Exploring a solvated dimer of Gefitinib: a quantitative analysis

Gefitinib or Iressa is an orally administered anilinoquinazoline used in cancer chemotherapy for the treatment of lung and breast cancer. It is reported to exist in two polymorphic forms, a stable form I and a metastable form II. Both of the forms belong to the triclinic P (1) over bar space group. In this work, we report the crystallization of Gefitinib to form a methanol solvate [ systematic name: N-(3-chloro-4-fluorophenyl)-7-methoxy-6-[3-(morpholin- 4-yl)propoxy] quinazolin-4amine methanol hemisolvate, C22H24ClFN4O3 center dot 0.5CH(3)OH] that was theoretically and experimentally investigated. The unit cell is composed of two independent Gefitinib molecules (A and B) that form a stable molecular complex with methanol in the crystal lattice. To understand the crystal lattice stabilization, a combination of techniques, namely X-ray diffraction, IR spectroscopy, thermogravimetric/differential scanning calorimetry (TG-DSC), Hirshfeld surface analysis and CLP-PIXEL methods were used. The analysis of the crystal structure of this dimer revealed a three-dimensional isostructurality with the already reported form II. The A and B molecules are connected via trifurcated C-H center dot center dot center dot O and N-H center dot center dot center dot O hydrogen bonding. In addition, the presence of the methanol molecule stabilizes the crystal structure via C-H center dot center dot center dot O, N-H center dot center dot center dot O and C-H center dot center dot center dot Cl interactions between the two monomers. The IR analysis of the dimer has shown characteristic fingerprint values when compared to the commercial form. The TG-DSC analysis of the solvated dimer is in good agreement with the patent reporting cocrystals of Gefitinib. Finally, theoretical calculations by the CLP-PIXEL method and Hirshfeld surface and two-dimensional (2D) fingerprint plot analysis were carried out in order to quantify the different intermolecular interactions and their energies in the crystal packing.