Investigation on Photoluminescence Behaviour of 2 , 3-Diphenylquinoxalin-6-Vinyl Benzaldehyde

been successfully incorporated in small molecules and polymers for use as electron-transport materials in multilayer OLEDs based on PPV.[10-13] Furthermore, quinoxaline possess an excellent π-deficient aromatic heterocycle, capable as electron withdrawing portion in push-pull structures for Intermolecular Charge Transfer (ICT) such important ICT along the backbone of the molecule can induce luminescence properties.[14]


Introduction
A polymer that can be used as light-emission material must have two basic characteristics: electrical conductivity (semi conductive polymer) and high Photoluminescence (PL) efficiency.Electroluminescence (EL), an electrically driven radioactive emission process, is a phenomenon that exists in a wide range of conventional semiconductors, and organic EL was first reported and extensively studied during 1960s [1,2].Electroluminescence (EL) from OLEDs arises from the radioactive decay of excitations generated by the recombination of electrons and holes injected from two opposite electrodes into the emissive polymeric layer.Balanced rates of injection and transport of both electrons and holes are essential to achieving high External Quantum Efficiency (EQE) in an OLED.However, most emissive conjugated polymers such as PPVs have much higher hole mobility than electron mobility and low electron affinities, causing an imbalance in charge injection and transport results in poor EQEs from singlelayer OLEDs.[3][4][5][6][7][8][9] Quinoxaline is a useful n-type building block with high electron affinity and good thermal stability.It has

Investigation on Photoluminescence Behaviour of 2, 3-Diphenylquinoxalin-6-Vinyl Benzaldehyde
Copyright: © 2017 Guhanathan, et al. signal at 4.7δ confirmed the bromomethylation occurred in the methyl group of quinoxaline derivatives. 1 H NMR spectra of phosphonium ylide compound justifies the signal shifted from 4.7 δ to 2.7 δ (ppm).The aromatic ring protons signal was appeared at 7.2-7.9δ.The signals at 25.60 δ have been noticed in 31 P NMR for the presence of phosphorous in the ylide compound.
Similarly, FTIR spectra of VB-QUI the carbonyl (aldehyde) stretching band have identified near 1689.09cm -1 . 1 H NMR spectra of VB-QUI shows that 7.2-7.9δ and 8.1-9.9δ for quinoxaline ring protons and phenylene proton respectively.The vinylene proton and aldehyde proton have appeared at 6.9δ, and 10.0 δ.The λ max was observed from UV spectrum at 250nm indicated π-π* transition and 348nm suggested for n-π* transition in VB-QUI.The MASS spectrum of 2, 3-diphenylquinoxalin-6vinyl benzaldehyde clearly pointed out that the molecular ion peak identical to the theoretical value of 413.2.

Photo luminescent properties
The uv-vis absorption and Photoluminescence spectra of the VB-QUI compound in the ethanol solution have been taken to know about the luminescence behavior of VB-QUI.The uv-vis absorption spectra of the solution exhibited the band around 200-250nm may be due to the π-π* electronic transition associated with the π-conjugation in the compound.In the PL spectra excitation at 348nm exhibits a bluish-green emission approximately around 454nm.

Conclusions
The vinyl benzaldehyde capped quinoxaline derivative was synthesised through Wittig reaction using Phosphonium salt and terephthaldehyde.The resulting compound was characterised by FTIR, 1 H, 13 C, 31 P NMR.Photo luminescent property of the synthesized vinyl benzaldehyde capped quinoxaline derivative was investigated using UV-Vis and fluorescent spectrometer.The VB-QUI compound found to have the photoluminescence with bluish-green emission at 454nm.

Experimental Materials
All the chemicals were obtained from Avra chemicals, Hyderabad, India and were used as supplied.Solvents used were purified and dried according to the standard procedure.

Characterization Methods
The UV-Visible spectra were recorded on an Alpha-Bruker UV spectrophotometer equipped in the range between 200-800nm.Room temperature FTIR spectra were recorded as KBr pellet with an Alpha-Bruker FTIR spectrophotometer in the range of 4000-400cm -1 .Nuclear magnetic resonance spectra with different core viz., 1 H NMR, 13 C NMR and 31 P NMR were recorded in either DMSO-d 6 or CDCl 3 on Bruker ADVANCE III 500mHz spectrometer.
The fluorescence spectra of the synthesised compound in ethanol were recorded on fluorescence spectrophotometer, FP-8500, JASCO.Mass spectroscopy was recorded on ES-FIGIEAN ionization mass spectrometer.

Synthesis of 6-methyl-2,3-diphenylquinoxaline
The 2mmol of benzil was dissolved in 3ml of methanol and was made homogeneous by vigorous stirring at room temperature.To this 2mmol of 4-methylbenzene-1, 2-diamine was added in the form of powder.The progress of the reaction was monitored by TLC.The solvent methanol was evaporated under reduced pressure the solid product thus formed was recrystallized from