9,10-Dihydroxybenzo[ℎ]quinoline (1), a 10-hydroxybenzo[ℎ]quinoline (2) derivative, was synthesized and characterized by ¹H NMR, ¹³C NMR, UV-vis and fluorescence spectra, and single-crystal X-ray diffraction. Compound 1 possesses an intramolecular six-membered-ring hydrogen bond, from which excitedstate intramolecular proton transfer (ESIPT) takes place from the phenolic proton to the pyridinic nitrogen, resulting in a proton-transfer tautomer emission of 650 nm in dichloromethane. Its molecular geometry in the ground state has also been calculated using density functional theory (DFT) at the B3LYP/6-31G^∗∗ level and compared with its crystal structure. Results show that the optimized geometry can well reproduce the crystal structure. Furthermore, both absorption and emission spectra of 1 and 2 were calculated using time-dependent DFT (TD-DFT) calculations, and were in good agreement with the experimental results.

1,6-Diaminoperylene bisimide (1) was synthesized and characterized by single-crystal X-raydiffraction. To the best of our knowledge, this is the first time that the structure of 1,6-disubstituted perylene bisimide has been reported. The crystal belongs to triclinic, space group P-1, with a = 10.3966(10), b = 15.3398(16), c = 16.8495(17) Å, α = 79.490(4)◦, β = 87.055(3)◦, γ = 79.423(3)◦, and Z = 2. Compound1 possesses two intramolecular C–H· · ·N hydrogen bonds, which generate two S(6) ring motifs. The central perylene core of 1 is twisted with dihedral angles of 19.48(2)◦ and 19.50(2)◦; this twist configuration induces the axial chirality in this family of perylene bisimide chromophores. Density functional theory (DFT) calculations also show that the core twist angles of 1,6-diaminoperylene bisimide are larger than those of 1,7-diaminoperylene bisimide, which may account for the fact that the 1,7-regioisomer has a more extended effective conjugation length than the 1,6-regioisomer.