Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

Iron- and cobalt-catalyzed Sonogashira coupling reactions are becoming central areas of research in organic synthesis. Owing to their significant importance in the formation of carbon-carbon bonds, numerous green and nanoparticle protocols have emerged during the past decades. The non-toxic and inexpensive nature of catalysts gained much attention in recent times. In this context, their catalytic nature and activity in Sonogashira coupling reactions were well explored and compared. Most importantly, one of the highlights of this review is the emphasis given to green strategies. This is the first review on iron- and cobalt-catalyzed Sonogashira coupling reactions which comprehends literature up to 2020.

Hexabenzocoronene functionalized with antiaromatic S- and Se-core-modified porphyrins (isophlorins): comparison with the dyad with regular porphyrin

The important and perspective molecular building blocks composed of hexaphenylbenzenes (HPBs) or their oxidized derivatives, hexa-peri-hexabenzocoronenes (HBCs), and metalloporphyrins have recently received significant attention of the researchers. In this study, motivated by recent findings, we have addressed the modifications of structures and properties of HBC-porphyrin compounds by using instead of aromatic porphyrins antiaromatic 20π isophlorin derivatives of thiophene or selenophene. We have reported the first comparative computational investigation of the following systems: (i) HBC with one non-metallated aromatic porphyrin, P(N4H2), unit, HBC-P(N4H2), (ii) HBC with one S-core-modified antiaromatic porphyrin (S-isophlorin), PS4, unit, HBC-PS4, and (iii) HBC with one Se-core-modified antiaromatic porphyrin (Se-isophlorin), PSe4, unit, HBC-PSe4. The study has been done employing the B3LYP/6-31G* approach (in the gas phase and in the implicit solvents, benzene and dichloromethane), and comparison with the B3LYP/6-31G** and B3LYP/6-311G* approaches was performed, where relevant. The effects of the core-modified antiaromatic isophlorins on the structures, electronic, and other properties, potentially including reactivity, of the whole building block HBC-isophlorin have been shown to be quite pronounced and to be noticeably stronger than the effects of the original aromatic non-metallated porphyrin. Thus, we have demonstrated theoretically that the complete porphyrin core-modification with other elements, this time with S and Se leading to the formation of the antiaromatic isophlorins, should be considered as a promising way for modifying and tuning structures, electronic properties and reactivity of the hexabenzocoronene-porphyrin(s) building blocks.

Hexaarylbenzene based high-performance p-channel molecules for electronic applications

Hexaarylbenzene-based molecules find potential applications in organic electronics due to wider energy gap, high HOMO level, higher photoconductivity, electron-rich nature, and high hole-transporting property. Due to the unique propeller structure, these molecules show low susceptibility towards self-aggregation. This property can be tailored by proper molecular engineering by the incorporation of appropriate groups. Therefore, hexaarylbenzene chromophores are widely used as the materials for high-efficiency light-emitting materials, charge transport materials, host materials, redox materials, photochemical switches, and molecular receptors. This review highlights the diverse structural modification techniques used for the synthesis of symmetrical and unsymmetrical structures. Also, the potential applications of these molecules in organic light-emitting diodes, organic field-effect transistors, organic photovoltaics, organic memory devices, and logic circuits are discussed.

'Light-Up' AIE-Active Materials: Self-Assembly, Molecular Recognition and Catalytic Applications

Aggregation induced emission enhancement (AIEE) is one of the most widely explored phenomena to develop 'light up' (fluorescent) materials having potential applications in the field of supramolecular chemistry, analytical chemistry and material chemistry. By applying the principles of host-guest chemistry, we have developed a variety of aggregation induced emission (AIE/AEE) active materials having specific affinity for metal ions, electron deficient/electron rich analytes. The interactions between AIE active assemblies and metal ions are further tuned to prepare nanohybrids having potential applications as catalytic/photocatalytic systems in various organic transformations under eco-friendly conditions. This account summarizes various design strategies developed in our labortary for the preparation of AIE/AEE active building blocks having sensing and catalytic applications.

Multiple-Porphyrin Functionalized Hexabenzocoronenes

Porphyrin-hexabenzocoronene architectures serve as good model compounds to study light-harvesting systems. Herein, the synthesis of porphyrin functionalized hexa-peri-hexabenzocoronenes (HBCs), in which one or more porphyrins are covalently linked to a central HBC core, is presented. A series of hexaphenylbenzenes (HPBs) was prepared and reacted under oxidative coupling conditions. The transformation to the respective HBC derivatives worked well with mono- and tri-porphyrin-substituted HPBs. However, if more porphyrins are attached to the HPB core, Scholl oxidations are hampered or completely suppressed. Hence, a change of the synthetic strategy was necessary to first preform the HBC core, followed by the introduction of the porphyrins. All products were fully characterized, including, if possible, single-crystal XRD. UV/Vis absorption spectra of porphyrin-HBCs showed, depending on the number of porphyrins as well as with respect to the substitution pattern, variations in their spectral features with strong distortions of the porphyrins' B-band.

