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- George, Sumod, et al.
(författare)
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Crystal engineering of neutral N-arylpyrimidinones and their HCl and HNO3 adducts with a C-HO supramolecular synton : Implications for non-linear optics
- 2001
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Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 25:12, s. 1520-1527
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Tidskriftsartikel (refereegranskat)abstract
- In a previous crystallographic study of some N-arylpyrimidinones 1, we noted that: (1) C-HO hydrogen bonds connect molecules in a linear array; (2) the charge transfer axis of the chromophore is aligned with the main symmetry operator of point groups 2 or m at ca. 57°, a value that is close to the ideal angle of 54.74°; (3) the methyl and chloro derivatives are isostructural. In this paper, we report the characterisation of chloride and nitrate salt adducts of 1 by X-ray diffraction and the analysis of their packing motifs. Recurrence of the same C-HO supramolecular synthon in three neutral and five HCl and HNO3 adducts of 1 signifies the robustness of this weak hydrogen bond. The occurrence of a mirror plane m in a family of eight crystal structures (four Pnma, two P21/m, one Pbcm, and one Pmn21) is unusual because this symmetry operation is generally avoided due to close packing considerations. Ab initio calculations show that the bisected phenyl conformation present in these crystal structures is the most stable conformation of the pyrimidinone molecule. The presence of aryl and pyrimidinone chromophores in 1, the correct alignment of the aromatic ring in the crystal and the occurrence of 2D polar layers in some crystal structures are favourable factors for non-linear optical applications. However, a strategy for the crystallisation of these achiral molecules in non-centrosymmetric space groups is yet to be achieved. This crystal engineering study simplifies the challenge of complete 3D structural control into a modular 2D+1D problem
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| 4. |
- Muthuraman, Meiyappan, et al.
(författare)
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C-H···O and C-H···N Hydrogen Bond Networks in the Crystal Structures of Some 1,2-Dihydro-N-aryl-4,6-dimethylpyrimidin-2-ones
- 2000
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 152:1, s. 221-228
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Tidskriftsartikel (refereegranskat)abstract
- A set of three aryl dimethyl pyrimidinones have been studied and their crystal structures described in terms of networks of C-HO and C-HN hydrogen bonds. Two of the three molecules in this study differ in the replacement of a chloro group by a methyl group and obey the chloro-methyl exchange rule in that they have nearly identical crystal structures. However, and in contrast to other pairs of compounds so related, the chloro and methyl groups here are not merely isosteric but also form similar polarization-induced ClPh and CH3Ph contacts. These conjugated molecules may offer some scope for nonlinear optical studies.
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