Effect of substituents on the electron transport properties of bay substituted perylene diimide derivatives

Electron donating substituents such as 3,4,5-trimethoxy phenyl (PDI1), thiophene (PDI2), 6-methoxy naphthyl (PDI3), 5-hexyl dithiophene (PDI4) and thioanthrenyl (PDI5) moieties incorporated at the bay region of N,N'-dodecylperylene diimide (PDI) derivatives have been synthesized and characterised. The absorption maxima of PDI1-5 showed a bathochromic shift with considerable peak broadening and merging of vibronic fine structure as compared to that of PDI. The photoinduced intramolecular charge transfer (ICT) from electron donating substituents to the perylene-acceptor has been observed from fluorescence self-quenching. The molecules are stable up to 400 degrees C and amorphous in nature. The cyclic voltammetry results revealed that the oxidation potential can be tuned by the electron donating capacity of the substituents and the dithiophene-attached perylene derivative (PDI4) showed a very low band gap of 1.57 eV. The electron transporting properties have been studied using xerographic time-of-flight method and the highest electron mobility reached up to 4.4 x 10(-4) cm(2) V-1 s(-1) at 6.4 x 10(5) V cm(-1) for 1,7-di(3,4,5-trimethoxyphenyl)perylene diimide (PDI1) under ambient conditions.