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10. Pyrazolone Containing Azine Based Molybdenum Complexes Having μ‐O{MoO2}2 Core and their Catalytic Applications for the Cycloaddition of CO2 with Epoxides to Cyclic Carbonates.

Author

Maurya, Mannar R., Singh, Devesh, Sharma, Astha, and Avecilla, Fernando

Subjects
STYRENE oxide, RING formation (Chemistry), NUCLEAR magnetic resonance spectroscopy, THERMAL analysis, CARBON dioxide, AZINES
Abstract

Tetradentate ONNO donor ligands H2hz(fp)2 (I), H2hz(butp)2 (II) and H2hz(bp)2 (III) synthesized by the reaction of hydrazine hydrate with 4‐formyl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (fp), 4‐butyryl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (butp) and 4‐benzoyl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (bp), respectively, react with [MoVIO2(acac)2] in 1 : 2 molar ratio in refluxing methanol to give binuclear complexes [(μ‐O){MoVIO2(H2O)}2hz(fp)2] (1) and [(μ‐O){MoVIO2(H2O)}2hz(butp)2] (2) and [(μ‐O){MoVIO2(H2O)}2hz(bp)2] (3). All ligands and complexes are characterized by several techniques that include, FT‐IR, UV/Vis, 1H NMR, 13C NMR spectroscopy, elemental and thermal analysis, and single crystal X‐ray analysis of 2 and 3. Ligands coordinate through a set of ON functionalities of the same ligand to two MoVIO2 groups attached through an oxido‐bridge. Additional coordination of water to each vanadium makes each of them to maintain an octahedral geometry. Azine moiety coordinates to two molybdenum through the symmetrical μ‐{η2‐(N−N)} fashion. Catalytic activity of these complexes was studied for the cycloaddition of CO2 with epoxides. A pressure of 4 bar CO2, 3.0 mg catalyst, 1 mmol of tetrabutylammonium bromide (TBAB) at 120 °C for 6 h were found to be most suited reaction condition for 10 mmol epoxide. Under the optimized reaction conditions, the product yield and selectivity of alkene carbonate for all complexes were investigated. As high as 96 % yield with almost 99 % selectivity for styrene carbonate under these optimized reaction conditions was achieved. [ABSTRACT FROM AUTHOR]

Published
2024
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18. DEPÓSITO DE SEDIMENTOS EÓLICOS EN UN PARCHE FORESTAL DEL AGROECOSISTEMA DEL SEMIÁRIDO PAMPEANO.

Author

Avecilla, Fernando, Esteban Panebianco, Juan, Noelia Comas, Rocio, Antonela Iturri, Laura, Andrea de Oro, Laura, and Eduardo Buschiazzo, Daniel

Subjects
*SOIL management, *ATMOSPHERIC temperature, *FOREST soils, *AGRICULTURE, *WIND speed, *WIND erosion
Abstract

The aim of this study was to assess the deposition rates (Td) of mineral aeolian sediments in a forest patch in the semiarid Pampas agroecosystem and to analyze the seasonal variability of such deposition. The average Td was 520.15 kg ha-1 year-1 with high interannual variability. In spring-summer, Td was higher than in autumn-winter. Air temperature and average maximum wind speed influenced Td more significantly. However, the soil cover and management of the agricultural fields surrounding the forest would determine the production of sediment from wind erosion and consequent deposition within the forest. These results show the importance of maintaining forest patches within the agricultural matrix in the semi-arid environment, since they retain eolian sediments that would eventually be deposited on the forest soil, minimizing the negative impacts of wind erosion processes on these ecosystems. [ABSTRACT FROM AUTHOR]

Published
2024

33. Polymer-Supported Oxidovanadium(IV) Complexes and Their Catalytic Applications in One-Pot Multicomponent Reactions Producing Biologically Active 2,4,5-Trisubstituted-1H-imidazoles

Author

Maurya, Mannar, Nandi, Monojit, Patter, Akhil, Avecilla, Fernando, Ghosh, Kaushik, Maurya, Mannar, Nandi, Monojit, Patter, Akhil, Avecilla, Fernando, and Ghosh, Kaushik

