The present invention relates to novel donor-acceptor fluorene compounds, which can be used as for the fabrication of electroluminescent devices, and a process of preparing said novel compounds. More particularly, the present invention relates to amine donor and nitrile/ester acceptor fluorenes, fluorenones their π-conjugated systems and related compounds, processes for preparing the said compounds including oxidation of fluorenes to corresponding fluorenones and their use in preparing organic electronic devices such as organic light emitting diodes (OLEDs), photovoltaic/solar cell, Field effect transistors and other useful electroluminescent devices. The compounds are prepared by reacting 2H-pyran-2-ones in isolated or rigid conformations with cyclic ketones containing methylene carbonyl moiety in the presence of a base in an organic solvent. The present invention also relates to a new concept and approach to overcome the problem of ‘Green emission defect’ in 9-unsubstituted fluorene-based organic light emitting diodes which occurs due to the conversion of fluorenes to fluorenones that show emission mainly in green-yellow region. In the present invention we have placed donor-acceptor substituents in such a way that donor-acceptor fluorenones show emission in the blue region (instead of green-yellow region) thus improving the blue colour purity and overcoming the problem of green emission defect.