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The knowledge of accurate bond strengths is a fundamental basis for a proper analysis of chemical reaction mechanisms. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Feâ€'O and Feâ€'S bond energies of paraâ€substituted phenoxydicarbonyl( η5â€cyclopentadienyl) iron [ pâ€Gâ€C6H4O( η5â€C5H5)Fe(CO)2, abbreviated as pâ€Gâ€C6H4OFp ( 1), where G = NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2] and paraâ€substituted benzenethiolatodicarbonyl( η5â€cyclopentadienyl) iron [ pâ€Gâ€C6H4S( η5â€C5H5)Fe(CO)2, abbreviated as pâ€Gâ€C6H4SFp ( 2)] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of Î' Hhet(Feâ€'O)'s and Î' Hhet(Feâ€'S)'s. The excellent linear freeâ€energy relations [ r = 0.99 (g, 1a), 1.00 (g, 2b)] among the Î'Î' Hhet (Feâ€'O)'s and Î'p ka's of Oâ€'H bonds of pâ€Gâ€C6H4OH or Î'Î' Hhet(Feâ€S)'s and Î'p ka's of Sâ€'H bonds of pâ€Gâ€C6H4SH imply that the governing structural factors for these bond scissions are similar. And the linear correlations [ r = âˆ'0.99 (g, 1g), âˆ'0.98 (g, 2h)] among the Î'Î' Hhet (Feâ€O)'s or Î'Î' Hhet(Feâ€S)'s and the substituent σpâˆ' constants show that these correlations are in accordance with Hammett linear freeâ€energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of Î' Hhet(Feâ€'O)'s or Î' Hhet(Feâ€'S)'s. Î'Î' Hhet(Feâ€'O)'s(g) ( 1) and Î'Î' Hhet(Feâ€'S)'s(g)( 2) follow the Captoâ€dative principle. The substituent effects on the Feâ€'O bonds are much stronger than those on the less polar Feâ€'S bonds. Insight from this work may help the design of more effective catalytic processes. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Metal-ligand bond enthalpy data can afford invaluable insights into important reaction patterns in organometallic chemistry and . In this paper, the Fe-O and Fe-S homolytic bond dissociation energies [Δ Hhomo(Fe-O)'s and Δ Hhomo(Fe-S)'s] of two series of para-substituted phenoxydicarbonyl( η5-cyclopentadienyl) iron [ p-G-C6H4OFp ( 1)] and (para-substituted benzenethiolato)dicarbonyl( η5-cyclopentadienyl) iron [ p-G-C6H4SFp ( 2)] were studied using Hartree-Fock and density functional theory (DFT) methods with large basis sets. In this study, Fp is ( η5-C5H5)Fe(CO)2, and G are NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2. The results show that DFT methods can provide the best price/performance ratio and accurate predictions of Δ Hhomo(Fe-O)'s and Δ Hhomo(Fe-S)'s. The remote substituent effects on Δ Hhomo(Fe-O)'s and Δ Hhomo(Fe-S)'s [ΔΔ Hhomo(Fe-O)'s and ΔΔ Hhomo(Fe-S)'s] can also be satisfactorily predicted. The good correlations [ r = 0.98 (g, 1), 0.98 (g, 2)] of ΔΔ Hhomo(Fe-O)'s and ΔΔ Hhomo(Fe-S)'s in series 1 and 2 with the substituent σp+ constants imply that the para-substituent effects on Δ Hhomo(Fe-O)'s and Δ Hhomo(Fe-S)'s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. ΔΔ Hhomo(Fe-O)'s ( 1) and ΔΔ Hhomo(Fe-S)'s ( 2) conform to the captodative principle. Insight from this work may help the design of more effective catalytic processes. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The knowledge of accurate bond strengths is a fundamental basis for a proper analysis of chemical reaction mechanisms. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Feâ€'O and Feâ€'S bond energies of paraâ€substituted phenoxydicarbonyl( η5â€cyclopentadienyl) iron [ pâ€Gâ€C6H4O( η5â€C5H5)Fe(CO)2, abbreviated as pâ€Gâ€C6H4OFp ( 1), where G = NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2] and paraâ€substituted benzenethiolatodicarbonyl( η5â€cyclopentadienyl) iron [ pâ€Gâ€C6H4S( η5â€C5H5)Fe(CO)2, abbreviated as pâ€Gâ€C6H4SFp ( 2)] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of Î' Hhet(Feâ€'O)'s and Î' Hhet(Feâ€'S)'s. The excellent linear freeâ€energy relations [ r = 0.99 (g, 1a), 1.00 (g, 2b)] among the Î'Î' Hhet (Feâ€'O)'s and Î'p ka's of Oâ€'H bonds of pâ€Gâ€C6H4OH or Î'Î' Hhet(Feâ€S)'s and Î'p ka's of Sâ€'H bonds of pâ€Gâ€C6H4SH imply that the governing structural factors for these bond scissions are similar. And the linear correlations [ r = âˆ'0.99 (g, 1g), âˆ'0.98 (g, 2h)] among the Î'Î' Hhet (Feâ€O)'s or Î'Î' Hhet(Feâ€S)'s and the substituent σpâˆ' constants show that these correlations are in accordance with Hammett linear freeâ€energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of Î' Hhet(Feâ€'O)'s or Î' Hhet(Feâ€'S)'s. Î'Î' Hhet(Feâ€'O)'s(g) ( 1) and Î'Î' Hhet(Feâ€'S)'s(g)( 2) follow the Captoâ€dative principle. The substituent effects on the Feâ€'O bonds are much stronger than those on the less polar Feâ€'S bonds. Insight from this work may help the design of more effective catalytic processes. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The flower buds of Lonicera japonica are widely used in Chinese medicine for their anti-inflammatory properties. The reason why L. japonica has potent and significant effects is that it contains various active components, especially chlorogenic acid (CGA). In the present study, we isolated a hydroxycinnamoyl-CoA quinate hydroxycinnamoyl transferase (HQT) gene encoding a protein of 439 amino acids from L. japonica. The RT-PCR results showed that tissue distribution of HQT was in accordance with the pattern of CGA content. The corresponding cDNAs were expressed in Escherichia coli as fusion proteins. Recombinant HQT exhibited catalysis activity in esterification of quinic acid with caffeoyl-CoA to generate CGA. Purified proteins demonstrated similar kinetic properties as HQT isolated from other species. This work is of significance for further studies concerned with strengthening the efficacy of L. japonica by means of improved CGA content and exploring the biosynthesis of CGA in vitro., (© Georg Thieme Verlag KG Stuttgart · New York.)