ORCID Profile
0000-0002-2884-4884
Current Organisation
University College Dublin
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Publisher: Wiley
Date: 03-2005
Publisher: American Chemical Society (ACS)
Date: 25-07-2013
DOI: 10.1021/JO401326F
Abstract: The use of an inorganic oxidant with an acetic acid/acetonitrile solvent combination has been identified as optimal for direct arene/1,2-disubstituted alkene oxidative couplings, providing an efficient route to trisubstituted alkenes. The acetonitrile cosolvent dramatically accelerates the rate of reaction, and an insoluble inorganic oxidant limits unwanted oxidation of substrates. The scope of this procedure is illustrated with arenes and alkenes containing electron-donating and -withdrawing substituents resulting in a general synthetic strategy to trisubstituted alkenes. In situ ESI-MS analysis of the reaction components has identified the key Pd intermediates in the Fujiwara-Moritani catalytic cycle.
Publisher: International Union of Crystallography (IUCr)
Date: 26-01-2007
Publisher: International Union of Crystallography (IUCr)
Date: 16-10-2018
DOI: 10.1107/S2056989018013889
Abstract: Two independent s les of the title compound, alternatively 2-chloro- N -(4-methylphenyl)propanamide, C 10 H 12 ClNO, 1 , were studied using Cu K α, 1a , and Mo K α, 1b , radiation as part of a continuous crystallization study. The molecule crystallizes with disorder in the Cl/terminal methyl positions [occupancies for the major disorder component of 0.783 (2) in 1a and and 0.768 (2) in 1b ] and exhibits N—C bond lengths of 1.3448 (19), 1.344 (2) Å, C=O bond lengths of 1.2233 (18) and 1.2245 (19) Å and an acetamide moiety C—N—C—C torsion angle of 179.00 (13), 178.97 (14) ° for 1a and 1b , respectively. In the crystal, chains along the a axis are formed via N—H...O hydrogen bonds between acetamide groups, as well as C—H...O interactions. These chains arrange themselves into parallel running stacks which display weak C—Cl...O=C halogen bonding as well as weak C—H...π interactions.
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C001109F
Abstract: An unreported product outcome from an intended Sonogashira coupling is presented. The generality of this finding has been demonstrated by screening of a range of pre-catalysts. Mechanistic studies are consistent with the tetra-aryl benzene product forming by interception of the aryl halide oxidative addition intermediate by repeated acetylene insertion.
Publisher: American Chemical Society (ACS)
Date: 16-03-2022
Publisher: Wiley
Date: 08-11-2013
Abstract: Replaceable sieving polymers are the fundamental component for high resolution nucleic acids separation in CE. The choice of polymer and its physical properties play significant roles in influencing separation performance. Recently, reversible addition fragmentation chain transfer (RAFT) polymerization has been shown to be a versatile polymerization technique capable of yielding well defined polymers previously unattainable by conventional free radical polymerization. In this study, a high molecular weight PDMA at 765 000 gmol-1 with a PDI of 1.55 was successfully synthesized with the use of chain transfer agent - 2-propionic acidyl butyl trithiocarbonate (PABTC) in a multi-step sequential RAFT polymerization approach. This study represents the first demonstration of RAFT polymerization for synthesizing polymers with the molecular weight range suitable for high resolution DNA separation in sieving electrophoresis. Adjustment of pH in the reaction was found to be crucial for the successful RAFT polymerization of high molecular weight polymer as the buffered condition minimizes the effect of hydrolysis and aminolysis commonly associated with trithiocarbonate chain transfer agents. The separation efficiency of PABTC-PDMA was found to have marginally superior separation performance compared to a commercial PDMA formulation, POP™-CAP, of similar molecular weight range.
