Macrocyclic dinuclear, helical, layered and 3-D Ag(i) complexes constructed from AgX (X = NO3− and ClO4−) and flexible bis(pyridyl) ligands with a chelating spacer: syntheses, structures and photoluminescence properties

Abstract

Reaction of AgX (X = NO₃⁻ and ClO₄⁻) and three flexible bis(pyridyl) ligands with a chelating spacer leads to the formation of eight novel Ag(I)-bis(pyridyl) coordination complexes: {[Ag₂L1(NO₃)₂]_n·2nH₂O} (1), {[AgL1]_n·nClO₄} (2), {[AgL2]_n·nNO₃} (3), {[AgL2]_n·nClO₄} (4), [Ag₂(H₂L2)₂]·6ClO₄·9H₂O (5), {[AgL3]_n·nNO₃·nH₂O} (6), {[AgL3]_n·nClO₄·nH₂O} (7), and {[Ag₃(L3)₂(ClO₄)]_n·2nClO₄} (8) (L1 = N,N′-bis(pyridin-2-ylmethyl)propane-1,3-diamine, L2 = N,N′-bis(pyridin-3-ylmethyl)propane-1,3-diamine, L3 = N,N′-bis(pyridin-4-ylmethyl)propane-1,3-diamine), which have been characterized by elemental analysis, IR, TG, UV-Vis DRS, PL, powder and single-crystal X-ray diffraction. Complex 1 presents a (4,4) layered motif which is furnished by the bridging of L1 molecules and nitrate anions in μ₄ (κ¹N1:κ¹N2:κ¹N3:κ¹N4) and μ₂ (κ¹O4:κ¹O6) modes. With a different μ₂ (κ¹N1:κ¹N2:κ¹N3:κ¹N4) mode, L1 molecules in complex 2 join the adjacent Ag(I) cations to form a helical chain structure. Complexes 3 and 4 also show helical chain structures with the L2 molecules displaying the same μ₃ (κ¹N1:κ¹N2:κ¹N3:κ¹N4) mode. The protonation of –NH– groups in the chelating spacer leads to the formation of H₂L2²⁺ cations which further results in a macrocyclic dinuclear motif in complex 5. Complexes 6 and 7 are 3-D svi-x nets with the counter-anions and lattice water molecules being encapsulated in the 1-D channels. Complex 8 exhibits a snake-shaped chain with the L3 molecules presenting μ₃ (κ¹N:κ¹N′:κ¹N″:κ¹N‴) mode. The structural diversities of complexes 1–8 can be attributed to the coordination modes and conformations of L1–L3. The photoluminescence properties demonstrate that complexes 1, 2 and 5 exhibit ligand-based blue emission maxima from 455 to 462 nm at room temperature in the solid state.