Characterisation and investigation of structual relationships of 4,4'-disubstituted chalcones

Abstract

In this thesis the structural relationships of a family of fifty crystal structures of 4,4’-disubstitituted chalcones, X-C6H5-CO-C2H2-C6H5-Y, where X = CF3, Br, Cl, F, H, Me, Et, OMe and Y = Br, Cl, F, H, Me, Et, OMe are investigated by comparative study of the molecular packing in each of the structures. The members of this family contain no strong hydrogen bond donor functionalities and thus directionally more diffuse intermolecular interactions dominate in the crystal structures. The concept of supramolecular constructs (CrystEngComm., 2005, 7, 324) is used to compare this family and common zero- to three-dimensional structure fragments are identified and discussed. It is shown that five fragments of closely-packed chalcone molecules form the basic motifs for 94% of the crystal structures and that these structures can be divided into three groups based on the presence of one or more of these basic motifs.
The largest group comprises 68% of the crystal structures which contain a one-dimensional close-packed row of molecules. The majority of these structures are approximately close-packed and may be characterised by combinations of four basic two-dimensional sheet fragments based on the one-dimensional motif. The remaining two groups comprise 26% of the crystal structures and are each based on a combination of two of the five fragments. There is evidence of weak hydrogen bonding in many of the structures of these groups. Only the structures of Y = F, H, OMe substituted chalcones are found in these groups. The results of this thesis highlight the great importance that the molecular shape plays in the assembly of molecules in the solid state especially in such cases where only weak hydrogen bonds are present.

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