Metal-promoted hydrolysis of bis(p-nitrophenyl)phosphate by trivalent manganese complexes with Schiff base ligands in Gemini micellar solution

Artificial phosphatase upon premicellar nanoarchitectonics of lanthanum complexes with long-chained imidazole derivatives

Four novel long chain-containing tridentate imidazole derivatives (Lⁿ, n = 1, 2, 3, 4) were synthesized for in situ formation of mononuclear lanthanum(III) complexes as artificial phosphodiesterases. These in-situ formed La(III) complexes (named LaLⁿ) were used to catalyze the transesterification of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP), a classic RNA model. Critical aggregation concentrations (CAC) were determined for the as-prepared tridentate imidazole derivatives as ligands and corresponding mixtures of equivalent ligand and La³⁺ ion with a mole rate of 1:1. It denotes that the introduction of La³⁺ ion increases the CAC values of imidazole derivatives by about 2 to 3 folds. Foaming test shows that the foam height is positively correlated with the length of hydrophobic chain. Transesterification of HPNP mediated by LaLⁿ nanoarchitectonics indicates that the introducing of hydrophobic chain benefits rate enhancement, showing excess three orders of magnitude acceleration under physiological conditions (pH 7.0, 25 °C). Moreover, catalytic reactivities of these La(III) complexes increased along with the increase in chain length: LaL¹ < LaL² < LaL³ < LaL⁴, suggesting a positive correlation to hydrophobic chain length.

Mechanistic Insights into Promoted Hydrolysis of Phosphoester Bonds by MoO2Cl2(DMF)2

A phosphoester bond is a crucial structural block in biological systems, whose occurrence is regulated by phosphatases. Molybdenum compounds have been reported to be active in phosphate ester hydrolysis of model phosphates. Specifically, MoO₂Cl₂(DMF)₂ is active in the hydrolysis of para-nitrophenyl phosphate (pNPP), leading to heteropolyoxometalate structures. We use density functional theory (DFT) to clarify the mechanism by which these species promote the hydrolysis of the phosphoester bond. The present calculations give insight into several key aspects of this reaction: (i) the speciation of this complex prior to interaction with the phosphate (DMF release, Mo-Cl hydrolysis, and pH influence on the speciation), (ii) the competition between phosphate addition and the molybdate nucleation process, (iii) and the mechanisms by which some plausible active species promote this hydrolysis in different conditions. We described thoroughly two different pathways depending on the nucleation possibilities of the molybdenum complex: one mononuclear mechanism, which is preferred in conditions in which very low complex concentrations are used, and another dinuclear mechanism, which is preferred at higher concentrations.

Structures and esterolytic reactivity of novel binuclear copper(ii) complexes with reduced l-serine Schiff bases as mimic carboxylesterases

Three novel binuclear copper(ii) complexes with reduced l-serine Schiff bases were synthesized and their structures were analyzed with single-crystal X-ray diffraction and DFT calculations. The crystal data revealed that all of these binuclear complexes are chiral. Both 5-halogenated (bromo- and chloro-) binuclear complexes exhibit right-handed helix structural character. Interestingly, the 5-methyl-containing analogue has a two-dimensional pore structure. In this paper, the esterolysis reactivity of the as-prepared complexes shows that in the hydrolysis of p-nitrophenyl acetate (PNPA) these three complexes provide 26, 18, 40-fold rate acceleration as compared to the spontaneous hydrolysis of PNPA at pH 7.0, respectively. Under selected conditions, in excess buffered aqueous solution a rate enhancement by three orders of magnitude was observed for the catalytic hydrolysis of another carboxylic ester, p-nitrophenyl picolinate (PNPP). These complexes efficiently promoted PNPP hydrolysis in a micellar solution of cetyltrimethylammonium bromide (CTAB), giving rise to a rate enhancement in excess of four orders of magnitude, which is approximately 2.0-3.2 times higher than that in the buffer.

Fabrication of highly active phosphatase-like fluorescent cerium-doped carbon dots for in situ monitoring the hydrolysis of phosphate diesters

The hydrolytic cleavage of BNPP was catalyzed and monitored by the fluorescent CeCDs.

Degradation of four organophosphorous pesticides catalyzed by chitosan-metal coordination complexes

Three types of chitosan with high (3.40 × 10(6)), medium (2.11 × 10(5)), and low (5.89 × 10(4)) molecular weights were chosen as ligands to synthesize chitosan magnesium, calcium, iron(III), and zinc coordination complexes. Degradation of four organophosphorous pesticides (dichlorvos, omethoate, dimethoate, and chlorpyrifos) by the above complexes in a heterogeneous system was studied using solid-phase extraction (SPE) and gas chromatography (GC). The degradation effect is related to the different types of chitosan, metal, and organophosphorus pesticides (OPs). Complexes of transition metals and the low molecular weight chitosan showed high hydrolytic activity. The chitosan-iron(III) complex was further used to study its catalytic kinetics on the hydrolysis of OPs. At pH 7.0 and 20 °C, the half-life of dichlorvos hydrolyzed by chitosan iron(III) was 52 h, whereas that of spontaneous dichlorvos hydrolysis was 105 h. The degradation ratio of omethoate and dimethoate increased to 38 and 52 %, respectively, which were 34 and 48 % higher than the control after 6 days at pH 7.0 and 20 °C. For all tested conditions, an increase of pH and temperature resulted in a higher degradation rate.

