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All total 109 Articles be foundBroensted Acidities of Carbonyl Hydride Complexes of Iron, Ruthenium, and Osmium: pKa Values and Deprotonation Rates in Methanol Solution
Walker, Howard W.,Pearson, Ralph G.,Ford, Peter C.
, p. 1179 - 1186 (1983)
Reported are kinetics studies of the reaction of methoxide ion with several mononuclear and polynuclear carbonyl hydride complexes HxMy(CO)z of the iron triad.Deprotonation of the hydrides to give the conjugate base anions occurs with moderate second-order rate constants (ca. 101-104 M-1s-1), considerably smaller than those of oxygen or nitrogen acids of comparable thermodynamic strength under similar conditions.The relative slowness of these reactions is interpreted in terms of possible electronic and structural rearrangements of substrate and solvent occuring as the result of the deprotonation.In addition the kinetics technique allows the measurement of the reverse reacton (protonation of the conjugate base by methanol) rate constants which are also comparatively small (ca. 0.05-25 s-1).The ratio of the forward and reverse rates gives the equilibrium constants from which the pKa's in methanol can be calculated.In several cases pKa's were confirmed by buffer/indicator techniques.From these and other published data are drawn the conclusions that bridging hydrides are more acidic than terminal hydrides and that hydrides of the lighter metals are more acidic than those of homologous heavier metals.Furthermore, it is shown than the substituent effect of replacing CO of a cluster by a trimethyl phosphite is to decrease significantly the acidity of that cluster's hydrides.
Kinetic Studies on the Decomposition of Most Typical Meisenheimer Complex of Sodium 1,1-Dimethoxy-2,4,6-trinitrocyclohexadienide in Methanol
Abe, Takehiro
, p. 1399 - 1405 (1980)
The whole decomposition of the Meisenheimer complex formed from 2,4,6-trinitroanisole (TNA) and sodium methoxide proceeds in three steps and obeys the first-order kinetics in each step.The rate of the whole decrease of concentration of the complex is given by -d(+->)/dt=(k1+>+k2)*+(k3+>+k4)*->-k5->*, where k denotes a rate constant.This leads to the modification of the conventional unimolecular mehanism shown by TNA*CH3O- -> TNA +CH3O-.
Standard molar enthalpies of formation of sodium alkoxides
Chandran,Srinivasan,Gopalan,Ganesan
, p. 449 - 454 (2007)
The molar enthalpies of solution of sodium in methanol, ethanol, and n-propanol and of sodium alkoxides in their corresponding alcohols were measured at T = 298.15 K using an isoperibol solution calorimeter. From these results and other auxiliary data, the standard molar enthalpies of formation Δf Hm{ring operator} (RONa,cr) of sodium methoxide, sodium ethoxide, and sodium n-propoxide were calculated and found to be {(-366.21 ± 1.38), (-413.39 ± 1.45), and (-441.57 ± 1.18)} kJ · mol-1, respectively. A linear correlation has been found between Δf Hm{ring operator} (RONa) and Δf Hm{ring operator} (ROH) for R = n-alkyl, enabling the prediction of data for other sodium alkoxides.
Synthesis and evaluation of the cytotoxic activity of water-soluble cationic organometallic complexes of the type [Pt(η1-C2H4OMe)(L)(phen)]+ (L = NH3, DMSO; phen = 1,10-phenanthroline)
De Castro, Federica,Stefàno, Erika,Migoni, Danilo,Iaconisi, Giorgia N.,Muscella, Antonella,Marsigliante, Santo,Benedetti, Michele,Fanizzi, Francesco P.
, (2021)
Starting from the [PtCl(η1-C2H4OMe)(phen)] (phen = 1,10-phenanthroline, 1) platinum(II) precursor, we synthesized and characterized by multinuclear NMR new [Pt(η1-C2H4OMe)(L)(phen)]+ (L = NH3, 2; DMSO, 3) complexes. These organometallic species, potentially able to interact with cell membrane organic cation transporters (OCT), violating some of the classical rules for antitumor activity of cisplatin analogues, were evaluated for their cytotoxicity. Interestingly, despite both complexes 2 and 3 resulting in greater cell uptake than cisplatin in selected tumor cell lines, only 3 showed comparable or higher antitumor activity. General low cytotoxicity of complex 2 in the tested cell lines (SH-SY5Y, SK-OV-3, Hep-G2, Caco-2, HeLa, MCF-7, MG-63, ZL-65) appeared to depend on its stability towards solvolysis in neutral water, as assessed by NMR monitoring. Differently, the [Pt(η1-C2H4OMe)(DMSO)(phen)]+ (3) complex was easily hydrolyzed in neutral water, resulting in a comparable or higher cytotoxicity in cancer cells with respect to cisplatin. Further, both IC50 values and the uptake profiles of the active complex appeared quite different in the used cell lines, suggesting the occurrence of diversified biological effects. Nevertheless, further studies on the metabolism of complex 3 should be performed before planning its possible use in tissue- and tumor-specific drug design.
