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ABSTRACT 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. [ABSTRACT FROM AUTHOR]

Two novel phenoxo-bridged homobinuclear copper(II) complexes with L-threonine Schiff bases as artificial hydrolases were prepared and screened for catalytic activity in the hydrolysis ofp-nitrophenyl picolinate (PNPP), a classic model of carboxylic acid esters. Kinetic analysis testified that the two complexes exhibited good activity with rate acceleration of two orders of magnitude in aqueous solution. In addition, the one copper(II) complex containing 5’-bromo substituent was much more efficient than its bromo-free analogue, showing approximately 1.1∼5.3 times kinetic advantage over a pH range of 7.00–8.20. [Supplementary materials are available for this article. Go to the publisher's online edition ofSynthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistryfor Figures 1S–3S.] [ABSTRACT FROM PUBLISHER]

In this article, the effects of different micelles and Schiff base ligands on the hydrolytic kinetics of p-nitrophenyl picolinate (PNPP) were evaluated. The results reveal that the biggest rate enhancement for PNPP hydrolysis was given in Gemini 16-6-16 micellar solution relative to other four reaction media, that is, cetyltrimethylammonium bromide (CTAB), n-lauroylsarcosine sodium (LSS), polyoxyethylene (23) lauryl ether (Brij35) and pure buffer. Moreover, the hydrolytic rates of PNPP in other four media decreased in the order LSS > CTAB > Buffer > Brij35. The structural effects of Mn(III) catalysts clearly testify that a relatively open active site facilitates the formation of reactive substrate-catalyst complex. [ABSTRACT FROM AUTHOR]

Hydrolysis of p-nitrophenyl picolinate (PNPP) catalyzed by three Schiff base Mn(III) complexes (MnL2Cl) were investigated in Gemini 16-6-16 micelle media. [image omitted], [image omitted] and [image omitted] systems give 835-, 969-, and 1931-fold rate enhancements in the hydrolysis of PNPP under the comparable conditions, respectively. Moreover, Effects of varied micelles on the reactivity of PNPP hydrolysis were especially studied. The results obtained indicate that rates of hydrolysis of PNPP are approximately 1.5- and 4-fold larger in Gemini 16-6-16 micelles than in CTAB micelles and Brij35 micelles, respectively. Effects of ligand structure on the activities of these three complexes are discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: Two crowned Schiff base manganese(III) complexes (MnL2Cl, L=L1, L2) were used to catalyze the hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) in Gemini surfactants [bis(hexadecyldimethylammonium)hexane bromide (abbreviation 16-6-16, 2Br−)] solution. In comparison with the rate of BNPP spontaneous hydrolysis, a six orders of magnitude in rate enhancement was observed in /16-6-16 and /16-6-16 systems. Owing to the different structure, shows better activity than . Especially, the effects of three different micelles, i.e., 16-6-16 micelles, CTAB (hexadecyltrimethylammonium bromide) micelles, LSS (n-lauroooylsarcosine sodium) micelles, on the hydrolysis of BNPP catalyzed by were evaluated at pH7.50. Experimental observations clearly demonstrate that Gemini 16-6-16 micelle is the best one for BNPP hydrolysis among three kinds of micellar media. [Copyright &y& Elsevier]

Two Schiff base cobalt(II) complexes containing crowned substituents have been synthesized and employed to promote the hydrolysis of p-nitrophenyl picolinate (PNPP) in a buffered micellar solution formed by a cationic Gemini surfactant, bis(hexadecyldimethylammonium)hexane bromide (G(hex)C16, 2Br-) over a pH range of 6.50–8.50. In comparison, the reactivity of PNPP hydrolysis catalyzed by the same catalysts in the other micellar system, formed by a conventional single-chain analogue, that is, hexadecyltrimethylammonium bromide (CTAB), has also been evaluated under a selected condition. The results clearly reveal that the two metallomicelles made of the aforementioned Co(II) complexes and the G(hex)C16 are both efficient for catalyzing PNPP hydrolysis with about 3 orders of magnitude in rate acceleration compared with the background rate of PNPP spontaneous hydrolysis. Moreover, the rates of PNPP hydrolysis catalyzed by the two cobalt(II) complexes in G(hex)C16 micelles are about 2 times higher than in CTAB micelles, correspondingly. In addition, observations show that steric hindrance of substituents of the two complexes is also one of the major influencing factors in the PNPP hydrolytic reaction. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 672–680, 2007 [ABSTRACT FROM AUTHOR]

