Synthesis and Structural Characterization of a Novel Mixed-Valent CuIICuICuII Triangular Metallomacrocycle Using an Imine-Based Rigid Ligand

A novel neutral mixed-valent CuICuII2 triangular metallomacrocycle [Cu3L2(HL)]·3CH3OH·2H2O (1) was assembled by reaction of the tetradentate ligand bis(N-salicylidene-4,4‘-diphenylamine), H2L, with a copper(II) salt. ESI-MS show peaks only corresponding to the triangular structural species, indicating the high stability of the trimer structure in solution. Magnetic study confirms that there are two CuII ions and one CuI ion in a discrete triangular molecule. The crystal structure of 1 reveals that the triangle is formed by three deprotonated ligands and three copper ions with a Cu···Cu separation of ca. 11.8 A. Each copper atom is coordinated by two oxygen atoms and two nitrogen atoms from two different bis-bidentate ligands in a heavily distorted tetrahedral geometry, while each ligand is bound to two metal ions in a bis-bidentate coordination mode and links the metal centers overlapping in an unprogressive manner. Strong intramolecular π···π interactions between the ligands are found to stabilize the co...