Synthesis, optical properties and self-assemblies of three novel asymmetrical perylene diimides modified with functional hydrogen bonding groups at bay positions

Three new perylene diimide derivatives PDI-NH 2 , PDI-OH and PDI-COOH modified with functional hydrogen bonding groups at bay positions by ethynyl bridges were successfully synthesized via Pd-catalyzed Sonogashira couplings. The structures were characterized by 1 H-NMR, MS, and FT-IR. The photophysical properties were studied by UV-Vis absorption and fluorescence spectroscopy, and the three PDIs showed typical pronounced aggregation in the film state. PDI-NH 2 showed "off-on" fluorescence behavior upon the addtion of trifluoroacetic acid due to the inhibition of photoinduced electron transfer between the PDI core and the phenylamine moiety. In addition, we studied the self-assembly behaviors of PDI-NH 2 , PDI-OH and PDI-COOH on the HOPG surface by using STM. PDI-NH 2 and PDI-COOH formed a dumbbell-shaped dimer with a zigzag ridge structure and a linear ridge structure, respectively. PDI-OH first formed a dumbbell-shaped dimer and furthermore six dimers are connected head to tail to form a flower-shaped hexagonal 2D porous self-assembled structures. Cyclic voltammograms (CVs) were investigated. The LUMO energy levels of PDI-NH 2 , PDI-OH and PDI-COOH are −3.89 eV and the HOMO energy levels are −5.76 eV, −5.97 eV and −6.05 eV, respectively. The highly ordered supermolecular self-assembly monolayers and outstanding photophysical-electrochemical properties endow the three novel PDIs with good potential for application in organic devices such as organic field-effect transistors, solar cells and so on. Three new perylene diimides modified with functioned hydrogen bonding groups at bay positions were successfully prepared. Their optical properties and self-assemblies on HOPG were investigated.