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A dicationic diradical has been synthesized from the N,N′- trans-1,4-cyclohexylene bridged bis-NHC–CAAC dimer.

Molecular dioxygen is activated across the C(sp3)–C(sp3) bond of a piperazine derivative. This unprecedented reaction proceeds without any catalyst and at ambient condition yielding a 8-membered cyclic organic peroxide.

Herein we report the first metal-free regioselective Markovnikov ring-opening of epoxides (selectivity up to 99%) using an abnormal N-heterocyclic carbene (aNHC) to yield secondary alcohols. DFT calculations and X-ray crystallography suggest that the Markovnikov selectivity originates from the high nucleophilicity and steric factors associated with the aNHC.

Herein we report the development of a new methodology for the synthesis of various quinodimethane derivatives under two-electron oxidation of bis-Nheterocyclic olefins linked by different pi-conjugated aromatic spacers. In case of paraand ortho-phenylene bridge, we obtained air and moisture stable diimidazolium paraand ortho-quinodimethane derivatives. Analogues of the para-phenylene spacer such as tetrafluoro-p-phenylene and p-anthracene also led to the corresponding air and moisture stable quinodimethane derivatives. This emphasizes the influence of imidazolium substituents which facilitate the air and moisture stability of the quinodimethane derivatives. Differences were observed for the electron transfer processes: two one-electron vs one two-electron redox transitions between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes depending on the employed pi-conjugated aromatic spacer. The formation of the pi-conjugated radical-cations, transient redox intermediates between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes, was addressed by an EPR investigation.

Tetrel Lewis acids are a prospective alternative to commonly employed neutral boranes in frustrated Lewis pair (FLP) chemistry. While cationic tetrylium Lewis acids, being isolobal and iso(valence)electronic, are a natural replacement to boranes, neutral tetrel Lewis acids allude as less trivial options due to the absence of a formally empty p orbital on the acceptor atom. Recently, a series of intramolecular geminal FLPs (C2F5)(3)E-CH2-P(tBu)(2) (E = Si, Ge, Sn) featuring neutral tetrel atoms as acceptor sites has been reported for activation of small molecules including H-2. In this work, through density functional theory computations, we elucidate the general mechanistic picture of H-2 activation by this family of FLPs. Our findings reveal that the acceptor atom derives the required Lewis acidity utilizing the antibonding orbitals of its adjacent bonds with the individual contributions depending on the identity of the acceptor and the donor atoms. By varying the identity of the Lewis acid and Lewis base sites and attached substituents, we unravel their interplay on the energetics of the H-2 activation. We find that switching the donor site from P to N significantly affects the synchronous nature of the bond breaking/formations along the reaction pathway, and as a result, N-bearing FLPs have a more favorable H-2 activation profile than those with P. Our results are quantitatively discussed in detail within the framework of the activation-strain model of reactivity along with the energy-decomposition analysis method. Finally, the reductive elimination decomposition route pertinent to the plausible extension of the H-2 activation to catalytic hydrogenation by these FLPs is also examined.

We report the synthesis of donor-free stibenium cations and their subsequent use as efficient catalysts in the cyanosilylation of carbonyl compounds.

Strategic designs to develop highly sensitive stimuli-responsive photoluminescence (PL)-switching materials are vastly preferred, but hard to achieve. This work describes the design and straightforward economic synthesis of small, conformationally twisted, and thermally stable π-conjugates as solid-state emitters with highly sensitive stimuli-responsive properties, including brightest-red emission. A metal-free, economic and facile synthetic route affords the π-conjugates conveniently at room temperature in a large quantity. The rigid carbazole and flexible diphenylamine rotors harvest four to five distinct bright emission colors that are reversibly switchable with high contrast in response to various external stimuli by tuning the conformational mobility and intermolecular interactions. Variations in the molecular conformation and arrangement in diphenylamine offer two controlled polymorphs with blue and green emissions. The blue polymorph displays highly sensitive PL-switching [blue to greenish-yellow (Δλ = 68 nm)] by fingertips rubbing, whereas the other polymorph needs rigorous grinding. These polymorphs are not interconvertible, but reach identical molecular phases with an almost intact brightness under the same stimuli. A remarkable protonation/deprotonation-induced, reversibly redshifted PL-switching with enhanced quantum yield (Φf) was observed for all. The access of the brightest red-emitting small molecules with Φf = 63–64% is noteworthy via the protonation process and unique. The highly intense stimuli-responsive emission change and sensitivity differences in these molecules were elucidated by analyzing the molecular twisting ability and packing, powder X-ray diffraction pattern, and differential scanning calorimetry. The lifetime was measured to illustrate a dominant radiative relaxation pathway to describe the high quantum yield. Furthermore, theoretical support is provided to explain the sensitivity of the blue polymorph by determining the favorable optical bandgap and dimer formation energy. Even the tetramer unit for the blue polymorph also exhibited a greater number of non-covalent interactions, which was further quantitatively deciphered by Hirshfeld surface analysis. Such sensitive stimuli-responsive multicolored emissive materials can be utilized for various applications in optical recording devices and haptic sensing. Finally, these solid-state emitters were employed to fabricate a portable device for optical recording as an efficient multicolored ink-free writing platform.

