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

For a series of substituted dithieno[3,2-a:2 & PRIME;,3 & PRIME;-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.

Automated summary

X-ray diffraction studies were conducted on a series of substituted dithieno[3,2-a:2 & PRIME;,3 & PRIME;-c]phenazine derivatives. Depending on crystallization conditions, two or three packing polymorphs were obtained for phenazine derivatives with H, F and Cl substituents. An unusual number of symmetrically independent molecules were found among the crystalline polymorphs of the F-substituted compounds. Comparisons of calculated lattice energies revealed insignificant energy differences between the polymorphs, explaining the large number of polymorphs in this series of materials. TD-DFT calculations of the HOMO-LUMO gap for these molecules showed close correspondence to previously published electrochemical measurements.