Joyce McMahon

Dublin City University, Dublin, L, Ireland

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Publications (4)2.26 Total impact

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    ABSTRACT: The four isomers 2,4-, (I), 2,5-, (II), 3,4-, (III), and 3,5-difluoro-N-(3-pyridyl)benzamide, (IV), all with formula C(12)H(8)F(2)N(2)O, display molecular similarity, with interplanar angles between the C(6)/C(5)N rings ranging from 2.94 (11) degrees in (IV) to 4.48 (18) degrees in (I), although the amide group is twisted from either plane by 18.0 (2)-27.3 (3) degrees. Compounds (I) and (II) are isostructural but are not isomorphous. Intermolecular N-H...O=C interactions form one-dimensional C(4) chains along [010]. The only other significant interaction is C-H...F. The pyridyl (py) N atom does not participate in hydrogen bonding; the closest H...N(py) contact is 2.71 A in (I) and 2.69 A in (II). Packing of pairs of one-dimensional chains in a herring-bone fashion occurs via pi-stacking interactions. Compounds (III) and (IV) are essentially isomorphous (their a and b unit-cell lengths differ by 9%, due mainly to 3,4-F(2) and 3,5-F(2) substitution patterns in the arene ring) and are quasi-isostructural. In (III), benzene rotational disorder is present, with the meta F atom occupying both 3- and 5-F positions with site occupancies of 0.809 (4) and 0.191 (4), respectively. The N-H...N(py) intermolecular interactions dominate as C(5) chains in tandem with C-H...N(py) interactions. C-H...O=C interactions form R(2)(2)(8) rings about inversion centres, and there are pi-pi stacks about inversion centres, all combining to form a three-dimensional network. By contrast, (IV) has no strong hydrogen bonds; the N-H...N(py) interaction is 0.3 A longer than in (III). The carbonyl O atom participates only in weak interactions and is surrounded in a square-pyramidal contact geometry with two intramolecular and three intermolecular C-H...O=C interactions. Compounds (III) and (IV) are interesting examples of two isomers with similar unit-cell parameters and gross packing but which display quite different intermolecular interactions at the primary level due to subtle packing differences at the atom/group/ring level arising from differences in the peripheral ring-substitution patterns.
    Acta Crystallographica Section C Crystal Structure Communications 08/2009; 65(Pt 7):o345-51. · 0.78 Impact Factor
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    ABSTRACT: The isomers 2,3-, (I), 2,4-, (II), and 2,5-difluoro-N-(4-pyridyl)benzamide, (III), all with formula C(12)H(8)F(2)N(2)O, all exhibit intramolecular C-H...O=C and N-H...F contacts [both with S(6) motifs]. In (I), intermolecular N-H...O=C interactions form one-dimensional chains along [010] [N...O = 3.0181 (16) A], with weaker C-H...N interactions linking the chains into sheets parallel to the [001] plane, further linked into pairs via C-H...F contacts about inversion centres; a three-dimensional herring-bone network forms via C-H...pi(py) (py is pyridyl) interactions. In (II), weak aromatic C-H...N(py) interactions form one-dimensional zigzag chains along [001]; no other interactions with H...N/O/F < 2.50 A are present, apart from long N/C-H...O=C and C-H...F contacts. In (III), N-H...N(py) interactions form one-dimensional zigzag chains [as C(6) chains] along [010] augmented by a myriad of weak C-H...pi(arene) and O=C...O=C interactions and C-H...O/N/F contacts. Compound (III) is isomorphous with the parent N-(4-pyridyl)benzamide [Noveron, Lah, Del Sesto, Arif, Miller & Stang (2002). J. Am. Chem. Soc. 124, 6613-6625] and the three 2/3/4-fluoro-N-(4-pyridyl)benzamides [Donnelly, Gallagher & Lough (2008). Acta Cryst. C64, o335-o340]. The study expands our series of fluoro(pyridyl)benzamides and augments our understanding of the competition between strong hydrogen-bond formation and weaker influences on crystal packing.
    Acta Crystallographica Section C Crystal Structure Communications 10/2008; 64(Pt 9):o493-7. · 0.78 Impact Factor
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    ABSTRACT: The title compound, C12H8F2N2O, crystallizes with two independent molecules in the asymmetric unit. The independent molecules differ slightly in conformation; the dihedral angles between the benzene and pyridine rings are 51.58 (5) and 49.97 (4)°. In the crystal structure, molecules aggregate via N-H...Npyridine interactions as hydrogen-bonded dimers with the structural motif R22(8), and these dimers are linked via C-H...O interactions to form a supramolecular chain.
    Acta Crystallographica Section E Structure Reports Online 01/2008; · 0.35 Impact Factor
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    ABSTRACT: The title compound, C(12)H(8)F(2)N(2)O, crystallizes with two independent mol-ecules in the asymmetric unit. The independent mol-ecules differ slightly in conformation; the dihedral angles between the benzene and pyridine rings are 51.58 (5) and 49.97 (4)°. In the crystal structure, mol-ecules aggregate via N-H⋯N(pyridine) inter-actions as hydrogen-bonded dimers with the structural motif R(2) (2)(8), and these dimers are linked via C-H⋯O inter-actions to form a supra-molecular chain.
    Acta Crystallographica Section E Structure Reports Online 01/2008; 64(Pt 12):o2394. · 0.35 Impact Factor