Monomeric Model Compounds Research Articles

Heteroleptic Organostannylenes and an Organoplumbylene Bearing Phosphorus‐Containing Pincer‐Type Ligands – Structural Variations and Insights into the Configurational Stability

AbstractThe syntheses of the arylphosphonic esters 3‐Br‐5‐tBu‐1‐{P(O)(OiPr)2}C6H3 (1), 5‐tBu‐1,3‐{P(O)(OiPr)2}2C6H3 (2), of the heteroleptic intramolecularly coordinated organostannylenes [4‐tBu‐2,6‐{P(O)(OiPr)2}2C6H2]SnX (3, X = Cl; 4, X = Br; 5, X = I; 6, X = SPh), the organoplumbylene [4‐tBu‐2,6‐{P(O)(OiPr)2}2C6H2]PbCl (7), and the transition metal complex [4‐tBu‐2,6‐{P(O)(OiPr)2}2C6H2]Sn(Cl)Cr(CO)5 (8) are reported. The compounds were characterized by 1H, 13C, 31P, 31P MAS (3), 119Sn, and 119Sn MAS (3) NMR spectroscopy, electrospray ionization mass spectrometry (3), Mössbauer spectroscopy (3–5, 8) and single‐crystal X‐ray diffraction analyses (2, 3–5, 6–8). In contrast to its ethoxy‐substituted analogue [4‐tBu‐2,6‐{P(O)(OEt)2}2C6H2]SnCl, compound 3, like the thiophenolate derivative 6, is monomeric in solution as well as in the solid state. This difference is also manifested by the Mössbauer as well as solid state NMR spectroscopic data. On the other hand, the corresponding organoplumbylene 7 shows a similar chlorido‐bridged polymeric structure as its ethoxy‐substituted analogue. Variable‐temperature and concentration‐dependent 1H and 31P NMR spectra reveal, on the respective time scales, the tin atom in compound 3 to be configurationally unstable and those in compounds 6 and 8 to be configurationally stable. DFT calculations support a chlorido‐bridged dimer to account for the configurational instability in compound 3. Surprisingly and in contrast to compounds 3 and 6, the organobromido‐ and organoiodidostannylenes 4 and 5, respectively, show intermolecular Sn···Sn distances of 3.6809(4) and 3.5953(4) Å being shorter than twice the van der Waals radius of tin (2.20 Å). Quantum chemical calculations were performed on monomeric and dimeric model compounds, which revealed a weak Sn···Sn bonding interaction for dimer 3 (16 kJ·mol–1) as well as for dimer 5 (20 kJ·mol–1) whereas the hypothetical model compound p‐tBuC6H4SnI showed an iodido‐bridged dimer rather than a Sn···Sn bonding interaction.

Synthesis and characterization of a novel kind soluble, conjugated, and fluorescent chelate polymer containing fluorene ring in the backbone: Optical, electrical, and electrochemical properties

A novel highly soluble coordination polymer, poly(3,4-HBA-Cr-FDA), containing Cr(III) ion in the backbone was synthesized. Monomeric model compounds (MC-1 and MC-2) were also synthesized as the comparison materials. The structures were characterized by FT-IR, UV–vis, 1H and 13C NMR, and size exclusion chromatography (SEC). SEC results showed that the novel polymer had 65–68 repeated units. ICP-AES was used to determine the chromium content of MC-2. Thermal data were obtained by TGA and DSC techniques showing that MC-2 and the novel polymer had high rate of hydrate water. Cyclic voltammetry (CV) measurements were carried out and the HOMO–LUMO energy levels and electrochemical band gaps (E′g) were calculated. Additionally, the optical band gaps (Eg) were determined using UV–vis spectra of the materials. Electrical conductivity measurements of the doped (with iodine) and undoped polymer related to temperature and doping time were carried out by four point probe technique using a Keithley 2400 electrometer. Measurements were made using the polymeric film deposited on ITO glass plate by dip-coating method. Also, absorption spectra of doped polymeric film were recorded by a single beam spectrophotometer showing that doping procedure causes peak growing in absorption spectra. Ability of processing of poly(3,4-HBA-Cr-FDA) in gas sensors was discussed. Fluorescence spectra of the polymer in a series of solvents were obtained and it was found that poly(3,4-HBA-Cr-FDA) had green–red emitting emission in different solvents.

