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1.
Katsukiyo Ito 《Journal of polymer science. Part A, Polymer chemistry》1973,11(7):1673-1681
The thermal decomposition and hydrolysis of 2,2′-azobis(2-amidinopropane) were examined as functions of pH. The rate of decomposition decreased with increasing pH. The specific rates at 60°C were 3.85 × 10?5 1/sec at pH 0.90 and 2.5 × 10?5 1 see at pH ≥ 8.5. The hydrolysis in alkaline solution yielded 2,2′-azobis(2-carbamylpropane) which was stable to thermal decomposition. The relation between the specific rate of hydrolysis kh′ and the concentration of hydroxyl ion was obtained as kh′ = 4.0 × 10?2 [OH]0.50 1/sec at 60°C. In alkaline solution, the rate of hydrolysis was considerably larger than that of thermal decomposition. A mechanism for this hydrolysis is propesed. 相似文献
2.
Si‐Ping Tang Ying‐Hua Zhou Huo‐Yan Chen Cun‐Yuan Zhao Zong‐Wan Mao Liang‐Nian Ji 《化学:亚洲杂志》2009,4(8):1354-1360
A new β‐cyclodextrin dimer, 2,6‐dimethylpyridine‐bridged‐bis(6‐monoammonio‐β‐cyclodextrin) (pyridyl BisCD, L), is synthesized. Its zinc complex (ZnL) is prepared, characterized, and applied as a catalyst for diester hydrolysis. The formation constant (log KML=7.31±0.04) of the complex and deprotonation constant (pKa1=8.14±0.03, pKa2=9.24±0.01) of the coordinated water molecule were determined by a potentiometric pH titration at (25±0.1)°C, indicating a tridentate N,N′,N′′‐zinc coordination. Hydrolysis kinetics of carboxylic acid esters were determined with bis(4‐nitrophenyl)carbonate (BNPC) and 4‐nitrophenyl acetate (NA) as the substrates. The resulting hydrolysis rate constants show that ZnL has a very high rate of catalysis for BNPC hydrolysis, yielding an 8.98×103‐fold rate enhancement over uncatalyzed hydrolysis at pH 7.00, compared to only a 71.76‐fold rate enhancement for NA hydrolysis. Hydrolysis kinetics of phosphate esters catalyzed by ZnL are also investigated using bis(4‐nitrophenyl)phosphate (BNPP) and disodium 4‐nitrophenyl phosphate (NPP) as the substrates. The initial first‐order rate constant of catalytic hydrolysis for BNPP was 1.29×10?7 s?1 at pH 8.5, 35 °C and 0.1 mM catalyst concentration, about 1600‐fold acceleration over uncatalyzed hydrolysis. The pH dependence of the BNPP cleavage in aqueous buffer was shown as a sigmoidal curve with an inflection point around pH 8.25, which is nearly identical to the pKa value of the catalyst from the potentiometric titration. The kBNPP of BNPP hydrolysis promoted by ZnL is found to be 1.68×10?3 M ?1 s?1, higher than that of NPP, and comparatively higher than those promoted by its other tridentate N,N′,N′′‐zinc analogues. 相似文献
3.
Reactivity of Dinuclear Copper(II) Complexes with N‐Salicylidene Glycine Schiff Bases as Carboxylesterase Models
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Two phenoxo‐bridged dinuclear copper(II) complexes (Cu2L12, Cu2L22) with N ‐salicylidene glycine Schiff bases were prepared and evaluated their performance for catalyzing the hydrolysis of p‐nitrophenyl picolinate (PNPP). The observations reveal that the as‐prepared dinuclear copper(II) complexes exhibited better activity by two to three orders of magnitude rate enhancement in comparison with the autohydrolysis rate of PNPP. Chloro‐containing Cu2L22 aroused approximately three times kinetic advantage over chloro‐free Cu2L12 at pH 7.0, which is probably contributed to the electron‐withdrawing inductive effect of the 5′‐chloride group. Moreover, it was found that the pH‐responded kinetic behavior displayed an enzyme‐like property for the PNPP hydrolysis by the two complexes. 相似文献
4.
