Considerable attention has been devoted to the immobilization of discrete epoxidation catalysts onto solid supports due to the possible benefits of site isolation such as increased catalyst stability, catalyst recycling, and product separation. A synthetic metal-template/metal-exchange method to imprint a covalently attached bis-1,10-phenanthroline coordination environment onto high-surface area, mesoporous SBA-15 silica is reported herein along with the epoxidation reactivity once reloaded with manganese. Comparisons of this imprinted material with material synthesized by random grafting of the ligand show that the template method creates more reproducible, solution-like bis-1,10-phenanthroline coordination at a variety of ligand loadings. Olefin epoxidation with peracetic acid shows the imprinted manganese catalysts have improved product selectivity for epoxides, greater substrate scope, more efficient use of oxidant, and higher reactivity than their homogeneous or grafted analogues independent of ligand loading. The randomly grafted manganese catalysts, however, show reactivity that varies with ligand loading while the homogeneous analogue degrades trisubstituted olefins and produces trans-epoxide products from cis-olefins. Efficient recycling behavior of the templated catalysts is also possible.

Angewandte Chemie International EditionVolume 46, Issue 6 p. 945-947 Communication Site Isolation and Epoxidation Reactivity of a Templated Ferrous Bis(phenanthroline) Site in Porous Silica† Tracy J. Terry, Tracy J. Terry Department of Chemistry, Stanford University, Stanford, CA 94305, USA, Fax: (+1) 650-725-0259Search for more papers by this authorGeraud Dubois Dr., Geraud Dubois Dr. Department of Chemistry, Stanford University, Stanford, CA 94305, USA, Fax: (+1) 650-725-0259Search for more papers by this authorAndrew Murphy Dr., Andrew Murphy Dr. Department of Chemistry, Stanford University, Stanford, CA 94305, USA, Fax: (+1) 650-725-0259Search for more papers by this authorT. Daniel P. Stack Prof., T. Daniel P. Stack Prof. [email protected] Department of Chemistry, Stanford University, Stanford, CA 94305, USA, Fax: (+1) 650-725-0259Search for more papers by this author Tracy J. Terry, Tracy J. Terry Department of Chemistry, Stanford University, Stanford, CA 94305, USA, Fax: (+1) 650-725-0259Search for more papers by this authorGeraud Dubois Dr., Geraud Dubois Dr. Department of Chemistry, Stanford University, Stanford, CA 94305, USA, Fax: (+1) 650-725-0259Search for more papers by this authorAndrew Murphy Dr., Andrew Murphy Dr. Department of Chemistry, Stanford University, Stanford, CA 94305, USA, Fax: (+1) 650-725-0259Search for more papers by this authorT. Daniel P. Stack Prof., T. Daniel P. Stack Prof. [email protected] Department of Chemistry, Stanford University, Stanford, CA 94305, USA, Fax: (+1) 650-725-0259Search for more papers by this author First published: 22 January 2007 https://doi.org/10.1002/anie.200603423Citations: 43 † This work was supported by the NIH (grant GM-50730). We thank Dr. G. Li from the Soils and Environmental Biogeochemistry laboratory at Stanford University for ICP analysis, and Prof. E. I. Solomon for EPR instrument time. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract Teaching an old ligand new tricks: Attachment of a CuI–bis(phenanthroline) complex to mesoporous silica and metal exchange create site-isolated FeII–bis(phenanthroline) complexes which efficiently epoxidize terminal olefins with peracetic acid (see scheme). This strategy side-steps the formation of a FeII–tris(phenanthroline) complex, which predominates in solution. Citing Literature Supporting Information Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2007/z603423_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume46, Issue6January 29, 2007Pages 945-947 RelatedInformation

The crystal structure of rhodopsin revealed a cytoplasmic helical segment (H8) extending from transmembrane (TM) helix seven to a pair of vicinal palmitoylated cysteine residues. We studied the structure of model peptides corresponding to H8 under a variety of conditions using steady-state fluorescence, fluorescence anisotropy, and circular dichroism spectroscopy. We find that H8 acts as a membrane-surface recognition domain, which adopts a helical structure only in the presence of membranes or membrane mimetics. The secondary structural properties of H8 further depend on membrane lipid composition with phosphatidylserine inducing helical structure. Fluorescence quenching experiments using brominated acyl chain phospholipids and vesicle leakage assays suggest that H8 lies within the membrane interfacial region where amino acid side chains can interact with phospholipid headgroups. We conclude that H8 in rhodopsin, in addition to its role in binding the G protein transducin, acts as a membrane-dependent conformational switch domain.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The first 1,3,5-triaza-7-phosphaadamantane (PTA) ligated iridium compounds have been synthesized. The reaction of PTA with [Ir(COD)Cl]2 (COD = 1,5-cyclooctadiene) under a CO atmosphere produces an inseparable mixture of [Ir(PTA)3(CO)Cl] (1) and the PTA analogue of Vaska's compound, [Ir(PTA)2(CO)Cl] (2). Compound 1 and [Ir(PTA)4(CO)]Cl (3) were prepared via ligand substitution reactions of PTA with Vaska's compound, trans-Ir(PPh3)2(CO)Cl, in absolute and 95% ethanol, respectively. Complex 3 crystallizes in the orthorhombic space group Pbca with a = 20.3619(4) A, b = 14.0345(3) A, c = 24.1575(5) A, and Z = 8. Single-crystal X-ray diffraction studies show that 3 has a trigonal bipyramidal structure in which the CO occupies an axial position. This is the first crystallographically characterized [IrP4(CO)]+ complex in which the CO is axially ligated. Compound 1 was converted into 3 by ligand substitution with 1 equiv of PTA in water. Interestingly, the reaction of 3 with excess NaCl did not result in the production of 1, but instead the formation of the dichloro species, [Ir(PTAH)2(PTA)2Cl2]Cl3 (4) (PTAH = protonated PTA). Dissolution of 1 or 3 in dilute HCl produced 4 and a dihydrido species, [Ir(PTAH)4(H)2]Cl5 (5), which were readily separated by inspection due to their different crystal habits. Compound 5 crystallizes in the triclinic space group P1 with a = 12.4432(9) A, b = 12.5921(9) A, c = 16.3231(12) A, alpha = 76.004(1) degrees, beta = 71.605(1) degrees, gamma = 69.177(1) degrees, and Z = 2. Complex 5 exhibits a distorted octahedral geometry with two hydride ligands in a cis configuration. A rationale consistent with these reactions is presented by consideration of the steric and electronic properties of the PTA ligand.