Synthesis and conformational switching of partially and differentially bridged resorcin[4]arenes bearing fluorescent dye labels - Preliminary communication

We report the synthesis of modified Cram-type cavitands bearing one or two fluorescent labels for single-molecule spectroscopic studies of vase-kite conformational switching (Scheme 3). Syntheses were performed by stepwise bridging of the four couples of neighboring H-bonded OH groups of resorcin[4]arene bowls (Schemes 2 and 3). The new substitution patterns enable the construction of a large variety of future functional architectures. H-1-NMR Investigations showed that the new partially and differentially bridged cavitands feature temperature- and pH-triggered vase-kite conformational isomerism similar to symmetrical cavitands with four identical quinoxaline bridges (Table). It was discovered that vase-kite switching of cavitands is strongly solvent-dependent.