@article {32775, title = {Iron Porphyrins Embedded into a Supramolecular Porous Organic Cage for Electrochemical CO2 Reduction in Water}, journal = {Angewandte Chemie International Edition}, volume = {57}, year = {2018}, pages = {9684-9688}, abstract = {

Abstract A porous organic cage composed of six iron tetraphenylporphyrins was used as a supramolecular catalyst for electrochemical CO2-to-CO conversion. This strategy enhances active site exposure and substrate diffusion relative to the monomeric catalyst, resulting in CO generation with near-quantitative Faradaic efficiency in pH 7.3 water, with activities reaching 55\ 250 turnovers. These results provide a starting point for the design of supramolecular catalysts that can exploit the properties of the surrounding matrix yet retain the tunability of the original molecular unit.

}, keywords = {CO2 reduction, ELECTROCHEMISTRY, porous organic cages, porphyrins, supramolecular chemistry}, doi = {10.1002/anie.201803873}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201803873}, author = {Smith, Peter T. and Benke, Bahiru Punja and Cao, Zhi and Kim, Younghoon and Nichols, Eva M. and Kim, Kimoon and Chang, Christopher J.} } @article {ISI:000227764700020, title = {Spectroscopy of non-heme iron thiolate complexes: insight into the electronic structure of the low-spin active site of nitrile hydratase.}, journal = {Inorg. Chem.}, volume = {44}, number = {6}, year = {2005}, month = {mar}, pages = {1826{\textendash}36}, abstract = {Detailed spectroscopic and computational studies of the low-spin iron complexes [Fe(III)(S2(Me2)N3 (Pr,Pr))(N3)] (1) and [Fe(III)(S2(Me2)N3 (Pr,Pr))]1+ (2) were performed to investigate the unique electronic features of these species and their relation to the low-spin ferric active sites of nitrile hydratases. Low-temperature UV/vis/NIR and MCD spectra of 1 and 2 reflect electronic structures that are dominated by antibonding interactions of the Fe 3d manifold and the equatorial thiolate S 3p orbitals. The six-coordinate complex 1 exhibits a low-energy S(pi) {\textendash}> Fe 3d(xy) (approximately 13,000 cm(-1)) charge-transfer transition that results predominantly from the low energy of the singly occupied Fe 3d(xy) orbital, due to pure pi interactions between this acceptor orbital and both thiolate donor ligands in the equatorial plane. The 3d(pi) {\textendash}> 3d(sigma) ligand-field transitions in this species occur at higher energies (>15,000 cm(-1)), reflecting its near-octahedral symmetry. The Fe 3d(xz,yz) {\textendash}> Fe 3d(xy) (d(pi) {\textendash}> d(pi)) transition occurs in the near-IR and probes the Fe(III)-S pi-donor bond; this transition reveals vibronic structure that reflects the strength of this bond (nu(e) approximately 340 cm(-1)). In contrast, the ligand-field transitions of the five-coordinate complex 2 are generally at low energy, and the S(pi) {\textendash}> Fe charge-transfer transitions occur at much higher energies relative to those in 1. This reflects changes in thiolate bonding in the equatorial plane involving the Fe 3d(xy) and Fe 3d(x2-y2) orbitals. The spectroscopic data lead to a simple bonding model that focuses on the sigma and pi interactions between the ferric ion and the equatorial thiolate ligands, which depend on the S-Fe-S bond angle in each of the complexes. These electronic descriptions provide insight into the unusual S = 1/2 ground spin state of these complexes: the orientation of the thiolate ligands in these complexes restricts their pi-donor interactions to the equatorial plane and enforces a low-spin state. These anisotropic orbital considerations provide some intriguing insights into the possible electronic interactions at the active site of nitrile hydratases and form the foundation for further studies into these low-spin ferric enzymes.