Weidong Jiang

Distinguishable effects of varied micelles on the hydrolysis of PNPP by dinuclear copper(II) complexes containing oxo-bridged unit

Two alkoxo/hydroxide-bridged dinuclear copper(II) complexes (Cu2L1 and Cu2L2) were prepared for evaluating their activity towards the hydrolysis of p-nitrophenyl picolinate (PNPP). Importantly, this work investigated the effects of varied micelles of four surfactants, e.g., cationic gemini 16-2-16 and 16-6-16, single-chain CTAB (hexadecyltrimethylammonium bromide), and LSS (n-lauroylsarcosine sodium), on the PNPP hydrolysis by the as-prepared copper(II) complexes. The experimental results indicate that at neutral pH both of complexes exhibited much better activity by excess four-order of magnitude rate enhancement. For instant, rate constants of PNPP hydrolysis by Cu2L1 and bromo-containing Cu2L2 are approximate 49,569.6- and 31,123.5-fold than that of PNPP spontaneous hydrolysis. In addition, the hydrolytic reactivity of the bromo-containing Cu2L2 is subordinate to that one without bromine, Cu2L1. Moreover, it is found that the micellar solution of gemini 16-6-16 is proved to be the best medium, and whereas LSS micellar solution is the worst one. Particularly, the pKa values of the Cu(II)-bound H2O are determined by a new methodology which is correlative to second derivatives.

Hydrolytic cleavage of p-nitrophenyl picolinate by mononuclear Zn(II) and Co(II) complexes with imidazole derivative in CTAB micellar solution

One new hydroxyl-functionalized imidazole derivative (L) was synthesized and characterized. Further, the related mononuclear zinc(II) and cobalt(II) complexes were prepared and used as mimic hydrolases to catalyze the hydrolytic cleavage of p-nitrophenyl picolinate (PNPP) in buffered aqueous solution and a micellar solution of cetyltrimethylammonium bromide (CTAB). Observations show that for all of catalytic systems, the hydrolysis of PNPP was pH-dependent in the pH range of 7.00–8.20. Besides, hydrolysis rates of PNPP displayed a constant increase with the increasing concentration of substrate. In the case of CoL-containing system, moreover, much greater acceleration for PNPP hydrolysis was observed in comparison with the ZnL-containing system. However, micellar effect of CTAB micelle aggregates on the PNPP hydrolysis was not obvious only showing 1.0 ∼ 1.3 folds rate difference in contrast to buffered aqueous solution.

Highly regioselective hydroformylation of higher olefins catalysed by rhodium-phosphine complexes in ionic liquid medium

Hydroformylation of higher olefins was performed efficiently in ionic liquids 1-n-alkyl-3-methylimidazolium p-toluenesulfonate ([Rmim][p-CH3C6H4SO3], R = n-butyl, n-octyl, n-dodecyl, n-cetyl) with the rhodium-phosphine complex Rh-BISBIS (Rh = rhodium complex catalyst precursor; BISBIS = sodium salt of sulfonated 2,2′-bis (diphenylphosphinomethyl)-1,1′-biphenyl) as catalyst. The catalytic system offers excellent regioselectivity towards the linear aldehyde with high activity and chemoselectivity for aldehyde. Furthermore, the ionic liquid containing catalyst can be facilely separated and reused three times without a significant decrease in the activity and selectivity. The ionic liquids [Rmim][p-CH3C6H4SO3] used as the reaction media bring some definitive advantages over the halogen-containing analogues [bmim]BF4 and [bmim]PF6.