CataLight: The Collaborative Research Center for Light-Driven Catalysis in Soft Matter

This invited Team Profile was created by the Collaborative Research Center for Light-Driven Catalysis in Soft Matter, CataLight , located at Friedrich Schiller University Jena, Ulm University, Max Planck Institute of Polymer Research (MPI) and Johannes Gutenberg University Mainz, University of Vienna, and the Center of Electron Microscopy, Ulm University. The authors, who include members of the Kranz and Leopold Groups , the Schacher Group , and the Streb Group , recently published an article on local measurements of light-driven activity at heterogenized water oxidation catalysts using nanoporous block copolymers: “Multimodal Analysis of Light-Driven Water Oxidation in Nanoporous Block Copolymer Membranes”, J. Kund, J.-H. Kruse, A. Gruber, I. Trentin, M. Langer, C. Read, G. Neusser, D. Blaimer, U. Rupp, C. Streb, K. Leopold, F. H. Schacher, C. Kranz, Angew. Chem. Int. Ed. 2023 , e202217196 .     

The Book Corner

Abstract

Liquid Chromatography/Mass Spectrometry, Techniques and Applications, A. L. Yergey, C. G. Edmonds, I. A. S. Lewis, and M. L. Vestal, Modern Analytical Chemistry Series, D. Hercules, Editor, 306 pages, Plenum Press, New York and London, 1989. $65.00; price 20% higher outside USA and Canada.

Analytical Microbiology Methods, Chromatography and Mass Spectrometry, A. Fox, S. L. Morgan, L. Larsson and G. Odham, Editors, Plenum Press, New York and London, 1920, 280 pages. $65.00; prices 20% higher outside USA and Canada.

Ion Chromatography, H. Small, Modern Analytical Chemistry Series, D. Hercules, Editor, Plenum Press, New York and London, 1990, 376 pages. $49.50; prices 20% higher outside USA and Canada.     

Siloxane Compounds of the Transition Metals

Heterosiloxanes of transition metals contain the characteristic grouping Si? O? X; in the compounds known so far, X may be Au, Zn, Cd, Hg, Ti, Zr, Hf, V, Nb, Ta, Cr, U, Re, Fe, Co, Ni, or Pt. Most of these compounds are obtained from silanols, metal silanolates, acyloxysilanes, disiloxanes, or alkoxysilanes, i.e. from compounds that already contain an Si? O bond. The transition metal may be introduced e.g. as a halide, as an organometailic compound, as an alkoxy compound, or as an oxide. Heterosiloxanes are also formed on reaction of many silicon compounds that do not contain oxygen with transition metal compounds containing oxygen. Some of these compounds, e.g. some titanosiloxanes, are very stable, whereas others decompose explosively. Oligomeric and polymeric heterosiloxanes exist in addition to the monomeric compounds.     

Determinants of cyanuric acid and melamine assembly in water

While the recognition of cyanuric acid (CA) by melamine (M) and their derivatives has been known to occur in both water and organic solvents for some time, analysis of CA/M assembly in water has not been reported (Ranganathan, A.; Pedireddi, V. R.; Rao, C. N. R. J. Am. Chem. Soc.1999, 121, 1752-1753; Mathias, J. P.; Simanek, E. E.; Seto, C. T.; Whitesides, G. M. Macromol. Symp.1994, 77, 157-166; Zerkowski, J. A.; MacDonald, J. C.; Seto, C. T.; Wierda, D. A.; Whitesides, G. M. J. Am. Chem. Soc.1994, 116, 2382-2391; Mathias, J. P.; Seto, C. T.; Whitesides, G. M. Polym. Prepr.1993, 34, 92-93; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc.1993, 115, 905-916; Zerkowski, J. A.; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc.1992, 114, 5473-5475; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc.1990, 112, 6409-6411; Wang, Y.; Wei, B.; Wang, Q. J. Chem. Cryst.1990, 20, 79-84; ten Cate, M. G. J.; Huskens, J.; Crego-Calama, M.; Reinhoudt, D. N. Chem.-Eur. J.2004, 10, 3632-3639). We have examined assembly of CA/M, as well as assembly of soluble trivalent CA and M derivatives (TCA/TM), in aqueous solvent, using a combination of solution phase NMR, isothermal titration and differential scanning calorimetry (ITC/DSC), cryo-transmission electron microscopy (cryo-TEM), and synthetic chemistry. While the parent heterocycles coprecipitate in water, the trivalent system displays more controlled and cooperative assembly that occurs at lower concentrations than the parent and yields a stable nanoparticle suspension. The assembly of both parent and trivalent systems is rigorously 1:1 and proceeds as an exothermic, proton-transfer coupled process in neutral pH water. Though CA and M are considered canonical hydrogen-bonding motifs in organic solvents, we find that their assembly in water is driven in large part by enthalpically favorable surface-area burial, similar to what is observed with nucleic acid recognition. There are currently few synthetic systems capable of robust molecular recognition in water that do not rely on native recognition motifs, possibly due to an incomplete understanding of recognition processes in water. This study establishes a detailed conceptual framework for considering CA/M heterocycle recognition in water which enables the future design of molecular recognition systems that function in water.     

