Self-Assembly of Discrete Metallocycle versus Coordination Polymer Based on Silver(I) and Di-2- and Di-3-pyridines with Flexible Spacer

Four flexible bis(pyridyl) ligands, namely, 1,3-bis(2-pyridylaminomethyl)benzene (L1), 1,3-bis(3-pyridylaminomethyl)benzene (L2), 1,4-bis(3-pyridylaminomethyl)benzene (L3), and 1,4-bis(2-pyridylaminomethyl)benzene (L4), have been synthesized, and the reactions of these ligands with AgX salts (X = NO₃⁻, ClO₄⁻) lead to the formation of six new complexes, [Ag(L1)]₂(ClO₄)₂ (1), [Ag(L2)ClO₄]_n (2), [Ag(L1)NO₃]_n (3), [Ag(L3)(PPh₃)₂]_n(NO₃)_n·nCH₃OH (4), [Ag₂(L4)(PPh₃)₂(NO₃)₂]_n·nH₂O (5), and [Ag(L4)NO₃]_n (6), exhibiting from zero-dimensional (0-D) to three-dimensional (3-D) frameworks. In complex 1, the L1 ligand bridges two silver atoms to form a dinuclear with a 24-membered macrometallacyclic ring, while the L1 ligand coordinates to silver atoms to generate a 2-D (4,4) network with two pyridine rings oriented in a divergent fashion (or trans conformation) in complex 3. With a similar trans conformation, L2 in complex 2, L3 in complex 4, and L4 in complex 5 connect the adjacent silver atoms or Ag₂O₂ units which formed by the bridging of nitrate anions in a η₂:μ₂ fashion to give rise to infinite helical chains, respectively. Complex 6 exhibits a 3-D framework with diamond topology, which is combined by two kinds of helical chains: one is a -Ag-NO₃-Ag-NO₃- chain with the nitrate anions in a η₁:η₁:μ₂ fashion, and another is a -Ag-L4-Ag-L4- chain with the L4 ligand in trans conformation. All of these complexes are photoluminescent in the solid state with spectra that closely resemble those of the ligand precursor.