Simple molecular structures capable of emitting over the entire visible range are still a challenge. Planar molecular structures have the drawback of fluorescence quenching in the solid state thus limiting their application fields. Combining long range excimer/exciplex emissions with a compound emission have been used to get white light. In this work, a series of new coumarin derivatives having a planar structure have been synthesized and characterized. The effects of systematic variation in

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... yl chain functionalization providing morphological variations that permit interesting solid state emitting properties have been discussed simultaneously with electrochemical behavior and OLED (organic light emitting diode) device applications. Carbon chains containing 0-16 carbon atoms have been studied in order to conclude the results that systematic changes in alkyl group substitution can be utilized as a tool to tune the emitting color of these planar coumarins. Alkyl chains were introduced by O-acylation and O-benzoylation reaction on the hydroxyl group of parent coumarin 5. Thus the present strategy is also helpful in establishing a template to control the unproductive interchromophore electronic couplings. Solid state fluorescence properties support the crystal studies. Theoretical studies are also in agreement with experimental data. Electroluminescence of Device 2 with a turn on voltage (V on ) around 5-6 V having s-CBP doped with 1% of 8 having alkyl substitution of 2-carbons is found to exhibit white emission with CIE co-ordinates of (0.29, 0.34) which is close to white emission while the alkyl substitution of 14-carbons (compound 17) in Device 7 (V on ¼ 7 V) exhibited green emission. Thus a strategy helpful to tune the electroluminescence has been discussed.