Heterofluorenes containing group 13 atoms such as aluminum (alumafluorene) and gallium (gallafluorene) were synthesized and characterized. The synthesized heterofluorenes had five-coordinated states in their single crystals. From UV-vis absorption measurements, the heterofluorenes presented similarly shaped spectra. Interestingly, in the emission spectra at room temperature, gallafluorene presented the phosphorescence property. At 77K, gallafluorene showed larger phosphorescence than alumafluorene did. The heavy atom effect of gallium should be responsible for the phosphorescence property of gallafluorene.