Influence of chlorine substituents on the aggregation behavior of chlorobenzoyl-substituted ferrocene derivates

Abstract

The influence of chlorine substituents on the molecular arrangement in the solid state of chlorinated benzoyl-ferrocene derivates with restricted molecular flexibility was investigated by crystal structure determinations and theoretical calculations. Four different chlorinated benzoyl-ferrocene derivates were crystallized from a saturated CHCl₃ solution and analyzed by X-ray diffraction. Under consideration of the structural restrictions, a comparable trend of rearrangement in the crystal organization with increasing number of chlorine atoms is observed, which is analogous to findings for chlorine-substituted benzenes. More important, the molecules arrange in layers (1 and 4) and columns (2 and 3) and in all cases with repulsively orientated CF3···CF3 substituents. In addition, Cl···Cl interactions are visible in 1 (type I) and 4 (type II). Furthermore, the crystal packing motifs were also analyzed based on ab initio quantum-chemical calculations of the intermolecular interaction energy, using the B97-D3/def2-TZVP method. According to the topology of intermolecular interaction, the crystal structures have either columnar or layered structure depending on the presence of Cl substituent in para-position of benzene ring. It was also found that Cl···Cl interactions play a secondary role in crystal organization, and the substituent effect is maybe due to polarization of the aromatic ring, which leads ultimately to an increase in the energy of stacking interactions between the aryl substituents.

Graphical Abstract

Analysis of the crystal structures of chlorine substituents on the molecular arrangement in the solid state of restricted molecular flexible chlorinated benzoyl-ferrocene derivates shows a trend of rearrangement in the crystal organization with increasing number of chlorine atoms.