Photoinduced ferrimagnetic systems in Prussian blue analogues C(I)xCo4[Fe(CN)6]y (C(I) = alkali cation). 3. Control of the photo- and thermally induced electron transfer by the [Fe(CN)6] vacancies in cesium derivatives.

We synthesized a series of CoFe Prussian blue analogues along which we tuned the amount of cesium cations inserted in the tetrahedral sites of the structure. Structure and electronic structure have been investigated, combining XANES, infrared spectroscopy, powder X-ray diffraction experiments, and magnetization measurements. The change of the magnetization induced by light along the series shows that the efficiency of the photoinduced magnetization, evidenced a few years ago in similar compounds by Hashimoto et al. (Sato, O.; Iyoda, T.; Fujishima, A.; Hashimoto, K. Science 1996, 272, 704-705; Sato, O.; Einaga, Y.; Iyoda, T.; Fujishima, A.; Hashimoto, K. J. Electrochem. Soc. 1997, 144, L11-L13; Sato, O.; Einaga, Y.; Iyoda, T.; Fujishima, A.; Hashimoto, K. J. Phys. Chem. B 1997, 101, 3903-3905; Einaga, Y.; Ohkoshi, S.-I.; Sato, O.; Fujishima, A.; Hashimoto, K. Chem. Lett. 1998, 585-586; and Sato, O.; Einaga, Y.; Fujishima, A.; Hashimoto, K. Inorg. Chem. 1999, 38, 4405-4412), depends on a compromise between the number of excitable diamagnetic pairs and the amount of [Fe(CN)6] vacancies giving the network flexibility. Besides the efficiency of the photoinduced process, the amount of [Fe(CN)6] vacancies also controls a thermally induced electron transfer.     

A study of sorption and decomposition of ozone on microfibrous filtering materials

Decomposition of ozone on commercial and pilot filtering microfibrous materials based on polymers, glass fibers, and carbonized polymeric fibers was studied. Original Russian Text A.I. Klimuk, L.A. Obvintseva, A.D. Shepelev, V.L. Kuchaev, M.P. Dmitrieva, E.N. Ushakova, A.K. Avetisov, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 4, pp. 593–597.     

纳米碳酸钙及其表面处理对等规聚丙烯结晶行为的影响

应用差示扫描量热方法研究了不同表面改性碳酸钙纳米粒子对聚丙烯 (PP)等温与非等温结晶动力学的影响 ,并研究了上述各聚丙烯结晶样品的熔融行为和晶型 .研究发现纳米碳酸钙具有明显的成核效应 ,并具有较强的诱导 β 型结晶的能力 ,而且与粒子的表面处理密切相关 .     

火焰原子吸收法测定夏枯草果穗的微量元素

使用灰化法处理样品,火焰原子吸收光谱法测定夏枯草果穗中的铬、银、锌、镍、镉、铁、铜的含量。结果表明,除Ag元素未检出外,夏枯草果穗的微量元素含量Cr、Zn、Ni、Cd、Fe、Cu分别为1．024、1．096、36．152、0．580、0．656、6．872μg/g,各元素含量由高到低顺序为：Ni,Cu,Zn,Cr,Fe,Cd,加标回收率为98．6％～115．2％,该法测定快速、简单,原子吸收光谱法测定夏枯草果穗中微量元素具有可行性。     

The Conquest of Taxol

Much has been written about taxol, one of the newest weapons against cancer, and its producer, the Pacific Yew tree (Taxus brevifolia).

