1 , 5-Bis ( 4-chlorophenyl )-3-( 2-chloro-quinolin-3-yl ) pentane-1 , 5-dione : sheets of R 4 4 ( 26 ) rings built from CÐH N and CÐH O hydrogen bonds

Grupo de InvestigacioÂn de Compuestos Heterocõ Âclicos, Departamento de Quõ Âmica, Universidad de Valle, AA 25360 Cali, Colombia, Departamento de Ciencias BaÂsicas, Universidad Nacional de Colombia Sede Palmira, Crra. 32, Chapinero võ Âa Candelaria, AA 237 Palmira-Valle, Colombia, Departamento de Quõ Âmica InorgaÂnica y OrgaÂnica, Universidad de JaeÂn, 23071 JaeÂn, Spain, Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and School of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland Correspondence e-mail: cg@st-andrews.ac.uk

Molecules of the title compound, C 26 H 18 Cl 3 NO 2 , are linked into sheets of R 4 4 (26) rings by a combination of CÐHÁ Á ÁN and CÐHÁ Á ÁO hydrogen bonds.

Comment
With the aim of developing new classes of fused heterocyclic systems, we have prepared a range of novel chalcones appropriately functionalized for use as intermediates. The reactions used to prepare such chalcones involve methyl aryl ketones and aryl or heteroaryl aldehydes. We report here the structure of the title compound, (I) (Fig. 1), obtained in low yield as a by-product in the preparation of the pyrazolylquinoline (II) via the corresponding chalcone (III), formed by the reaction between 2-chloroquinoline-3-carbaldehyde and 4-chlorophenyl methyl ketone.
The bond distances within the quinoline portion of the molecule (Table 1) show evidence for signi®cant bond ®xation; the N31ÐC32 bond is thus signi®cantly shorter than N31Ð C38A, while the C33ÐC34, C35ÐC36 and C37ÐC38 bonds are all signi®cantly shorter than the other peripheral CÐC bonds. The two independent 4-chlorobenzoylmethylene components adopt different conformations relative to the quinoline component so that the molecules have no internal symmetry and hence are chiral; however, the centrosymmetric space group Pbca accommodates equal numbers of the two enantiomorphic forms.
The molecules are linked into sheets by two hydrogen bonds, one each of the CÐHÁ Á ÁN and CÐHÁ Á ÁO types (Table 2), and the sheet formation is readily analysed in terms of two one-dimensional substructures. Quinolinyl atom C34 in the molecule at (x, y, z) acts as a hydrogen-bond donor to atom N31 in the molecule at (À 1 2 + x, y, 1 2 À z), so forming a C(5) (Bernstein et al., 1995) chain running parallel to the [100] direction and generated by the a-glide plane at z = 1 4 (Fig. 2). In addition, quinolinyl atom C37 in the molecule at (x, y, z) acts as a hydrogen-bond donor to atom O17 in the molecule at (1 À x, À 1 2 + y, 1 2 À z), so forming a C(11) chain running parallel to the [010] direction and generated by the 2 1 screw axis along ( 1 2 , y, 1 4 ) (Fig. 3).
The combination of the [100] and [010] chains generates a (001) sheet in the form of a (4,4)-net (Batten & Robson, 1998) built from a single type of R 4 4 (26) ring, lying in the domain À0.02 < z < 0.52, and generated by the glide plane and screw axes at z = 1 4 (Fig. 4). A second sheet, related to the ®rst by inversion, lies in the domain 0.48 < z < 1.02, and is generated by the glide plane and screw axes at z = 3 4 . The only direction-speci®c interaction between adjacent sheets is a rather long CÐHÁ Á ÁO contact with aryl atom C15 as the donor (Table 2) but whose HÁ Á ÁO distance is close to the van der Waals limit; this interaction is therefore probably of little or no structural signi®cance.
The molecular constitution of (I) has some resemblance to that of the thienyl compound (IV), but the supramolecular arrangement is entirely different in (IV), where the molecules are linked into cyclic centrosymmetric dimers by paired CÐ HÁ Á Á%(thienyl) hydrogen bonds (Trilleras et al., 2005).

Figure 3
Part of the crystal structure of (I), showing the formation of a hydrogenbonded C(11) chain along [010]. For the sake of clarity, H atoms not involved in the motif shown have been omitted. Atoms marked with an asterisk (*) or a hash (#) are at the symmetry positions (1 À x, À 1 2 + y, 1 2 À z) and (1 À x, 1 2 + y, 1 2 À z), respectively.

Figure 4
A stereoview of part of the crystal structure of (I), showing the formation of a (001) sheet built from R 4 4 (26) rings. For the sake of clarity, H atoms not involved in the motifs shown have been omitted.
The space group Pbca was uniquely assigned from the systematic absences. All H atoms were located from difference maps and then treated as riding atoms, with CÐH distances of 0.95 (aromatic), 0.99 (CH 2 ) and 1.00 A Ê (aliphatic CH), and with U iso (H) values of 1.2U eq (C).