346
H. Katagiri
Scheme 17.2 Synthesis of DAzBT and DAzTT
azulene was introduced at two places in DAzTT through reaction with thienothiophene diboronic acid bis (pinacol) ester. DAzBT and DAzTT were purified by sublimation because they are poorly soluble in many organic solvents; both compounds
are highly thermally stable.
17.3.3 Crystal Structures and Optical Properties of DAzBT
and DAzTT
Single crystals of DAzBT and DAzTT obtained by sublimation were subjected to
X-ray crystallography; both were found to be planar with herringbone-type packing
structures (Fig. 17.5). Edge-to-edge-type layered structures were also observed along
the molecular long axes. This overall structure is a typical packing pattern found
for molecules with large aspect ratios, such as pentacene and oligothiophene, as
discussed above. These molecules are closely packed, and no repulsion due to the
dipole moment of azulene was observed. DAzTT has a denser structure with more
interatomic contacts than DAzBT; packing coefficients of 73.8 and 73.1% were found
for DAzTT and DAzBT, respectively. The ionization energy (IP) of each molecule
was determined by atmospheric photoelectron spectroscopy; low values of −5.43 eV
H. Katagiri
Scheme 17.2 Synthesis of DAzBT and DAzTT
azulene was introduced at two places in DAzTT through reaction with thienothiophene diboronic acid bis (pinacol) ester. DAzBT and DAzTT were purified by sublimation because they are poorly soluble in many organic solvents; both compounds
are highly thermally stable.
17.3.3 Crystal Structures and Optical Properties of DAzBT
and DAzTT
Single crystals of DAzBT and DAzTT obtained by sublimation were subjected to
X-ray crystallography; both were found to be planar with herringbone-type packing
structures (Fig. 17.5). Edge-to-edge-type layered structures were also observed along
the molecular long axes. This overall structure is a typical packing pattern found
for molecules with large aspect ratios, such as pentacene and oligothiophene, as
discussed above. These molecules are closely packed, and no repulsion due to the
dipole moment of azulene was observed. DAzTT has a denser structure with more
interatomic contacts than DAzBT; packing coefficients of 73.8 and 73.1% were found
for DAzTT and DAzBT, respectively. The ionization energy (IP) of each molecule
was determined by atmospheric photoelectron spectroscopy; low values of −5.43 eV