1 K. C. Nicolaou, W.-M. Dai, R. K. Guy, Angew. Chem. 1994, 106, 38–69; Angew. Chem. Int. Ed. Engl. 1994, 33, 15–44.

In this article, the authors give a frank and behind-the-scenes account of their encounter with this well-known molecule, which they and their collaborators faced as a synthetic target.

2 K. C. Nicolaou, Z. Yang, J.-J. Liu, H. Ueno, P. G. Nantermet, R. K. Guy, C. F. Claiborne, J. Renaud, E. A. Couladouros, K. Paulvannan, E. J. Sorensen, Nature (London) 1994, 367, 630–634.

3 K. C. Nicolaou, J.-J. Liu, Z. Yang, H. Ueno, R. K. Guy, E. A. Couladouros, E. J. Sorensen, J. Am. Chem. Soc. 1995, 117, 624–633.

4 K. C. Nicolaou, J.-J. Liu, Z. Yang, H. Ueno, E. J. Sorensen, C. F. Claiborne, R. K. Guy, C.-K. Hwang, M. Nakada, P. G. Nantermet, J. Am. Chem. Soc. 1995, 117, 634–644.

5 K. C. Nicolaou, Z. Yang, J.-J. Liu, P. G. Nantermet, C. F. Claiborne, J. Renaud, R. K. Guy, K. Shibayama, J. Am. Chem. Soc. 1995, 117, 645–652.

6 K. C. Nicolaou, H. Ueno, J.-J. Liu, P. G. Nantermet, Z. Yang, J. Renaud, K. Paulvannan, R. Chadha, J. Am. Chem. Soc. 1995, 117, 653–659.

Once again total synthesis is found to offer excellent opportunities for developing new synthetic strategies and novel reactions. The team of chemists who took up this challenge emerged with valuable experience and confidence in their skills.     

The synthesis, structure, and properties of carbon-containing nanocomposites based on nickel, palladium, and iron

Nickel, iron, palladium, and bimetallic nickel-palladium nanoparticles encapsulated in carbon were synthesized by contactless levitation fusion of metals in a magnetic field in a flow of an inert gas containing a hydrocarbon. The products were characterized by X-ray diffraction, differential thermal analysis, thermogravimetry, high-resolution transmission electron microscopy, and adsorption. A layered carbon shell preventing agglomeration and oxidation formed on the surface of nickel- and iron-containing particles. The size of particles depended on preparation conditions and could be of 5–15 nm. Original Russian Text ? A.E. Ermakov, M.A. Uimin, E.S. Lokteva, A.A. Mysik, S.A. Kachevskii, A.O. Turakulova, V.S Gaviko, V.V. Lunin, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 7, pp. 1338–1345.     

Perkin-Elmer introduce new gas chromatograph

Abstract

APPLICATIONS OF MASS SPECTROMETRY TO TRACE ANALYSIS. Ed. S. Facchetti, Elsevier, US $78.75, Dfl. 185.00.

QUANTITATIVE AQUATIC BIOLOGICAL INDICATORS. by David J. H. Phillips, Fisheries Research Station Aberdeen, Hong Kong, POLLUTION MONITORING SERIES (1980), 488 pages (including 99 figures, 103 tables, 44 pages of literature references up to 1978, an author index of 10 pages, a species index of 4 pages, and a subject index of 18 pages), linen, format 228 × 148 mm, ISBN 0-85334-884-7, Applied Science Publishers Ltd., London, £26.

DIRECTORY OF POLLUTION CONTROL EQUIPMENT COMPANIES IN WESTERN EUROPE, Third Edition (1980), 588 pages (including an index of 127 pages, which is however-structured somewhat arbitrarily according to types of equipment and according to countries), stiff paper cover, format 210 × 147 mm, ISBN 0 906685 00 1, European Directories, a Division of Inter Company Comparisons Ltd., 23, City Road, London EC1Y 1AA, £30.

HALOGENATED BIPHENYLS, TERPHENYLS, NAPHTHALENES, DIBENZODIOXINS AND RELATED PRODUCTS, by R. D. Kimbrough (ed.) (Elsevier Biomedical Press, R.V., Amsterdam, NL. U.S. $95.00, Dfl 195.

