(E)-3-(4-Chlorophenyl)-1-(1-naphthyl)prop-2-en-1-one

In the title compound, C19H13ClO, the benzene ring and the naphthalene system, are twisted by 12.3 (3) and 36.1 (2)°, respectively, and in opposite directions with respect to the central propenone bridge. The bond-angle pattern within the benzene ring is influence by both substituents; these influences are almost additive. In the crystal, the molecules are linked by C—H⋯O and C—H⋯Cl interactions.

SS thanks Mangalore University for the research facilitie.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FK2008).  (Dimmock et al., 1999;Satyanarayana et al., 2004). Some chalcones demonstrated the ability to block voltage-dependent potassium channels (Yarishkin et al., 2008). Chalcones are also finding application as organic nonlinear optical materials (NLO) for their SHG conversion efficiency (Sarojini et al., 2006). Chalcone derivatives are recognized material in the NLO applications because of their excellent blue light transmittance and good crystallization ability (Goto et al.,1991;Uchida et al.,1998;Indira et al., 2002). Chemically chalcones consists of open-chain flavonoids in which the two aromatic rings are joined by α,\&s-unsaturated carbonyl system. The radical quenching properties of the phenolic groups present in many chalcones have raised interest in using these compounds or chalcone rich plant extracts as drugs or food preservatives (Di Carlo et al., 1999). As a part of our efforts on the synthesis of naphthyl chalcones, this paper describes the crystal structure of a new naphthyl chalcone, (2E)-3-(4-Chlorophenyl)-1-(naphthalen-1-yl)prop-2-en-1-one (I, Scheme 1). There are 298 structures in the Cambridge Crystallographic Database (Allen, 2002: Ver. 5.30, Nov. 2008, last update Sep. 2009) that posses two aromatic moieties connected via CH=CH-CO-fragment, but only 10 of them are naphthyl chalcones, and the single one example with 1-naphthalene substituent (1-(1-Naphthalenyl)-3-(4-nitrophenyl)-2-propenone, Eswaramoorthy et al., 1994). It might be noted, that this structure apparently has errors: one of the torsion angles in the aromatic ring is as large as 5°.
The molecule of I is built of three approximately planar fragments ( Fig. 1): the phenyl ring (A, maximum deviation form the least-squares plane is 0.006 (3) Å), propenone fragment C=C-C=O (B, 0.014 (2) Å), and the naphtalene ring system (C). This last fragment however is significantly folded, even though both individual rings are almost planar, the dihedral angle between these planes is as high as 5.05 (13)°. The overall conformation of I can be described in terms of dihedral angles between these fragments: A/B 36.1 (2)°, B/C 12.3 (3)°, and A/C 25.51 (9)°. These values show that the terminal planes are twisted in opposite sense with respect to the central bridging fragment. This situation is relatively rare, the majority of chalcones found in the CDB shows the same sense of rotation with respect to the central bridge.
The bond lengths within the conjugated linear fragment suggest the large degree of localization: C-C bond length of 1.480 (4) Å, C=C of 1.329 (4)Å and C=O 1.232 (3) Å. The bond angles within the phenyl ring are influenced by both Cl and C=C-substituents, and these influences are almost additive, as suggested e.g., by Domenicano (1988). The distribution is almost symmetrical with respect to the C15···C18 line, and the values are close to those calculated by summing the effects of both substituents.
In the crystal structure there is one relatively short C-H···O potential hydrogen bond, C17-H17···O12(x,1 + y,z), that link molecules into infinite chains along y direction, and few weak C-H···O and C-H···π contacts, which can stabilize the packing otherwise determined by the van der Waals interactions and close packing requirements (Fig. 2).

Refinement
Hydrogen atoms were located geometrically and refined as a riding model; their U iso values were set at 1.2 times U eq of their carrier carbon atom. Fig. 1. Anisotropic ellipsoid representation of the compound I together with atom labelling scheme. The ellipsoids are drawn at 50% probability level, hydrogen atoms are depicted as spheres with arbitrary radii.