Coordination studies on Zn(II) complexes of 1,3,5‐tri(2,5‐diazahexyl)benzene (L) show that by comparison with the non‐deprotonation of complex ZnL in a 1:1 system, the three‐dimensional complexiaton decreases the pKa of the Zn‐bound water molecule, that is, pKa = 7.47 for trinulclear complex Zn3L in a 3:1 metal–ligand ratio. These two types of zinc(II) complexes have been examined as catalysts for the hydrolysis of 4‐nitrophenyl acetate (NA) in 10% (v/v) CH3CN at 298 K, I = 0.10 mol dm?3 KNO3 at pH range 6.5–8.2 and 8.5–10, respectively. Kinetic studies show that the second‐order rate constants of NA‐hydrolysis catalyzed by complexes ZnL, Zn3L, and Zn3LH?1 are 0.021, 0.0082, and 0.342 mol?1 dm3 s?1, respectively. In all the cases, the pH‐dependent observed first‐order rate constant, kobs, shows sigmoidal pH–rate profile. The 1:1 complex ZnL–H2O undergoes NA hydrolysis by direct rate‐determining hydrolysis to produce 4‐nitrophenol(ate) (NP?) and ZnL(OOCCH3); while in the 3:1 system the oxygen atom of acetic group forms a H‐bond with the Zn(II)‐bound water of the second branch of tripod indicating that the polynuclear centers are associated and bi‐functional. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 41–48 2004 相似文献
5.
含吡啶的抗肿瘤转移NAMI-A衍生物的制备和水解机理动力学 总被引:1,自引:0,他引:1
目的研究配体结构对NAMI-A衍生物水解机理、电化学性质的影响。方法制备了trans-[RuCl4(DMSO)(3-MePy)][(3-MePy)H](3-MePy=3-甲基吡啶,化合物1)和trans-[RuCl4(DMSO)(4-MePy)][(4-MePy)H](4-MePy=4-甲基吡啶,化合物2)。用UV、NMR、CV法研究化合物1、化合物2的水解机理-动力学、溶液稳定性及电化学性质。结果化合物1和化合物2与NAMI-A相似,在pH7.40的缓冲液中发生脱氯水解反应(Ⅰ氯水解及Ⅱ氯水解)(分步反应);在pH 5.00缓冲液中DMSO(二甲亚砜)及少量吡啶水解。测定各水解反应表观速率常数及半衰期、溶液稳定性及氧化还原电位。结论化合物1、化合物2的Ⅰ氯、Ⅱ氯及DMSO水解反应机理与NAMI-A相似,而且各水解速率与NAMI-A相差不大,即用甲基吡啶取代咪唑环,对NAMI-A衍生物的Ⅰ氯、Ⅱ氯及DMSO水解反应速率影响较小。化合物在酸性溶液中的稳定性明显高于中性溶液。 相似文献
6.
Sohodeb C. Saha Sasank Kunadharaju Balasubramanian Sivakumar Michalakis Savva 《国际化学动力学杂志》2010,42(12):693-703
Kinetic and thermodynamic analysis of the 9‐nitrocamptothecin (9NC) hydrolysis reaction in the presence and absence of human serum albumin (HSA) in phosphate‐buffered saline (PBS) of pH 7.4 was carried out by first derivative absorption spectroscopy. The thermodynamic parameters determined in these studies provided a mechanistic explanation toward the endothermic but yet thermodynamically favorable hydrolysis of 9NC at physiological temperature and pH. In the presence of HSA, the apparent rate constant of 9NC hydrolysis was 3–3.5 times higher than in 9NC solutions alone, whereas the apparent equilibrium constant of 9NC hydrolysis was found to increase at a higher extent in the presence of HSA than in PBS with increasing temperature, reaching almost complete hydrolysis of the 9NC to the 9NC‐carboxylate at 315.15 K. Importantly, the Ea of the 9NC hydrolysis reaction in the presence of HSA was determined to be on average 17 kJ mol?1 lower than the Ea determined in plain PBS. Moreover, analysis of binding isotherms constructed for the HSA interaction with 9NC, using infinitely cooperative and independent binding models, demonstrated an incredibly higher binding constant for the 9NC‐carboxylate form as compared to the very weak and concentration‐dependent binding for the 9NC‐lactone species at 310.15 K. Taken together, the preferential association of the carboxylate form with HSA and the lower Ea of 9NC hydrolysis in the presence of HSA provide a mechanistic explanation for the shift of lactone–carboxylate equilibria toward the carboxylate product under physiological conditions of pH and ionic strength. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 693–703, 2010 相似文献
7.