Abstract

[Abstract] Two new monobasic tridentate O⁀N⁀N donor ligands, HL1 (I) and HL2 (II) have been obtained in two steps by reacting phenylhydrazine and salicylaldehyde or 3,5-di-tert-butylsalicylaldehyde and then reacting the resulting compounds with 2-chloromethylbenzimidazole in the presence of triethylamine. The reaction of [VIVO(acac)2] with these ligands in a 1:1 molar ratio in dry methanol led to the formation of homogeneous oxidovanadium(IV) complexes [VIVO(acac)L1] (1) and [VIVO(acac)L2] (2). Immobilization of these complexes on chloromethylated polystyrene (PS-Cl) cross-linked with divinyl benzene resulted in corresponding polymer-supported heterogeneous complexes PS-[VIVO(acac)L1] (3) and PS-[VIVO(acac)L2] (4). Ligands (I and II), homogeneous complexes (1 and 2) and heterogeneous complexes (3 and 4) have been characterized using elemental analysis and various spectroscopic techniques. A single crystal X-ray diffraction study of I and 1 further confirms their structures. The oxidation state IV of vanadium in these complexes was assured by recording their EPR spectra while heterogeneous complexes were further characterized using field emission-scanning electron microscopy (FE-SEM) combined with energy dispersive X-ray analysis (EDS) and atomic force microscopy (AFM). All vanadium complexes have been explored for their catalytic potential to one-pot-three-component reactions (reagents: benzil, ammonium acetate and various aromatic aldehydes) for the efficient synthesis of 2,4,5-triphenyl-1H-imidazole derivatives (nine examples). Various reaction conditions have been optimized to obtain a maximum yield (up to 96%) of catalytic products. It has been found that heterogeneous complexes show excellent catalytic activity and are recyclable up to five catalytic cycles.

Published
2023

34. Mononuclear/Binuclear [VIVO]/[VVO2] Complexes Derived from 1,3-Diaminoguanidine and Their Catalytic Application for the Oxidation of Benzoin via Oxygen Atom Transfer

Author

Maurya, Mannar, Kumar, Naveen, Avecilla, Fernando, Maurya, Mannar, Kumar, Naveen, and Avecilla, Fernando

Abstract

[Abstract] Ligands H4sal-dag (I) and H4Brsal-dag (II) derived from 1,3-diaminoguanidine and salicylaldehyde or 5-bromosalicylaldehyde react with one or 2 mol equivalent of vanadium precursor to give two different series of vanadium complexes. Thus, complexes [VIVO(H2sal-dag) (H2O)] (1) and [VIVO(H2Brsal-dag) (H2O)] (2) were isolated by the reaction of an equimolar ratio of these ligands with [VIVO(acac)2] in MeOH. In the presence of K+/Cs+ ion and using aerially oxidized [VIVO(acac)2], the above reaction gave complexes [K(H2O){VVO2(H2sal-dag)}]2 (3), [Cs(H2O){VVO2(H2sal-dag)}]2 (4), [K(H2O){VO2(H2Brsal-dag)}]2 (5), and [Cs(H2O){VVO2(H2Brsal-dag)}]2 (6), which could also be isolated by direct aerial oxidation of complexes 1 and 2 in MeOH in the presence of K+/Cs+ ion. Complexes [(H2O)VIVO(Hsal-dag)VVO2] (7) and [(H2O)VIVO(HBrsal-dag)VVO2] (8) were isolated upon increasing the ligand-to-vanadium precursor molar ratio to 1:2 under an air atmosphere. When I and II were reacted with aerially oxidized [VIVO(acac)2] in a 1:2 molar ratio in MeOH in the presence of K+/Cs+ ion, they formed [K(H2O)5{(VVO2)2(Hsal-dag)}]2 (9), [Cs(H2O)2{(VVO2)2(Hsal-dag)}]2 (10), [K2(H2O)4{(VVO2)2(Brsal-dag)}]2 (11), and [Cs2(H2O)4{(VVO2)2(Brsal-dag)}]2 (12). The structures of complexes 3, 4, 5, and 9 determined by single-crystal X-ray diffraction study confirm the mono-, bi-, tri-, and tetra-anionic behaviors of the ligands. All complexes were found to be an effective catalyst for the oxidation of benzoin to benzil via oxygen atom transfer (OAT) between DMSO and benzoin. Under aerobic condition, this oxidation also proceeds effectively in the absence of DMSO. Electron paramagnetic resonance and 51V NMR studies demonstrated the active role of a stable V(IV) intermediate during OAT between DMSO and benzoin.

