Ligand-controlled Regiodivergent C-H Alkenylation of Pyrazoles and its Application to the Synthesis of Indazoles.

Regioselective C4-, C5-, and di-alkenylations of pyrazoles were achieved. An electrophilic Pd catalyst generated by trifluoroacetic acid (TFA) and 4,5-diazafluoren-9-one (DAF) leads to C4-alkenylation, whereas KOAc and mono-protected amino acid (MPAA) ligand Ac-Val-OH give C5-alkenylation. A combination of palladium acetate, silver carbonate, and pivalic acid affords dialkenylation products.

Revealing Germylene Compounds to Attain Superbasicity with Sigma Donor Substituents: A Density Functional Theory Study.

Compounds of Ge are shown for the first time to function as superbases. Two B(N=PiPr ) groups attached to a germanium(II) center show a gas-phase proton affinity of 296.2 kcal mol , which is close to the range of a hyperbase as revealed by B3LYP-D3/6-31G(2d,p) level of theory.

Visible-Light-Induced Efficient Selective Oxidation of Nonactivated Alcohols over {001}-Faceted TiO with Molecular Oxygen.

In the presence of molecular oxygen, a {001}-faceted nanocrystalline anatase TiO catalyst enabled the selective oxidation of nonactivated aliphatic alcohols to the corresponding aldehydes or ketones under visible light. The reaction shows excellent conversion and selectivity towards the formation of the carbonyl products without over-oxidation to the corresponding carboxylic acids. The exceptional reactivity of the catalyst is possibly due to the absorption of visible light originating from a stronger interaction of alcohol with the {001} facet, which facilitates the modification of the band structure of TiO , thus facilitating the photogenerated hole transfer and subsequent oxidation processes.

Does the position of the electron-donating nitrogen atom in the ring system influence the efficiency of a dye-sensitized solar cell? A computational study.

We have reported a number of new metal-free organic dyes (2-6) that have cyclic asymmetric benzotripyrrole derivatives as donor groups with peripheral nitrogen atoms in the ring, fluorine and thiophene groups as π-spacers, and a cyanoacrylic acid acceptor group. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were employed to examine the influence of the position of the donor nitrogen atom and π-conjugation on solar cell performance. The calculated electron-injection driving force (ΔG inject), electron-regeneration driving force (ΔG regen), light-harvesting efficiency (LHE), dipole moment (μ normal), and number of electrons transferred (∆q) indicate that dyes 3, 4, and 6 have significantly higher efficiencies than reference dye 1, which exhibits high efficiency.

Can silicon substituted metal-free organic dyes achieve better efficiency compared to silicon free organic dyes? A computational study.

The power conversion efficiency of metal-free organic dyes in dye-sensitized solar cells (DSSCs) is now comparable to ruthenium-based polypyridyl and zinc-based porphyrin dyes. We have computationally investigated the structural, electronic and optical properties of a series of metal free organic dyes and their corresponding silicon substituted dyes. The DFT and TD-DFT calculations revealed that silicon substituted organic dyes have higher efficiency than the corresponding silicon free organic dyes.

Unprecedented iminobenzosemiquinone and iminobenzoquinone coordinated mononuclear Cu(ii) complex formation under air.

Two non-innocent 2-anilino-4,6-di-tert-butylphenol units were connected through an -ortho bridging S atom and provided the ligand . The ligand reacted with CuCl2·2H2O in the presence of Et3N under air and generated a mononuclear Cu(ii) complex (1, [CuL(S(IBQ/ISQ))Cl](0)). A single crystal X-ray diffraction analysis confirmed that in the complex one of the two 2-anilido-4,6-di-tert-butylphenol arms was present in its one-electron oxidized iminobenzosemiquinone form, while the other was in its two-electron oxidized iminobenzoquinone form.

Fluoride free synthesis of anatase TiO2 nanocrystals with exposed active {001} facets.

A novel fluoride free protocol for highly truncated anatase TiO2 nanocrystals with exposed {001} facets by preferential adsorption of CO3(2-) ions is developed. Experimental observations were corroborated by first principle quantum chemical DFT calculations. The synthesized anatase TiO2 showed improved photocatalytic activity.

New Ru(II)/Os(II)-polypyridyl complexes for coupling to TiO2 surfaces through acetylacetone functionality and studies on interfacial electron-transfer dynamics.

New Ru(ii)- and Os(ii)-polypyridyl complexes have been synthesized with pendant acetylacetone (acac) functionality for anchoring on nanoparticulate TiO2 surfaces with a goal of developing an alternate sensitizer that could be utilized for designing an efficient dye-sensitized solar cell (DSSC). Time-resolved transient absorption spectroscopic studies in the femtosecond time domain have been carried out. The charge recombination rates are observed to be very slow, compared with those for strongly coupled dye molecules having catechol as the anchoring functionality.

Superbasicity of silylene derivatives achieved via non-covalent intramolecular cation···π interactions and exploited as molecular containers for CO2.

We have reported for the first time designed silylene superbases involving intramolecular H(+)···π interaction using density functional theory (DFT) calculations. The non-covalent interactions augment the proton affinity values by 13 kcal mol−1 in the designed superbase (1) compared to the acyclic silylene, [:Si(NMe2)2]. These divalent Si(II) compounds can act as powerful neutral organic superbases in gas and solvent phases.

Conformational preference of glycinamide in solution: an answer derived from combined experimental and computational studies.

Conformational problems are often subtle but very important in controlling many intricate features in chemistry and biochemistry. We have performed the conformational analysis of glycinamide using NMR experiments and computational studies. (1)H NMR experiments suggest the prevalence of intramolecular hydrogen bonded conformation of glycinamide (2B) in acetonitrile, whereas, non-intramolecular hydrogen bonded conformation 2A is favoured in dimethylsulfoxide.

First principles studies toward the design of silylene superbases: a density functional theory study.

In this paper we have reported for the first time some designed silylene superbases using DFT calculations. These divalent Si(II) compounds can act as powerful neutral organic superbases in the gas phase and in the solvent phase. The DFT calculations performed with the B3LYP/6-311+G**//B3LYP/6-31+G* level of theory showed that one of the designed silylene derivatives :Si(N═PY3)2 [Y = -N═C(NMe2)2] (8) can fall in the range of hyperbase with gas phase proton affinity ∼310 kcal/mol.