Synthesis of a Zirconium Complex of an N,O-type p-tert-Butylcalix[4]arene and Its Application in Some Multicomponent Reactions.

The synthesis and characterization of a new octahedral Zr(IV) complex of oxygen-depleted N,O-type calixarene ligand comprising two distal-functionalized pyrazole rings have been reported. The cone shape and structure of the prepared complex were confirmed univocally by single-crystal X-ray diffraction and NMR studies. The Zr metal lies at 2.091 Å from the plane of the calixarene ring. This complex has been utilized as an efficient catalyst for the synthesis of Biginelli adducts, bis(indolyl)methanes, and coumarins. This complex (Cl2Zr-calixarene) showed superior activity for these multicomponent reactions in comparison to the corresponding Ti(IV) and Zn(II) analogues. Ferrocene-appended bis(indolyl)methane, prepared using this catalyst, was also evaluated for its anticancer activity against the A-172 cell line.

Catalytically active nanosized Pd9Te4 (telluropalladinite) and PdTe (kotulskite) alloys: first precursor-architecture controlled synthesis using palladium complexes of organotellurium compounds as single source precursors.

Several intermetallic binary phases of Pd-Te including Pd3Te2, PdTe, PdTe2, Pd9Te4, Pd3Te, Pd2Te, Pd20Te7, Pd8Te3, Pd7Te2, Pd7Te3, Pd4Te and Pd17Te4 are known, and negligible work (except few studies on PdTe) has been done on exploring applications of such phases and their fabrication at nanoscale. Hence, Pd(ii) complexes Pd(L1)Cl2 and Pd(L2-H)Cl (L1): Ph-Te-CH2-CH2-NH2 and L2: HO-2-C6H4-CH[double bond, length as m-dash]N-CH2CH2-Te-Ph were synthesized. Under similar thermolytic conditions, complex Pd(L1)Cl2 with bidentate coordination mode of ligand provided nanostructures of Pd9Te4 (telluropalladinite) whereas Pd(L2-H)Cl with tridentate coordination mode of ligand yielded PdTe (kotulskite). Bimetallic alloy nanostructures possess high catalytic potential for Suzuki coupling of aryl chlorides, and reduction of 4-nitrophenol. They are also recyclable upto six reaction cycles in Suzuki coupling.

Erratum: Majumder, S. et al. Zinc Oxide Nanoparticles Functionalized on Hydrogel Grafted Silk Fibroin Fabrics as Efficient Composite Dressing. Biomolecules 2020, 10, 710.

The authors wish to make the following correction to this paper [...].

Zinc Oxide Nanoparticles Functionalized on Hydrogel Grafted Silk Fibroin Fabrics as Efficient Composite Dressing.

Recent advances in woundcare is targeted towards developing active-dressings, where multiple components are combined to provide a suitable environment for rapid healing. The aim of the present research is to study the preparation of biomimic composite wound dressings by the grafting of hydrogel on silk fibroin fabric. The swelling ability of hydrogel grafted silk fibroin fabric was optimized by changing the initiator concentration. In order to impart antimicrobial properties, these dressing are further coated sono-chemically with zinc oxide nanoparticles. The water vapor transmission rate of the prepared samples was measured. The conformation of silk fibroin proteins after grafting with hydrogel was also confirmed using Fourier Transform Infrared Spectroscopy (FTIR). The morphology of the zinc oxide-coated silk fibroin fabric and hydrogel-coated silk fibroin was studied using Scanning Electron Microscope (SEM). The antimicrobial activity of the zinc oxide-coated samples was studied against E coli. The cytocompatibility of the prepared dressing materials were evaluated using L929 fibroblast cells. MTT assay and phase contrast microscopic studies showed that the adherence, growth, and proliferation of the L929 fibroblast cells that were seeded on zinc oxide nanoparticles on the functionalized hydrogel-coated silk fibroin dressing was significantly higher than that of pure silk fibroin due to the highly porous, bio-mimic structure that allowed ease of passage of nutrients, growth factors, metabolites, and the exchange of gases which is beneficial for successful regeneration of damaged tissues. The expression of TNF-α and IL-2 were not significantly higher than that of control. The proposed composite dressing would be a promising material for wound dressing and regenerative medicine but in order to prove the efficacy of these materials, more in vivo experiments and clinical tests are required to be conducted in future.

Palladacycles of unsymmetrical (N,C⁻,E) (E = S/Se) pincers based on indole: their synthesis, structure and application in the catalysis of Heck coupling and allylation of aldehydes.

Unsymmetrical (N,C,E)-type pincer ligand precursors [ and : E = S/Se] with an indole core were synthesized for the first time by the condensation of 1-(2-phenylsulfanyl/selenylethyl)-1H-indole-3-carbaldehyde with benzyl amine. The synthetic protocols are easy and give good yields (>85%). and on reaction with sodium tetrachloropalladate(ii) in the presence of CH3COONa result in complexes [Pd(/-H)Cl] (/), where they bind in a tridentate (N,C(-),E) mode. and , their aldehyde precursors and Pd(ii)-complexes, and , have been characterized by (1)H, (13)C{(1)H} and (77)Se{(1)H} NMR and HR-MS. Palladium(ii) complexes and and precursor aldehydes of and were verified using single crystal X-ray diffraction. The catalytic activities of complexes and were investigated for Heck coupling and allylation of aldehydes. The two reactions require 0.1-0.3 and 1 mol% loading of complexes as catalysts, respectively.