One multidentate ligand, 1,13-di-(1,10-phenanthroline-2-methylene)-1,4,7,10,13-pentaazatridecane(L), has been synthesized
and characterized. The kinetics of hydrolysis of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) and p-nitrophenyl phosphate (NPP) catalyzed by complexes of L with Zn2+ have been studied. Both Zn2L and Zn2LH−1 had the ability to catalysis a hydrolysis of HPNP and NPP, and the kinetics of hydrolysis of HPNP and NPP were examined in
aqueous solution at 25.0 ± 0.1 °C, I = 0.1 mol dm−3 KNO3 at the pH range of 7.0–8.5, respectively. Kinetic studies showed that Zn2LH−1 was a more active species than Zn2L in the hydrolysis of HPNP and NPP. A new mechanism was proposed for the hydrolysis of HPNP and NPP catalyzed by Zn2L and Zn2LH−1. 相似文献
8.
Junji Furukawa Eiichi Kobayashi Toshiki Doi 《Journal of polymer science. Part A, Polymer chemistry》1979,17(1):255-266
Alternating polyampholytes (MA-VA) containing two acidic groups and one basic group were prepared by the copolymerization of maleic anhydride (M1) and N-vinylsuccinimide (M2) at 60°C with AIBN as the initiator, followed by acid hydrolysis with 1N hydrochloric acid at 140°C for 24 hr. The monomer reactivity ratios r1 and r2 are 0.025 and 0.06, respectively. The structure of polymers was discussed on the basis of the data of their elementary, infrared (IR), and thermal analyses and the binding ability of heavy metal ion. Polyampholytes were soluble in strong acidic and basic media but were precipitated in the pH range 3–4. An isoelectric point at pH 3 was determined by potentiometric titration and the turbidimetric method. By thermal treatment above 205°C the polyampholyte turned quantitatively into a cyclized lactam. This suggests that the polyampholyte MA–VA has an intramolecular hydrogen bond between the amino and γ-carboxyl groups. The binding of Cu2+ and Hg2+ by the polyelectrolyte was evaluated by equilibrium dialysis. 相似文献
9.
C. G. Overberger Y. Kawakami 《Journal of polymer science. Part A, Polymer chemistry》1978,16(6):1237-1248
The water-soluble monomers, 1-methyl-4-vinylimidazole, 1-methyl-5-vinylimidazole, 1-ethyl-5-vinylimidazole, and 1-propyl-5-vinylimidazole have been synthesized, polymerized, and copolymerized with 4(5)-vinylimidazole. The copolymers were characterized by 14C-labeling, NMR, pKa determination and viscosity measurements. The monomer reactivity ratios determined by 14C counting are r1 = 1.04; r2 = 0.94 [M1 = 4(5)-vinylimidazole, M2 = 1-methyl-4-vinylimidazole] and r1 = 1.01; r2 = 0.86 [M1 = 4(5)-vinylimidazole, M2 = 1-methyl-5-vinylimidazole]. The esterolytic activity of the copolymers for the hydrolysis of p-nitrophenyl acetate (PNPA) at pH 7–8 in 28.5% ethanol–water was higher than that of the mixtures of homopolymers. At pH 5–6 the esterolytic activities of the copolymers and the mixtures were similar. The most efficient esterolytic activity for PNPA hydrolysis at pH 7.11 in 28.5% ethanol–water occurred for copolymers containing 75 mole % 4(5)-vinylimidazole and for copolymers containing 1-methyl-4-vinylimidazole rather than 1-methyl-5-vinylimidazole. 相似文献
10.
Raquel G. Rocha Jssica S. Stefano Iana V. S. Arantes Michelle M. A. C. Ribeiro Mario H. P. Santana Eduardo M. Richter Rodrigo A. A. Munoz 《Electroanalysis》2019,31(1):153-159
Levamisole is the most common adulterant found in cocaine samples and its electrochemical determination in cocaine seized samples is a challenge due to peak overlapping with cocaine. Herein, we propose a deconvolution procedure for levamisole determination in seized cocaine samples using screen‐printed carbon electrodes (SPE). Square‐wave voltammetry in 0.04 mol L?1 Britton Robinson buffered solution (pH 8.0) was selected in combination with optimized SWV parameters (f=8 s?1, a=10 mV and ΔEs=1 mV) to result in the best peak resolution to apply the deconvolution procedure. Deconvoluted responses of levamisole in the presence of cocaine were similar to untreated signals of standard levamisole solutions in absence of cocaine. A linear response was obtained in the range of 20–100 μmol L?1 (r=0.995). The results obtained for the analysis of a seized cocaine sample was statistically similar to that obtained by gas chromatography. Other adulterants found in cocaine street samples (paracetamol, glucose, phenacetin, caffeine, boric acid and lidocaine) did not affect the treated of voltammetric responses of levamisole. A pharmaceutical sample containing levamisole was also analyzed on SPEs and a recovery of 93±2 % was obtained (no deconvolution required for this sample), showing great applicability of SPEs for forensic and pharmaceutical analyses. 相似文献
11.