}, keywords = {BINDING SITES, Computational Biology, ELECTROCHEMISTRY, Ferric Compounds, Ferric Compounds: chemical synthesis, Ferric Compounds: chemistry, Hydro-Lyases, Hydro-Lyases: chemistry, iron, Iron: chemistry, models, MOLECULAR, Molecular Conformation, molecular structure, PhD, SPECTROPHOTOMETRY, Sulfhydryl Compounds, Sulfhydryl Compounds: chemistry}, issn = {0020-1669}, doi = {10.1021/ic0487068}, url = {http://www.ncbi.nlm.nih.gov/pubmed/15762709}, author = {Kennepohl, Pierre and Neese, Frank and Schweitzer, Dirk and Jackson, Henry L and Kovacs, Julie A and Solomon, Edward I} } @article {754, title = {Synthesis and characterization of beta-trifluoromethyl-meso-tetraphenylporphyrins}, journal = {Journal of Organic Chemistry}, volume = {68}, number = {5}, year = {2003}, note = {ISI Document Delivery No.: 651PVTimes Cited: 18Cited Reference Count: 59}, month = {Mar}, pages = {1892-1900}, type = {Article}, abstract = {beta-Trifluoromethyl-meso-tetraphenylporphyrins were synthesized to investigate the electronic and steric effects of the trifluoromethyl groups on the macrocycle. Preparation of these novel porphyrins was carried out by copper-assisted trifluoromethylation of beta-tetrabromo-meso-tetraphenylporphyrin metal complexes and in situ generated CF3Cu. For comparison, the beta-methyl analogues were also prepared. Analysis of beta-trifluoromethylporphyrins by UV-vis, NMR, and cyclic voltammetry (CV) showed that the electron-withdrawing effects of the trifluoromethyl groups on the antipodal pyrroles required the macrocycle to take a fixed 18pi-electron pathway. UV-vis, CV, and molecular modeling studies suggest that the novel porphyrins are distorted following introduction of trifluoromethyl groups onto the pyrrolic beta-position of meso-tetraphenylporphyrin. The pK(a) difference of beta-tetrakis(trifluoromethyl)-meso-tetraphenylporphyrin from that of DBU in CH2Cl2, obtained by spectrophotometric titration, affirms that it is one of the most electron-deficient porphyrins so far prepared.}, keywords = {BROMINATED-PYRROLE TETRAPHENYLPORPHYRIN, COMPLEXES, EFFICIENT CATALYSTS, ELECTROCHEMISTRY, ELECTRON-DEFICIENT PORPHYRINS, HYDROXYLATION, METALLOPORPHYRINS, REDOX POTENTIALS, SUBSTITUENTS, X VARIES}, isbn = {0022-3263}, url = {://000181329900033}, author = {Terazono, Y. and Dolphin, D.} } @article {753, title = {Synthesis of the hemin of beta-tetrakis(trifluoromethyl)-meso-tetraphenylporphyrin and its evaluation as a P-450 mimic}, journal = {Inorganica Chimica Acta}, volume = {346}, year = {2003}, note = {ISI Document Delivery No.: 660EJTimes Cited: 4Cited Reference Count: 24}, month = {Mar}, pages = {261-264}, type = {Article}, abstract = {The hemin of beta-tetrakis(trifluoromethyl)-meso-tetraphenylporphyrin has been synthesized. Conventional methods for iron insertion failed; iron in low oxidation states (0 or II) brought about reduction of the macrocycle and Fe(III) failed to insert. Thus, insertion of iron into the macrocycle required the formation of the lithium complex, from lithium bis(trimethylsilyl)amide, followed by ferrous chloride. The novel hemin was tested as a catalyst for oxidations of cyclohexane and cyclohexene using iodosylbenzene as an oxidant and was found to be ineffective. (C) 2002 Elsevier Science B.V. All rights reserved.}, keywords = {CATALYSIS, CATALYSTS, cytochrome P-450, ELECTROCHEMISTRY, METALLOPORPHYRINS, OXIDATION, PORPHYRIN, porphyrins, POSITIONS, POTENTIALS}, isbn = {0020-1693}, url = {://000181820600033}, author = {Terazono, Y. and Dolphin, D.} } @article {5117, title = {Tensor LEED analysis for the electrodeposited Pt(111)-(3x3)-Ag,I surface structure}, journal = {Surface Science}, volume = {490}, number = {3}, year = {2001}, note = {ISI Document Delivery No.: 473XWTimes Cited: 5Cited Reference Count: 34}, month = {Sep}, pages = {256-264}, type = {Article}, abstract = {A crystallographic analysis is reported using low-energy electron diffraction (LEED) in the tensor LEED approach for the electrodeposited coadsorption (3 x 3) structure with 4/9 monolayer (ML) of silver and 4/9 ML of iodine on the Pt(1 1 1) surface. The structure approximates a two-layer slice of bulk AgI cut parallel to its (1 1 1) plane and superimposed on the substrate with the Ag atoms in contact with the topmost Pt(1 1 1) layer, and the I atoms forming an overlayer on the Ag atoms. There are two types of Ag atoms in the (3 x 3) unit mesh; one type bonds to a single Pt atom, while the other type bonds to three Pt atoms. The average Ag-Pt bond distances are close to 2.48 and 2.82 (A) over circle respectively for the one and three-coordinate Ag atoms, but both types of Ag atoms bond to three I atoms with an average Ag-I distance of 2.67 (A) over circle. No significant corrugation is observed for either the I layer or the Ag layer. (C) 2001 Elsevier Science B.V. All rights reserved.