Pyridinium salts and ylides as partial structures of photoresponsive Merrifield resins

Merrifield resin was treated with 4,4′-bipyridine and 2,4′-bipyridine, respectively, to give photochromic materials. On exposure to light, reversible color changes are observable. These resins also serve as indicators because reversible color changes are observable on addition of bases, which deprotonate the benzylic position of the N-benzylpyridinium salts to ylides. These can be detected spectroscopically and by trapping reactions on monomeric model compounds. EPR and HYSCORE measurements in combination with DFT calculations prove that radical species are formed in either case. Evidence is found that the carbanionic centers of the ylide partial structures serve as electron donators in these reversible color changes, thus setting them apart from known photochromic materials.

Detection of muconic acid type structures in oxidised lignins using 2D NMR spectroscopy 10th EWLP, Stockholm, Sweden, August 25–28, 2008

Abstract The identification of muconic acid type structures (MATS) in oxidised lignins employing 2D NMR spectroscopy was carried out. The primary database for MATS detection by single bond 1H-13C (HSQC) and long-range 1H-1H and 1H-13C correlation (COSY and HMBC) NMR experiments was obtained with a series of model compounds: cis, cis- and trans, trans-muconic acids and their methylated analogues and MATS derived from monomeric lignin model compounds oxidised by ClO2. Additional information was obtained from the study of oxygen-organosolv lignin obtained from spent liquor after the spruce wood delignification with oxygen in an acetone-water solution. This work allowed the reliable assignment of MATS signals in the HSQC spectra of oxidised lignin and provides a methodology for detection and distinguishing of MATS from structurally similar moieties.

Efficient Electron Delocalization Mediated by Aromatic Homoconjugation in 7,7-Diphenylnorbornane Derivatives

Efficient electron delocalization by aromatic homoconjugated 7,7-diphenylnorbornane (DPN) in alternated homoconjugated-conjugated block copolymers and reference compounds is revealed by photophysical and electrochemical measurements. The synthesis of the polymers was achieved by Suzuki polycondensation reaction. Effective electron delocalization by DPN is demonstrated by the significant red shifts observed in the absorption and emission spectra and the variation of the energy band gap of the polymers and monomeric model compounds in comparison to a series of oligophenylenes used as references (p-quaterphenyl, p-terphenyl, and biphenyl). The electron delocalization is also clearly demonstrated by the lower oxidation potential measured for homoconjugated model compound in comparison to p-terphenyl. The results show that the electron delocalization caused by two homoconjugated aryl rings is comparable to the effect produced by one conjugated aryl ring.

EPR spectroscopic investigation of radical-induced degradation of partially fluorinated aromatic model compounds for fuel cell membranes

EPR spectroscopic investigations of reactions between monomeric model compounds representing typical structural moieties of poly(aryl) ionomers and photochemically generated hydroxyl radicals are reported. Deoxygenated solutions of the model compounds (in a water/methanol mixture) containing hydrogen peroxide at defined pH values were exposed to UV light in the flow cell within the cavity of an EPR spectrometer. Spectra were analyzed by computer simulation and the formed radicals were assigned by comparing their g-factors and hyperfine coupling constants (hfccs) with those from the literature and from density functional theory (DFT) calculations. The relevance for polymer electrolyte membrane fuel cells (PEMFCs) and alkaline-anion exchange membrane fuel cells (AAEMFCs) is discussed.

A study on the preparation and photophysical properties of an iridium(iii) complexed homopolymer

We have prepared a poly(styrene) [poly(Irppy2acac)] that has a bis(2-phenylpyridyl)iridium(III) acetylacetonate complex attached to every ‘monomer’ via a methylene unit. The polymer is solution processable and can be spin-coated to give good quality neat thin films. We show that despite the close proximity of the phosphorescent chromophores along the polymer backbone there is only a modest reduction in the solution photoluminescence quantum yield (PLQY) relative to a monomer model compound. The PLQY of the 4-ethylbenzyl substituted bis(2-phenylpyridyl)iridium(III) acetylacetonate complex was 52% while the poly(Irppy2acac) had a PLQY of 34%. Time-resolved photoluminescence measurements showed that the photoluminescence decay of the poly(Irppy2acac) in solution was bi-exponential indicating the presence of more than one emissive species, which was attributed to intra-polymer chromophore interactions. In contrast to the solution measurements the solid-state PLQY was very low (<1%) due to quenching arising from inter-chromophore interactions. When 6 wt% of the poly(Irppy2acac) was blended with the small molecule host 4,4′-bis(N-carbazolyl)-2,2′-biphenyl (CBP), which is a ratio similar to that used for small molecule iridium(III) complexes, significant emission from the CBP was observed suggesting that there was not an even distribution of the polymer in the film. In contrast a 19 wt% blend showed almost complete energy transfer [the CBP peak was 100 times smaller than that of the poly(Irppy2acac)] and there was an increase in the PLQY relative to the neat films.

