Room temperature diazotization and coupling reaction using a DES-ethanol system: a green approach towards the synthesis of monoazo pigments.

An environmentally benign, one-pot diazotization and coupling reaction using ChCl:tartaric acid DES at room temperature is described. The bulky tartrate ion renders stability to the diazonium salt at room temperature, also evidenced by H NMR. The isolated diazonium salt is stable and active even after 192 h at room temperature.

Graphene Oxide Promoted Oxidative Bromination of Anilines and Phenols in Water.

The mildly acidic and oxidative nature of graphene oxide, with its large surface area available for catalytic activity, has been explored in aromatic nuclear bromination chemistry for the first time. The versatile catalytic activity of graphene oxide (GO) has been used to selectively and rapidly brominate anilines and phenols in water. The best results were obtained at ambient temperatures using molecular bromine in a protocol promoted by oxidative bromination catalyzed by GO; these transformations proceeded with 100% atom economy with respect to bromine and high selectivities for the tribromoanilines and -phenols.

Solvatochromic fluorescence properties of phenothiazine-based dyes involving thiazolo[4,5-b]quinoxaline and benzo[e]indole as strong acceptors.

The present work describes the photophysical properties of two newly synthesized compounds, namely (E)-10-butyl-3-(2-(thiazolo[4,5-b]quinoxalin-2-yl)vinyl)-10H-phenothiazine (PTQ) and (E)-10-butyl-3-(2-(1,1-dimethyl-1H-benzo[e]indol-2-yl)vinyl)-10H-phenothiazine (PBI). A strong intramolecular charge transfer (ICT) is observed in both dyes as indicated from absorption and emission studies on varying the solvent polarity. This can be concluded from the large Stokes shifts among these dyes as PTQ exhibits large Stokes shift with >270nm and PBI around 200nm.

m-CPBA Mediated Metal Free, Rapid Oxidation of Aliphatic Amines to Oximes.

An efficient, rapid oxidation of various aliphatic amines to oximes using m-CPBA as an oxidant in ethyl acetate is described. High conversion (100%) with >90% oxime selectivity is achieved at room temperature under catalyst-free conditions. Mild reaction conditions along with an easy work up procedure offer lower byproduct formation and high selectivity for oximes in good yield and purity.

Exciton delocalization and hot hole extraction in CdSe QDs and CdSe/ZnS type 1 core shell QDs sensitized with newly synthesized thiols.

The present work describes ultrafast thermalized and hot hole transfer processes from photo-excited CdSe quantum dots (QDs) and CdSe/ZnS core-shell QDs (CSQDs) to newly synthesized thiols. Three thiols namely 2-mercapto-N-phenylacetamide (AAT), 3-mercapto-N-phenylpropanamide (APT) and 3-mercapto-N-(4-methoxyphenyl) propanamide (ADPT) were synthesized and their interaction with both CdSe QDs and CdSe/ZnS CSQDs was monitored. Steady state absorption study suggests the exciton delocalization from CdSe QDs in the presence of the thiols.

Steric-Hindrance-Induced Regio- and Chemoselective Oxidation of Aromatic Amines.

Unusual regio- and chemoselective oxidation of aromatic amines hindered with ortho substituents (except -NH2, -NHCH3, and -OH) to the corresponding nitro compounds is described by use of nonanebis(peroxoic acid). The mechanistic investigation for selective oxidation of amines ortho-substituted with -NH2 or -OH showed the involvement of H-bonding between the ortho hydrogen of the adjacent -XH group (where X = NH, NR, or O) and an oxygen atom from the diperoxy acid. Various mono- and diamines are oxidized into corresponding mononitro derivatives in high yield and purity without employing any protection strategies.

Maleimide fused boron-fluorine complexes: synthesis, photophysical and electrochemical properties.

Novel boron fluorine complex molecules were designed and synthesized using the maleimide core moiety. Significant features such as a large Stoke shift, high quantum yield, and long range absorption and emission wavelengths were observed for these molecules. The lower LUMO level of these molecules indicates their potential application as electron transport materials.

