Complexation of triptycene-based macrotricyclic host toward (9-anthracylmethyl)benzylammonium salt: a Ba2+ selective fluorescence probe.

A new triptycene-based macrotricyclic host containing two dibenzo-30 crown-10 moieties (1) has been synthesized. It could form a 1:2 stable complex 1 x 3(2) with (9-anthracylmethyl)benzylammonium salt (3) in both solution and solid state, in which the 9-anthracyl groups were selectively positioned inside the cavity of the host. Moreover, the complexation and disassociation of complex 1 x 3(2) could be chemically controlled by the addition of base and acid. It was also found that Ba(2+) ion could considerably induce the fluorescence enhancement of complex 1 x 3(2), which might thus be utilized as a selective supramolecular fluorescence probe for Ba(2+) ion. Fluorescence and (1)H NMR spectroscopic titrations further showed that the complexation between complex 1 x 3(2) and barium ions underwent a two-step process.