Ligand-directed molecular architectures: Self-assembly of two-dimensional rectangular metallacycles and three-dimensional trigonal or tetragonal prisms

Three angular ditopic ligands (1,3-bis(benzimidazol-1 -ylmethyl)-4,6-dimethylbenzene L-1, 1,3-bis (benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene L-2, and 1,4-bis(benzimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene L-3) and one tripodal ligand 1,3,5-tris(benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene L-4 have been prepared. Reaction of these shape-specific designed ligands with different metal salts affords a series of discrete molecular architectures: [Ag2L21(BF4)(2) 1, [Ag2L22](CF3SO3)(2) 2, [CF3SO3- subset of Ag2L23]-CF3SO3 3, [CF3SO3- subset of Ag2L33]CF3SO3 4, [ClO4- subset of Cu2L42](Clo(4))(3) 5, [4H(2)O subset of (Ni2L4Cl4)-Cl-2].6H(2)O 6, [EF4- subset of Ag3L24](BF4)(2) 7, [ClO4- subset of Ag3L24](ClO4)(2) 8, and [Cul(3)(2-) subset of Cu3L24](2)[Cu2I4] 9. The compounds were characterized by elemental analysis, ESI-MS, IR, and NMR spectroscopy, and X-ray crystallography. 1 is a dinuclear metallacycle with 2-fold rotational symmetry in which two syn-conformational L-1 ligands are connected by two linearly coordinated Ag+ ions. 2 and 3 are structurally related, consisting of rectangular structures assembled from two linearly coordinated Ag+ ions and two L-2 or L-3 ligands. The structure of 4 is a trigonal prismatic box consisting of two Ag+ ions in trigonal planar coordination linked by three L3 ligands, while the structures of 5 and 6 are tetragonal prismatic cages constructed by two square planar Cu2+ or Ni2+ ions linked by four L-2 ligands. The topologies of 7-9 are similar to that of 4; however, these three structures are assembled from three linearly coordinated Ag+ or Cu+ ions and two tripodal ligands, representing an alternative strategy to assembling a trigonal prism. H-1 NMR and ESI-MS were utilized to elucidate the solution structures of these macrocycles.