Synthesis and Solid-State Polymerization of Triyne and Enediyne Derivatives with Similar π-Conjugated Structures

Abstract Three diacetylene monomer model compounds with similar π-conjugation systems, 10-phenyl-5,7,9-decatriynyl N-phenylcarbamate (1), (E)-10-phenyldec-9-en-5,7-diynyl N-phenylcarbamate (2), and (E)-10-phenyldec-5-en-7,9-diynyl N-phenylcarbamate (3), were synthesized and their properties and solid-state polymerization were investigated. Based on the absorption spectra of the monomers, it was found that the conjugation effect of a double bond was different from that of a triple bond in solution. Monomers 1, 2, and 3 gave one, two, and five crystal forms, respectively, of which 1 and one of the crystal forms of 2 (2a) could be polymerized in the solid state. The conversions after γ-ray irradiation (1 MGy dose) were 53% and 20%, respectively. The longest-wavelength absorption maxima of the polymers prepared from 1 and 2a were 645 and 655 nm, respectively. The polymerizable crystals 1 and 2a were found to have layered monomer structures with spacing of 3.1–3.6 nm. Based on solid-state 13C NMR spectra, the polymerization sites of 1 were determined to be the 1,4- and 3,6-positions with respect to the phenyl ring, and that of 2a was determined to be the 3,6-position with respect to the phenyl ring.

Structure−Property Relationships of Polyselenoethers [−(CH2)ySe−]x (y = 1, 2, and 3) and Related Polyethers and Polysulfides

Conformational characteristics, solution (melt) properties, and thermal properties of polyselenoethers [-(CH2)ySe-]x ( y=1, 2, and 3) have been revealed by the rotational isomeric state analysis of ab initio molecular orbital calculations and (1)H and (13)C NMR experiments for monomeric model compounds and compared with those of typical polyethers and polysulfides. The comparative results are summarized here as correlations in conformation among model compounds and unperturbed and crystalline states of the polymers, and thermal properties of the polymer crystals are discussed in terms of intramolecular and intermolecular interactions. By ab initio molecular orbital calculations under periodic boundary conditions, helical structures of poly(methylene oxide), poly(methylene sulfide), and poly(methylene selenide), and the crystal structure of poly(ethylene selenide) have been optimized, and their electronic structures have been predicted. A systematic methodology to predict and characterize up to higher-order structures and various physical properties of polymers incorporated in different phases has been attempted to be developed.

N-Channel Polymers by Design: Optimizing the Interplay of Solubilizing Substituents, Crystal Packing, and Field-Effect Transistor Characteristics in Polymeric Bithiophene-Imide Semiconductors

Electron transporting (n-channel) polymer semiconductors for field-effect transistors are rare. In this investigation, the synthesis and characterization of new electron-depleted N-alkyl-2,2'-bithiophene-3,3'-dicarboximide-based pi-conjugated homopolymers and copolymers containing the 2,2'-bithiophene unit are reported. A novel design approach is employed using computational modeling to identify favorable monomer properties such as core planarity, solubilizing substituent tailorability, and appropriate electron affinity with gratifying results. Monomeric model compounds are synthesized to confirm these properties, and a crystal structure reveals a short 3.43 A pi-pi stacking distance with favorable solubilizing substituent orientations. A family of 10 homopolymers and bithiophene copolymers is then synthesized via Yamamoto and Stille polymerizations, respectively. Two of these polymers are processable in common organic solvents: the homopolymer poly(N-(2-octyldodecyl)-2,2'-bithiophene-3,3'-dicarboximide) (P1) exhibits n-channel FET activity, and the copolymer poly(N-(2-octyldodecyl)-2,2':5',2'':5'',2'''-quaterthiophene-3,3'-dicarboximide) (P2) exhibits air-stable p-channel FET operation. After annealing, P1 films exhibit a very high degree of crystallinity and an electron mobility > 0.01 cm (2) V(-1) s(-1) with a current on-off ratio of 10 (7), which is remarkably independent of film-deposition conditions. Extraordinarily, P1 films also exhibit terracing in AFM images with a step height matching the X-ray diffraction d spacing, a rare phenomenon for polymeric organic semiconductors. Another fascinating property of these materials is the air-stable p-channel FET performance of annealed P2 films, which exhibit a hole mobility of approximately 0.01 cm(2) V(-1) s(-1) and a current on-off ratio of 10(7).