Frustrated Lewis pairs (FLP) which rely on the cooperative action of Lewis acids and Lewis bases, played a prominent role in the advancement of main-group catalysis. While the early days of FLP chemistry witnessed the dominance of boranes, there is a growing body of reports on alternative Lewis acids derived from groups 14 and 15. This short review focuses on the discovery of such non-boron candidates reported since 2015.

The activation of atmospheric molecular dioxygen (O

A storable bicyclic (alkyl)(amino)carbene (BICAAC) stabilized two coordinate zinc(0) complex [(BICAAC)2Zn] (2) was synthesized. DFT calculations reveal that BICAAC plays a decisive role in imparting the stability to 2. This complex activates the C(sp3)–Cl bond of trityl chloride generating the Gomberg's free radical with greater efficiency than metallic Zn powder.

The much-needed renewable alternatives to fossil fuel can be achieved efficiently and sustainably by converting solar energy to solar fuels via hydrogen generation from water or CO2 reduction. In this regard, a soft processable metal-organic hybrid semiconducting material has been developed and studied for photocatalytic activity towards H2 production and CO2 reduction to CO and CH4 under visible light and direct sunlight irradiation. A tetrapodal low molecular weight gelator is synthesized by integrating tetrathiafulvalene and terpyridine through amide linkage (TPY-TTF). The TPY-TTF acts as a linker and by self-assembly with ZnII results in a charge-transfer (CT) coordination polymer gel (CPG); Zn-TPY-TTF. The Zn-TPY-TTF shows impressive photocatalytic activity towards H2 production (rate = 530 μmol g-1h-1) and CO2 reduction to CO (rate = 438 μmol g-1h-1, selectivity >99%) regulated by charge-transfer interaction. Furthermore, in-situ stabilization of Pt nanoparticles to CPG (Pt@Zn-TPY-TTF) exhibits remarkably enhanced H2 evolution (rate =14727 μmol g-1h-1). Importantly, Pt@Zn-TPY-TTF modulate the CO2 reduction from CO to CH4 (rate = 292 μmol g-1h-1, selectivity >97%). Real-time CO2 reduction reaction is monitored by in-situ DRIFT study and subsequent plausible mechanism is derived computationally. The photocatalytic activity of Zn-TPY-TTF and Pt@Zn-TPY-TTF composite was also examined under sunlight that display excellent H2 evolution and CO2 reduction.

The much-needed renewable alternatives to fossil fuel can be achieved efficiently and sustainably by converting solar energy to fuels via hydrogen generation from water or CO2 reduction. Herein, a soft processable metal-organic hybrid material is developed and studied for photocatalytic activity towards H2 production and CO2 reduction to CO and CH4 under visible light as well as direct sunlight irradiation. A tetrapodal low molecular weight gelator (LMWG) is synthesized by integrating tetrathiafulvalene (TTF) and terpyridine (TPY) derivatives through amide linkages and results in TPY-TTF LMWG. The TPY-TTF LMWG acts as a linker, and self-assembly of this gelator molecules with ZnII ions results in a coordination polymer gel (CPG); Zn-TPY-TTF. The Zn-TPY-TTF CPG shows high photocatalytic activity towards H2 production (530 μmol g−1h−1) and CO2 reduction to CO (438 μmol g−1h−1, selectivity > 99%) regulated by charge-transfer interactions. Furthermore, in situ stabilization of Pt nanoparticles on CPG (Pt@Zn-TPY-TTF) enhances H2 evolution (14727 μmol g−1h−1). Importantly, Pt@Zn-TPY-TTF CPG produces CH4 (292 μmol g−1h−1, selectivity > 97%) as CO2 reduction product instead of CO. The real-time CO2 reduction reaction is monitored by in situ DRIFT study, and the plausible mechanism is derived computationally., Designing active materials for efficient photocatalysis are of great interests. Herein the authors report coordination polymer gel assembled by low molecular weight gelator as photocatalysts for visible light driven H2 production and CO2 reduction regulated by charge-transfer interactions.

