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A ruthenium(II) aquo complex [Ru(dipic)(PPh3)2(OH2)], (1 A), bearing O,N,O‐coordinated 2,6‐dipicolinate was synthesized via reaction of [Ru(PPh3)3Cl2] with 2,6‐dipicolinic acid. Crystal structure of 1 A was determined. Utilizing 1 A as a synthon, three new complexes were synthesized. Reaction of 1 A with a bidentate NHC‐ligand, viz. 1‐methyl‐3‐(2′‐pyridyl)imidazole (IMeCN), afforded [Ru(dipic)(IMeCN)(PPh3)], (2 A). Similar reactions of 1 A with two pincer ligands, viz. 2,6‐bis(1′‐methyl imidazolyl)pyridine (IMeCNC) and 2,2′;6′,2"‐terpyridine (trpy), respectively yielded [Ru(dipic)(IMeCNC)(PPh3)], (3 A) and [Ru(dipic)(trpy)(PPh3)], (3 B). Structure of 2 A was optimized by DFT method. Structures of 3 A and 3 B were determined by X‐ray crystallography. In both 3 A and 3B the 2,6‐dipicolinate ligand was found to be N,O‐coordinated with one carboxy end remaining unbound to the metal center. Anticancer property of 2 A, 3 A and 3 B was studied and compared. Cytotoxicity of 3 A, studied against three selected cancer cell lines, viz. chronic myelogenous leukemia cell line (K562), hepatocellular carcinoma cell line (HepG2) and breast adenocarcinoma cell line (MCF7), was found to be the most promising. It displayed the best activity against K562, while it did not have any appreciable effect on its normal counterpart, viz. the human peripheral blood mononuclear cells (hPBMC). The comparative cytotoxicity studies indicated that presence of the C,N,C‐coordinated pincer NHC ligand in 3 A, together with presence of the free carboxylate end of N,O‐coordinated dipic ligand, are presumably responsible for its superior cytotoxic behavior. [ABSTRACT FROM AUTHOR]

In single‐step conversion of glycerol to propene, the intricate catalytic pathways with molybdenum and niobium catalysts remain elusive. While these catalysts can effectively accelerate the hydrogenolytic cleavage of the glycerol CO bonds, resulting in a high selectivity to propene, the routes have not been thoroughly studied. This study explores the reaction routes and the role hydrogen plays in determining the product distribution. The hydrodeoxygenation (HDO) of glycerol was investigated using various glycerol purities in both batch and continuous reaction modes. Remarkably, Mo(PO4)x and Nb(PO4)x demonstrated catalytic performance with raw glycerol, indicating that impurities had no detrimental effect on the catalyst's activity. In batch mode, a propene selectivity of 53% was achieved over Mo(PO4)x as the catalyst, highlighting the catalyst's stability under these conditions. In continuous operation, the highest product selectivity to propene (12%) was observed at low temperatures (573 K), while more C2 to C6 alkanes were formed at increased temperatures (623 and 673 K). Whereas a hydrogen atmosphere promotes formation of 2‐propenol, as primary precursor to propene, an inert atmosphere leads to increased formation of propanal and dissociation products. Our work has elucidated new routes to upcycle biorenewable glycerol to propene over Mo(PO4)x and Nb(PO4)x catalysts. [ABSTRACT FROM AUTHOR]

Chemical fixation of CO2 for the synthesis of valuable chemicals is very demanding in the context of green and sustainable chemistry. Herein, we report highly efficient silver‐loaded porous organic polymer catalysts for the exclusive N‐formylation and N‐methylation of amines under ambient reaction conditions using CO2 as a green C1 source. By adjusting the solvent and temperature of the reaction, the successful production of formamides and methylamines could be accomplished with high levels of selectivity and efficiency. POP‐based materials Ag@TTP‐1 and Ag@PAN‐T are utilized as low‐cost catalysts for both the N‐methylation and N‐formylation of primary and secondary amines and the product yields up to 98 % could be achieved. Ag@TTP‐1 demonstrated superior catalytic efficiency compared to Ag@PAN‐T in the N‐methylation and N‐formylation reactions. This result suggests that the grafting of Ag nanoparticles onto POP surface with a high surface area plays a crucial role in these CO2 fixation reactions. The above‐mentioned catalysts (Ag@TTP‐1 and Ag@PAN‐T) are characterized through powder XRD, FT IR spectroscopy, FE‐SEM, TEM, thermogravimetric techniques, N2 sorption and XPS analysis. Ag‐nanocatalysts demonstrated heterogeneous nature and high recycling efficiency for several cycles in this CO2 fixation reaction. [ABSTRACT FROM AUTHOR]

