Dendrophanes: Water‐Soluble Dendritic Receptors. Preliminary communication

Abstract

Abstract The dendr itic cycl ophanes (dendrophanes ) 1–3 containing a [6.1.6.1]paracyclophane as the initiator core embedded in dendritic poly(ether‐amide) shells of first ( 1 ), second ( 2 ), and third ( 3 ) generation were prepared and characterized. The X‐ray crystal‐structure analyses of esters 7 and 4 , derivatives of cyclophane core 9 and first‐generation dendrophane 1 , respectively, displayed open cavity binding sites suitable for the inclusion complexation of aromatic substrates. With their carboxylate surface groups, dendrophanes 1–3 were readily soluble in aqueous phosphate buffer (p H 8.0), and the complexation of naphthalene derivatives was investigated by 1 H‐NMR and fluorescence titrations. The binding studies demonstrated that the cyclophane cavity remains open and accessible to appropriate substrates even at higher dendritic generations. The 1:1 complexes formed in aqueous buffer were of similar stability to those formed by the unbranched core 9 ( K a between 1000 and 10000 1 mol −1 , 300 K). Investigations with the fluorescent probe 6‐( p ‐toluidino)naphthalene‐2‐sulfonate ( 12 ) showed that the micropolarity at the dendrophane core decreases with increasing generation number.