Coulombic repulsion between two adjacent cation centres of 1,2-carbodications are known to decrease with π- and/or n-donor substituents by the positive charge delocalization. Here we report the delocalization of positive charge of transient 1,2-carbodications having one H-substituent by an intramolecular base-coordination. N-heterocyclic olefin (NHO) derived 2-pyrrolidinyl appended trisubstituted geminal diazaalkenes were employed for the generation of transient 1,2-carbodications through a 2-e chemical oxidation process. We have also studied the 1-e oxidation reaction of trisubstituted geminal diazaalkenes (electrochemically and chemically) and also studied them by in situ EPR spectroscopy. Fil: Mandal, Debdeep. Indian Institute of Technology; India Fil: Stein, Felix. Freie Universität Berlin; Alemania Fil: Chandra, Shubhadeep. Universitat Stuttgart; Fil: Neuman, Nicolás Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Sarkar, Pallavi. Indian Institute of Technology; India Fil: Das, Shubhajit. Indian Institute of Technology; India Fil: Kundu, Abhinanda. Indian Institute of Technology; India Fil: Sarkar, Arighna. Indian Institute of Technology; India Fil: Rawat, Hemant. Indian Institute of Technology; India Fil: Pati, Swapan. Indian Institute of Technology; India Fil: Chandrasekhar, Vadapalli. Indian Institute of Technology; India Fil: Sarkar, Biprajit. Universität Stuttgart; Fil: Jana, Anukul. Indian Institute of Technology; India

Using the self-consistent charge density-functional based tight-binding (SCC-DFTB) method, coupled with time-dependent density functional theory (TDDFT) calculations, for the first time we explore the possibility of use of phosphorene quantum dots in solar energy harvesting devices. The phosphorene quantum dots-fullerene (PQDs-PCBA) nanocomposites show type-II band alignment indicating spatial separation of charge carriers. The TDDFT calculations also show that the PQD-fullerene nanocomposites seem to be exciting material for future generation solar energy harvester, with extremely fast charge transfer and very poor recombination rate.

Being monocyclic planar, benzene retains 6π Huckel aromatic backbone. However, for larger analogues, the repulsion between vicinal C-H bonds makes them nonplanar, as for [10]-annulene. Thus, on this basis, a planar 10-π-aromatic C10H10 is unreachable. A detailed structural comparison among the C3H3+, C4H42+, C5H5−, C6H6, C7H7+, C8H82+, C9H9−, and C10H10 systems supports that the repulsion between vicinal C-H bonds is the primary reason for the loss of planarity, despite the favorable aromatic electron count. In this respect, here we have discussed ten-membered monocyclic planar 10-π-aromatic, (CH)5(XH)5 {X = Si, Ge, Sn} systems, modeled by using DFT. From NBO analysis and the overall magnetic behavior it is shown that (CH)5(GeH)5, (CH)5(SnH)5 molecules are promising planar 10-π-aromatic system. Thus, such species represent plausible Huckel aromatic rings retaining a ten-membered backbone as discussed here, which may lead to the characterization of novel species expanding the chemistry of larger aromatic rings. We believe that the present study may open new avenues in the formation of 10-π-aromatic species.

Being monocyclic planar, benzene retains 6π Hückel aromatic backbone. However, for larger analogues, the repulsion between vicinal C-H bonds makes them nonplanar, as for [10]-annulene. Thus, on this basis, a planar 10-π-aromatic C

Chrysopids (Chrysopidae: Neuroptera), also commonly known as lacewings, are common predatory components of the agricultural and horticultural pest guilds. The adults are free-living and usually nonpredatory in nature, surviving on nectar and pollen, while the three larval stages are highly predatory. The chrysopids are especially effective against soft-bodied insect pests, in particular aphids. This chapter reviews how these potential biocontrol agents can be effectively harnessed against intended target pests by using effective mass-production, storage, and release techniques. We also discuss their usage in various integrated pest management programs, particularly in India.

Frustrated Lewis pair (FLP) chemistry has gained significant attention in the past decade as the main group hydrogenation catalysts. The majority of the reported FLP catalysts utilize either boron-containing Lewis acids (LAs) or alternatively isolobal and iso(valence)electronic tetrylium analogues for hydrogenation. Recently, a new family of intramolecular FLPs R3E-CH2-PR'(2) (E = Si, Ge, Sn) featuring neutral sp(3) tetrel atoms as LA centers were reported for activation of a range of small molecules under ambient conditions. They have been shown to perform heterolytic cleavage of the hydrogen molecule, a key step in hydrogenation catalysis. In this work, we computationally examine their ability to perform catalytic hydrogenation using CO2, carbonyls, and imines as substrates. Our mechanistic analyses reveal that the transfer of the activated hydrogens from FLP to the unsaturated bond follows a concerted yet asynchronous pathway. The sequence of proton/hydride transfer is largely influenced by the donor/acceptor centers of the FLP as well as the corresponding unsaturated functional group. We find that by varying the donor centers in these FLPs, the dihydrogen release barrier can be tuned, and nitrogen-bearing FLPs have a lower dihydrogen release barrier than those with phosphorus. The reactivity trends are rationalized within the framework of the activation strain model. Finally, two major side reactions pertinent to the performance of the hydrogenation cycle, such as dimer formation of the catalyst and decomposition through reductive elimination, are also investigated in detail.