Complexation with Small Molecules

It was demonstrated that a complexation of trans-stilbene with cyclodextrin led to a decrease in stereoselectivity of additive bromination and to a significant yield of DL-stilbene dibromide in contrast to the formation of meso-stilbene dibromide in nonpolar solvents [98]. The authors suggested that this reversal of stereoselectivity was attributed to the polar environment provided by the secondary hydroxyl groups of 

It was shown that bis(18-crown-6)stilbene formed bimolecular (D-A) and sand-wich-like (D-A-D) complexes with a di(quinolyl)ethylene derivative [100]. Unusual three-decker structures of a D-A-D complex were shown. Chiral stilbenophanes with small and large rigid cavities and bis-cydophanes with a stilbene-bridging unit formed charge transfer complexes with either TCNQ or TCNE [101]. Stilbenophanes formed complexes with TCNQ [102]. 

Dinuclear Ba(II) complexes of cis- and trans-stilbenobis(18-crown-6) have been prepared [105]. These complexes catalyzed size-selective ester and anilide cleavage. 

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The Reactivity of Transition Metal Complexes with Small Molecules... 

The reaction of these yellow square-planar complexes with small molecules was shown to yield stable five-co-ordinate adducts of the type [RhClLA] (A = BF3, CO, HgClj, SO2, O2, S2, H, NO, or N2ph ). I.r. measurements confirmed the presence of co-ordinated BF3, and supported symmetrical Tt-bonding of the O2 and S2 complexes (28). The greater stability of these adducts... 

Cyclodextrins (CD) can form inclusion complexes with small molecules by hydrophilic-hydrophobic interactions [33-37], Three CDs are readily available - 20, 21, and 22, denoted a, / , and y-CD, respectively. As the number of saccharides in the cyclic increases from 20 to 22, the cavity becomes larger. The hydroxy groups occupy the outside surface, resulting in hydrophilicity and high solubility in polar solvents. Their interiors consist of hydrocarbon units, making the cavity hydro-phobic. Thus when CD and a hydrophobic chain dissolve in a common polar solvent, the chain tends to occupy the cavity of the CD to achieve a lower energy level relative to its state in the polar medium this is hydrophobic-hydrophilic interaction. 

Fig. 10.7 I integration of SIFt into the structure-based drug design workflow. The experimental structure(s) of a drug target in complex with small molecules are used to generate SIFt and p-SIFt. This is used to filter a...

The NMR studies of carbohydrates provides information about structure, conformation, and complexation with small molecules and ions. 

Information on molecular recognition is also found in the crystal structures of proteins or oligonucleotides complexed with small molecules. 

A second example illustrates the ability of transition metals to form complexes with small molecules and ions. Copper metal and hot concentrated sulfuric acid ( oil of vitriol ) react to form solid copper(II) sulfate, commonly called blue vitriol by virtue of its deep blue color. There is more to this compound than copper and sulfate, however it contains water as well. When the water is driven away by heating, the blue color vanishes, leaving greenish white anhydrous copper(II) sulfate (Fig. 8.11). The blue color of blue vitriol comes from a... 

The full relaxation matrix approach for distance determination from 2D NOESY data has been used in many groups to refine solution structures of DNA, including mismatched duplexes, variously chemically modified duplexes, complexes with small molecules, and so on.93 174 176 178-195 However, there are fewer RNA structures... 

There are three classes of cyclic chiral selectors in use as CSPs cyclodextrins, crown ethers and macrocyclic glycopepetide antibiotics. They can undergo host-guest complexes with small molecules if these can fit into the ring structure for enantio-differentiation this fit needs to be stereochemically controlled. 

Dirhodium(l) Complexes with Small Molecule Ligands 123... 

Experimental investigation of the factors that control the rates of biological redox reactions has not come as far as the study of the electron transfers of metal complexes, because many more variables must be dealt with (e.g., asymmetric surface charge, nonspherical shape, uncertain details of structures of proteins complexed with small molecules or other proteins). Many experimental approaches have been pursued, including the covalent attachment of redox reagents to the surfaces of metalloproteins. 

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