Mohmmad Younus Wani

Porphyrins as nanoreactors in the carbon dioxide capture and conversion: a review

On account of their unique properties and robust structures, porphyrins are natures favorite catalysts. Porphyrins have attracted the attention of researchers for many decades as a result of their intense colors; but in recent years, interest in these molecules has sharply increased, due to their potential use in solving difficult problems in the fields of medicine and environmental protection. Much attention is currently focused on the development of materials for the capture and conversion of CO2 into value-added products, and porphyrins are proving to be of interest in this area of research. Porphyrins were previously thought to be poorly-absorbant materials, as they are generally planar compounds. However, the development of new, efficient porphyrin-based materials and reliable synthetic routes for porphyrin-based nanoreactors, such as covalent–organic frameworks and metal–organic frameworks, for use as porous materials has helped to overcome the underlying challenges in CO2 reactivity. Porphyrin-based materials that behave as nanoreactors are promising candidates in the capture and conversion of CO2 as a result of the presence of the basic pyrrole structure that contains a macrocyclic cavity and large aromatic rings, which facilitate strong interactions with CO2. This review provides an overview of progress in the area of CO2 capture and conversion using porphyrin-based molecular materials and nanoreactors. These materials have important structural features in terms of surface area, porosity, CO2 uptake and the possibility of the catalytic conversion of CO2 to chemically valuable products.

Imidazole clubbed 1,3,4-oxadiazole derivatives as potential antifungal agents.

A series of compounds in which 2-(4-ethyl-2-pyridyl)-1H-imidazole was clubbed with substituted 1,3,4-oxadiazole was synthesized and subjected to antifungal activity evaluation. In vitro assays indicated that several clubbed derivatives had excellent antifungal activity against different strains of laboratory and clinically isolated Candida species. Structural Activity Relationship (SAR) studies revealed that the presence and position of substituents on the phenyl ring of the 1,3,4-oxadiazole unit, guides the antifungal potential of the compounds, where compound 4b, 4c and 4g were found to be active against all the tested fungal strains. Impairment of ergosterol biosynthesis upon the concomitant treatment of 4b, 4c and 4g, revealed the possible mechanisms of antifungal action of these compounds. Inhibitors snugly fitting the active site of the target enzyme, as revealed by molecular docking studies, may well explain their excellent inhibitory activity.

Studies of Carbon Dioxide Capture on Porous Chitosan Derivative

Chitosan was modified with 4-formyltriphenylamine to obtain a material with better surface morphology and adsorption profile. Surface morphology and Brunauer–Emmett–Teller (BET) analysis has proved that the chitosan derivative presents higher porosity. CO2 adsorption analysis results reveal that the triphenyl amine chitosan derivative shows better adsorption than pure chitosan. The results revealed that this material may open new vistas in environmental and industrial applications for carbon dioxide capture, in order to help to reduce the adverse impact of large emissions of the greenhouse gas is the atmosphere. GRAPHICAL ABSTRACT

Cycloaddition of CO2 to epoxides using di-nuclear transition metal complexes as catalysts

Studies on the reaction and conversion of CO2 to valuable products have made much progress in recent years, and the search for efficient catalysts is also expanding. Cycloaddition of CO2 to epoxides was carried out selectively using di-nuclear CuII, CoII and NiII complexes (C1, C2 and C3, respectively) as catalysts. The complexes were synthesized in good yield and characterized by various physical and spectroscopic methods. In all complexes the ligand L acted as a bidentate NO donor favouring distorted octahedral, tetrahedral or square planar geometry for C1, C2 and C3, respectively. Complex C2 in the presence of n-Bu4NI as a cocatalyst showed the highest activity among the reported complexes in the cycloaddition reaction.

Synergistic Interactions of Eugenol-tosylate and Its Congeners with Fluconazole against Candida albicans

We previously reported the antifungal properties of a monoterpene phenol “Eugenol” against different Candida strains and have observed that the addition of methyl group to eugenol drastically increased its antimicrobial potency. Based on the results and the importance of medicinal synthetic chemistry, we synthesized eugenol-tosylate and its congeners (E1-E6) and tested their antifungal activity against different clinical fluconazole (FLC)- susceptible and FLC- resistant C. albicans isolates alone and in combination with FLC by determining fractional inhibitory concentration indices (FICIs) and isobolograms calculated from microdilution assays. Minimum inhibitory concentration (MIC) results confirmed that all the tested C. albicans strains were variably susceptible to the semi-synthetic derivatives E1-E6, with MIC values ranging from 1–62 μg/ml. The test compounds in combination with FLC exhibited either synergy (36%), additive (41%) or indifferent (23%) interactions, however, no antagonistic interactions were observed. The MICs of FLC decreased 2–9 fold when used in combination with the test compounds. Like their precursor eugenol, all the derivatives showed significant impairment of ergosterol biosynthesis in all C. albicans strains coupled with down regulation of the important ergosterol biosynthesis pathway gene-ERG11. The results were further validated by docking studies, which revealed that the inhibitors snugly fitting the active site of the target enzyme, mimicking fluconazole, may well explain their excellent inhibitory activity. Our results suggest that these compounds have a great potential as antifungals, which can be used as chemosensitizing agents with the known antifungal drugs.

