Synthesis and Photophysical Properties of N-Arylcarbazolophanes

Two carbazolophanes bearing benzene or naphthalene rings on the nitrogen atoms of carbazole were successfully synthesized by the intramolecular etherification of the precursor tetraols, and their photophysical properties were investigated in detail based on the absorption spectra, fluorescence spectra, fluorescence lifetimes, quantum yields, phosphorescence spectra, and transient absorption spectra. It was concluded that the carbazolophane bearing benzene rings forms carbazole excimer in both excited singlet and triplet states, while the carbazolophane bearing naphthalene rings forms carbazole excimer only in the excited singlet state and has a locally excited state of naphthalene in the excited triplet state. These results are reasonably explained by the relationship of excitation energies between carbazole and benzene (or naphthalene) and their arrangement such as the extent of overlap. The introduction of aromatic rings on the carbazole nitrogen atoms was found to affect the electronic and photophysical properties of carbazolophanes sensitively.