Catalytic Mechanism and Activity of a Nitrogen Heterocycle Lanthanum(III) Complex in the Hydrolysis of bis(4-nitrophenyl) Phosphate Ester

The system made up of a nitrogen heterocycle ligand and lanthanum(III) ion was used in the catalytic hydrolysis of bis(4-nitrophenyl) phosphate ester (BNPP). This catalytic system showed higher catalytic activity in this hydrolysis and better reproducibility and stability than other similar lanthanum(III) ion systems. The rate of the catalytic hydrolysis was about 108-fold faster than that of its spontaneous hydrolysis under the same conditions. Compared with previous Cu(II) or Ni(II) complexes containing the same ligand in water, the activity of the macrocyclic La(III) complexe is increased ca 104-fold. The experimental evidence showed that the mon-hydroxy complex made of the nitrogen heterocycle ligand and lanthanum(III) ion is the active species as catalyst in the catalytic hydrolysis of BNPP.

Kinetic and Mechanistic Investigations of Cleavage of P-Nitrophenyl Picolinate Catalysed by Ethylenediamine Cobalt(Ii) Complexes

Two novel ethylenediamine cobalt(II) complexes, CoL1 and CoL2, were synthesized and characterized, and were used as mimic hydrolases in the catalytic hydrolysis of a carboxylic ester p-nitrophenyl picolinate, (PNPP). Analysis of the specific absorption spectra of the hydrolytic reaction systems indicated that the catalytic hydrolysis involved key intermediates formed by PNPP with the cobalt(II) complexes. A mechanism for the PNPP hydrolysis has been proposed and the associated kinetic parameters have been calculated. The effects of acidity of the buffer solution, of the structure of the complexes, and of temperature on the rate of the catalysed hydrolysis have also been discussed.

Kinetic Studies of the Hydrolysis of Carboxylic Esters Catalysed by Ethylenediamine Nickel(Ii) Complexes

Three novel ethylenediamine nickel(II) complexes, NiL1, NiL2 and NiL3, were synthesized and characterized, and used as mimic hydrolases in the catalytic hydrolysis of a carboxylic ester (PNPP, p-nitrophenyl picolinate). Analysis of the specific absorption spectra of the hydrolytic reaction systems indicated that the catalytic hydrolysis involved the key intermediates formed by PNPP with the nickel(II) complexes. The catalytic mechanism of PNPP hydrolysis was also proposed. The kinetic parameters of the catalytic hydrolysis were calculated, thus the activation energies (∓ 5%) for the catalytic hydrolyses are 15.1, 12.4 and 11.2 kJ mol −1, respectively.

Synthesis and Kinetic Studies of Mono-Schiff Base Manganese(Iii) and Cobalt(Ii) Complexes with Aza-Crown Ether or Morpholino Pendants as Synthetic Hydrolases for P-Nitrophenyl Picolinate

Two mono-Schiff base manganese(III) and cobalt(II) complexes with benzo-10-aza-crown ether pendants (MnL12Cl, CoL12), and the analogues with morpholino pendants (MnL22Cl, CoL22) have been synthesised and employed as models for hydrolase enzymes to promote the hydrolysis of p-nitrophenyl picolinate (PNPP) in buffer solution. A kinetic model of PNPP cleavage catalysed by these complexes is proposed. The effects of the structures of the complexes and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit high catalytic activity and the rate increases with pH. In comparison with the crown-free analogues MnL22Cl and CoL22, the crowned Schiff base complexes MnL12Cl and CoL12 exhibit higher catalytic activity for promoting PNPP hydrolysis.

Metallomicellar Catalysis: Hydrolysis of Pnpp by Crowned Schiff Base Cobalt(Ii) Complexes in Micellar Solution

It has been reported that three aza crowned Schiff cobalt(II) complexes have been synthesised and characterised, and that the metallomicelles, made up of the three cobalt(II) complexes and surfactants(LSS, Brij35, CTAB) as mimic hydrolytic metalloenzyme, were used in the catalytic hydrolysis of carboxylic ester (PNPP) over a pH range of 7.0 - 8.2. The results revealed that the metallomicelles made up of the three cobalt(II) complexes and the surfactants are both efficient for catalysing PNPP hydrolysis with about three orders of magnitude in rate acceleration compared with the background rate of PNPP spontaneous hydrolysis. The effect of different surfactant micelles on the catalytic hydrolysis of PNPP in the metallomicelles follows the order: LSS > Brij35 > CTAB. The results showed that using the aza crowned Schiff base cobalt(II) complexes and their metallomicelles as the hydrolase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme.

Synthesis and Studies of Hydrolysis of p-nitrophenyl picolinate catalysed by Schiff base zinc (II) complexes with aza-crown ether or morpholino-pendants

Four Schiff base zinc (II) complexes with either benzo-10-aza-crown ether pendants or morpholino-pendants have been synthesised and employed as models for hydrolase enzymes by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP). A kinetic model of PNPP cleavage catalysed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of catalytic PNPP hydrolysis have been also examined. The rate increases with pH of the buffer solution; all four complexes exhibited high activity in the catalytic PNPP hydrolysis. Compared with their crown-free analogues, the crowned Schiff base complexes exhibit higher catalytic activity. The catalytic activity of a phenyl-bridged Schiff base complex is larger than that of an ethyl-bridged Schiff base complex under the same substitute groups and metal ion.