Carbon dioxide adsorption and cycloaddition reaction of epoxides using chitosan–graphene oxide nanocomposite as a catalyst

One of todays major challenges is to provide green materials for a cleaner environment. We have conducted studies on carbon dioxide (CO2) adsorption and conversion to valuable products by an ecofriendly approach based in chitosan/graphene oxide (CSGO) nanocomposite film. Rheological behavior indicates that the CSGO has a better solvation property than the pure chitosan. An adsorption capacity of 1.0152mmolCO2/g of CSGO nanocomposite at 4.6bar was observed. The catalytic behavior of the CSGO nanocomposite in the presence of tetra-n-butylammonium iodide (n-Bu4NI) as co-catalyst was evaluated for the cycloaddition of CO2 to epoxides, to give cyclic carbonates, in the absence of any solvent. These results strongly suggest that the CSGO nanocomposite may open new vistas towards the development of ecofriendly material for catalytic conversion and adsorption of CO2 on industrial scale.

Carbon dioxide capture and conversion by an environmentally friendly chitosan based meso-tetrakis(4-sulfonatophenyl) porphyrin

We have demonstrated the facile, environmentally friendly and sustainable preparation of chitosan based meso-tetrakis(4-sulfonatophenyl)porphyrin (CS-TPPS) for adsorption and catalytic conversion of carbon-dioxide (CO2). The ionic complexation between chitosan (CS) and meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) is confirmed by ultraviolet-visible (UV-vis) and Fourier transform infrared spectroscopy (FTIR). Physical properties, such as crystallinity, thermal stability, surface morphology and porosity were analyzed by X-ray diffraction, thermal analysis, scanning electron microscopy and BET isotherm analysis. CS-TPPS shows adsorption capacity of 0.9mmol CO2/g compared to the adsorption capacity of 0.05mmol CO2/g of pure chitosan and an adsorption capacity of 0.2mmol CO2/g of pure TPPS. It also exhibits higher conversion of CO2 and propylene oxide into cyclic carbonate (66%), compared to pure chitosan (31%). The results are encouraging, and may open new perspectives for the use of biopolymers involving porphyrin based material in environmental and industrial applications.

Synthesis, physicochemical and optical properties of bis-thiosemicarbazone functionalized graphene oxide

Fluorescent materials are important for low-cost opto-electronic and biomedical sensor devices. In this study we present the synthesis and characterization of graphene modified with bis-thiosemicarbazone (BTS). This new material was characterized using Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible (UV-Vis) and Raman spectroscopy techniques. Further evaluation by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic-force microscopy (AFM) allowed us to fully characterize the morphology of the fabricated material. The average height of the BTSGO sheet is around 10nm. Optical properties of BTSGO evaluated by photoluminescence (PL) spectroscopy showed red shift at different excitation wavelength compared to graphene oxide or bisthiosemicarbazide alone. These results strongly suggest that BTSGO material could find potential applications in graphene based optoelectronic devices.

Mononuclear transition metal complexes containing iodo-imidazole ring endowed with potential anti-Candida activity

Special attention is directed to design and synthesize antimicrobial drug candidates by the complexation of bioactive ligands with transition metals. In this pursuit a ligand with imidazole ring was synthesized and treated with CuII, CoII and ,NiII salts to afford the mononuclear metallic complexes IHC1, IHC2 and IHC3, respectively, being assigned the general formula [M(L)2]. Physical and spectral characterization supported octahedral geometry for the complexes. Both the ligand and the synthesized metal complexes were evaluated for their antifungal activity against three different strains of Candida, by determining the minimum inhibitory concentrations and minimum fungicidal concentrations. The antifungal activity results showed that the target compounds display remarkable antifungal activity, with metal complex IHC1 showing the most potent antifungal activity. Mechanism of action of the ligand and metal complexes appears to originate from membrane disruption as revealed by confocal scanning laser microscopy.

Paal–Knorr synthesis of pyrroles: from conventional to green synthesis

ABSTRACT The pyrrole molecular framework is found in a large number of natural and synthetic compounds of great importance. Since functionalized pyrroles are essential for the progress of many branches of science, its synthesis by simple, efficient and eco-friendly routes are particularly attractive in modern organic and bio-organic chemistry. To this end, a number of synthetic methods have been developed, in which the Paal–Knorr pyrrole synthesis stands out to be the easiest route to synthesize pyrroles. In spite of the efficiency, Paal–Knorr synthesis of pyrroles is considered limited by harsh reaction conditions, such as prolonged heating in acid, which may degrade sensitive functionalities in many potential precursors. Through this route almost all dicarbonyls can be converted to their corresponding heterocycles and therefore it is a synthetically valued process. To address the adverse issues this reaction route has undergone numerous modifications recently and today it can be said that this reaction route is a prominent green route for the synthesis of pyrroles. This review is a tour from the evolution and application of this harsh synthetic route to the eco-friendly greener route developed for the synthesis of pyrroles.