The effects of substitution on the halochromism of 2 and 3 were also elucidated (Figure and Table ). The series of 1-hydroxy compounds 2 exhibited similar absorption spectra and hyperchromic properties, independent of the substitution of electron-donating (2b) or electronwithdrawing (2c) groups at the 9 position (Figure ). In contrast, for the series of 9-hydroxy derivatives 3c, presence of an electron-withdrawing group at the 1 position leads to absorption at longer wavelengths than 3a and 3b. A bathochromic shift of 3 was observed upon the addition of DBU (Figure ). Notably, 1-cyano-9-hydroxy 3c exhibited absorption red-shifted by more than 100 nm and near-infrared fluorescence (em = 764 nm, ex =365 nm) under basic conditions. Interestingly, comparing the donor--acceptor type molecules 2c and 3c, the introduction of the CN group at the 9 position of 1-hydroxydibenzofluoranthene (2c) had little effect on the absorption and fluorescence, while the introduction of this electron-withdrawing group at the 1 position of the 9-hydroxy group (3c) resulted in a significant bathochromic shift.