Investigation of the crystal structures and magnetic features of two bis(dithiolato)nickelate salts with flexible organic cations
Chen, Xuan-Rong,Zhang, Zhen-Min,Luo, Min,Liu, Hang,Yuan, Jia-Yi
, p. 353 - 362 (2021)
Two bis(dithiolato)nickel salts with different flexible ammonium counterions, [Et3MeN][Ni(dmit)2] (1) and [(i-Bu)Et3N][Ni(dmit)2] (2) (dmit2? = 2-thioxo-1,3-dithiole-4,5-dithiolate, Et3MeN+ = triethylmethylammonium, (i-Bu)Et3N+ = triethylisobutylammonium), are prepared and identified by powder X-ray diffraction (PXRD) patterns and single-crystal X-ray diffraction. Salt 1 crystallizes in the triclinic space group P???1 at 293?K. The anions and cations in 1 form alternating layered arrangements along the a-axis direction. Salt 2 belongs to the monoclinic crystal system and space group P21/n. The anions and cations in 2 form separate columnar stacks along bc-plane direction. The neighboring anions are stacked as dimers in the anion columnar stacks of 2. The magnetic features of salts 1 and 2 show 1D alternating spin chain magnetic exchange behavior, and the magnetic experimental data are well fitted through a spin chain magnetic model. The difference in the crystal structures and magnetic properties between the two new salts 1 and 2 fully demonstrates that the magnetic properties are dependent on the alignment of the [Ni(dmit)2]? anions, which are related to the flexible organic cations. Graphical abstract: [Figure not available: see fulltext.]
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Crampton,M.R. et al.
, p. 825 - 826 (1975)
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Chemical transformations and biological studies of terpenoids isolated from essential oil of Cyperus scariosus
Sharma,Utreja,Bedi
, p. 2153 - 2158 (2016)
Cyperus scariosus is a potential medicinal herb belonging to the family Cyperaceae. The GC-MS analysis of the oil showed cyprene (18.57 %) as the major terpene present in it. Cyprene was isolated from the non-polar fraction of the oil using hexane as solvent and characterized using TLC and spectral techniques (IR and 1H NMR). Cyprene was derivatized to cyprene epoxide by two methods i.e. using perbenzoic acid and epichlorohydrin. Further, the oil, it's polar fraction (dichloromethane), non-polar fraction (hexane), cyprene and cyprene epoxide were screened for their plant growth regulating property in case of wheat seedlings (HD 2967 and PBW 621). Complete germination was observed above 2.5 μg/mL of all the test fractions in both the cultivars. Moreover, cyprene epoxide was found to be the most effective in enhancing the length of roots and shoots. Seedling vigour index was calculated in order to analyze the enhancement shown by the oil and its various components on the seedlings.
Synthesis, monoamine oxidase inhibition activity and molecular docking studies of novel 4-hydroxy-N′-[benzylidene or 1-phenylethylidene]-2-H/methyl/benzyl-1,2-benzothiazine-3-carbohydrazide 1,1-dioxides
Saddique, Furqan Ahmad,Zaib, Sumera,Jalil, Saquib,Aslam, Sana,Ahmad, Matloob,Sultan, Sadia,Naz, Humera,Iqbal, Mazhar,Iqbal, Jamshed
, p. 1373 - 1386 (2018)
Three series of 4-hydroxy-N′-[benzylidene/1-phenylethylidene]-2-H/methyl/benzyl-1,2-benzothiazine-3-carbohydrazide 1,1-dioxides (9–11)a-l were synthesized and unraveled to be highly potent dual inhibitors of monoamine oxidases (MAO-A and MAO-B). All the examined compounds demonstrated IC50 values in lower micro-molar range for both MAO-A as well as MAO-B. The most active MAO-A inhibitor was 4-hydroxy-N′-(1-phenylethylidene)-2H-benzo[e][1,2]thiazine-3-carbohydrazide 1,1-dioxide (9i) with an IC50 value of 0.11 ± 0.005 μM, whereas, methyl 4-hydroxy-2H-benzo[e][1,2]thiazine-3-carboxylate 1,1-dioxide (3) was the most active MAO-B inhibitor with an IC50 value of 0.21 ± 0.01 μM. Enzyme kinetics studies revealed that the most potent compounds inhibited both MAO enzymes (A & B) in a competitive fashion. Molecular docking studies were also performed to obtain an intuitive picture of inhibition potential for potent inhibitors. The high potency of these compounds is optimally combined with highly favorable ADME profile with predicted good oral bioavailability.
Ni-Catalyzed 1,2-Diarylation of Alkenyl Ketones: A Comparative Study of Carbonyl-Directed Reaction Systems
Apolinar, Omar,Derosa, Joseph,Engle, Keary M.,Karunananda, Malkanthi K.,Kleinmans, Roman,Li, Zi-Qi,Tran, Van T.,Wisniewski, Steven R.
supporting information, p. 5311 - 5316 (2021/07/26)
A nickel-catalyzed 1,2-diarylation of alkenyl ketones with aryl iodides and arylboronic esters is reported. Ketones with a variety of substituents serve as effective directing groups, offering high levels of regiocontrol. A representative product is diversified into a wide range of useful products that are not readily accessible via existing 1,2-diarylation reactions. Preliminary mechanistic studies shed light on the binding mode of the substrate, and Hammett analysis reveals the effect of electronic factors on initial rates.