Publisher: Elsevier BV
Date: 2010
Publisher: American Chemical Society (ACS)
Date: 05-06-2008
DOI: 10.1021/OM800122K
Publisher: Elsevier BV
Date: 02-2007
Publisher: International Union of Crystallography (IUCr)
Date: 08-12-2007
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3OB25867J
Abstract: A synthetic, structural and theoretical investigation into the solid-state, solution and gas phase structure(s) of six 2-acylmethyl-4,4-dimethyl-2-oxazolines is reported. Four of these materials, viz.α-[(4,5-dihydro-4,4-dimethyl-2-oxazolyl)methylene]benzenemethanol (3a), α-[(4,5-dihydro-4,4-dimethyl-2-oxazolyl)methylene]-(4-nitrobenzene)methanol (3b), 1-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)-3,3-dimethyl-1-buten-2-ol (3d) and (E)-1-phenyl-2-((3aR)-3,3a,8,8a-tetrahydro-2H-indeno[1,2-d]oxazol-2-ylidene)ethanone (3f) have been characterised in the solid-state by single crystal X-ray diffraction studies. These data represent the first solid-state structural studies of this class of compounds and details the first synthesis and full characterisation of chiral derivative 3f. All four of these materials are shown to exist in the solid phase in the enamine tautomeric form (e.g., 3a is best described as 2-[4,4-dimethyl-2-oxazolidinylidene]-1-phenylethanone) and it is suggested (NMR, IR) that this isomeric form is likely also retained in solution (e.g., CDCl3) as the more stable isomer. An investigation of the relative gas phase stabilities of the three possible (i.e., the (Z)-enol, keto and enamine) isomers of all five compounds by DFT at the B3LYP/6-311G(d) level of theory confirms the latter as the most stable form. The energy differences between the enamine and keto tautomers have been calculated to be the lowest for derivative 3d. These results are compared and contrasted with the previously reported NMR studies of such compounds which have identified the keto form as being a minor (albeit solution) tautomer. Equilibrium solution tautomer distributions for 3d are found to be solvent dependent. The protonated form of 3a, isolated as the HSO4(-) salt (i.e.4a), has been further characterised in the solid state by single crystal X-ray diffraction. These data represent the first ex le of a protonated oxazoline to be structurally elucidated and confirms that upon protonation, the keto (oxazoline) tautomer is the energetically favoured form in the solid-state. This observation is further supported by DFT studies for the gas phase protonated forms of such materials. Further DFT (B3LYP/6-311G(d)) calculations employing the SM8 or SMD solvation models were then applied to address the observed solution isomeric distribution for 3d these results corroborate the gas phase theoretical treatment and also yield values that predict the higher solution stability of the enamine form as observed, although they fail to account for the existence of the keto form as a minor solution state tautomer. To access the availability of an enol-form, via hypothetical de-protonation to the enolate, compound 3a was treated with hydrated Cu(NO3)2 in EtOH solution. The resulting isolated green-coloured product (5), the first metal derivative of this entire class of ligands, is best described (IR, X-ray diffraction) as a coordinated enolate complex, i.e., Cu(3a-H)2. Complex 5 crystallizes in the P21/c space group with four molecules in the unit cell. The coordination geometry around the formal Cu(2+) metal centre is determined to be highly distorted square planar in nature (τ4 = 0.442). TD-DFT is used to give a reasonable explanation for the intensity of the absorbance band observed in the visible region for solutions of 5. These latter experiments strongly suggest that the title class of compounds may have considerable potential as ligands in coordination chemistry and/or metal-mediated catalysis.
Publisher: International Union of Crystallography (IUCr)
Date: 09-01-2014
DOI: 10.1107/S2053229614000084
Abstract: The structural chemistry of the title compound, [Pd(C 32 H 22 N 3 ) 2 ], at 173 K is described. The compound is comprised of two deprotonated (3,5-diphenyl-1 H -pyrrol-2-yl)(3,5-diphenylpyrrol-2-ylidene)amine ligands coordinated to a central Pd II cation, which lies on an inversion centre and has distorted square-planar geometry. The Pd—N bond lengths range from 2.008 (4) to 2.014 (4) Å and the bite angle is 84.16 (14)°. The chelate plane makes a dihedral angle of 45.3 (2)° with respect to the central PdN 4 plane, giving a stepped conformation to the molecule. The complex displays simple intramolecular C—H...N hydrogen bonds, while the unit cell consists of discrete monomeric Pd(C 32 H 22 N 3 ) 2 units which display intermolecular C—H...π interactions and limited intra- and intermolecular π–π stacking.