Two new copper(II) complexes (1 and 2) with reduced L -histidine Schiff bases were synthesized and characterized using single-crystal X-ray diffraction, powder X-ray diffraction, UV-visible spectroscopy, and thermal analysis. Single-crystal analysis reveals that 5-methyl-containing 1 possesses a simple phenoxo-bridged binuclear unit, while 5-bromine-substituted 2 possesses a metal–organic cage (MOC) structure. The as-prepared complexes as artificial metallohydrolases displayed catalytic activity towards the hydrolysis of both PNPP (p-nitrophenyl picolinate) and PNPA (p-nitrophenyl acetate). These two complexes provided 28-fold (for 1) and 39-fold (for 2) rate enhancements in comparison with spontaneous hydrolysis of PNPA, respectively. With regard to PNPP, its hydrolysis was accelerated by two orders of magnitude in the presence of 1 or 2. Additionally, positive micellar effects of bis(hexadecyldimethylammonium)hexane bromide (16-6-16) and N-octyldocosylammonium bromide (C22H45N(CH3)2C8H17Br, abbr. C22/8) were observed for the PNPA hydrolysis by 1 or 2, resulting in 1.3 to 3.9 times acceleration compared to that in buffered aqueous solution. In micellar solution of N,N-dimethyl-n-lauroylsarcosine sodium (LSS), no obvious rate enhancement was observed for the PNPA hydrolysis by 1 or 2. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Three new bi- or tetranuclear copper (II) complexes (complexes 1, 2 and 3) with reduced N-salicylate threonine were synthesized and characterized by single crystal X-ray diffraction, X-ray powder diffraction, UV–vis, and thermogravimetric analysis. Single-crystal diffraction analysis reveals that these complexes have similar coordination modes and conformations which were linked into multidimensional networks through some weak interactions. These three complexes were employed to promote the hydrolytic cleavage of p-nitrophenyl picolinate (PNPP) and p-nitrophenyl acetate (PNPA). Catalytic reactivities of the as-prepared complexes show that in the hydrolysis of p-nitrophenyl acetate (PNPA) these three complexes provide 51, 45, 39-fold rate acceleration as compared to spontaneous hydrolysis of PNPA at pH 7.0, respectively. Under selected conditions, excess three orders of magnitude rate enhancement were observed for the catalytic hydrolysis of another carboxylic ester, p-nitrophenyl picolinate (PNPP). Furthermore, these complexes efficiently promote the PNPA hydrolysis in micellar solution of cetyltrimethylammonium bromide (CTAB) or bis(hexadecylhexmethyl ammonium)ethane bromide (16−6−16) giving rise to excess two orders of magnitude rate enhancement which is approximate 2.0 − 4.0 times higher than that in the buffer. However, the introduction of micelles of n-lauroylsarcosine sodium (LSS) or double-chained C 22/8 surfactant did not increase the rate or even inhibited the hydrolysis reaction in contrast with buffered aqueous medium. [Display omitted] [ABSTRACT FROM AUTHOR]

Organic small-molecules of multiple stimuli-responses were widely paid attention, which can be applied in multiple fields simultaneously, such as thermal sensor, force response, pH probe, reagents for the detection of metal ion and so forth. In the present work, three novel coumarin derivatives (XDS-R) were synthesized from various salicylaldehydes containing different substituents (R = H, Cl, Br), following by investigations about their multiple stimuli-responsive properties concerning aggregation-induced emission (AIE), mechanochromism, thermochromism and pH response. Single crystals of XDS-R indicate that intramolecular hydrogen bonds cause the restriction of intramolecular vibration, leading to AIE character and mechanochromic property. Interestingly, two substituents (H, Cl) have little effect on fluorescence intensity and color, and whereas have distinguishable influences on functionalized fluorescence response. In the pH range of 2.00–8.00, only XDS-H exhibited regular pH-response, while XDS-Cl and XDS-Br showed excellent pH tolerance. Mechanochromic XDS-R is able to recover to original state under heating. A simple multilevel anticounterfeit label was made by the combination of XDS-Cl and previous-reported DDHAC without an automatic heat-inspired recovery. Combined multilevel stimuli-responsive material of XDS-Cl and previous DDHAC displayed potential application of anti-counterfeiting mark. [Display omitted] • Coumarin-Salicylaldehyde Schiff Bases were evaluated their stimuli responses. • Multi-stimuli responses were gained including AIE, pH-response, mechano- and thermochromism. • Combining XDS-Cl and previous DDHAC provided a multilevel anti-counterfeiting material. [ABSTRACT FROM AUTHOR]

Multi-stimuli-responsive materials, which can show color/fluorescence change in response to external chemical or physical stimuli, have received increasing attention due to the capacities for facile realization of multifunctional sensing. Herein, we presented a Et 2 N-substituted salicylaldehyde Schiff base compound (DDHAC) with multi-stimuli-responsive behaviors. An investigation of the photophysical properties in solution demonstrated DDHAC was an excited-state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) active molecule. Owing to structural flexibility from salicylaldehyde Schiff base, the compound displayed reversible mechanochromic and thermochromic behavior, which were associated with the crystalline-to-amorphous and crystalline-to-crystalline, respectively. Moreover, the Et 2 N group endowed DDHAC with the capability that response of protonation. Due to its protonation effect, DDHAC could serve as a unique optical probe for discriminating CHCl 3 from organic solvents assisted by UV irradiation. The selectivity was attributed to the interaction of DPPTP with HCl gas from photodecomposition product of chloroform. [Display omitted] • A multi-stimuli-responsive compound DDHAC based on Et 2 N-substituted salicylaldehyde Schiff base was developed. • DDHAC showed mechanochromism, thermochromism and acdichromism behaviors. • DDHAC could serve as a unique optical probe for discrimination CHCl 3 from organic solvents assisted by UV irradiation. [ABSTRACT FROM AUTHOR]