Coordination behaviors of a 23-membered NO4S2-macrocycle: Mononuclear silver(I) complex and conformational isomers of tetranuclear bis(macrocycle) mercury(II) complexes exhibiting exo- and endo/exocyclic coordination modes

摘要

A ditopic 23-membered NO4S2-macrocycle (L) incorporating both semi-rigid and flexible binding sites was synthesized and its silver(I) and mercury(II) complexes exhibiting different stoichiometries and coordination modes were prepared. First, silver(I) perchlorate reacts with L to afford an endocyclic mononuclear complex [Ag(L)]ClO4 (1) in which the silver(I) ion locates at the semi-rigid binding site in the cavity. The solution study for the silver(I) complexation via the H-1 NMR titration agrees with the corresponding solid state data that show the endo-mode. Interestingly, the reaction of L with HgI2 led to the isolation of two conformational isomers with a tetranuclear bis(macrocycle) composition, [((HgLI2)-Hg-exo)(2)(mu-Hg2I4)] (2a) and [((HgLI2)-Hg-endo)(2)(mu-Hg2I4)] (2b), which are dominated by the coordination modes of L toward the mercury(II) center. In both conformers, two exocyclic mercury(II) complex units ((HgLI2)-Hg-exo)(2) in 2a or two endocyclic complex units [((HgLI2)-Hg-endo)(2) in 2b are linked by tetraiododimercury(II) core (mu-Hg2I4) to give a 4:2 (metal-to-ligand) stoichiometry. Based on the packing structures and high temperature experiment, the intermolecular interactions might be responsible for the formation of 2a and 2b which are kinetically and thermodynamic controlled, respectively.