Highly selective synthesis of diphenyl methane via liquid phase benzylation of benzene over cobalt doped zinc nanoferrite catalysts at mild conditions

Liquid phase benzylation of benzene with benzyl chloride was investigated over different compositions of cobalt zinc ferrite (Co_xZn_1-xFe₂O_4, x-0.0, 0.25, 0.5, 0.75, 1.0) nano composites, synthesized by sol–gel method. The un-substituted cobalt ferrite catalyst exhibited excellent activity among the series effecting complete conversion of benzyl chloride in 60?min at 90?°C with 100% selectivity for diphenyl methane. The effect of various reaction parameters on the reaction was studied. Higher benzylation activity of cobalt ferrite nanocomposite is attributed to the presence of higher quantities of moderately acidic sites and a good correlation was observed between surface acidity and benzylation activity of catalysts. The catalysts are reusable without any significant structural change as indicated by X-ray Diffraction (XRD) and Atomic Absorption Spectrophotometer (AAS).     

Diketopyrrolopyrrole-based functional supramolecular polymers: next-generation materials for optoelectronic applications

The very concept of dye and pigment chemistry that was long known to the industrial world underwent a radical revision after the discovery and commercialization of dyes such as mauveine, indigo, and so on. Apart from their conventional role as coloring agents, organic dyes, and pigments have been identified as indispensable sources for high-end technological applications including optical and electronic devices. Simultaneous with the advancement in the supramolecular chemistry of π-conjugated systems and the divergent evolution of organic semiconductor materials, several dyes, and pigments have emerged as potential candidates for contemporary optoelectronic devices. Of all the major pigments, diketopyrrolopyrrole (DPP) better known as the ‘Ferrari Pigment’ and its derivatives have emerged as a major class of organic functional dyes that find varied applications in fields such as industrial pigments, organic solar cells, organic field–effect transistors, and in bioimaging. Since its discovery in 1974 by Farnum and Mehta, DPP-derived dyes gained rapid attention because of its attractive color, synthetic feasibility, ease of functionalization, and tunable optical and electronic properties. The advancement in supramolecular polymerization of DPP-based small molecules and oligomers with directed morphological and electronic features have led to the development of high performing optoelectronic devices. In this review, we highlight the recent developments in the optoelectronic applications of DPP derivatives specifically engineered to form supramolecular polymers.     

Self‐Assembled Helical Arrays for the Stabilization of the Triplet State

Room‐temperature phosphorescence of metal and heavy atom‐free organic molecules has emerged as an area of great potential in recent years. A rational design played a critical role in controlling the molecular ordering to impart efficient intersystem crossing and stabilize the triplet state to achieve room‐temperature ultralong phosphorescence. However, in most cases, the strategies to strengthen phosphorescence efficiency have resulted in a reduced lifetime, and the available nearly degenerate singlet‐triplet energy levels impart a natural competition between delayed fluorescence and phosphorescence, with the former one having the advantage. Herein, an organic helical assembly supports the exhibition of an ultralong phosphorescence lifetime. In contrary to other molecules, 3,6‐phenylmethanone functionalized 9‐hexylcarbazole exhibits a remarkable improvement in phosphorescence lifetime (>4.1 s) and quantum yield (11 %) owing to an efficient molecular packing in the crystal state. A right‐handed helical molecular array act as a trap and exhibits triplet exciton migration to support the exceptionally longer phosphorescence lifetime.     

Kinetics and mechanism of electron transfer reactions in aqueous solutions: Silver(I) catalyzed oxidation of aspartic acid by cerium (IV) in acid perchlorate medium

Silver(I) catalyzed oxidation of aspartic acid by cerium(IV) was studied in acid perchlorate medium. The stoichiometry of the reaction is represented by the eq. (i) Dimeric cerium(IV) species has been indicated and employed in calculations of monomeric cerium(IV) species concentrations. The reaction is second-order and uncatalyzed reaction also simultaneously occurs along with the silver(I) catalyzed reaction conforming to the rate law (ii) where k is an observed second-order rate constant. A probable reaction mechanism is suggested. © 1995 John Wiley & Sons, Inc.     

Nitromethyl benzoate annulation reactions: a rapid construction of the stealthin skeleton

The annulation of 2-(nitromethyl)benzoates with enones gave 4-nitro-1-naphthols in good yields. The carbocyclic framework of the stealthins was synthesized.     