The hydrolysis of bis(p‐nitrophenyl)phosphate (BNPP) catalyzed by N‐methyldiethanolamine‐Ce(III) complex in the presence and absence of cetyltrimethylammonium bromide (CTAB) and Brij35 surfactants at pH 7.20 and 303 K has been studied. The experimental results indicate that N‐methyldiethanolamine‐Ce(III) complex remarkably accelerates the hydrolysis of BNPP. The observed first‐order rate constant of the hydrolysis of BNPP catalyzed by N‐methyldiethanolamine‐Ce(III) complex at pH 7.20 and 303 K is 1.22 × 10?2 s?1, which is 1.09 × 109 times of that of spontaneous hydrolysis of BNPP at pH 7. It is close to the activity of natural enzyme. A general quantitative treatment of the catalytic reaction involved a ternary complex as MmLlS has also been proposed in this paper. Applying this method to the catalytic hydrolysis of BNPP, we have obtained its thermodynamic and kinetic parameters. CTAB and Brij35 surfactant micelles obviously influence the rate constants of the catalytic hydrolysis of BNPP. Brij35 micelles promote the catalytic hydrolysis of BNPP, while CTAB micelles inhibit it. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 687–692, 2004 相似文献
12.
Johannes Ewald Dr. Jan Blankenburg Dr. Matthias Worm Laura Besch Dr. Ronald E. Unger Prof. Wolfgang Tremel Prof. Holger Frey Dr. Hannah Pohlit 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(13):2947-2953
PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring-opening copolymerization of ethylene oxide with 3,4-epoxy-1-butene (EPB) and subsequent modification to introduce acid-degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross-linking. Copolymers with different molar ratios of EPB, molecular weights (Mn) up to 10 000 g mol−1 and narrow dispersities (Đ<1.05) were prepared. Both the P(EG-co-isoEPB)MA copolymer and the hydrogels showed pH-dependent, rapid hydrolysis at pH 5–6 and long-term storage stability at neutral pH (pH 7.4). By designing the degree of polymerization and content of degradable vinyl ether groups, the release time of an entrapped protein OVA-Alexa488 can be tailored from a few hours to several days (hydrolysis half-life time t1/2 at pH 5: 13 h to 51 h). 相似文献
13.
Jian‐mei Li Rong‐rong Zang Min Li Dong Kou Juan Du 《Journal of Dispersion Science and Technology》2013,34(5):681-687
The kinetics of hydrolysis of p‐nitrophenyl picolinate(PNPP) catalyzed by metallomicelles formed from Cu (II), Ni (II) Schiff base complexes (CuL, NiL) and CTAB micelle were investigated in the pH range of 6.0–9.0 at 30°C. For the Cu (II) Schiff base complex CuL, the apparent rate constants (k obsd) of PNPP hydrolysis initially increased with the increasing pH of reaction media, then fell off. For the Ni (II) Schiff base complex NiL, the k obsd always increased with the increasing pH. The kinetic and thermodynamic parameters were calculated. The hydrolysis rate of PNPP catalyzed by Cu (II) complex was much larger than that by Ni (II) complex in CTAB micellar solution. The catalytic mechanism of the PNPP hydrolysis was discussed in detail, and the possibly active specie for the catalytic hydrolysis of PNPP was the monohydroxo metal complex. 相似文献
14.
