Polymorphism in 1-(4-Fluorophenyl)-3,6,6-trimethyl-2- phenyl-1,5,6,7-tetrahydro-4H-indol-4-one:  A Subtle Interplay of Weak Intermolecular Interactions

An understanding of structural features associated with polymorphism in an anti-implantation agent has been made in terms of morphology, single-crystal structure, powder X-ray diffraction, and differential scanning calorimetric measurements. Polymorph 1 ( P1 ) crystallizes from a solution in dichloromethane/hexane in monoclinic, noncentro symmetric P 2 1 (as plates), whereas the second polymorph ( P2 ) crystallizes from a solution in EtOH/acetone in tetragonal, centro symmetric P 4 2 / n (as blocks). P1 is stabilized by C−H···O and C−H···π intermolecular interactions forming molecular chains, while P2 is stabilized by C−H···O and C−H···π dimers and a not so common F···F intermolecular interaction.