Publisher: Elsevier BV
Date: 02-2009
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/CH11095
Abstract: Synchrotron data have been used to determine the structures of the yellow polymorph of dichlorido(2,2′-bipyridine)platinum(ii) (1), and diiodido(2,2′-bipyridine)palladium(ii) (2), allowing a detailed comparison of the crystal chemistry of [MX2(bipy)] (M = Pd, Pt X = Cl, Br, I), which exhibit polymorphism involving nine structures distributed over five space groups. Complex 1 crystallizes in space group Pbca (a = 18.2540(7), b = 15.6970(7), c = 7.3560(6) Å), and 2 in space group C2/c (a = 17.149(1), b = 9.8050(8), c = 7.548(1) Å, β = 110.72(1) °).
Publisher: Royal Society of Chemistry (RSC)
Date: 2008
DOI: 10.1039/B801951G
Abstract: The treatment of cold ( approximately 3 degrees C) methanolic solutions of Li(2)PdCl(4) with two equivalents of 2-phenyl-2-oxazoline (Phox) results in the isolation of [PdCl(2)(Phox)(2)] (3). This complex undergoes remarkably slow isomerisation (CHCl(3)-d) at room temperature to a corresponding thermodynamic form. In addition to a theoretical treatment (DFT), the isomerisation behaviour has been analysed both kinetically and thermodynamically. These investigations lead to the conclusion that the initially formed (i.e. kinetic) isomer of 3 is the cis-form which undergoes conversion to the corresponding thermodynamic trans-form via a dissociative (D) mechanism involving loss of a Phox ligand. The activation parameters DeltaS(double dagger) and DeltaH(double dagger) are found to be +304 (+/-3) J K(-1) mol(-1) and +176 (+/-1) kJ mol(-1), respectively and indicate a high barrier to Pd-N bond cleavage under these conditions. The thermodynamic parameters show the expected endothermic nature of this process (+140 +/- 17 kJ mol(-1)) and a slight positive overall entropy (DeltaS degrees = +17 +/- 2 J K(-1) mol(-1)) this latter parameter is presumably due to the formation of the lower dipole moment trans-product when compared to the cis-isomer. Calculated (DFT) values of DeltaG(double dagger) and DeltaH(double dagger) are in excellent agreement to those found experimentally. Further theoretical investigation suggests that two 14-electron three-coordinate T-shaped transition states (i.e., [PdCl(2)(Phox)](double dagger)) are involved the form pre-disposed to yield the thermodynamic trans-product following re-attachment of the released oxazoline is found to be energetically favoured. The analogous alkyloxazoline system [PdCl(2)(Meox)(2)] (4: Meox = 2-methyl-2-oxazoline) has likewise been investigated. This material gives no indication of cis-trans isomerisation behaviour in solution (NMR) and is shown to exist (X-ray) in the trans-form in the solid-state (as do previously reported crystalline s les of 3). A DFT study of 4 reveals similar values of DeltaS(double dagger) and DeltaH(double dagger) if a D type mechanism were operating to rapidly convert cis- to trans-4. However, a significantly higher thermodynamic stability of the trans-isomer relative to the cis-form is revealed versus similar calculations of the Phox derivative 3. This suggests the possibility that (i) reactions of Meox with Li(2)PdCl(4) may lead directly to the trans-form of [PdCl(2)(Meox)(2)] or alternatively (ii) that alkyloxazoline complexes such as 4 may have a different, and presumably much more rapid, mechanism for isomerisation. The results are placed into the context that isomerisation behaviour, or lack thereof, could play a key preliminary role in later substrate modification. This is due to the fact that [PdX(2)(oxazoline)(2)] compounds are well-known (pre-)catalysts for C-C bond forming chemistry.
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/CH10006
Abstract: Structural analogues of the phytotoxic thaxtomin natural products have been synthesized by building upon a piperazinedione core and from l-phenylalanine. The compounds were evaluated for their phytotoxic activity against Arabidopsis thaliana seedlings and some of the key features for activity have been identified.
