A new class of highly fluorescent 9,9'-bis-(alkyl)-2,7-diarylfluorene having electron withdrawing or electron donating groups on the 𝑝-phenyl positions were synthesized and characterized. The highly luminescent fluorene derivatives, 1-6 showed blue emission (376-416 nm), narrow FWHM (∼ 50 nm), high quantum yield ($\phi_{\text{F}} = 0.12-0.87$) and short fluorescence lifetimes, $\tau_{\text{F}} = 0.23-1.14$ ns. The HOMO levels of 9,9'-bis-(alkyl)-fluorene were tuned by the p-substituents at 2,7-phenyl group. Hammett correlation with $E_{\text{HOMO}}$ of these new molecules provides an effective tool to predict the HOMO level of similar molecules prior to the synthesis. These data indicate that they are useful as emitting materials for organic light emitting devices, OLEDs.

A series of 2,8-𝑝-diaryldibenzothiophene derivatives were synthesized and characterized. These molecules have electron withdrawing or electron donating groups at the para phenyl position, which alters the electronic properties of these derivatives. The quantum yield, fluorescence lifetime, singlet, triplet and E_HOMO energy levels of these compounds were determined by fluorescence, phosphorescence and cyclic voltammetry. A plot of Hammett constants of the para substituents vs E_HOMO revealed a linear relationship. The usefulness of these molecules in organic light emitting diodes, OLEDs is discussed vis-à-vis the energy levels and properties.

Synthesis, structure, optical absorption, emission and electroluminescence properties of a new blue emitting Al complex, namely, bis-(2-amino-8-hydroxyquinolinato), acetylacetonato Al(III) are reported. Multilayer OLED using the Al complex showed blue emission at 465 nm, maximum brightness of ∼ 425 cd/m² and maximum current efficiency of 0.16 cd/A. Another multilayer OLED using the Al complex doped with phosphorescent Ir complex showed `white’ light emission, CIE coordinate (0.41, 0.35), maximum brightness of ∼ 970 cd/m² and maximum current efficiency of 0.53 cd/A.