Electronic absorption spectra were recorded on an Agilent Technologies model Cary 100 Series UV-visible spectrometer. Steady-state f luorescence (excitation and emission) spectra were recorded on a Horiba Jobin Yvon model FL3-22 Fluorolog spectrof luorimeter; right angle geometry was used. Microcrystalline solid samples were prepared by mildly grinding the ROR′-DADQ crystals and rubbing them on a quartz plate; the quantity of sample was adjusted to achieve an optical density between 0.1-0.2 to avoid inner-f ilter ef f ects. Quantum yield of the solid samples was determined using an integrating sphere and the PLQY calculator (Jobin Yvon, ver.