Luminescent transition-metal-containing cyclophanes ("molecular squares"): Covalent self-assembly, host-guest studies and preliminary nanoporous materials applications

An overview is given of the synthesis and characterization of a family of transition-metal cyclophanes containing rhenium tricarbonyl chloro corners and bridging diimine edges. The synthesis of both heterometallic (Re₂M₂, M = Pd, Pt) and homometallic (Re₄) cyclophanes is described. Also briefly described are studies aimed at shedding light on the probable mechanism of high-yield assembly of homometallic molecular squares. The use of these cavity-containing assemblies as hosts in the condensed-phase binding of selected molecular guests is discussed. Also described are preliminary applications of the compounds as thin film nanoporous sensing elements. These studies suggest that the compounds may prove useful in mass-responsive or light-responsive volatile organic chemical sensing devices.