Two New Polymorphs of Meso-Chlorinated BODIPY Dyes

New polymorphs of (2-(chloro(pyrrol-2-ylidene)methyl)pyrrole)-difluoro-borane (1) and (2-(chloro(4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)methyl)pyrrole)-4-ethyl-3,5-dimethyl-1H-pyrrolato)-difluoro-borane (2) were identified using single crystal X-ray diffraction. The new polymorph of 1 crystallises in the triclinic, P-1 space group with an asymmetric unit comprising two crystallographically-independent molecules (Z′ = 2). The differences between this structure and that of the known polymorph of 1 are attributed to the formation of two distinct dimer motifs in each polymorph and the packing between these dimer units. The new polymorph structure of 2, exhibits a similar asymmetric unit to the known form, comprising 3 molecules (Zʹ = 3). The two structures differ in the orientation of the molecules within the trimeric asymmetric unit and the manner in which these trimers pack along the crystallographic [010] direction.

The triclinic polymorph of 8-chloro BODIPY exhibits an asymmetric unit with two crystallographically-independent molecules.