Complexes of (η(6)-benzene)ruthenium(II) with 1,4-bis(phenylthio/seleno-methyl)-1,2,3-triazoles: synthesis, structure and applications in catalytic activation of oxidation and transfer hydrogenation.

1,4-Bis(phenylthio/seleno methyl)-1,2,3-triazoles (L1-L4) synthesized by a 'Click' reaction react with [{(η(6)-C6H6)RuCl(µ-Cl)}]2 and NH4PF6 resulting in complexes [(η(6)-C6H6)RuClL]PF6 (1-4 for L = L1-L4) in which the ligands coordinate in a bidentate mode through S/Se and N of triazole. The CH2EPh (E = S or Se) attached to nitrogen of triazole remains pendent. Ligands and complexes have been authenticated with multinuclei NMR, IR and HR-MS. Single crystal structures of complexes 1-4 have been solved. The Ru-S and Ru-Se bond lengths (Å) are respectively 2.388(2)/2.3902(19) and 2.5007(4)/2.5262(19). The disposition of benzene ring, N, S/Se and Cl around Ru is of a piano stool type. For catalytic oxidation of alcohols [Oppenauer-type and with N-methylmorpholine-N-oxide (NMO)] and transfer hydrogenation (TH) of carbonyl compounds [with 2-propanol and glycerol] all the four complexes have been found efficient. The optimum catalyst loadings (in mol%) are: 0.01 (NMO), 0.1 (Oppenauer), 0.01 (TH with 2-propanol) and 0.5 (TH with glycerol). Interestingly, time profiles (under optimum conditions) of two catalytic oxidations and TH's are almost similar, suggesting that they are competitive on appropriate catalyst loading. DFT calculations are consistent with somewhat low reactivity of 1 in comparison to those of 2-4.

Complex of 2-(methylthio)aniline with palladium(II) as an efficient catalyst for Suzuki-Miyaura C-C coupling in eco-friendly water.

2-(Methylthio)aniline (L1), a bidentate (S,N) ligand synthesized by the reaction of o-aminothiophenol with methyl iodide, on reacting with Na2PdCl4 in acetone and water gives a complex [PdL1Cl2] (1). Single crystal X-ray diffraction studies have revealed that the geometry of palladium in 1 is nearly square-planar and the ligand L1 is bound to the palladium through S and N in a bidentate coordination mode forming a five membered chelate ring. This complex functions as a thermally and air stable catalyst of high efficiency for Suzuki-Miyaura CC coupling reactions in water. It catalyzes CC coupling between various aryl bromides and phenylboronic acid under mild reaction conditions in water. TON value up to 93,000 has been obtained.

Palladium(II)-(E,N,E) pincer ligand (E = S/Se/Te) complex catalyzed Suzuki coupling reactions in water via in situ generated palladium quantum dots.

The (E,N,E) pincer ligands (ArECH2CH2)2NH (L1/L2: Ar = Ph, E = S/Se; L3: Ar = CH3O-p-C6H4, E = Te) synthesized by reaction of PhS(-)/PhSe(-)/CH3O-p-C6H4Te(-) with bis(2-chloroethyl)amine react with Na2PdCl4 in aqueous ethanol, resulting in nearly square planar diamagnetic complexes [Pd(L)Cl]Cl (1-3), where L = L1-L3. All the ligands (L1-L3) and their complexes (1-3) have been characterised with (1)H, (13)C{(1)H}, (77)Se{(1)H} and (125)Te{(1)H} NMR spectra and high resolution mass spectrometry. The single crystal structures (determined with X-ray diffraction) of 2 and 3 have been solved (Pd-Se: 2.4104(5)/2.4222(6) Å; Pd-Te: 2.560(2)/2.588(2) Å). The conversions for Suzuki-Miyaura coupling (SMC) of various aryl bromides with phenylboronic and 4-formyl/acetyl phenylboronic acid in water using 2-3 mol% of each of the complexes 1-3 have been found good. Complexes 1 and 2 show better catalytic activity than 3, as higher yields were observed with them in a relatively short time. The coupling reactions appear to be catalyzed with Pd(0) nanoparticles (NPs) generated in situ in the course of reaction. The NPs have been isolated and HRTEM studies on them have revealed their size as ∼1-3 nm. The SEM-EDX indicates their protection with organochalcogen fragments. Addition of TBAB was essential in some cases to get good yield of cross coupled product. The isolated NPs show catalytic activity for SMC independently. The yields of cross coupled product were excellent when NPs were reused. The two phase test suggests a relatively low contribution of homogeneous Pd species in catalysis.

Organoselenium ligands in catalysis.

Organoselenium ligands are building blocks of several transition metal complexes which catalyze various organic reactions efficiently in solution. In this review the survey of developments pertaining to the designing of such complexes (along with their Se-ligands), and their uses as catalysts for various organic reactions has been presented with critical analysis of present status of the subject. Undoubtedly a new family of catalysts or their precursors has been generated by organoselenium ligands. The catalytic activity and selectivity of their metal complexes can sometimes be fine-tuned efficiently by changing the ligand's framework. They show good thermal and air-stability. This, coupled with ease in their handling and synthesis, may make them not only attractive but good alternatives to several popular catalysts.