Published
2023

39. Controlled Modification of Triaminoguanidine-Based μ3Ligands in Multinuclear [VIVO]/[VVO2] Complexes and Their Catalytic Potential in the Synthesis of 2-Amino-3-cyano-4H-pyrans/4H-chromenes

Author

Maurya, Mannar R., Kumar, Naveen, and Avecilla, Fernando

Abstract

Reaction of tris(2-hydroxybenzylidene)-triaminoguanidinium chloride (I·HCl) and tris(5-bromo-2-hydroxybenzylidene)-triaminoguanidinium chloride (II·HCl) with [VIVO(acac)2] (1:1 molar ratio) in refluxing methanol resulted in mononuclear [VIVO] complexes, [VIVO(H2L1′)(MeOH)] (1) and [VIVO(H2L2′)(MeOH)] (2), respectively, where Iand IIundergo intramolecular triazole ring formation. Aerial oxidation of 1and 2in MeOH in the presence of Cs2CO3gave corresponding cis-[VVO2] complexes Cs[(VO2)(H2L1′)] (3) and Cs[(VO2)(H2L2′)] (4). However, reaction of an aerially oxidized methanolic solution of [VIVO(acac)2] with I·HCl and II·HCl in the presence of Cs2CO3(in 1:1:1 molar ratio) gave mononuclear complexes Cs[(VO2)(H3L1)] (5) and Cs[(VO2)(H3L2)] (6) without intramolecular triazole ring formation. Similar anionic trinuclear complexes Cs2[(VO2)3(L1)] (7) and Cs2[(VO2)3(L2)] (8) were isolable upon increasing the amounts of the vanadium precursor and Cs2CO3to 3 equiv to the reaction applied for 5and 6. Keeping the reaction mixture of 1in MeOH under air gave [VVO(H2L1’)(OMe)] (9). Structures of 3, 7, 8, and 9were confirmed by X-ray crystal structure study. A permanent porosity in the crystalline metal–organic framework of 7confirmed by single-crystal X-ray investigation was further verified by the BET study. Along with a suitable reaction mechanism, these synthesized compounds were explored as effective catalysts for the synthesis of biomolecules 4H-pyran/4H-chromenes.

Published
2024
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40. Catalytic, Antifungal, and Antiproliferative Activity Studies of a New Family of Mononuclear [VIVO]/[VVO2] Complexes

Author

Maurya, Mannar R., Nandi, Monojit, Chaudhary, Pankaj Kumar, Singh, Sain, Avecilla, Fernando, Prasad, Ramasare, and Ghosh, Kaushik

Abstract

Ligands derived from 2-(1-phenylhydrazinyl)pyridine and salicylaldehyde (HL1), 3-methoxysalicylaldehyde (HL2), 5-bromosalicylaldehyde (HL3), and 3,5-di-tert-butylsalicylaldehyde (HL4) react with [VIVO(acac)2] in MeOH followed by aerial oxidation to give [VVO2(L1)] (1), [VVO2(L2)] (2), [VVO2(L3)] (3), and [VVO2(L4)] (4). Complex [VIVO(acac)(L1)] (5) is also isolable from [VIVO(acac)2] and HL1in dry MeOH. Structures of all complexes were confirmed by single-crystal X-ray and spectroscopic studies. They efficiently catalyze benzyl alcohol and its derivatives’ oxidation in the presence of H2O2to their corresponding aldehydes. Under optimized reaction conditions using 1as a catalyst precursor, conversion of benzyl alcohol follows the order: 4(93%) > 2(90%) > 1(86%) > 3(84%) ≈ 5(84%). These complexes were also evaluated for antifungal and antiproliferative activities. Complex 3with MIC50= 16 μg/mL, 4with MIC50= 12 μg/mL, and 5with MIC50= 16 μg/mL are efficient toward planktonic cells of Candida albicansand Candida tropicalis. On Michigan cancer foundation-7 (MCF-7) cells, they show comparable cytotoxic effects and exhibit IC50in the 27.3–33.5 μg/mL range, and among these, 4exhibits the highest cytotoxicity. A similar study on human embryonic kidney cells (HEK293) confirms their less toxicity at lower concentrations (4 to 16 μg/mL) compared to MCF-7.

Published
2024
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