Crystal structures of tetrakis(4,4 '-(2,2-diphenylvinyl)-1,1-biphenyl)methane: Transmission electron microscopy and X-ray diffraction

The crystal structures of tiny crystallites (micron to submicron in size) o f tetrakis(4,4 '-(2,2-diphenylvinyl)-1,1 ' -biphenyl)methane (C(DPVBi)4) ha ve been investigated by using a combination of transmission electron micros copy (TEM) and X-ray powder diffraction techniques. The crystal structure o f as-synthesized C(DPVBi)4 is hexagonal. The lattice parameters are a = 2.0 68 nm and c = 2.194 nm with possible space group P6. After C(DPVBi)(4) was annealed up to 280 degreesC, the crystal structure converted to a different hexagonal structure with lattice parameters: a = 2.102 nm and c = 3.370 nm . The possible space group is P6/m. The two hexagonal structures correspond to different packing of the individual molecules, which may result in diff erent bulk optical and electronic properties.