RESUMEN
A series of novel nickel complexes 1-9 supported by NNO-tridentate Schiff-base derivatives have been synthesized and characterized. Treatment of the pro-ligands [L(1)-H = 2,4-di-tert-butyl-6-(((2-(dimethylamino)ethyl)imino)methyl)phenol, L(2)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4,6-bis(2-phenylpropan-2-yl)phenol, L(3)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)phenol] with Ni(OAc)2·4H2O in refluxing ethanol afforded mono- or bimetallic nickel complexes {[(L(1))Ni(OAc)] (1); (L(2))Ni(OAc)] (2); (L(3))2Ni2(OAc)2(H2O)] (3)}. Alcohol-solvated trimetallic nickel acetate complexes {[(L(3))2Ni3(OAc)4(MeOH)2] (4); (L(3))2Ni3(OAc)4(EtOH)2] (5)} could be generated from the reaction of L(3)-H and anhydrous nickel(II) acetate with a ratio of 2:3 in refluxing anhydrous MeOH or EtOH. The reaction of nickel acetate tetrahydrate and L(4)-H to L(6)-H [L(4)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-5-methoxyphenol, L(5)-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4-methoxy-phenol, L(6)-H = 2-(((2-(dimethylamino)ethyl)imino)(phenyl)methyl)phenol] produced, respectively, the alcohol-free trinuclear nickel complexes {[(L(4))2Ni3(OAc)4] (7); [(L(5))2Ni3(OAc)4] (8); [(L(6))2Ni3(OAc)4] (9)} with the same ratio in refluxing EtOH under the atmospheric environment. Interestingly, recrystallization of [(L(3))2Ni3(OAc)4(MeOH)] (4) or [(L(3))2Ni3(OAc)4(EtOH)] (5) in the mixed solvent of CH2Cl2/hexane gives [(L(3))2Ni3(OAc)4] (6), which is isostructural with analogues 7-9. All bi- and trimetallic nickel complexes exhibit efficient activity and good selectivity for copolymerization of CO2 with cyclohexene oxide, resulting in copolymers with a high alternating microstructure possessing ≥99% carbonate-linkage content. This is the first example to apply well-defined trinuclear nickel complexes as efficient catalysts for the production of perfectly alternating poly(cyclohexene carbonate).
RESUMEN
A series of bimetallic penta-coordinated copper complexes [Ln2Cu2(OAc)2] (1, 3-7), a mononuclear tetra-coordinated copper complex [LnCu(OAc)] (8 and 9), and a penta-coordinated copper complex [L2Cu(OAc)(H2O)] (10) were prepared by the reaction of Cu(OAc)2·H2O with a variety of NNO-tridentate Schiff-base ligands (L1-H-L9-H) in refluxing 95% ethanol, respectively. However, a dinuclear copper complex [(L2)2Cu2(OAc)2] (2) can be obtained from the treatment of L2-H with a stoichiometric amount of anhydrous Cu(OAc)2 in refluxing absolute EtOH under a dry nitrogen atmosphere. All of these copper complexes are active for the alternating copolymerization of cyclohexene oxide and cyclic anhydride, affording polyesters with moderate polydispersity. In particular, dinuclear copper complexes 1 and 2 performed satisfactorily to produce polyesters with controllable molecular weights and high ester linkages. This is the first example of well-defined copper acetate catalysts active for the copolymerization of cyclohexene oxide-phthalic anhydride or cyclohexene oxide-succinic anhydride which may be advantageous in terms of obviating the use of co-catalysts and low cost as well as an effective copolymerization for the formation of biodegradable polyesters in a controlled fashion.
RESUMEN
A rapid, sensitive, and selective ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) in the multiple reaction monitoring (MRM) mode has been developed and validated to investigate the distribution of trans-Resveratrol (Resv) and its metabolites in rats following intravenous (IV) administration at 20mg/kg body weight (BW). Resv and Resv metabolites were analyzed in the negative electrospray ionization mode and eluted with retention times of about 0.69-2.22min with a runtime of 7min. Stable deuterium-labeled Resv and its metabolites were used as the internal standards to correct for matrix effects and to allow for accurate quantification of Resv and its metabolites in a complex biological system. The method was validated with respect to linearity, within- and between-day precision, limit of quantification, recovery, and accuracy for all analytes. Upon examination at 0.5, 1, 2, and 4h post-administration, concentrations of Resv and its metabolites were the highest in the kidney, followed by plasma; specifically, the glucuronidated forms were the most abundant. In the liver and the brain, the predominant forms were the sulfated derivatives. In contrast, heart tissue contained the highest concentration of unmodified Resv at 0.5h post IV administration. The combined use of UPLC-MS/MS and isotope-dilution analysis, proved to be accurate and reliable in identifying and quantifying Resv and its various metabolites in biological samples at the nanomolar range. This technology is potentially applicable for other pharmacokinetic studies.