CHROMATOGRAPHY AND THE ENVIRONMENT, Environmental problem solving using gas and liquid chromatography, R. L. Grob and M. A. Kaiser, Elsevier, Amsterdam, 1982, XII + 240 pages, ISBN 0-444-42065-7     

Elemental content in wheat products of Al-Qusim region, Saudi Arabia using the INAA technique

Wheat is one of the most grown crops in Saudi Arabia. It is grown in various regions of the country. Accurate knowledge of the elemental concentrations in wheat and its products (bran and flour) is of great importance from a nutritional point of view. Wheat samples were obtained from the Al-Qusim region, 300 km northwest of Riyadh, and analyzed. Up to 50 elements (Al, Sb, As, Ba, Br, Cd, Ca, Cs, Cl, Cr, Co, Cu, Ga, Au, Hf, In, I, Ir, Fe, Mg, Mn, Hg, Mo, Ni, K, Rb, Sc, Se, Ag, Na, Sr, Ta, Te, Th, Sn, Ti, W, U, V, Zn, Zr, Ce, Dy, Eu, La, Lu, Nd, Sm, Tb and Yb) were determined in the wheat products. It was observed that the elemental content of bran was much higher than that of white flour.     

Some derivatives of 2,5-dimercapto-1,3,4-thiadiazole

Reaction of 2,5-dimercapto-1,3,4-thiadiazole with diethylamine, morpholine, and piperidine under the conditions of the Mannich reaction gives N,S-aminomethylated thiadiazoles, but urea, thiourea, semicarbazide, and thiosemicarbazide form N,N-aminomethylated thiadiazoles. Condensation of 2,5-dimercapto-1,3,4-thiadiazole with formaldehyde leads, depending on the pH, to an N,N-, N,S-, or S,S-derivative, but reaction with 1,3-propanesultone or with the sodium salt of bromoethanesulfonic acid in alkaline medium leads to an S,S-derivative of thiadiazole. Institute of Chemistry, Vilnius LT-2600, Lithuania. E-mail: lorka@ktl.mii.lt. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1685–1689, December, 1998.     

A Review of: “Membrane Applications and Research in Food Processing”

Abstract

C. M. Mohr, S. A. Leeper, D. E. Engelgau, B. L. Charboneau, Noyes Publications, Park Ridge, NJ, November, 1989, cloth, 305 pages, $45.00.     

Coordination polymers based on inorganic lanthanide(II) sulfate skeletons and an organic isonicotinate N-oxide connector: segregation into three structural types by the lanthanide contraction effect

Fourteen three-dimensional coordination polymers of general formula [Ln(lNO)(H2O)(SO4)]n, where Ln = La, 1.La; Ce, 2.Ce; Pr, 3.Pr; Nd, 4.Nd; Sm, 5.Sm; Eu, 6.Eu; Gd, 7.Gd; Tb, 8.Tb; Dy, 9.Dy; Ho, 10.Ho; Er. 11.Er; Tm, 12.Tm; Yb, 13.Yb; and Lu, 14.Lu; INO = isonicotinate-N-oxide, have been synthesized by hydrothermal reactions of Ln3+, MnCO3, MnSO4 x H2O, and isonicotinic acid N-oxide (HINO) at 155 degrees C and characterized by single-crystal X-ray diffraction, IR, thermal analysis, luminescence spectroscopy, and the magnetic measurement. The structures are formed by connection of layer, chain, or dimer of Ln-SO4 by the organic connector, INO. They belong to three structural types that are governed exclusively by the size of the ions: type I for the large ions, La, Ce, and Pr; type II for the medium ions, Nd, Sm, Eu, Gd, and Tb; and type III for the small ions, Dy, Ho, Er, Tm, Yb, and Lu. Type I consists of two-dimensional undulate Ln-sulfate layers pillared by INO to form a three-dimensional network. Type II has a 2-fold interpenetration of "3D herringbone" networks, in which the catenation is sustained by extensive pi-pi interactions and O-H...O and C-H...O hydrogen bonds. Type III comprises one-dimensional chains that are connected by INO bridges, resulting in an alpha-Po network. The progressive structural change is due to the metal coordination number decreasing from nine for the large ions via eight to seven for the small ions, demonstrating clearly the effect of lanthanide contraction. The sulfate ion acts as a micro4- or micro3-bridge, connecting two, three, or four metals, and is both mono- and bidentate. The INO ligand acts as a micro3- or micro2-bridge with carboxylate group in syn-syn bridging or bidentate chelating mode. The materials show considerably high thermal stability. The magnetic properties of 4.Nd, 6.Eu, 7.Gd, and 13.Yb and the luminescence properties of 6.Eu and 8.Tb are also investigated.     

