Tetradentate bis(pyridyltriazole) ligands containing aromatic spacers of different sizes react with Cu(2+) to produce metallo-supramolecular hosts that bind 1,4-diazabicyclo[2.2.2]octane molecules internally.
The concentration of carbon dioxide (CO2) has risen continuously in atmosphere due to human induced activities, and has been considered the predominant cause of global climate change. Paulowina tomentosa Steud. (P. tomentosa), a multipurpose tree is popular around global market for its timber and its potential role in CO2 sequestration. In this study, the total biomass carbon of five years old and newly planted P. tomentosa has been estimated. The results indicated that the average total biomass carbon of five years old plant was found to be 4.52±0.53Kg C Year-1 per tree i.e. 9.04±1.06-ton C ha-1 Year-1 (assuming 2000 plants per hector). Likewise, the average total biomass carbon of newly planted P. tomentosa within 4 months was found to be 6.07±0.38 Kg in remote village area in Nepal. The estimated biomass carbon in one year of newly planted plants was found to be 18.21±1.14 Kg Year-1 i.e. 0.36-ton C ha-1 Year-1. These findings reveled that short rotational trees like P. tomentosa can be implemented in agroforestry system to reduce the green house emission in cities and emphasizes the carbon storage potential of agroforestry. In vitro micro propagation technique could be implemented to produce genetically uniform clone of P. tomentosa and can be applied in agroforestry system for the adaptation and to mitigate global climate change.Int. J. Appl. Sci. Biotechnol. Vol 6(3): 220-226
Five functionalized bis(β-diketones) and their Cu(II) molecular squares are described. The new bis(β-diketones), m-pbhxH2 (3), 5-MeO-m-pbaH2 (4), 5-BuO-m-pbaH2 (5), 2-MeO-m-pbaH2 (6), and 2-MeO-m-pbprH2 (7), were prepared by reaction of the corresponding aldehydes with phospholenes, as we previously reported for m-pbaH2 (1) and m-pbprH2 (2). Ligand 3 has long alkyl chains in its β-diketone moieties, while ligands 4-7 have alkoxy substituents on their aromatic rings. When treated with Cu(2+), the new bis(β-diketones) 3, 4, 5, and 7 afford molecular squares, Cu4(m-pbhx)4 (10), Cu4(5-MeO-m-pba)4 (11), Cu4(5-BuO-m-pba)4 (12), and Cu4(2-MeO-m-pbpr)4 (13), respectively. Two of the new molecular squares, 10 and 12, contain longer-chain substituents and are soluble in a wider range of organic solvents. The other squares, 11 and 13, contain external and internal methoxy groups, respectively, and they show smaller changes in solubility. Single-crystal X-ray analyses are reported for three of the molecular squares without guest molecules, and for five adducts of the squares with σ- (polypyridine) and π-bonded (fullerene) guests. The Cu···Cu distances in the "empty" squares range from 14.047 to 14.904 Å; those in the adducts vary over a wider range depending on the guest molecule involved.
In the previous publication, some of us reported the conversion of a copper(I) complex to a copper(II) oxalate complex, and claimed that this conversion involved a reduction of CO 2 to oxalate (C 2 O 4 2− ). Herein, we show that the oxalate is produced not by reduction of CO 2 , but by reaction of ascorbate with oxygen. We also present new results that explain in a more comprehensive way the behaviour of these copper compounds under O 2 and CO 2 .Selective reduction of carbon dioxide to C ≥2 compounds using homogeneous metal complexes is a challenging transformation. Only a limited number of examples have been reported over the past decades [1][2][3][4][5][6][7][8][9][10][11][12] . In contrast, there has been a vast increase in reported catalysts for selective CO 2 reduction to C 1 compounds [13][14][15] . Among the examples reported for the reductive coupling of CO 2 to oxalate is a dinuclear Cu complex introduced by some of us in 2014 (ref. 16 ). The in situ generated Cu(I) complex [Cu 2 (m-xpt) 2 ](PF 6 ) 2 (3) formed by reduction of the Cu (II) precursor (1) with sodium ascorbate generated an oxalatebridged dinuclear complex (4), proposed to occur via reductive coupling of atmospheric CO 2 (Fig. 1). Release of the oxalate by addition of mineral acids was described, potentially enabling stepwise conversion of CO 2 into oxalic acid using sodium ascorbate as a comparatively mild reductant. Interestingly, oxidation of ascorbic acid by transition metal compounds, especially those of copper, has been well-known for more than a century 17,18 . Since then, the reaction mechanisms for such oxidations have been intensely studied [18][19][20][21][22] . More specifically, oxidative degradation of ascorbic acid by (a) inorganic oxidants (sodium periodate 23 , sodium hypoiodite 24 ); (b) oxygen 25,26 ; and (c) O 2 in the presence of Gd 27,28 , Co 27 , Pd 29 , Pt 29 , Cd 30 , Fe 31 , or Cu 32 compounds is reported to yield oxalate as a degradation product (see Supplementary Fig. 21 for a typical reaction sequence).We now report that the true origin of the oxalate in the communication published in 2014 is not CO 2 , as it was described, but oxidative degradation of sodium ascorbate.
The dehydration of 1′,2′,3′,4′,5′-pentamethylruthenocene-1,2-dicarboxylic acid with acetic anhydride gives 1′,2′,3′,4′,5′-pentamethylruthenocene-1,2-dicarboxylic anhydride, the first crystallographically characterized, metallocene-fused carboxylic anhydride. Treatment of the diacid with oxalyl chloride/DMF produces its 1,2-diacyl chloride, which is an excellent precursor for AlCl3-promoted double Friedel–Crafts acylation reactions with a variety of arenes, including benzene, toluene, o-xylene, p-dimethoxybenzene, and ferrocene. X-ray structural determinations of an acenequinone and a unique ferrocene/ruthenocene-fused benzoquinone show distortions attributed to strong electron donation from pentamethylruthenocene.
The title compound, [Fe(C13H11N4)2], was synthesized starting from 1,1′-ferrocenedicarboxylic acid in a three-step reaction sequence. The dicarboxylic acid was reduced to 1,1′-ferrocenedimethanol using LiAlH4 and subsequently converted to 1,1′-bis(azidomethyl)ferrocene in the presence of NaN3. The diazide was treated with 2-ethynylpyridine under `click' conditions to give the title compound in 75% yield. The FeII center lies on an inversion center in the crystal. The two pyridyltriazole wings are oriented in an anti conformation and positioned exo from the FeII center. In the solid state, the molecules interact by C—H...N, C—H...π, and π–π interactions. The complexation of the ligand with [Cu(CH3CN)4](PF6) gives a tetranuclear dimeric complex.
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