Application of the amount of oxygen consumption to the investigation of the oxidation mechanism of lignin during oxygen-alkali treatment

The dioxygen consumption by kraft lignin and several lignin model compounds during oxygen-alkali treatments were directly analyzed using a dioxygen fl owmeter. The average dioxygen consumption by 200 g of kraft lignin was about 3 moles. Because this value was as much as those obtained for monomeric phenolic lignin model compounds, guaiacol and vanillyl alcohol, it was postulated that not only phenolic but also nonphenolic moieties in kraft lignin are extensively oxidized. The dioxygen consumption by 0.5 moles (one equivalent of aromatic units) of a dimeric lignin model compound, guaiacylglycerol-β-guaiacyl ether (GG), was also similar to that for 1 mole of guaiacol and vanillyl alcohol, regardless of the type of the aromatic moiety, which supports the above postulation. The most plausible mechanism for the oxidation of nonphenolic moieties is the oxidation of side chains of residual β-O-4 substructures by active oxygen species. By this mechanism, nonphenolic moieties in kraft lignin and GG are converted into corresponding phenolic moieties, and the oxidation by dioxygen progresses.

A new method for the titration of free phenolic groups in pulps

Abstract A fast and semi-quantitative wet chemical method was developed for the titration of free phenolic groups in residual lignins of pulps. The method is based on selective chlorine dioxide reaction with phenolic units of lignin at 0°C. A known amount of ClO2 is reacted for up to 30 min with various substrates and ClO2 consumption is measured. Experiments with monomeric lignin-like model compounds, a dioxane/HCl lignin (isolated from kraft pulp), kraft pulp, and one thermomechanical pulp (TMP) were performed. The ideal stoichiometric consumption of 1 mol of ClO2 per Ar-OH was approximated in a few cases. More model compound experiments are necessary to establish the possibilities and limitations of the method, but the results of these preliminary experiments are promising. First studies on pulps and comparison of the data with those obtained by 13C NMR analysis on dioxane/HCl lignins showed some deviations in the first instance, which were attributed to reaction of the intermediates HClO and Cl2 involved in the overall mechanism. However, using DMSO as HClO trapping agent improved the ClO2/Ar-OH stoichiometric ratio close to the theoretical value of 2, which essentially yielded better results. This improved stoichiometry was verified for three model compounds, one kraft pulp and one TMP, yielding results were similar to those obtained by 13C NMR analysis.

Oligoribonucleotide Analogues Containing a Mixed Backbone of Phosphodiester and Formacetal Internucleoside Linkages, Together with Vicinal 2′‐O‐Methyl Groups

Oligoribonucleotides containing formacetal internucleoside linkages have been prepared and studied by UV melting experiments. In RNA duplexes, the formacetal substitution is stabilizing (Deltat(m)=0 to +0.9 degrees C per modification) at physiological salt concentrations (0.1 M) but destabilizing (Deltat(m)=-0.4 to -0.8 degrees C per modification) at high salt concentrations (1 M); this suggests that reduction of electrostatic repulsion contributes substantially to the stabilization. The presence of 2'-O-Me substituents increases the stabilities of the duplexes (Deltat(m)=+0.5 to +1.1 degrees C per modification). The positive effects of formacetals and 2'-O-Me groups were independent and additive. (1)H NMR studies on monomeric model compounds containing 3'-(ethyl phosphate) or 3'-O-ethoxymethyl groups showed that the formacetal and 2'-O-Me substitutions shift the conformational equilibria of the ribose residues towards the North conformers by 5 to 12 %. Although the preference for the North conformers qualitatively correlates with increased duplex stabilities, changes in thermodynamic parameters (DeltaH degrees and TDeltaS degrees ) for formation of oligonucleotide duplexes and differences in dependence on concentrations of sodium acetate, sodium chloride and sodium perchlorate suggest that solvation effects are also important for the duplex stabilities. Overall the formacetal linkages fit well in A-type RNA duplexes, making them potentially interesting modifications for RNA-based gene-control strategies (e.g., antisense and RNA interference).

