V. Jayathirtha Rao

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.

Synthesis, anticancer activity and photophysical properties of novel substituted 2-oxo-2H-chromenylpyrazolecarboxylates.

2-Oxo-2H-chromenylpyrazolecarboxylates (8a-h and 12a-zb) have been synthesized by [3 + 2] cycloaddition of 2H-chromenophenylhydrazones (7a-h and 11a-w) with diethyl/dimethylbut-2-ynedioates. Phenylchromeno[4,3-c]pyrazol-4(1H)-ones (13i-n) were prepared from corresponding phenylhydrazones (7a-h) with catalytic amount of piperidine in presence of pyridine as a solvent at 100 °C. All the synthesized compounds (8a-h, 12a-zb and 13a-n) were screened for anticancer activity against three human cancer cell lines such as prostate (DU-145), lung adenocarcinoma (A549), and cervical (HeLa) by standard MTT assay method. Further, photophysical properties (UV and fluorescence) for these compounds were discussed.

First stereoselective total synthesis and anticancer activity of new amide alkaloids of roots of pepper.

The first stereoselective total synthesis of new natural amide alkaloids 1-3 have been achieved from commercially available starting materials. Wittig olefination, Sharpless asymmetric dihydroxylation, epoxidation, a trans regioselective opening of 2,3-epoxy alcohol, Horner-Wadsworth-Emmons (HWE) olefination and amide coupling are the key steps. The amide alkaloids 1-3 are evaluated for their anticancer activity against colon (HT-29), breast (MCF-7) and lung (A-549) human cancer cell lines for the first time.

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.

Synthesis and anticancer activity of some new s-triazine derivatives

New s-triazine derivatives 13a–h were synthesized for the structure–activity relationship studies as potent anticancer agents. The prepared analogues were evaluated for their in vitro inhibitory activity against the growth of PA-1 (Ovarian cancer), A549 (Lung cancer), MCF-7 (Breast cancer), and HT-29 (Colon cancer). Tri-substituted s-triazine derivatives (13e–h) with morpholino group on s-triazine scaffold exhibited potent anticancer activities compared to di-substituted s-triazine derivatives. Compounds 13e–h also showed relatively selective PA-1 and HT-29 cancer cell inhibition over other cancer cell lines. Structure–activity relationships provided useful insights in these classes of compounds and paved the way to design novel analogues with more potency.

Facile and Selective Synthesis of Chloromethylpyridines and Chloropyridines Using Diphosgene/Triphosgene

Abstract Diphosgene and triphosgene in the presence of amines were found to be an excellent chlorinating agents with high selectivity for the preparation of chloromethylpyridines and chloropyridines from picoline‐N‐oxides and pyridine‐N‐oxides respectively. #IICT Communication No: 030808.

Metal-free organic dyes containing thiadiazole unit for dye-sensitized solar cells: a combined experimental and theoretical study

We have designed and synthesized four new metal free D–A–π–A type dyes (9–12) with variations in their acceptor/anchor groups. The four dyes carry tert-butyl substituted triphenylamine as donor, thiadiazole as acceptor and bithiophene as π-spacer. Cyanoacetic acid, rhodanine-3-acetic acid, 2-(4-methoxyphenyl)acetic acid and 2-phenylacetic acid are used as acceptor/anchor groups, respectively in the dyes 9–12. The acceptor/anchor effect on their photophysical, electrochemical and photovoltaic properties was investigated. The dyes exhibited good power conversion efficiency ranging from 1.95–4.12%. Among the four dyes, 9 showed the best photovoltaic performance: short-circuit current density (Jsc) of 8.50 mA cm−2, open-circuit voltage (Voc) of 645 mV and fill factor (FF) of 0.75, corresponding to an overall conversion efficiency of 4.12% under standard global AM 1.5 solar light conditions.

Synthesis, photochemical E (trans)-->Z (cis) isomerization and antimicrobial activity of 2-chloro-5-methylpyridine-3-olefin derivatives.

2-Chloro-5-methylpyridine-3-olefin derivatives (3a-e) have been synthesized from 2-chloro-5-methylnicotinaldehyde (1) and studied their photochemical E (trans)-->Z (cis) isomerization upon direct irradiation and triplet sensitized excitation for the first time. The triplet sensitized excitations of the compounds yielded high Z (4a-e) isomer composition, whereas the direct excitation results in less Z (4a-e) isomer composition, indicating triplet pathway is very efficient in converting the E (trans)-->Z (cis) isomer. Thus synthesized E (3a-c and 3e) and generated Z (4a-c and 4e) isomers were tested for antimicrobial activity. Antifungal activity of these pyridine derivatives are closely comparable to the standard used.

ZrCl4 catalysed solvent free synthesis of coumarins

ZrCl4 is an efficient catalyst in the Pechmann condensation of phenols with ethyl acetoacetate and propynoic acid under solvent free conditions leading to formation of coumarins in very good yields.