Metal nanoparticles embedded in AIEE active supramolecular assemblies: robust, green and reusable nanocatalysts

In modern organic synthesis, the utilization of metal NPs for carrying out fundamental organic transformations is an area of great interest. This frontier article describes the exploitation of supramolecular assemblies of AIEE-active materials as nanoreactors, stabilizers and shape directing agents for the preparation of various types of metal NPs without using any additives, reducing agents, stabilizing agents, etc. This article further summarizes the utilization of the as-prepared supramolecular ensembles as reusable nanocatalysts for carrying out various organic transformations under mild conditions.

Pd2+fluorescent sensors based on amino and imino derivatives of rhodamine and improvement of water solubility by the formation of inclusion complexes with β-cyclodextrin

Mono- and bis-rhodamine derivatives appended with amino (RhB1) and imino (BRI) groups, respectively, have been designed as fluorescent sensors for Pd²⁺ions.

Aggregates of perylene bisimide stabilized superparamagnetic Fe3O4 nanoparticles: an efficient catalyst for the preparation of propargylamines and quinolines via C-H activation

Aggregates of the perylene bisimide derivative act as reactors and stabilizers for the preparation of superparamagnetic Fe3O4 nanoparticles (NPs) which exhibit excellent catalytic efficiency in (i) A(3)-coupling and aldehyde free coupling reactions for the preparation of propargylamines and (ii) tandem intramolecular cyclization reaction for the synthesis of quinolines via C-H activation.

Pentacenequinone-Stabilized Silver Nanoparticles: A Reusable Catalyst for the Diels-Alder [4 + 2] Cycloaddition Reactions

Silver nanoparticles (AgNPs) stabilized by aggregates of derivative 4 have been used as catalyst for the construction of synthetically and biologically important [4 + 2] cycloadducts at room temperature.

Hexaphenylbenzene-Stabilized Luminescent Silver Nanoclusters: A Potential Catalytic System for the Cycloaddition of Terminal Alkynes with Isocyanides

A hexaphenylbenzene (HPB)-based derivative bearing thiol groups has been designed and synthesized that undergoes aggregation-induced emission enhancement in mixed aqueous media to form rodlike fluorescent aggregates. These rodlike aggregates behave as a "not quenched" probe for the detection of silver ions and further act as reactors and stabilizers for reducing-agent-free preparation of blue luminescent silver nanoclusters at room temperature. The utilization of fluorescent supramolecular aggregates for the preparation of Ag NCs in mixed aqueous media is unprecedented in the literature. Moreover, the wet chemical method that we are reporting in the present paper for the preparation of luminescent silver nanoclusters is better than the other methods reported in the literature. Further, these in situ generated Ag NCs showed exceptional catalytic activity in the preparation of pyrroles involving cocyclization of isocyanides and terminal alkynes. Interestingly, the catalytic efficiency of in situ generated Ag NCs was found to be better than the other catalytic systems reported in the literature.

One-pot multicomponent synthesis of tetrahydropyridines promoted by luminescent ZnO nanoparticles supported by the aggregates of 6,6-dicyanopentafulvene

Pot-shaped fluorescent aggregates of 6,6-dicyanopentafulvene derivative serve as reactors and stabilizers for the preparation of luminescent ZnO nanoparticles, which exhibit high catalytic efficiency in one-pot multicomponent synthesis of tetrahydropyridines.

Fluorescent aggregates of AIEE active triphenylene derivatives for the sensitive detection of picric acid

Fluorescent aggregates of triphenylene derivatives 3 and 5 having aggregation induced emission enhancement (AIEE) characteristics have been developed which selectively detect picric acid.

Aggregates of the pentacenequinone derivative as reactors for the preparation of Ag@Cu2O core–shell NPs: an active photocatalyst for Suzuki and Suzuki type coupling reactions

Aggregates of the pentacenequinone derivative stabilized Ag@Cu₂O core–shell nanoparticles (NPs) enabled efficient visible light harvesting to catalyse the palladium free Suzuki–Miyaura and Suzuki type cross coupling reactions at room temperature.

Silver nanoparticles: facile synthesis and their catalytic application for the degradation of dyes

The aggregates of pentacenequinone, HPB and PDI derivatives 3, 5 and 7 having aldehyde groups bind strongly with Ag⁺ and serve as reactors and stabilizers for the preparation of AgNPs at room temperature. In situ generated AgNPs show high catalytic efficiency for industrially important organic dye degradation.

AIEE active perylene bisimide supported mercury nanoparticles for synthesis of amides via aldoximes/ketoximes rearrangement

AIEE active perylene bisimide derivatives 3 serve as reactors and stabilizers for the preparation of HgNPs which exhibit high catalytic efficiency in the synthesis of amides via aldoximes/ketoximes rearrangement.

Copper nanoparticles generated from aggregates of a hexarylbenzene derivative: a reusable catalytic system for ‘click’ reactions

Copper nanoparticles stabilized by aggregates of a hexaphenylbenzene derivative display excellent catalytic activity in ‘click’ reactions under solvent-free conditions.