}, keywords = {ADSORBATES, ADSORPTION, AG, chemisorption, ELECTROCHEMISTRY, ENERGY-ELECTRON-DIFFRACTION, IODINE, LOW ENERGY ELECTRON DIFFRACTION (LEED), METAL-SURFACES, platinum, PT(111), SCANNING-TUNNELING-MICROSCOPY, silver}, isbn = {0039-6028}, url = {://000171075300007}, author = {Labayen, M. and Harrington, D. A. and Saidy, M. and Mitchell, K. A. R.} } @article {4656, title = {Tensor LEED analyses for three chemisorbed structures formed by iodine on a Pt(111) surface}, journal = {Surface Review and Letters}, volume = {6}, number = {5}, year = {1999}, note = {ISI Document Delivery No.: 300LQTimes Cited: 17Cited Reference Count: 406th International Conference on the Structure of Surfaces (ICSOS-6)JUL 26-30, 1999VANCOUVER, CANADAUniv British Columbia}, month = {Oct}, pages = {871-881}, type = {Proceedings Paper}, abstract = {Three distinct ordered iodine structures on a Pt(lll) surface have been studied with LEED crystallography in the coverage range 0.33-0.44 monolayers. These surfaces have translational symmetries of the ((root 3 x root 3)R30 degrees, (root 7 x root 7)R19.1 degrees and (3 x 3) types, and they all involve overlayer adsorption on the basically unreconstructed metal structures. The root 3 surface phase is indicated to have essentially all I atoms adsorbed at the regular threefold sites of the fee type (i.e. 3f sites), with no significant involvement by the corresponding sites of the hcp type (i.e. 3h sites). The root 7 structure has one I on an atop Pt site, and one each at 3f and 3h sites per unit mesh, while the (3 x 3) surface has one I on an atop site and three on bridge sites per unit mesh. The I corrugation is about 0.5 Angstrom for the root 7 structure, but is reduced to around 0.1 Angstrom at the (3 x 3) surface. The surface I-Pt bond lengths from these analyses show a general tendency to follow trends expected with the varying I coordination numbers. A preliminary discussion is given for uncertainties associated with some relaxations indicated in the metallic structures.}, keywords = {ADSORBATES, ADSORPTION, ELECTROCHEMISTRY, ENERGY-ELECTRON-DIFFRACTION, METAL-SURFACES, PT(100), RELIABILITY, RH(111), SCANNING TUNNELING MICROSCOPY, TRANSFORMATIONS}, isbn = {0218-625X}, url = {://000086254800043}, author = {Saidy, M. and Mitchell, K. A. R. and Furman, S. A. and Labayen, M. and Harrington, D. A.} } @article {2891, title = {THE EFFECT OF METAL-COMPLEXES IN THE ELECTROCHEMICALLY MEDIATED OXYGEN BLEACHING OF WOOD PULP}, journal = {Tappi Journal}, volume = {76}, number = {10}, year = {1993}, note = {ISI Document Delivery No.: MA717Times Cited: 13Cited Reference Count: 34}, month = {Oct}, pages = {139-147}, type = {Article}, abstract = {The electrochemical behavior of transition-metal complexes is correlated with their effect in promoting electrochemically mediated oxygen bleaching of unbleached kraft softwood pulp. Ions of Fe, Mn, Co, Cr, Cu, and V with various ligands were examined in oxygen bleaching experiments at pH 9.4, 11.2, and 14. Only ferricyanide, iron/2,2{\textquoteright}-dipyridyl, and ferrate exhibited significant synergistic effects with oxygen. Chemicals with reduction potential lower than that of the ferrocyanide couple at the pH of reaction, or those without reversible redox behavior, showed no synergistic effect. A mechanism is proposed in which the reaction of lignin with oxygen is initiated by oxidation of lignin with the higher valent species of the metal redox couple The metal redox couple may also catalyze peroxide decomposition via Fenton chemistry to generate the hydroxyl radical and thus promote degradation of cellulose.}, keywords = {AMPEROMETRY, BIBLIOGRAPHIES, bleaching, CATALYSTS, ELECTROCHEMISTRY, OXYGEN, REDOX POTENTIAL, transition metals}, isbn = {0734-1415}, url = {://A1993MA71700024}, author = {Perng, Y. S. and Oloman, C. W. and James, Brian R.} }