Synthesis, crystal structure and Hirshfeld surface analysis of the orthorhombic polymorph of 4-bromo-N-(4-bromobenzylidene)aniline

The crystal structure of the title compound, C13H9Br2N [systematic name: (E)N,1-bis(4-bromophenyl)methanimine], is a second polymorph (Form II) crystallizing in the orthorhombic space group Pccn. The first polymorph (Form I) crystallizes in the monoclinic space group P21/c [Bernstein & Izak (1975). J. Cryst. Mol. Struct. 5, 257-266; Marin et al. (2013). J. Mol. Struct. 1049, 377-385]. The molecule is disordered about an inversion center situated in the middle of the C N bond, similar to the situation in the monoclinic polymorph: the C N bond length is 1.243 (7) A degrees. In the crystal, molecules stack along the b-axis direction and are linked by C-H center dot center dot center dot pi interactions. The interatomic contacts in the crystal for both polymorphs were studied by Hirshfeld surface analysis and have notable differences. The solid-state fluorescence spectrum of Form II shows an emission peak at ca 469 nm. The two-photon absorption coefficient measured from the open aperture Z-scan technique is 1.3 x 10(-1)1 m W-1, hence, Form II shows optical limiting behaviour.

Automated summary

The crystal structure of the compound C13H9Br2N has been determined. It exists in two polymorphs, with Form II crystallizing in the orthorhombic space group Pccn and Form I crystallizing in the monoclinic space group P21/c. The molecules are disordered about an inversion center and show stacking along the b-axis in the crystal. Form II exhibits fluorescence and optical limiting behavior.