金属有机化合物中金属-配体键能的研究进展

介绍了金属有机物质热力学研究的进展,概述了过渡金属-配体键能的基本概念、估测方式、实验和理论研究方法.收集了已测得的第三副族到第八族所有中性金属有机络合物金属-配体σ-单键绝对键焓的实验值.对第三副族及锕系元素,收集了钪-氢、钪-碳、钍-氢、钍-碳、钍-氮、钍-氧、钍-硫、钍-氯、铀-氢、铀-碳、铀-硅、铀-氧、铀-氯、铀-溴、铀-碘、钐-氢、钐-碳、钐-硅、钐-氮、钐-磷、钐-氧、钐-硫、钐-氯、钐-溴和钐-碘键的键焓.对第四副族元素,收集了钛-碳、锆-氢、锆-碳、锆-硅、锆-氮、锆-氧、锆-氯、锆-碘、铪-氢、铪-碳键的键焓.对第五副族元素,收集了钒-氢、钽-碳键的键焓.对第六副族元素,收集了铬-氢、铬-碳、铬-硅、铬-氮、铬-氙、钼-氢、钼-碳、钼-硅、钼-氮、钼-磷、钼-氯、钼-溴、钼-碘、钼-氙、钨-氢、钨-碳、钨-硅、钨-氮、钨-氩、钨-氪、钨-氙键的键焓.对第七副族元素,收集了锰-氢、锰-碳、锰-硅、锰-氧、锰-硫、锰-氯、锰-溴、锰-碘、锝-氯、锝-溴、锝-碘、铼-氢、铼-碳、铼-氯、铼-溴、铼-碘键的键焓.对第八族元素,收集了铁-氢、铁-碳、铁-氮、铁-氩、铁-氪、铁-氙、钌-氢、钌-碳、钌-磷、锇-氢、锇-碳、钴-氢、钴-碳、铑-氢、铑-碳、铱-氢、铱-碳、铱-氯、铱-溴、铱-碘、镍-碳、镍-硫、钯-碳、铂-氢、铂-碳键的键焓.但未包括平均键焓值.此外,还收集了铁-氢、铁-碳、铁-氮、铁-磷、铁-羰基、铁-亚硝基、铁-氧分子、铁-硼、铁-铝、铁-镓、铁-铟、铁-铊键的理论计算值以及金属有机片断和离子的键焓.     

Spurenelementbestimmung in Luftstaubproben mittels Neutronenaktivierung

Zusammenfassung Die Neutronenaktivierungsanalyse kann zur Bestimmung von Spurenelementen in Luftstaubproben auch bei Sammelzeiten von nur wenigen Stunden vorteilhaft eingesetzt werden. Für die Sammeltechnik haben sich Cellulose-Papierfilter als besonders spurenarm erwiesen. Für die meisten Elemente sind die Abscheidegrade befriedigend. In einer Reaktor-Kurzzeitbestrahlung von ca. 1 min können die Elemente Se, V, Al, Mg, Br, Cl, In, Mn, in einer nachgeschalteten Langzeitbestrahlung von ca. 1 Tag die Elemente Na, K, Cu, As, W, La, Cd, Au, Sb, Sm, Ca, Fe, Co, Zn, Cr, Sc quantitativ analysiert werden. Im Kernforschungszentrum Karlsruhe und an der Autobahn Karlsruhe—Bruchsal wurden Luftstaubkonzentrationen für die Elemente Se, V, Br, Mn, Cu, As, Zn, Fe, Co ermittelt. Erhöhte Werte an der Autobahn wurden lediglich für Brom gefunden. Blei, mit Atomabsorption bestimmt, verhält sich analog wie Brom.Zu danken ist Herrn Prof. C. Keller, der die Durchführung der Bleianalysen mittels Atomabsorption im Institut für Radiochemie der GfK Karlsruhe ermöglicht hat.     