Porous organic polymers (POPs) have attracted substantial attentions over the years due to their exceptionally high specific surface areas, high chemical stability of the organic network and ease of surface functionalization with the desired organic groups. In this work, a triazine based POP (TrzPOP) was synthesized through Schiff base polycondensation reaction between a tetramine bearing triazine rings and phenolic–OH group rich dialdehyde. Ni nanoparticles (NiNP) synthesized independently were immobilized over TrzPOP to obtain the NiNP@TrzPOP composite catalyst. This TrzPOP possesses a high BET surface area of 1494 m2 g−1 and low band gap, which facilitates its role as visible light absorbent. NiNP@TrzPOP with N‐rich surfaces and phenolic–OH moieties displayed excellent photocatalytic activity in the CO2 photoreduction under mild reaction conditions. NiNP@TrzPOP composite selectively reduces CO2 to methanol. The turn over number (TON) for this photoreduction of CO2 under optimized reaction conditions is 270, which is considerably high comparing to other reported photocatalytic systems. Moreover, NiNP@TrzPOP composite catalytic system showed high recycling efficiency without noticeable decrease in its performance over five consecutive reaction cycles, suggesting its huge potential for large‐scale methanol synthesis from the renewable carbon source. [ABSTRACT FROM AUTHOR]

Hydrogen evolution reaction (HER) by electrochemical water splitting is one of the most active areas of energy research, yet the benchmark electrocatalysts used for this reaction are based on expensive noble metals. This is a major bottleneck for their large‐scale operation. Thus, development of efficient metal‐free electrocatalysts is of paramount importance for sustainable and economical production of the renewable fuel hydrogen by water splitting. Covalent organic frameworks (COFs) show much promise for this application by virtue of their architectural stability, nanoporosity, abundant active sites located periodically throughout the framework, and high electronic conductivity due to extended π‐delocalization. This study concerns a new COF material, C6‐TRZ‐TFP, which is synthesized by solvothermal polycondensation of 2‐hydroxybenzene‐1,3,5‐tricarbaldehyde (TFP) and 4,4′,4′′‐(1,3,5‐triazine‐2,4,6‐triyl)tris[(1,1′‐biphenyl)‐4‐amine]. C6‐TRZ‐TFP displayed excellent HER activity in electrochemical water splitting, with a very low overpotential of 200 mV and specific activity of 0.2831 mA cm−2 together with high retention of catalytic activity after a long duration of electrocatalysis in 0.5 m aqueous H2SO4. Density functional theory calculations suggest that the electron‐deficient carbon sites near the π electron‐donating nitrogen atoms are more active towards HER than those near the electron‐withdrawing nitrogen and oxygen atoms. [ABSTRACT FROM AUTHOR]

Developing a robust metal‐organic framework (MOF) which facilitates proton hopping along the pore channels is very demanding in the context of fabricating an efficient proton‐conducting membrane for fuel cells. Herein, we report the synthesis of a novel tetradentate aromatic phosphonate ligand H8L (L=tetraphenylethylene tetraphosphonic acid) based Ni‐MOF, whose crystal structure has been solved from single‐crystal X‐ray diffraction. Ni‐MOF [Ni2(H4L)(H2O)9(C2H7SO)(C2H7NCO)] displays a monoclinic crystal structure with a space group of P 21/c, a=11.887 Å, b=34.148 Å, c=11.131 Å, α=γ=90°, β=103.374°, where a nickel‐hexahydrate moiety located inside the void space of the framework through several H‐bonding interactions. Upon treatment of the Ni‐MOF in different pH media as well as solvents, the framework remained unaltered, suggesting the presence of strong H‐bonding interactions in the framework. High framework stability of Ni‐MOF bearing H‐bonding interactions motivated us to explore this metal‐organic framework material as proton‐conducting medium after external proton doping. Due to the presence of a large number of H‐bonding interactions and the presence of water molecules in the framework we have carried out the doping of organic p‐toluenesulfonic acid (PTSA) and inorganic sulphuric acid (SA) in this Ni‐MOF and observed high proton conductivity of 5.28×10−2 S cm−1 at 90 °C and 98% relative humidity for the SA‐doped material. Enhancement of proton conductivity by proton doping under humid conditions suggested a very promising feature of this Ni‐MOF. [ABSTRACT FROM AUTHOR]

Alcoholic extract of Piper betle ( Piper betle L.) leaves was recently found to induce apoptosis of CML cells expressing wild type and mutated Bcr-Abl with imatinib resistance phenotype. Hydroxychavicol (HCH), a constituent of the alcoholic extract of Piper betle leaves, was evaluated for anti-CML activity. Here, we report that HCH and its analogues induce killing of primary cells in CML patients and leukemic cell lines expressing wild type and mutated Bcr-Abl, including the T315I mutation, with minimal toxicity to normal human peripheral blood mononuclear cells. HCH causes early but transient increase of mitochondria-derived reactive oxygen species. Reactive oxygen species-dependent persistent activation of JNK leads to an increase in endothelial nitric oxide synthase-mediated nitric oxide generation. This causes loss of mitochondrial membrane potential, release of cytochrome c from mitochondria, cleavage of caspase 9, 3 and poly-adenosine diphosphate-ribose polymerase leading to apoptosis. One HCH analogue was also effective in vivo in SCID mice against grafts expressing the T315I mutation, although to a lesser extent than grafts expressing wild type Bcr-Abl, without showing significant bodyweight loss. Our data describe the role of JNK-dependent endothelial nitric oxide synthase-mediated nitric oxide for anti-CML activity of HCH and this molecule merits further testing in pre-clinical and clinical settings. ( Cancer Sci 2012; 103: 88-99) [ABSTRACT FROM AUTHOR]