Complexation and (Templated) Synthesis of Rhenium Complexes with Cyclodextrins and Cyclodextrin Dimers in Water

Abstract

Several small, lipophilic rhenium complexes form inclusion complexes with native beta-cyclodextrin (beta-CD) and beta-CD dimers. Association constants larger than 10(9)M(-1) were obtained using dimers. The use of beta-CD also enabled the synthesis of these rhenium complexes in water, in excellent yields, through complexation of the otherwise insoluble corresponding ligands. The influence of the reaction time and temperature on the configuration of the reaction products has been investigated in depth for one of these complexes. Using a beta-CD dimer, it proved possible to specifically template the formation of one configuration. The strength of the complexes of the rhenium complexes in cyclodextrin dimers may allow radiolabeling of biomolecules.

Recent developments in cyclodextrin‐mediated aqueous biphasic hydroformylation and tsuji–trost reactions

“…The spacer alters the orientation and distance between the CDs and supplies additional binding ability towards included guests upon inclusion complexation. Such cooperative binding had already been observed with CD dimers in many fields such as template synthesis, catalysis, enzyme mimicking, photochemistry and molecular imprinting . Such effects could also help overcome mass transfer limitations in aqueous organometallic catalysis using water‐soluble CD‐based ditopic receptors.…”

Dimeric Diaminocationic β-Cyclodextrin Derivatives

“…[10,11] Moreover, the linker can supply a well-organized pseudo-cavity that in turns provides additional binding interactions with accommodated guest molecules. [11] Thus, dimeric CDs could be successfully utilized in carriers, [12] catalysis, [8] templated synthesis, [13] photochemical materials, [14,15] solubilizers, [16] etc. The dimeric complex, in com-parison with the monomeric complex, has an enhanced synergistic effect on the inclusion of "guests" in its cyclodextrin cavity, [17][18][19] which could help for more efficient and targeting site delivery.…”

Secondary Face‐to‐Face 2–2′ β‐Cyclodextrin Dimers Linked with Fluorescent Rigid Spacer Arms: A Cyclodextrin‐Based Ratiometric Sensor for Bile Salts

“…[14,15] In addition to the cooperative binding through which the two adjacent CD cavities of these bridged bis(CD)s can encapsulate guest molecules, the linker can contribute to the stabilization of such complexes by providing additional binding interactions or contributing to extending the overall binding site. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Secondary-face-linked β-CD dimers often show higher complexing constants than those bridged by primary faces, [18][19][20][21]35] probably due to the fact that guest Scheme 1. CD units can be linked through their primary faces, i.e., 6-6Ј bis(CD), through a head-to-tail fashion, i.e., 6-2Ј or 6-3Ј bis(CD), and through their secondary faces, i.e., 2-2Ј or 3-3Ј bis(CD).…”