M. Niyaz Khan 《国际化学动力学杂志》2009,41(9):599-611
Recent theoretical studies of the alkaline hydrolysis of the amide bond have indicated that the nucleophilic attack of the hydroxide ion at the carbonyl carbon of the amide group is rate limiting. This is shown to be inconsistent with a large amount of experimental observations where the expulsion of the leaving group has been shown to be rate limiting. A kinetic approach has been described, which allows us to diagnose whether the pH‐independent/uncatalyzed hydrolysis of amides involves (a) both the uncatalyzed water reaction (kw) and H+‐ (kH) and HO?‐catalyzed (kOH) water reaction, (b) only the kw reaction, or (c) only the k + kOH reaction. The analysis described in this critical review does not favor the recent theoretical claims of the absence of the water reaction in the pH‐independent/uncatalyzed hydrolysis of formamide and urea. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 599–611, 2009 相似文献
15.
Wei‐dong Jiang Bin Xu Jian‐zhang Li Fu‐an Liu Jia‐qing Xie Hua Chen 《Journal of Dispersion Science and Technology》2013,34(6):879-886
Two Schiff base Mn(III) complexes containing polyether side chain were synthesized and characterized. The catalytic hydrolysis of p‐nitrophenyl picolinate (PNPP) by the two complexes in the buffered CTAB micellar solution in the pH range of 6.60–8.20 was investigated kinetically in this study. The influences of acidity, temperature, and structure of complex on the catalytic cleavage of PNPP were also studied. The mechanism of PNPP hydrolysis catalyzed by Schiff base manganese(III) complexes in CTAB micellar solution was proposed. The relative kinetic and thermodynamic parameters were determined. Comparied with the pseudo‐first‐order rate constant (k 0) of PNPP spontaneous hydrolysis in water, the pseudo‐first‐order rate constants (k obsd) of PNPP catalytic hydrolysis are 1.93×103 fold for MnL1 2Cl and 1.06×103 fold for MnL2 2Cl in CTAB micellar solution at pH=7.00, T=25°C, and [S]=2.0×10?4mol · dm?3, respectively. Furthermore, comparing the k obsd of PNPP catalytic hydrolysis by metallomicelles with that of PNPP hydrolysis catalyzed only by metal complexes or CTAB micelle at the above‐mentioned condition, metallomicelles of MnL2(L=L1, L2) Cl/CTAB exhibit notable catalytic activities for promoting PNPP hydrolysis, and MnL1 2Cl/CTAB system is superior in promoting cleavage of PNPP relative to MnL2 2Cl/CTAB system under the same experimental conditions. The results indicate that the rate of PNPP catalytic cleavage is influenced by the structures of the two complexes, the acidity of reaction systems, and the solubilization of PNPP in CTAB micelles. 相似文献
16.
Long‐Hua Lee Wen‐Chang Chen Wei‐Chih Liu 《Journal of polymer science. Part A, Polymer chemistry》2002,40(10):1560-1571
Oligomeric methyl silsesquioxane (O‐MSSQ) precursors were prepared from methyl trimethoxysilane (MTMS) in a mixed solvent of methyl isobutyl ketone and tetrahydrofuran by variations in the pH and molar ratio of water to MTMS (R1). The molecular structures of O‐MSSQ were controlled by the reaction conditions. At a fixed pH value, the percentage of the end group, Si? OCH3, decreased with increasing R1, but that of Si? OH increased. With the pH increasing, the ratio of Si? OCH3 groups to Si? OH groups was enhanced, but ratio of the molecular weights was reduced. The molecular weight distribution was progressively broader as the pH value decreased. These results were explained by the effects of R1 and pH on the hydrolysis and condensation reactions. The prepared O‐MSSQ precursors consisted of mixed cage and network structures. The ratio of cage structures to network structures increased at low pH and high R1 values. Highly uniform thin films were spin‐coated from the O‐MSSQ precursors, and this was followed by multistep curing. The content of cage structures in O‐MSSQ films decreased with increasing curing temperatures, whereas the network content in O‐MSSQ films showed the opposite trend. Such a structural transformation resulted in significant variations in the physical properties. Both the refractive index and dielectric constant decreased with higher cage/network ratios because of changes in the molar volume. The prepared O‐MSSQ has potential applications as a low dielectric constant material. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1560–1571, 2002 相似文献
17.