Reversible structural isomerisation in rare thioether complexes of cobalt(ii)—effects of ligand architecture

Rare examples of (high spin) Co(II) complexes with geometrically constrained tetrathioether ligands exhibit a very unusual structural isomerism, switching reversibly between tetrahedral monomers in solution and octahedral chain polymers in the solid; the crystal structures of one polymeric species and a tetrahedral monomer model compound are described.

The Attractive Gauche Effect of Ethylene Oxides

Conformational energies of monomeric (1,2-dimethoxyethane, DME) and trimeric (triglyme) model compounds of poly(ethylene oxide) have been evaluated by accurate ab initio molecular orbital (MO) calculations at the MP2/6-311++G(3df, 3pd)//HF/6-31G(d) level. The first-order interaction energies (E σ 's) for gauche states around the C-C bonds of DME and the terminal repeating unit of triglyme are ca. +0.1 kcal mol -1 , whereas the central unit of triglyme has a slightly negative E σ value of ca. -0.1 kcal mol -1 . For the C-C bond conformations of triglyme, the MO calculations exactly agree with NMR observations using a nonpolar solvent of cyclohexane-d 22 . The attractive gauche effect of the ethylene oxides has been shown to exist independently of intramolecular (C-H)···O hydrogen bonds.

PAMAM Dendrimeric Conjugates with a Gd−DOTA Phosphinate Derivative and Their Adducts with Polyaminoacids: The Interplay of Global Motion, Internal Rotation, and Fast Water Exchange

A series of dendrimeric conjugates based on a PAMAM (polyamidoamine) backbone with macrocyclic Gd-DO3A-P(ABn) complexes (monophosphinated analogue of DOTA) was prepared. The chelates were covalently attached to the G1-, G2-, and G4-PAMAM dendrimers through a thiourea linker in high loads (>90%). The prepared conjugates G1-(Gd-DO3A-P(BnN{CS}))(8), G2-(Gd-DO3A-P(BnN{CS}))(16), and G4-(Gd-DO3A-P(BnN{CS}))(59) showed relaxivities of 10.1, 14.1, and 18.6 s(-)(1) mM(-)(1) at 20 MHz and 37 degrees C and pH = 7.5, respectively. A variable-pH study (range 2-12) revealed up to 30% increase in the relaxivity at low pH for the G2-(Gd-DO3A-P(BnN{CS}))(16) conjugate. As confirmed by (1)H NMR titration of the unmodified G2 dendrimer, this is due to protonation of core tertiary amines leading to a more open and rigid structure. The variable-temperature (17)O NMR and (1)H NMRD relaxometric studies confirmed that the relaxivity is not controlled by water exchange but by rotational dynamics. A multiparametrical data evaluation using the Lipari-Szabo approach revealed that the water residence lifetime, (298)tau(M), for the conjugates studied was ca. 45-70 ns, which is longer than the value found for the monomeric model compound Gd-DO3A-P(ABn) (16 ns) but short enough so as not to limit the relaxivity. The global rotational correlation time, (298)tau(Rg), varied from 1.5 to 3.1 ns and seemed to indicate a sufficiently slow molecular tumbling to achieve the high relaxivities measured; however, the rigidity factor S(2) (approximately 0.26), describing the internal flexibility, was far from optimum. The overall relaxivity was significantly increased (e.g. by a factor of 1.8 for the G1-(Gd-DO3A-P(BnN{CS}))(8) conjugate) when a positively charged polyaminoacid like poly(Arg) or poly(Lys) was added to the conjugate solutions. The electrostatic interactions partially "freeze" the internal mobility of the conjugate and also slow down global motion. This assumption was confirmed by an evaluation of (1)H relaxometric data obtained for the G2-(Gd-DO3A-P(BnN{CS}))(16)-poly(Lys)(59) adduct. Importantly, it was proved that the adduct formation did not hamper the water exchange process.

