Additive controlled packing polymorphism in a series of halogen-substituted dithieno[3,2-a:2′,3′-c]phenazine derivatives

Abstract

For a series of substituted dithieno[3,2-a:2′,3′-c]phenazine derivatives X-ray diffraction studies have been carried out. It was found that depending on crystallization conditions (solution or gas phase and additives) two or three packing polymorphs were obtained for phenazine derivatives with H, F and Cl substituents. For F-substituted compounds an unusual number of symmetrically independent molecules (six and four) were found among its crystalline polymorphs. Comparison of the calculated lattice energies revealed insignificant energy differences between the polymorphs, thus explaining the existence of the large number of polymorphs in this series of materials. TD-DFT calculations of the HOMO–LUMO gap for these molecules demonstrated close correspondence to the results of previously published electrochemical measurements.