Three closely related 1-(naphthalen-2-yl) prop-2-en-1-ones: pseudosymmetry, disorder and supra-moleular assembly mediated by C-H•••π and C-Br•••π interactions

It has been observed that when electron-rich naphthyl rings are present in chalcones they can participate in pi-pi stacking inter-actions, and this can play an important role in orientating inhibitors within the active sites of enzymes, while chalcones containing heterocyclic substituents additionally exhibit fungistatic and fungicidal properties. With these considerations in mind, three new chalcones containing 2-naphthyl substituents were prepared. 3-(4-Fluoro-phen-yl)-1-(naphthalen-2-yl)prop-2-en-1-one, C19H13FO, (I), crystallizes with Z' = 2 in the space group P (1) over bar and the four molecules in the unit cell adopt an arrangement which resembles that in the space group P2(1)/a. Although 3-(4-bromo-phen-yl)-1-(naphthalen-2-yl)prop-2-en-1-one, C19H13BrO, (II), with Z' = 1, is not iso-struc-tural with (I), the mol-ecules of (I) and (II) adopt very similar conformations. In 1-(naphthalen-2-yl)-3-(thio-phen-2-yl)prop-2-en-1-one, C17H12OS, (III), the thio-phene unit is disordered over two sets of atomic sites, with occupancies of 0.780 (3) and 0.220 (3), which are related by a near 180 rotation of the thio-phene unit about its exocyclic C-C bond. The mol-ecules of compound (I) are linked by three independent C-H pi(arene) hydrogen bonds to form centrosymmetric octa-molecular aggregates, whereas the mol-ecules of compound (II) are linked into mol-ecular ladders by a combination of C-H pi(arene) and C-C-Br pi(arene) inter-actions, and those of compound (III) are linked into centrosymmetric dimers by C-H pi(thio-phene) inter-actions.