Optically Active Photochromic Polymers with Three-Arm Star Structure by Atom Transfer Radical Polymerization

Atom transfer radical polymerization has been applied for the first time to synthesize optically active, photochromic methacrylic polymers having three-arm star structure, starting from a central core of C3 symmetry that can be used to investigate the conformational origin of chirality in this class of synthetic materials. By just changing the duration of the polymerization process, star-shaped macromolecules with distinct average chain lengths, low polydispersity values, and well-defined end groups have been obtained. The so-obtained polymers, fully characterized by spectroscopic and thermal techniques, exhibit relevant specific optical rotations and chiroptical properties with respect to the reference monomeric model compound as well as to the related linear derivatives previously investigated. This behavior is attributed to the stiffness of aromatic core, which limits the free movement of one chain end, thus favoring the macromolecules to assume a more elevated conformational rigidity with respect to t...

Conformational Characteristics of Poly(trimethylene sulfide) and Structure−Property Relationships of Representative Polysulfides and Polyethers

Conformational characteristics of poly(trimethylene sulfide) (PTMS) have been investigated by a rotational isomeric state analysis of ab initio molecular orbital calculations and 1H and 13C NMR experiments for a monomeric model compound, 1,3-bis(methylthio)propane, and the characteristic ratio and dipole moment ratio of the unperturbed PTMS chain. Both C−S (the first-order interaction energy, −0.30 kcal mol-1) and C−C (−0.58 kcal mol-1) bonds prefer the gauche conformation. For comparison, conformational analysis of the corresponding polyether, poly(trimethylene oxide), has also been carried out. The C−O (+0.97 kcal mol-1) and C−C (−0.47 kcal mol-1) bonds show trans and gauche preferences, respectively. These results are consistent with the conformational stabilities predicted by the natural bond orbital analysis on model compounds of poly(ethylene sulfide) (PES) and poly(ethylene oxide). Without the strong S···S repulsion, therefore, the C−C bond adjacent to the C−S bond exhibits its inherent gauche preference. Without the (C−H)···O attraction, the ethereal C−C bond is subject to the attractive gauche effect. For representative polysulfides and polyethers, relationships between conformations in the ϑ and crystalline states and thermal properties have been investigated. Even in the ϑ and crystalline states, the polymers mostly keep the conformational preferences found for their small model compounds; as an exception, poly(propylene sulfide) and poly(propylene oxide), having a methyl side chain, crystallize to adopt the metastable all-trans conformation. On average, the configurational entropy of the polymers amounts to 80−90% of entropy of fusion, and the configurational energy change between crystalline and molten states accounts for ca. 30% of enthalpy of fusion. Of the polymers investigated here, PES has an exceptionally high melting point; the dipole−dipole interaction in the PES crystal was evaluated to be −1.0 kcal mol-1 (ca. 30% of the enthalpy of fusion), thus being the source of the thermostability.

Thermal Properties of Monomeric, Dimeric, Trimeric, and Tetrameric Model Compounds for Biodegradable Poly(decamethylene sebacate)

Thermal Properties of Monomeric, Dimeric, Trimeric, and Tetrameric Model Compounds for Biodegradable Poly(decamethylene sebacate)

Steady‐State and Time‐Resolved Photophysical Studies on a Series of Gallium Phthalocyanine Monomers and Dimers

AbstractIntramolecular interaction between coplanar‐stacked phthalocyanine (Pc) and porphyrin molecules plays an importantrole in the energy‐ and electron‐transfer process. A series of results from different photophysical experiments on gallium phthalocyanine compounds are initially described. The PcGa dimer with a direct gallium–gallium bond, i.e. [tBu4PcGa]2·2dioxane, may exist in two different conformations: one in which the two phthalocyanines are poorly interacting and the other in which they are very close and strongly interacting. In the former, the emission lifetime is quite close to that of the monomer model compounds; in the latter, it is much shorter probably due to different radiative and nonradiative deactivation constants from those of the monomers. Because no significant difference between the absorption spectra of the monomer and dimer was observed in the photophysical experiments, implying that no ground‐state interaction can be assessed, the results regarding triplet excited state lifetimes of [tBu4PcGa]2·2dioxane can be attributed to strong intramolecular interactions existing only in the excited state. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)