CONFORMATIONAL ISOMERISM IN A CONFORMATIONAL POLYMORPH OF 2,5-DIBENZYLIDENECYCLOPENTANONE: CRYSTALLOGRAPHIC AND QUANTUM CHEMICAL STRUCTURES

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 P 2 1 space groupwith a = 6.0983 (2) A, b = 14.9200 (7) A, c = 15.0740 (6) A, V= 1368.69 A 3 , Z = 2 as compared to orthorhombic C 222 1 space group with a = 11.803 (2) A, b = 5.698 (4) A, c = 20.872 (2) A, V= 1403.6 A 3 , Z = 4 for previously reported polymorph (I) crystallized in CHC1 3 /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. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman,serif;}