Synthesis and spectroscopic study of highly fluorescent β-enaminone based boron complexes.

The newly synthesized 1, 1, 2-trimethyl-1H benzo[e]indoline based β-enaminone boron complexes exhibited the intense fluorescence (Fmax=522-547 nm) in solution as well as in solid state (F max=570-586 nm). These complexes exhibited large stoke shift, excellent thermal and photo stability when compared to the boron dipyrromethene (BODIPY) colorants. Optimized geometry and orbital distribution in ground states were computed by employing density functional theory (DFT).

Restriction of molecular twisting on a gold nanoparticle surface.

To understand the photophysical properties of intramolecular charge transfer (ICT) and twisted intramolecular charge transfer (TICT) states on a gold nanoparticle (Au NP) surface, we have designed and synthesized a new coumarin molecule (C3) that exists both as ICT and TICT states in its excited state in a polar environment. On a Au NP surface, an excited C3 molecule only exists as an ICT state owing to restricted molecular rotation of a diethylamino group; as a result, no conversion from the ICT to TICT state was observed. Selection of the preferential state of a molecule with dual emitting states can be helpful for selected biological applications.

Nonanebis(peroxoic acid): a stable peracid for oxidative bromination of aminoanthracene-9,10-dione.

A new protocol for the oxidative bromination of aminoanthracene-9,10-dione, which is highly deactivated towards the electrophilic substitution is investigated. The peracid, nonanebis(peroxoic acid), possesses advantages such as better stability at room temperature, it is easy to prepare and non-shock sensitiv as compared to the conventional peracids. The present protocol has a broad scope for the bromination of various substituted and unsubstituted aminoanthracene-9,10-diones.

Extensive reduction in back electron transfer in twisted intramolecular charge-transfer (TICT) coumarin-dye-sensitized TiO(2) nanoparticles/film: a femtosecond transient absorption study.

We report the synthesis, characterization, and optical and electrochemical properties of two structurally similar coumarin dyes (C1 and C2). These dyes have been deployed as sensitizers in TiO2 nanoparticles and thin films, and the effect of molecular structure on interfacial electron-transfer dynamics has been studied. Steady-state optical absorption, emission, and time-resolved emission studies on both C1 and C2, varying the polarity of the solvent and the solution pH, suggest that both photoexcited dyes exist in a locally excited (LE) state in solvents of low polarity.

Comparative material study and synthesis of 4-(4-nitrophenyl)oxazol-2-amine via sonochemical and thermal method.

The present paper deals with the synthesis of aminooxazole derivatives via thermal and ultrasonic methods using deep eutectic solvent as medium. It was observed that ultrasound-assisted method gave 90% yield in just 8min as against 3.5h required to get 69% yield by thermal method.

Ultrasound and deep eutectic solvent (DES): a novel blend of techniques for rapid and energy efficient synthesis of oxazoles.

The present work deals with the synthesis of novel oxazole compounds by using effective combination of ultrasound (US) and deep eutectic solvent (DES). The reaction was also conducted by thermal method (NUS) and the comparative studies are provided. It was observed that applying ultrasound not only improved yields and reduced reaction times but also saved more than 85% energy as shown by energy consumption calculations.

Synthesis of diphenylamine-based novel fluorescent styryl colorants by Knoevenagel condensation using a conventional method, biocatalyst, and deep eutectic solvent.

Novel Y-shaped acceptor-pi-donor-pi-acceptor-type compounds, synthesized from 4,4'-hexyliminobisbenzaldehyde as electron donors and different active methylene compounds as electron acceptors, were produced by conventional Knoevenagel condensation alone, with a deep eutectic solvent, or with a lipase biocatalyst to compare the yield and recyclability among the three methods. Yield, reaction time, reaction temperature, and recyclability were compared among the three methods. The photophysical properties and thermal stability of the products were also investigated.