under the cleavage conditions.)The main features of the results are the low reactivity of the 3-(aryl α-) and the normal reactivity of the 4-(aryl β-) position of 1,2-dihydrobenzocyclobutene in comparison with the corresponding positions of o-xylene. The aryl α-position of indan shows a somewhat lower reactivity, but the aryl β-position shows a slightly enhanced reactivity, as do both the aryl α- and β-positions of tetralin. It is suggested that strain and carbon-hydridization effects of the small rings operate jointly to determine the reactivities.Use of desilylation is suggested as a possible route to 3-substituted 1,2-dihydrobenzocyclobutenes.

Research paper thumbnail of Stereochemical Nonrigidity in a Chelated Platinum(0)-Diolefin Complex

Organometallics, Feb 1, 1994

Research paper thumbnail of Substituent effects of the groups CH2M(CH3)3(M = C to Pb) and M(CH3)3(M = Si to Pb) from proton and carbon-13 chemical shift measurements on 4-substituted styrenes

Journal of the Chemical Society, 1977

ABSTRACT

Research paper thumbnail of The mechanism of the methanolysis of N-(triakylsilyl)anilines

Journal of Organometallic Chemistry, Nov 1, 1970

The rates of methanolysis of some ArNHSiR3 compounds have been measured spectrophotometrically. T... more The rates of methanolysis of some ArNHSiR3 compounds have been measured spectrophotometrically. The reactions have been shown to be inhibited by base, and the solvolysis of XC6H4N+HSi-iPr3 compounds in methanol at 50° containing an acetic acid/sodium acetate buffer and lithium perchlorate has been shown to be subject to specific oxonium ion catalysis. The mechanism proposed for neutral and acid-catalysed alcoholysis involves rate-determining nucleophilic attact of solvent on the silicon atom in the protonated species ArN+H2SiR3. For the XC6H4NHS-i-Pr3 compounds, the effects of the substituents X correlate excellently with their Hammett σ-constants (p = −2.5).

Research paper thumbnail of The detection of various opiates and benzodiazepines by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

Rapid Communications in Mass Spectrometry, Feb 15, 2009

A technique using comprehensive two‐dimensional gas chromatography/time‐of‐flight mass spectromet... more A technique using comprehensive two‐dimensional gas chromatography/time‐of‐flight mass spectrometry (GC × GC/TOFMS) is applied to qualitative and quantitative drug testing. Human serum was ‘spiked’ with known quantities of benzodiazepines and a ‘street heroin’ mixture including some of the major metabolites and impurities. The sample components were extracted from the matrix by solid‐phase extraction (SPE). Constituents containing polar hydroxyl and/or secondary amine groups were derivatised with N‐methyl‐N‐(tert‐butyldimethyl)trifluoroacetamide (MTBSTFA) to improve the chromatographic performance. An orthogonal separation of the matrix constituents was achieved by coupling a DB‐5ms (5% phenyl) to a BPX50 (50% phenyl) GC column. The eluant was focused onto the second column by a twin‐stage cryo‐modulator. Rapid 6 s modulation times were achieved by transfer from a 30 m × 0.25 mm (length × internal diameter) to a 2 m × 0.1 mm column. TOFMS with rapid spectral acquisition (≤500 spectra/s) was employed in the mass range m/z 40–650. A clean mass spectrum was obtained for each analyte using mass spectral deconvolution software. The sensitivity and repeatability of the method were evaluated by the preparation of calibration standards for two benzodiazepines, flunitrazepam and its major metabolite 7‐aminoflunitrazepam (7‐amino‐FN), in the concentration range 5–1000 ng/mL. The limits of detection (LODs) and limits of quantitation (LOQs), calculated by repeat injections (×10) of the lowest standard, were 1.6 and 5.4 ng/mL (flunitrazepam); 2.5 and 8.5 ng/mL (7‐amino‐FN), respectively. There is scope to extend this protocol to screen a large number of drugs and metabolites stored in a library database. Copyright © 2009 John Wiley & Sons, Ltd.

Research paper thumbnail of The Structure of Silylated Amides: N-Methyl-N-Trimethylsilyltrifluoroacetamide, a Reassignment of structure

Journal of Organometallic Chemistry, Aug 1, 1979

ABSTRACT

Research paper thumbnail of Nanotechnology - New advanced hybrid polymeric nanomaterials

Research paper thumbnail of Facile Synthesis of Novel Functionalized Silsesquioxane Nanostructures Containing an Encapsulated Fluoride Anion

Organometallics, Aug 13, 2012

ABSTRACT The presence of strongly electron withdrawing groups on alkoxysilanes, EWG-(CH2)n-Si(OEt... more ABSTRACT The presence of strongly electron withdrawing groups on alkoxysilanes, EWG-(CH2)n-Si(OEt)3 (where n = 1–3 and the electron-withdrawing group EWG contains an Si–C(sp3) bond), facilitates the formation and encapsulation of the fluoride anion in a silsesquioxane cage. Such species have been studied by 19F and 29Si NMR spectroscopy and X-ray crystallography together with MALDI-TOF and ESI mass spectrometry. The EWG must not be a good leaving group. Interestingly, this strategy led only to the T8 cage and excellent yields were obtained (81–95%) even without solvent. A wide range of functionalities were used. This new route offers an opportunity to build novel nanometer-sized 3-D molecular structures with a variety of functionalities which have not been accessible in the past.

Research paper thumbnail of octakis(Isobutyl)octasilsesquioxane

Research paper thumbnail of Tetra-n-butylammonium octaphenyloctasilasesquioxane fluoride clathrate

Research paper thumbnail of octakis(4-Methoxycarbonyl)-3,3-dimethyl-n-butyl)octasilsesquioxane

Research paper thumbnail of On the non-existence of trimethylsilyl tetrafluoroborate in acetone and acetonitrile : the generation of boron trifluoride in weakly coordinating solvents

Tetrahedron Letters, 1984

ABSTRACT

Research paper thumbnail of Synthesis of optically active α,β-epoxysilanes and silylaminoalcohols

Tetrahedron Letters, 1996

ABSTRACT

Research paper thumbnail of Influence of the initial chemical conditions on the rational design of silica particles

Journal of Sol-Gel Science and Technology, Sep 24, 2018

The influence of the water content in the initial composition on the size of silica particles pro... more The influence of the water content in the initial composition on the size of silica particles produced using the Stöber process is well known. We have shown that there are three morphological regimes defined by compositional boundaries. At low water levels (below stoichiometric ratio of water:tetraethoxysilane), very high surface area and aggregated structures are formed; at high water content (>40 wt%) similar structures are also seen. Between these two boundary conditions, discrete particles are formed whose size are dictated by the water content. Within the compositional regime that enables the classical Stöber silica, the structural evolution shows a more rapid attainment of final particle size than the rate of formation of silica supporting the monomer addition hypothesis. The clearer understanding of the role of the initial composition on the output of this synthesis method will be of considerable use for the establishment of reliable reproducible silica production for future industrial adoption.

Research paper thumbnail of A higher yielding route to octasilsesquioxane cages using tetrabutylammonium fluoride, Part 2: further synthetic advances, mechanistic investigations and X-ray crystal structure studies into the factors that determine cage geometry in the solid state

Journal of Organometallic Chemistry, Oct 1, 2004