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  • Title: Supramolecular sheets in (4H-chromeno[4,3-c]isoxazol-3-yl)methanol and its hydrated 8-methyl-substituted analogue at 100 K.
    Author: Rajalakshmi P, Srinivasan N, Krishnakumar RV, Razak IA, Rosli MM.
    Journal: Acta Crystallogr C; 2012 Nov; 68(Pt 11):o481-4. PubMed ID: 23124468.
    Abstract:
    The title compounds, (4H-chromeno[4,3-c]isoxazol-3-yl)methanol, C(11)H(9)NO(3), (I), and (8-methyl-4H-chromeno[4,3-c]isoxazol-3-yl)methanol monohydrate, C(12)H(11)NO(3)·H(2)O, (II), crystallize in the monoclinic space groups P2(1)/c and C2/c, respectively. The simple addition of a methyl substituent in (II) results in a change in the structure type and substantially alters the intermolecular interaction patterns, while retaining the point-group symmetry 2/m. Compound (II) crystallizes as a hydrate and the resulting hydrogen-bonding interactions involving the water molecule are the cause of differences in the hydrogen-bonded supramolecular motifs present in (I) and (II). The water molecule in (II) is disordered over two positions having very similar orientations, with occupancies of 0.571 (18) and 0.429 (18), although the pattern of hydrogen-bonding interactions for the two disordered water molecules remains essentially the same. In both compounds, the primary donor hydroxy group adopts a trans conformation with respect to the isoxazole O atom, with a torsion angle of 170.65 (8)° for (I) and 179.56 (10)° for (II), the small difference being due to differences in the hydrogen-bonding environment of the hydroxy group. In (I), molecules are linked through two independent O-H···N and C-H···O hydrogen bonds and form sheets of centrosymmetric R(4)(4)(18) and R(4)(4)(14) rings extending parallel to the (100) plane. The supramolecular motifs in (II) generate two-dimensional sheets parallel to the (100) plane through a combination of O-H···X (X = N, O) and C-H···O hydrogen bonds, leading to water-assisted noncentrosymmetric R(2)(2)(8) and R(6)(6)(20) motifs. The present work is an example of how the simple replacement of a substituent in the main molecular scaffold may transform the structure type, paving the way for a variety of supramolecular motifs and consequently altering the complexity of the intermolecular interaction patterns.
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