Intriguing π+-π Interaction in Crystal Packing

The pi(+)-pi interactions are utilized to design the solid-state assembly of host-guest complexes where guests are anions. The doubly protonated MPTPH2 (MPTP = 4'-(4-methoxyphenyl)-2,2':6', 2 ''-terpyridine) complexed with H2O and Cl- or Br- are synthesized, crystallized, and characterized by X-ray analysis. By using the density functional theory calculations which can properly describe the dispersion energy, the assembling phenomena are analyzed in terms of pi(+)-pi and pi-pi interactions as well as H-bonding interactions. The planar structure of MPTPH2(Cl)(2)center dot 2H(2)O or MPTPH2(Br)(2)center dot 2H(2)O facilitates the crystal packing, since the interactions play in important role in the solid-state assembly.