Interprotein electron transfer in a confined space: uncoupling protein dynamics from electron transfer by sol-gel encapsulation

In this paper, we describe the first observations of photoinitiated interprotein electron transfer (ET) within sol-gels. We have encapsulated three protein-protein complexes, specifically selected because they represent a full range of affinities, are sensitive to different types of dynamic processes, and thus are expected to respond differently to sol-gel encapsulation. The three systems are (i) the [Zn, Fe(3+)L] mixed-metal hemoglobin hybrids, where the alpha(1)-Zn and beta(2)-Fe subunits correspond to a "predocked" protein-protein complex with a crystallographically defined interface (Natan, M. J.; Baxter, W. W.; Kuila, D.; Gingrich, D. J.; Martin, G. S.; Hoffman, B. M. Adv. Chem. Ser. 1991, 228 (Electron-Transfer Inorg., Org., Biol. Syst.), 201-213), (ii) the Zn-cytochrome c peroxidase complex with cytochrome c, [ZnCcP, Fe(3+)Cc], having an intermediate affinity between its partners (Nocek, J. M.; Zhou, J. S.; De Forest, S.; Priyadarshy, S.; Beratan, D. N.; Onuchic, J. N.; Hoffman, B. M. Chem. Rev. 1996, 96, 2459-2489), and (iii) the [Zn-deuteromyoglobin, ferricytochrome b(5)] complex, [ZnDMb, Fe(3+)b(5)], which is loosely bound and highly dynamic (Liang, Z.-X.; Nocek, J.; Huang, K.; Hayes, R. T.; Kurnikov, I. V.; Beratan, D. N.; Hoffman, B. M. J. Am. Chem. Soc. 2002, 124, 6849-6859. Intersubunit ET within the hybrid does not involve second-order processes or subunit rearrangements, and thus is influenced only by perturbations of high-frequency motions coupled to ET. For the latter two complexes, sol-gel encapsulation eliminates second-order processes: protein partners encapsulated as a complex must stay together throughout a photoinitiated ET cycle, while proteins encapsulated alone cannot acquire a partner. It further modulates intracomplex motions of the two partners.     

Mass selective gas phase study of ClO, OClO, ClOO and ClAr by anion-ZEKE-photoelectron spectroscopy

Anion-ZEKE-photoelectron spectra of ClO-, OClO-, ClOO- and the van der Waals cluster ArCl- have been measured. Refined or new values for the electron affinity of ClO, OClO and ClOO have been found. The peak positions in these spectra are in very good agreement with former ClO- and OClO- anion-photoelectron spectra (K. M. Gilles, M. L. Polak and W. C. Lineberger, J. Chem. Phys., 1992, 96, 8012) and a recent ArCl- anion-ZEKE spectrum (T. Lenzer, I. Yourshaw, M. Furlanetto, G. Reiser and D. Neumark, J. Chem. Phys., 1992, 110, 9578). The higher resolution of our anion-ZEKE-photoelectron spectrum of OClO- led to a refined assignment of the corresponding anion-photoelectron spectrum. In addition, a strong difference in the relative intensities of the vibrational peaks has been found in the anion-ZEKE-spectrum of OClO- in comparison with the anion-photoelectron spectrum. For the first time, mass selective spectroscopic information has been obtained for ClOO. The strong similarity to the ArCl- spectrum indicates a weakly bound van der Waals cluster Cl.O2. Binding energies of the anion, neutral ground and neutral excited state could be deduced. These are in good agreement with the electron affinities of Cl and ClOO, but differ from theoretical values (K. A. Peterson and H. J. Werner, J. Chem. Phys., 1992, 96, 8948) by a factor of 4.5 and from thermochemically determined values (J. M. Nicovich, K. D. Kreutter, C. J. Shackelford and P. H. Wine, Chem. Phys. Lett., 1991, 179, 367 and S. Baer, H. Hippler, R. Rahn, M. Siefke, N. Seitzinger and J. Troe, J. Chem. Phys., 1991, 95, 6463) by a factor of 9.