Molecular Shape Recognition by Using a Switchable Luminescent Nonporous Molecular Crystal

A nonporous molecular crystal (NMC) has been developed for use as a host material. The NMC comprises a platinum dibromide complex with coordinating 9-phenyl-9-arsafluorene ligands. The NMC also contains chlorobenzene (PhCl) molecules, which quench emissions from the platinum complex. On exposure to the vapors of several volatile organic compounds (VOC), the encapsulated PhCl was released. With the loss of PhCl, the crystal once again showed the intrinsic luminescence of the platinum complex. Furthermore, the NMC can recognize the molecular shape of VOCs; consequently, VOCs having small minimum diameters turn on emission, but large VOCs do not cause the release of the included PhCl quencher, and emission remains switched off. Interestingly, a wide range of VOCs (e.g., alcohol, ether, haloalkane, and alkane) could be used, implying that the shape recognition ability of the present NMC system is polarity independent. This is the first example of NMCs having widespread molecular shape recognition properties.