Nine compounds containing high‐nuclearity [CunX2n+2]2− (n = 4, 5 or 7; X = Cl or Br) quasi‐planar oligomers

The structures of seven A₂Cu₄X₁₀ compounds containing quasi‐planar oligomers are reported: bis(1,2,4‐trimethylpyridinium) hexa‐μ‐chlorido‐tetrachloridotetracuprate(II), (C₈H₁₂N)₂[Cu₄Cl₁₀], (I), and the hexa‐μ‐bromido‐tetrabromidotetracuprate(II) salts of 1,2,4‐trimethylpyridinium, (C₈H₁₂N)₂[Cu₄Br₁₀], (II), 3,4‐dimethylpyridinium, (C₇H₁₀N)₂[Cu₄Br₁₀], (III), 2,3‐dimethylpyridinium, (C₇H₁₀N)₂[Cu₄Br₁₀], (IV), 1‐methylpyridinium, (C₆H₈N)₂[Cu₄Br₁₀], (V), trimethylphenylammonium, (C₉H₁₄N)₂[Cu₄Br₁₀], (VI), and 2,4‐dimethylpyridinium, (C₇H₁₀N)₂[Cu₄Br₁₀], (VII). The first four are isomorphous and contain stacks of tetracopper oligomers aggregated through semicoordinate Cu...X bond formation in a 4(,) stacking pattern. The 1‐methylpyridinium salt also contains oligomers stacked in a 4(,) pattern, but is isomorphous with the known chloride analog instead. The trimethylphenylammonium salt contains stacks of oligomers arranged in a 4(,) stacking pattern similar to the tetramethylphosphonium analog. These six structures feature inversion‐related organic cation pairs and hybrid oligomer/organic cation layers derived from the parent CuX₂ structure. The 2,4‐dimethylpyridinium salt is isomorphous with the known (2‐amino‐4‐methylpyridinium)₂Cu₄Cl₁₀ structure, in which isolated stacks of organic cations and of oligomers in a 4(,) pattern are found. In bis(3‐chloro‐1‐methylpyridinium) octa‐μ‐bromido‐tetrabromidopentacuprate(II), (C₆H₇ClN)[Cu₅Br₁₂], (VIII), containing the first reported fully halogenated quasi‐planar pentacopper oligomer, the oligomers stack in a 5(,) stacking pattern as the highest nuclearity [Cu_nX_2n+2]²⁻ oligomer compound known with isolated stacking. Bis(2‐chloro‐1‐methylpyridinium) dodeca‐μ‐bromido‐tetrabromidoheptacuprate(II), (C₆H₇ClN)₂[Cu₇Br₁₆], (IX), contains the second heptacopper oligomer reported and consists of layers of interleaved oligomer stacks with a 7[(,)][(−,−)] pattern isomorphous with that of the known 1,2‐dimethylpyridinium analog. All the oligomers reported here are inversion symmetric.     

Selective colorimetric sensing of Cu using triazolyl monoazo derivative

Although the high sensitivity, high selectivity and fast response make emission (fluorescence) based technique as one of the most promising tool for developing the chemosensors for metal ions, the past few years have witnessed a demand for the absorption based chemosensors for paramagnetic heavy metal ions, especially Cu²⁺. Being paramagnetic, Cu²⁺ leads to the low signal outputs (“turn-off”) caused by decreased emission which may sometimes give false positive response, rendering the emission based technique less reliable for analytical purposes. Herein, we report synthesis and characterization of a hetarylazo derivative, characterized by a strong charge-transfer band which gets attenuated convincingly in the presence of Cu²⁺ leading to distinct naked-eye color change (yellow to purple), and to a lesser extent in the presence of Cd²⁺, Zn²⁺, Co²⁺, Pb²⁺, Fe²⁺, Ni²⁺, Fe³⁺ and Hg²⁺ for which the naked eye sensitivity was comparatively (w.r.t. Cu²⁺) much less. No response was observed for the other metal ions including Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Mn²⁺, Ag⁺, Zn²⁺, Cd²⁺, Pb²⁺, and lanthanides Ce³⁺, La³⁺, Pr³⁺, Eu³⁺, Nd³⁺, Lu³⁺, Yb³⁺, Tb³⁺, Sm³⁺, Gd³⁺. The proposed sensing mechanism has been ascribed to the stabilization of LUMO after complexation with Cu²⁺ and a 1:1 stoichiometry has been deduced.     

A total synthesis of (+)-isolaurepan

A versatile and efficient method for the enantioselective synthesis of 2,7-cis-disubstituted oxepane 1c, (+)-isolaurepan, using oxidative resolution of a secondary alcohol and highly diastereoselective Et₃SiH/TMSOTf-promoted reductive cyclization of a hydroxy ketone is described.