STRUCTURAL STUDIES OF 2,4-DIARYL-1,3-SELENAZOLES
4.8 and 4.10 have very weak π-stacking interactions in conjunctions.
In 4.7, the ‘zigzag chain’ polymeric network (Figure 4-22) is built up by some C-
H∙∙∙N hydrogen interactions [2.934(3) to 3.111(4) Å], the C-H∙∙∙Se hydrogen interactions [3.2887(16) to 3.613(2) Å] and C-H∙∙∙Cl hydrogen interactions [3.613(2) Å]. The packing networks for 4.8 and 4.10 are very similar to each other [Figures 4- 23 and 4-26]. The C-H···N interactions [2.901(4) to 3.970(4) Å] and C-H∙∙∙Cl hydrogen interactions [2.9159(16) to 4.2234(17) Å] create a complex 3-D network in
4.8. In the case of 4.10, the packing network is formed by the C-H···N interactions [2.470(2) to 3.228(2) Å], C-H∙∙∙O hydrogen interactions [2.720(2) to 3.945(2) Å], and C-H∙∙∙Se hydrogen interactions [3.4563(4) to 3.8945(4) Å]. In 4.9, the molecules are linked by the C-H∙∙∙Se [3.2680(7) Å], C-H∙∙∙N [3.063(5) and 3.698(5) Å] and C-H∙∙∙O [2.709(4) to 3.698(5) Å] interactions in a single sheet (Figure 4-24); the intermolecular C-H∙∙∙Se [3.2144(9) and 4.3056(13) Å] interactions result in the layers in the packing network (Figure 4-25).
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Figure 4-22. 3-D packing network in the structure of 4.7 shows ‘Zigzag chain’ polymeric network built up by the C-H···N, C-H···Se and C-H···Cl hydrogen interactions.
Figure 4-23. A view of 3-D packing network in the structure of 4.8 created by the intermolecular C-H···N/Cl interactions.
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Figure 4-24. A view of 3-D packing network in the structure of 4.9 created by the intermolecular C-H···N/Se/O interactions in the same layer.
Figure 4-25. A view of 3-D packing network in the structure of 4.9 created by the intermolecular C-H···N/Se/O interactions.
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Figure 4-26. A view of 3-D packing network in the structure of 4.10 created by the intermolecular C-H···N/Se/O interactions.
4.4. Conclusion
A series of 2,4-diaryl-1,3-selenazoles have been crystallographically characterised. Ten compounds are very structurally similar though there are some differences resulting from the consequence of the different substituents. The distances between the N atom and the neighbouring C atom range from 1.285(14) to 1.410(9) Å with the C-N-C bond angles from 112.4(5) to 118.3(4)°, meanwhile, the distances between the Se atom and the neighbouring C atom range from 1.803(13) to 1.909(3) Å with the C- Se-C bond angles from 84.24(15) to 85.2(5)°. The values of multiple bond distances in the selenazole ring are between the relevant single bond distance and double bond distance. N atom and Se atom deviate slightly from the C(2)-C(4)-C(5) mean plane less than 0.022(6) Å, therefore, they are nearly flat. There are some differences in the twist angles between the mean planes of the selenazole rings and the two aryl ring substituents, except for 4.8 [42.09°] and 4.10 [37.69°], other distortions are between 1.02 and 20.38°.
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The structures of compounds 4.1–4.10 contain some intramolecular and intermolecular interactions depending on the groups connecting to the selenazole moiety. Through some comparisons with these structures, the intramolecular interactions distances, the relevant torsion angles and deviations suggest that there are some possible intramolecular interactions or weak conjugations in these structures. Obviously, the intramolecular C-H∙∙∙N interactions in 4.9 and 4.10 are very strong [2.273(4) and 2.470(2) Å], but other intramolecular interactions are weak.
Packing frameworks are directed by soft hydrogen bonding interactions, additionally, very weak π-stacking interactions are occurring in some 3-D supramolecular aggregation arrangements. These intermolecular interactions and π-stacking interactions in 4.1–4.10 play an important role in stabilizing the crossed-layer packing network in the solid state.
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