A sweet almond β-glucosidase (EC 3.2.1.21) isozyme was purified from commercial crude product. The process of purification consisted of a Protein-Pak Q anion exchange chromatography following by a Superdex 75 HR gel filtration separation. The purified enzyme is a monomeric glycoprotein with molecular weight of 58 kDa and pI=4.55 which is distinguished from reported isozymes. The enzyme has apH optimum in the range of 5.2-5.6 when p-nitrophenyl-β-D-glycopyranosides are used as substrate and is stable up to 50 °C at that pH range. The purified protein also exhibits profound β-galactosidase and σ-L-arabinosidase activity. The study of substrate specificity revealed that lacking of hydroxymethyl group at C-5 of glycosides resulted in higher affinity for substrate binding to enzyme, whereas the chemical step of hydrolysis (kcst) was prevented significantly. The pH activity profile displayed a bell-shaped curve for all measured p-nitrophenyl-β-D-glycopyranosides with apparent pK1 and pK2 values of 4.4-4.7 and 6.2-6.4, respectively. This isozyme was strongly inhibited by δ-gluconolactone (Ki = 160 μM) and 4-phenylimidazole (Ki = 17.8 μM) reversibly at pH 6.2. Among the tested glycoses, the binding affinity of N-acetyl-β-D-glucosamine to the enzyme (Kl = 52 mM) was 6 times stronger than that of glucose and its epimers. 相似文献
18.
Cécile Zamy Patrick Mazellier 《International journal of environmental analytical chemistry》2013,93(14-15):1059-1068
The hydrolysis of six selected pesticides has been studied in aqueous solution. Four organophosphorus pesticides (disulfoton, isofenfos, isazofos and profenfos) and two N-methylcarbamate derivatives (oxamyl and ethiofencarb) were selected. Hydrolysis was performed in purified buffered water at different pH in the range 7.0–10.0 (ionic strength?=?2.5?mM, T?=?25°C). At pH?=?8.0, isofenfos and disulfoton (t 1/2?≈?4 years, t 1/2?≈?1 year, resp.) were found to be far more stable than isazofos (t 1/2?≈?5 months), ethiofencarb and profenofos (t 1/2<1 month), themselves more stable than oxamyl (t 1/2?≈?1 day). As expected, a strong dependence on pH was observed for all pesticides: the rate of degradation increased when the pH increased. Degradation products were identified by GC–MS and/or LC–MS. Possible structures are presented in the article. 相似文献
19.
《国际化学动力学杂志》2018,50(11):827-835
Rate constants for the hydrolysis reaction of phosphate (paraoxon) and thiophosphate (parathion, fenitrothion) esters by oximate (pyridinealdoxime 2‐PyOx− and 4‐PyOx−) and its functionalized pyridinium surfactants 4‐(hydroxyimino) methyl)‐1‐alkylpyridinium bromide ions (alkyl = CnH2n+1, n = 10, 12, 14, 16) have been measured kinetically at pH 9.5 and 27°C in micellar media of cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB). Acid dissociation constant, pKa, of oximes has also been determined by spectrophotometric, kinetic, and potentiometric methods. The rate acceleration effects of cationic micelles have been explored. Cationic micelles of the pyridinium head group (CPB) showed a large catalytic effect than the ammonium head group (CTAB). The effects of pH, oximate concentration, and surfactants have been discussed. 相似文献
20.
Jian-zhang Li Bin Xu Ying Wang Shen-xin Li Bo Zhou Wei Zeng Sheng-ying Qin 《Transition Metal Chemistry》2006,31(4):487-494
Two novel unsymmetrical bis-Schiff base manganese(III) and cobalt(II) complexes with benzo-10-aza-crown ether pendants (MnL1Cl, CoL1), and their analogoues with morpholino pendants (MnL2Cl, CoL2), have been synthesized and employed as models to mimic hydrolase in p-nitrophenyl picolinate (PNPP). The kinetics and the mechanism of PNPP hydrolysis catalyzed by these complexes were investigated.
A kinetic mathematical model of PNPP cleavage catalyzed by these complexes was proposed. The effects of the complexes structure
and reactive temperature on the rate of catalytic PNPP hydrolysis have been also examined. The results showed that the rate
for the catalytic PNPP hydrolysis increased following the increase in pH of the buffer solution; four complexes exhibited
high activity in the catalytic PNPP hydrolysis. Compared with the crown-free analogoues MnL2Cl and CoL2, the crowned Schiff base complexes (MnL1Cl, CoL1) exhibit a higher catalytic activity; the pseudo-first-order-rate (kobs) for the PNPP hydrolysis catalyzed by the complex MnL1Cl containing benzo-10-aza-crown ether is 1.04 × 103 that of spontaneous hydrolysis of PNPP at pH = 7.00, [S] = 2.0×10−4 mol dm−3. 相似文献