Optimized structures and photophysical properties of mer- and fac-Alq(3) have been generated by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) Investigating the substitution effect in the Alq(3) derivatives the role of the electron-donating (CH(3)- and NH(2)-) and electron-withdrawing (F- CN- NO(2)- and phenyl-) groups with 2- to 7-substitution have been analyzed According to the calculation results the 4- and 5- substituted Alq(3) exhibit an apparent spectral shift relative to the non-substituted Alq(3) The HOMO LUMO E(g) (the energy gap between LUMO and HOMO) lambda(max)(abs) (maximum absorption wavelength) and f (the relative oscillator strength) of mer-Alq(3) with the 4- or 5-phenyl substitution on the quinoline ligand in the ground electronic state were calculated by using the DFT/B3LYP/6-31G(d) and TD-DFT methods 5-phenyl substituted mer-Alq(3) with an electron-donating substituent showed an increase in the pi-delocalization as compared to the 4-phenyl substituted mer-Alq(3) derivatives Similarly 4-phenyl substituted mer-Alq(3) with electron-withdrawing substituents also exhibits increased pi-delocalization in the pyridine ring as compared to the non-substituted Alq(3) Replacing the CH group at the 4 5 and 4 5 positions of the quinoline ligand of mer-Alq(3) with the aza group (nitrogen atom) gives three Alq(3) analogous AlX Al(NQ)(3) and Al(NX)(3) the calculated energy gap E(g) of these derivatives decreases in the order Al(NQ)(3) > Al(NX)(3) > AX(3) Four quinoline with group III metals Mq(3) complexes were investigated for the photophysical properties the calculated energy gap E(g) decreases in the order Tlq(3) > Inq(3) Gaq(3) > Alq(3) The photophysical properties of 4-hydroxy-8-methyl-1 5-naphthyridine (mND) chelated with group III metals (MmND(3) complexes) were investigated also their calculated E(g) have the opposite order as those of Mq3 complexes (C) 2010 Elsevier B V All rights reserved
