H-bond switching mediated multiple flexibility in supramolecular host-guest Architectures

Two-dimensional (2D) self-assembled 1,3,5-tris(10-carboxydecyloxy) benzene (TCDB) networks connected by hydrogen bonds on highly oriented pyrolytic graphite (HOPG) surfaces are shown to accommodate a variety of unsubstituted metallophthalocyanine (MPc) molecules (such as H2PC, CuPc, VOPc, and ClGaPc) and halogen-substituted MPcs (such as F16CuPc, which have been observed by scanning tunneling microscopy (STM) under ambient conditions. Two types of dramatically different host-guest architectures are identified for each MPc/TCDB systems, that is, the architecture MPc/TCDB (I) (with MPc monomers entrapped in the TCDB cavities) and the architecture MPc/TCDB (II) (with MPc dimers entrapped in the TCDB cavities). The intermolecular interactions are calculated by density functional theory (DFT), which demonstrates that the host-guest intermolecular interactions (including van der Waals forces and electrostatic interactions caused by asymmetrical electronic distribution of MPcs) are important in determining the on-and-off of hydrogen bonds in the host lattice. The STM study combined with the DFT calculations reveal that the hydrogen bond switching through O-H center dot center dot center dot O bonds is responsible for the formation of TCDB cavities with multiple flexibility for guest molecule inclusion.