Kola Srinivas

Synthesis and characterization of 9,10-bis(2-phenyl-1,3,4-oxadiazole) derivatives of anthracene: Efficient n-type emitter for organic light-emitting diodes

With a general aim to make anthracene derivatives multifunctional (n-type emitter) and also study their suitability as electron transport layers for organic light emitting diodes (OLED), and with a more specific interest to understand the charge transport and packing pattern in the solid state due to the rotating side rings, we report the synthesis and characterization of six novel molecules (5–10) in which the 9 and 10 positions of anthracene have been directly substituted by phenyloxadiazole groups. We have carried out detailed studies of these molecules including photophysical, electrochemical, electroluminescent studies and solid state structure determination through crystallographic techniques. The electron affinity is very high, around 3.1–3.2 eV, and the ionization potential is around 5.9–6.0 eV, comparable to the more commonly used electron transport electroluminescent layer Alq3. The studies reveal that the new molecules being reported by us, in addition to the high thermal stability, are quite efficient in a two layer unoptimized device with the device structure ITO/α-NPD/5–10/LiF/Al and have an emission in pure green. They also show very high efficiency as electron transport layer in device structure ITO(120nm)/α-NPD(30nm)/Ir(ppy)3 doped CBP(35nm)/BCP(6nm)/5(28nm)/Al(150nm). From these studies we conclude that the anthracene derivatives also have considerable potential as multifunctional layers and as electron transport layers in OLED.

NLO Activity in some non-conjugated 3D triazine derivatives: a non-centrosymmetric crystal through conformational flexibility

Four derivatives of 2,4,6-tris(benzyloxy)-1,3,5-triazine are synthesized and detailed computational and non-linear optical investigations are carried out. Computations indicate four conformations with different energies in all the systems in the gas phase; and the individual dipole moments are also of different magnitude. HRS measurements of these molecules in solution reveal moderately large β values; structure–property relations are analyzed through computations. These molecules have one added advantage of nearly 100% optical transmission through the visible range, due to the non-conjugated structure. Molecule 1 [2,4,6-tris(benzyloxy)-1,3,5-triazine] crystallizes in a non-centrosymmetric space group by adopting the conformation with the lowest dipole moment but not the lowest energy. It also shows SHG activity in the solid state.

First hyperpolarizability of some nonconjugated donor–acceptor 3D molecules: noncentrosymmetric crystal through conformational flexibility

Four derivatives of 2,4,6-tris(benzylamino)-1,3,5-triazine are synthesized and detailed computational and nonlinear optical investigations are carried out. Computations indicate near degenerate conformations (C3 and C1 symmetry) in all systems in the gas phase; the dipole moments are also of similar magnitude in all of them except molecule 4 [2,4,6-tris(4-fluorobenzylamino)-1,3,5-triazine]. HRS measurements of these molecules in solution reveal moderately large β values; structure–property relations are analyzed through computations. These molecules have one added advantage of nearly 100% optical transmission through the visible range, due to the nonconjugated structure. Molecule 4 crystallizes in a noncentrosymmetric structure by adopting the conformation with the lower dipole moment; it also shows optical SHG in the solid state.