A Dendritic Structure Containing a Designed Cleft which Controls Ligand Coordination Behavior in an Analogous Way to Proteins This work was supported by the Leverhulme Trust. We thank the University of Warwick National 9.4T FT-ICR Mass Spectrometry Facility (EPSRC/BBSRC) for recording the FT-ICR mass spectra and the EPSRC National Mass Spectrometry Centre, Swansea, for recording other mass spectra.