Abstract

A new polymorph (II) of 2,5-dibenzylidenecyclopentanone (DBCP) has been obtained by slow evaporation of ethanol solvent at room
temperature. Interestingly, two conformational isomers of the title compound with slight difference in their bond lengths, torsion angles and
dihedral angles were found within the same crystal lattice of polymorph (II). The crystal structure of polymorph (II) showed monoclinic
P21 space group with a = 6.0983 (2) Å, b = 14.9200 (7) Å, c = 15.0740 (6) Å, V= 1368.69 Å3
, Z = 2 as compared to orthorhombic C2221
space group with a = 11.803 (2) Å, b = 5.698 (4) Å, c = 20.872 (2) Å, V= 1403.6 Å3
, Z = 4 for previously reported polymorph (I)
crystallized in CHC13/MeOH solvent. The concomitant origin of polymorphism and conformational isomerism was credited to C-H…O, π-π
and C-H…π interactions resulting in intriguing supramolecular sheet-like multilayered molecular packing of polymorph (II). The results of
the complementary electronic structure calculations, performed by DFT/B3LYP method using 6-31G* basis set were found in good
agreement with the experimental results.