Interaction coordinate

An expedient and stereoselective synthesis of bicyclic ketone 30 exemplifies the utility and elegance of Corey s new catalytic system (see Scheme 8). Reaction of the (R)-tryptophan-derived oxazaboro-lidine 42 (5 mol %), 5-(benzyloxymethyl)-l,3-cyclopentadiene 26, and 2-bromoacrolein (43) at -78 °C in methylene chloride gives, after eight hours, diastereomeric adducts 44 in a yield of 83 % (95 5 exo.endo diastereoselectivity 96 4 enantioselectivity for the exo isomer). After reaction, the /V-tosyltryptophan can be recovered for reuse. The basic premise is that oxazaborolidine 42 induces the Diels-Alder reaction between intermediates 26 and 43 to proceed through a transition state geometry that maximizes attractive donor-acceptor interactions. Coordination of the dienophile at the face of boron that is cis to the 3-indolylmethyl substituent is thus favored.19d f Treatment of the 95 5 mixture of exo/endo diastereo-mers with 5 mol % aqueous AgNC>3 selectively converts the minor, but more reactive, endo aldehyde diastereomer into water-soluble... 

Neutral transition-metal complexes that are not fully coordinatively saturated possess nucleophile metal centers capable of coordinating to electrophiles. On the other hand, group-IIIB halides serve as typical electron-pair acceptors and are, therefore, able to interact coordinatively with basic metal complexes. 

P2j Z = 2 DX = 1.43 R = 0.067 for 1269 intensities. The uracil residue is in the anti (63.4°) disposition. The conformation of the D-ribosyl group is 2T3 (176.8°, 37.5°). The orientation about the exocyclic, C-4 -C-5 bond is t (—174.2°). The phenyl and uracil ringsofthe same molecule lie in almost parallel planes, 120 pm apart. The phenyl group is disordered. The uracil ring is sandwiched by the phenyl rings, and vice versa. The 0-1 and N-a atoms of the peptide backbone are hydrogen-bonded to 0-4 and N-3 of atranslationally related uracil to form cyclic dimers. Such interactions serve as models for nucleic acid-protein interactions. [Coordinate errors H(02 ) x should be —1574, instead of —1474 H(Na)2 z should be —145 instead of— 645.]... 

Zinc carboxylate interactions have been exploited as part of a fluorescent molecular sensor for uronic acids. The sensors feature two interactions coordination of the carboxylate to the zinc and a boronic acid diol interaction.389 Photoluminescent coordination polymers from hydrothermal syntheses containing Zn40 or Zn4(OH)2 cores with isophthalate or fumarate and 4,4 -bipyridine form two- and three-dimensional structures. Single X-ray diffraction of both dicarboxylates identified the network structure.373... 

Fig. 6. Diagrammatic (two-dimensional) representation of different modes of lattice inclusions involving coordinative (H-bond) interactions (indicated by broken lines) (a) cross-linked matrix type of inclusion (host-host interaction, true clathrate) (b) coordinatoclathrate type of inclusion (coordinative host-guest interaction, coordination-assisted clathrate)...

In fact this "unhydrolyzed" polyacrylamide sample is slightly charged and its low polyectrolyte character is confirmed by a slight difference of red values at pH 7 and 5, for salt free solutions. A really neutral polymer should be necessary to differentiate low effects of electrostatic interactions from non ionic interactions. coordination binding at low pH and hydrogen bonds at pH 7. Nevertheless, at this pH, the adsorption of the chain on Al(0H)3 aggregates can probably be considered as the main origin of the loss of viscosity. 

At the water-air interface hydrophilic groups are oriented toward the water, hydro-phobic groups are oriented toward air. At solid-water interfaces, the orientation depends on the relative affinities for water and for the solid surface. The hydrophilic groups of amphipathic molecules may - if the hydrophobic tendency is relatively small - interact coordinatively with the functional groups of the solid surface (Ulrich et al., 1988) (see Fig. 4.10). 

The structure of 73 was substantiated spectroscopically (5 nB = 82.5 ppm) and confirmed crystallographically. A centrosymmetric chloro-bridged dimeric structure with tricoordinate copper centers was observed. The pendant character of the borane is apparent from the rather long the B- Cu (3.05 A) and B- Cl (4.06 A) distances associated with a trigonal planar geometry around boron. Compared to related mononuclear palladium and rhodium complexes (see Section IV.B), the presence of the chloro-bridge disfavors the formation of Cl-B interactions (coordination mode F) in 73. 

Strong interactions, such as p-p interactions, coordinative bonds, and hydrogen bonds between the selector and selectand... 

Fig. 10. Potential curves versus interaction coordinate. The evolution of the excitation during an absorption-emission cycle is shown by arrowed lines. The energy differences and let-...

Similarly the quadrupole interaction coordinate system can be related to the new one by an Eulerian angle transformation which will enable 1, 1, ly to be expressed in terms of S, Sy. In total, the angles d and Eulerian angles a, fi, and y are required to define the geometry uniquely. 

The synthesis and characterization of VOPO4 intercalation compounds with aliphatic amines from Cj to Cjo have been reported [13,14]. However, the synthetic approach for the intercalation of such classes of molecules in this work is quite different from those used here. Furthermore (and most important), we think that the use of diamines could provide interesting results, from a structural point of view, since they exhibit two coordination sites (N atoms), and so are able to interact (coordinate) with two different vanadium atoms of opposite layers. 

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