Publisher: Elsevier BV
Date: 04-2011
Publisher: Wiley
Date: 19-10-2017
Publisher: Elsevier BV
Date: 02-2020
Publisher: American Chemical Society (ACS)
Date: 08-09-2017
Publisher: Elsevier BV
Date: 10-2011
Publisher: MDPI AG
Date: 31-10-2011
DOI: 10.3390/CRYST1040229
Publisher: American Chemical Society (ACS)
Date: 04-05-2010
DOI: 10.1021/AC100417H
Abstract: The present study describes a preparative gas chromatographic (GC) approach employed to study a series of products arising from reaction of phenylacetylene with para-substituted aryl-iodides under Sonogashira catalysis conditions. GC analysis resolves the isomers from each reaction however, it cannot provide structural details (their MS data are virtually identical). Since classical liquid chromatography cannot resolve the isomers, preparative-scale GC is the only practical approach to provide further spectroscopic characterization of the isomers. The products are well separated by GC so a single thick-film capillary column is adequate for this case, with operation up to approximately +300 degrees C. By collection of 50+ repeat injections, sufficient material could be isolated for (1)H NMR spectral analysis of the isomers, and for one isomer (isomer I) of a number of analogous related catalytic reaction mixtures, X-ray crystal structure determination enabled complete structural elucidation (absolute configuration) of the substitution pattern of the structure of this isomer. This confirmed isomer I to be the 2-para-aryl-substituted 1,3,5-triphenylbenzene product in all cases. (1)H NMR spectra of isomer I products generally had similar patterns but differed markedly from the second major isomer product (isomer II).
Publisher: Elsevier BV
Date: 02-2021
Publisher: International Union of Crystallography (IUCr)
Date: 10-01-2007
Publisher: Wiley
Date: 25-03-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0DT01266A
Abstract: A synthetic and structural (X-ray) investigation into the bonding modes of benzoxazole (box) and 2-methylbenzoxazole (Mebox) ligands with halide precursors of Zn and Pd has been undertaken to clarify earlier discrepancies concerning the nature of the bonding mode(s) of the two azoles. In four structurally characterised ex les, all contain the title ligands in a κ(1)N bonding motif. Calculations at the density functional level (DFT) of theory (B3LYP) confirm the ground state stability of this class of coordination for several hypothetical Pd and Zn (gas phase) compounds. The attempt to obtain suitable crystalline material of PdCl(2)(box)(2) (i.e., 5) leads to substantial complex degradation. One minor product of this process has been identified (X-ray) as the diarylformamidinato complex C(26)H(22)N(4)O(4)Pd, presumably formed via a complex combination of the decomposition products of both free box and 5.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2DT31086D
Abstract: Synthetic routes to methyl(aryl)alkynylpalladium(IV) motifs are presented, together with studies of selectivity in carbon-carbon coupling by reductive elimination from Pd(IV) centres. The iodonium reagents IPh(C≡CR)(OTf) (R = SiMe(3), Bu(t), OTf = O(3)SCF(3)) oxidise Pd(II)Me(p-Tol)(L(2)) (1-3) [L(2) = 1,2-bis(dimethylphosphino)ethane (dmpe) (1), 2,2'-bipyridine (bpy) (2), 1,10-phenanthroline (phen) (3)] in acetone-d(6) or toluene-d(9) at -80 °C to form complexes Pd(IV)(OTf)Me(p-Tol)(C≡CR)(L(2)) [R = SiMe(3), L(2) = dmpe (4), bpy (5), phen (6) R = Bu(t), L(2) = dmpe (7), bpy (8), phen (9)] which reductively eliminate predominantly (>90%) p-Tol-C≡CR above ~-50 °C. NMR spectra show that isomeric mixtures are present for the Pd(IV) complexes: three for dmpe complexes (4, 7), and two for bpy and phen complexes (5, 6, 8, 9), with reversible reduction in the number of isomers to two occurring between -80 °C and -60 °C observed for the dmpe complex 4 in toluene-d(8). Kinetic data for reductive elimination from Pd(IV)(OTf)Me(p-Tol)(C≡CSiMe(3))(dmpe) (4) yield similar activation parameters in acetone-d(6) (66 ± 2 kJ mol(-1), ΔH(‡) 64 ± 2 kJ mol(-1), ΔS(‡)-67 ± 2 J K(-1) mol(-1)) and toluene-d(8) (E(a) 68 ± 3 kJ mol(-1), ΔH(‡) 66 ± 3 kJ mol(-1), ΔS(‡)-74 ± 3 J K(-1) mol(-1)). The reaction rate in acetone-d(6) is unaffected by addition of sodium triflate, indicative of reductive elimination without prior dissociation of triflate. DFT computational studies at the B97-D level show that the energy difference between the three isomers of 4 is small (12.6 kJ mol(-1)), and is similar to the energy difference encompassing the six potential transition state structures from these isomers leading to three feasible C-C coupling products (13.0 kJ mol(-1)). The calculations are supportive of reductive elimination occurring directly from two of the three NMR observed isomers of 4, involving lower activation energies to form p-TolC≡CSiMe(3) and earlier transition states than for other products, and involving coupling of carbon atoms with higher s character of σ-bonds (sp(2) for p-Tol, sp for C≡C-SiMe(3)) to form the product with the strongest C-C bond energy of the potential coupling products. Reductive elimination occurs predominantly from the isomer with Me(3)SiC≡C trans to OTf. Crystal structure analyses are presented for Pd(II)Me(p-Tol)(dmpe) (1), Pd(II)Me(p-Tol)(bpy) (2), and the acetonyl complex Pd(II)Me(CH(2)COMe)(bpy) (11).
Publisher: Wiley
Date: 04-12-2019
DOI: 10.1002/AIC.16466
Publisher: Wiley
Date: 26-08-2021
DOI: 10.1002/AIC.17377
Abstract: A bubble column was investigated as a method to achieve a desired and controllable rate of evaporation of a pharmaceutical solution. Applying a thermodynamic model to predict the rate of evaporation, all predicted values were observed to have accuracies within the bounds of instrumentation errors ( % absolute). The developed model accounted for the measured effect of reduced vapor pressure, caused by the dissolved solids as a function of their concentration. A general method to obtain accurate measurement of this effect is introduced and applied, improving the accuracy of model predictions. Consistent and repeatable evaporation rates ranging from 0.7 to 6.9 g/min were achieved experimentally, and errors between predicted rates and observed ranged from 0.219% to 4.19% absolute. This demonstrates a controllable and flexible method for the evaporation of process streams which can be compared to harsher conventional methods such as boiling. The column was configured in a continuous mode and coupled to a downstream crystallizer (MSMPR). Using the column as a controllable concentrator, the concentration of a dilute feed stream of paracetamol in methanol was increased in a single equilibrium stage. The column demonstrated the ability to concentrate the solution in flow by 179%, delivering a flow of 2 ml/min of concentrated liquor to the MSMPR. The MSMPR achieved steady‐state of control, measured by offline dissolved concentration analysis and particle count by FBRM in situ, highlighting the applicablity of the column to perform reliably in a continuous tandem.
Publisher: American Chemical Society (ACS)
Date: 07-05-2009
DOI: 10.1021/JA902799U
Abstract: A study of the reaction of PtMe(2)(bipy) with IPh(C[triple bond]CSiMe(3))(OTf) at low temperature in acetone, leading to detection of the Pt-Pt-bonded cation [Pt(2)Me(4)(C[triple bond]CSiMe(3))(bipy)(2)](+), an intermediate in the oxidation of Pt(II) to Pt(IV), is reported. The cation is assessed as Pt(III)-Pt(III) Pt(IV)-Pt(II), and at the other extreme may be regarded as a cationic alkynylplatinum(IV) center, "[Pt(IV)Me(2)(C[triple bond]CSiMe(3))(bipy)](+)", stabilized by "Pt(II)Me(2)(bipy)" as a donor ligand. The detection and isolation of the [Pt(2)Me(4)(C[triple bond]CSiMe(3))(bipy)(2)](+) cation provides a number of insights into the mechanisms of oxidation reactions.
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier BV
Date: 09-2009
Publisher: American Chemical Society (ACS)
Date: 13-04-2022
Start Date: 2022
End Date: 2026
Funder: Science Foundation Ireland
View Funded ActivityStart Date: 2020
End Date: 2021
Funder: Enterprise Ireland
View Funded ActivityStart Date: 2011
End Date: 2013
Funder: Irish Research Council
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