Synthetic supramolecular zipper complexes have been used to quantify substituent effects on the free energies of aromatic stacking interactions. The conformational properties of the complexes have been characterised using NMR spectroscopy in CDCl(3), and by comparison with the solid state structures of model compounds. The structural similarity of the complexes makes it possible to apply the double mutant cycle method to evaluate the magnitudes of 24 different aromatic stacking interactions. The major trends in the interaction energy can be rationalised using a simple model based on electrostatic interactions between the pi-faces of the two aromatic rings. However, electrostatic interactions between the substituents of one ring and the pi-face of the other make an additional contribution, due to the slight offset in the stacking geometry. This property makes aromatic stacking interactions particularly sensitive to changes in orientation as well as the nature and location of substituents.

A synthetic supramolecular complex has been adapted to quantify cation-interactions in chloroform by using chemical doublemutant cycles. The interaction of a pyridinium cation with the -face of an aromatic ring is found to be very sensitive to the -electron density. Electron-donating substituents lead to a strong attractive interaction (؊8 kJ͞mol ؊1 ), but electron-withdrawing groups lead to a repulsive interaction (؉2 kJ͞mol ؊1 ).T he interactions of cations with aromatic rings play an important role in a range of biological processes, including ion channels, membrane receptors, and enzyme substrate interactions (1-9). Supramolecular chemical model systems have been instrumental in establishing the basic properties of this important class of noncovalent interactions, but cation-interactions are still poorly understood at a quantitative level, and it is difficult to predict substituent effects. Dougherty and coworkers (10) used the interaction between a synthetic aromatic host and a pyridinium guest to estimate a value of Ϫ10 kJ͞mol Ϫ1 for the interaction of a cation with four -systems in water. This value agrees well with the value of Ϫ11 kJ͞mol Ϫ1 measured by using protein engineering for the interaction of S-methylmethionine with a cavity lined by three -systems (11). Schneider et al. (12) obtained a value of Ϫ3 kJ͞mol Ϫ1 for a single cation-interaction by using a positively charged lipophilic host and an aromatic guest in water.We have developed an approach to the quantitative measurement of noncovalent functional group interactions based on chemical double-mutant cycles. This approach has proved particularly valuable for investigating structure-activity relationships in edge-to-face aromatic interactions, providing new insight into the physical basis for substituent effects on the strengths of these interactions (13,14). Here, we apply this approach to the cation-interaction, or more specifically, to the interaction of a pyridinium cation with the -face of functionalized aromatic rings. The double-mutant cycle is illustrated in Fig. 1. The difference between the stabilities of complexes A and B (⌬G A -⌬G B ) provides an indication of the magnitude of the cation-interaction in complex A, but the value is perturbed by changes in H-bond strength and other secondary interactions associated with the A3B mutation. The secondary effects can be quantified by using complexes C and D where there are no cation-interactions, but the same chemical mutation is made. Thus, the difference ⌬G C -⌬G D provides a direct measure of the changes in H-bond strength and secondary interactions associated with the A3B mutation, and it is possible to dissect out the thermodynamic contribution of the pyridinium-interaction from all of the other interactions present in complex A (⌬⌬G in Eq.

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The C 3 vanadium(V) amine triphenolate complex 1f has been characterized as a structural and functional model of vanadium haloperoxidases. The complex catalyzes efficiently sulfoxidations at room temperature using hydrogen peroxide as the terminal oxidant, yielding the corresponding sulfoxides in quantitative yields and high selectivities (catalyst loading down to 0.01%, TONs up to 9900, and TOFs up to 8000 h (-1)) as well as bromination of 1,3,5-trimethoxybenzene (catalyst loading down to 0.05%, TONs up to 1260, and TOFs up to 220 h (-1)).

Triphenolamines are highly modular tetradentate molecules that effectively coordinate to transition metals and main group elements with podand topology. They form chiral complexes with intrinsically well defined coordination geometries controlled by the ligand, in particular by the nature of the substituents in ortho position to the phenol, which are able to influence their reactivity and stability. The metal complexes, especially Ti(iv) and V(v), have been found to be effective catalyst in polymerization reactions and oxygen transfer processes.

A new organic light‐emitting field‐effect transistor characterized by a metal oxide layer inserted between the organic layer and the gate insulator is proposed. The metal oxide is indirectly connected with source and drain electrodes through the organic layer. Upon increasing the potential difference between the source and drain electrodes, the emission becomes exceedingly strong and the emission region encompasses the whole channel zone.

Vanadium­(V) complexes derived from aminotriphenolate ligands are demonstrated to be highly active catalysts for the coupling of various terminal and internal epoxides with carbon dioxide to afford a series of substituted organic carbonates in good yields. Intriguingly, a V­(V) complex bearing peripheral chloride groups on the ligand framework allowed for the formation and isolation of a rare complex that incorporates a ring-opened epoxide with one of the phenolate-O atoms acting as a nucleophile and the metal center as a Lewis acidic site. This unusual structure was characterized by X-ray diffraction and 51V NMR and was shown to exhibit catalytic activity for the coupling of propylene oxide and CO2 when it was combined postsynthetically with these substrates. The results obtained herein clearly show that vanadium complexes in a high oxidation state are effective catalysts for the activation of challenging internal epoxides and their conversion into cyclic organic carbonates.

Iron(III) amino triphenolate complexes with different substituents in the ortho-position of the phenolate moiety (R = H, Me, tBu, or Ph) have been synthesized by the reaction of iron(III) chloride and the sodium salt (Na(3)L(R)) of the requisite ligand. The complexes have been shown to be of either monomeric ([FeL(R)(THF)]) or dimeric ([FeL(R)](2)) nature by a combination of X-ray diffraction, (1)H NMR, solution magnetic susceptibility, and cyclic voltammetry studies. These analytical studies have shown that the monomeric and dimeric [FeL(R)] complexes behave distinctively, and that the dimer stability is a function of the ortho-positioned groups. Both the dimeric as well as monomeric complexes were tested as catalysts for the catalytic cycloaddition of carbon dioxide to oxiranes, and the data show that the monomeric complexes are able to mediate this conversion with significantly higher activities than the dimeric complexes. This difference in reactivity is controlled by the substitution pattern on the ligand L(R), and is in line with the catalytic requisite of binding of the epoxide substrate by the iron(III) center.