A Rationally Designed NH(4)(+) Receptor Based on Cation-pi Interaction and Hydrogen Bonding We gratefully acknowledge the Korean Ministry of Science and Technology (Creative Research Initiative Program) for support of this work, and the Korean Ministry of Education (Brain Korea 21 program) for graduate studentships to J.H. and W.S.J. M.K. is grateful to POSTECH for an Undergraduate Research Fellowship. We also thank Professor P. K. Bharadwaj for helpful discussions.