Construction of a Square-Planar Molecular Box: Self-Assembly of Palladium(II) Complexes of 3,6,9,16,19,22-Hexaazatricyclo[22.2.2.2^11,14]triacon-11,13,24,26(1),27,29-hexaene through Hydrogen-Bonding Interactions

Binuclear palladium(II) complexes of the macrocyclic polyamine 3,6,9,16,19,22-hexaazatricyclo[22.2.2.211,14]triacon-11,13,24,26(1),2 7,29-hexaene (L) are used to construct molecules having special shapes. In this study two binuclear palladium(II) complexes [Pd2LI2]I2and [Pd2LCl2](NO3)2·H2O are synthesized and structurally characterized. X-ray crystallography shows that both complexes exist as one-dimensional chains formed via intermolecular hydrogen-bonding N(3)−H(3C)---X in which X is I and Cl. Moreover, the ligands in both complexes adopt a boatlike conformation that may facilitate the formation of the tetranuclear complex. The cationic aqua complex [Pd2L(H2O)m(NO3)n](4-n)+, obtained by the treatment of [Pd2LI2]I2and [Pd2LCl2]Cl2 with AgNO3, is used as a building block for the construction of a tetranuclear palladium(II) complex [Pd4L2(C2O4)2](NO3)4·6H2O. X-ray crystallography shows that the tetranuclear complex forms an open, hydrophobic box. These molecular boxes are connected via the hydrogen bond N(3)−H(3C)---O(4B) (symmetry code B: x, 1 + y, z) into a one-dimensional chain. A two-dimensional structure is formed via π−π stacking of the plane defined by C6 to C11 in the one chain and its symmetry-related plane (symmetry code C: −x, −1 − y, 2 − z) in another chain. This study exemplifies a new method for the assembly of molecular boxes using a macrocyclic ligand.