Abstract
The crystal structure of the title compound, C18H17FO4, reported here is a polymorph of the structure first reported by Patil et al. [Mol. Cryst. Liq. Cryst. Sci. Technol. Sect. A (2007), 461, 123–130]. It is a chalcone analog and consists of substituted phenyl rings bonded at the opposite ends of a propenone group, the biologically active region. The dihedral angle between the mean planes of the aromatic rings within the 4-fluorophenyl and trimethoxyphenyl groups is 28.7 (1)° compared to 20.8 (6)° in the published structure. The angles between the mean plane of the prop-2-ene-1-one group and the mean plane of aromatic rings within the 4-fluorophenyl and trimethoxyphenyl groups are 30.3 (4) and 7.4 (7)°, respectively, in contast to 10.7 (3) and 12.36° for the polymorph. While the two 3-methoxy groups are in the plane of the trimethoxy-substituted ring, the 4-methoxy group is in a synclinical [−sc = −78.1 (2)°] or anticlinical [+ac = 104.0 (4)°] position, compared to a +sc [53.0 (4)°] or −ac [−132.4 (7)°] position. While no classical hydrogen bonds are present, weak intermolecular C—H⋯π-ring interactions are observed which contribute to the stability of the crystal packing. The two polymorphs crystallize in the same space group, P21/c, but have different cell parameters for the a, b and c axes and the β angle. A comparison of the molecular geometries of both polymorphs to a geometry optimized density functional theory (DFT) calculation at the B3-LYP/6–311+G(d,p) level for each structure provides additional support to these observations.
Highlights
For a description of the Cambridge Structural Database, see: Allen (2002)
While the two 3-methoxy groups are in the plane of the trimethoxy-substituted ring, the 4-methoxy group is in a synclinical [sc = 78.1 (2) ] or anticlinical [+ac = 104.0 (4) ]
As a continuation of our work on chalcones (Jasinski et al 2009) and in view of the importance of fluoro-chalcones, this paper describes a new polymorphic form of (I), C18H17FO4, (2E)-1-(4-fluorophenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1one, first reported by Patil et al (2007)
Summary
A second polymorph of (2E)-1-(4-fluorophenyl)-3-(3,4,5-trimethoxyphenyl)prop2-en-1-one 2007); Chopra et al (2007); Fun et al (2008); Jasinski et al. (2009); Patil et al (2007); Qiu et al (2006); Teh et al (2007). For density functional theory (DFT), see: Becke (1988, 1993); Hehre et al (1986); Lee et al (1988); Schmidt & Polik (2007). For a description of the Cambridge Structural Database, see: Allen (2002). For the GAUSSIAN03 program package, see: Frisch et al (2004). B. Narayanac and H. S. Yathirajand a Department of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA, bDepartment of Chemistry, Howard University, 525 College Street NW, Washington DC 20059, USA, cDepartment of Studies in Chemistry, Mangalore University, Mangalagangotri 574 199, India, and dDepartment of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, India R factor = 0.040; wR factor = 0.126; data-to-parameter ratio = 15.2.
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