Macrocycles incorporating isomeric arms: synthesis and crystal structures of ligands and their mono-, di- and polynuclear supramolecular complexes

An isomeric series of NS2-macrocycles containing a pyridine-arm at the ortho (o-L), meta (m-L) and para (p-L) positions were synthesized and structurally characterised by X-ray analysis. A comparative investigation of the coordination behaviour of these ligands with Ag-I, Hg-II, Pb-II and Cu-II is reported. The X-ray structures of seven complexes (1-7) have been determined, and a range of structural types and coordination modes including mono-to multinuclear and discrete to continuous ones, are shown to occur. Reactions of these ligand isomers with Ag-I salts (ClO4- and NO3-) afforded four complexes (1-4): the monomer (1 : 1, metal-to-ligand) complex with a trigonal bipyramid (TBP) geometry [Ag(o-L)ClO4] (1), the anion-free cyclic dimer (2 : 2) complex with two separated units, [Ag-2(m-L)(2)](2)(ClO4)(4) (2), the cyclic dimer complex [Ag-2(p-L)(2)](ClO2)(2)center dot CH3CN (3) and the unique poly(cyclic dimer) network complex {[Ag-2(p-L)(2)(NO3)]NO3}(n) (4). Three divalent metal ion (mercury, lead and copper) complexes (5-7) of o-L were also isolated: the 1 : 1 monomer complexes with a square pyramid (SP) geometry [Hg(o-L)(NO3)(2)] (5) and [Cu(o-L)(H2O)ClO4] ClO4 (6) and the anion-linked dinuclear complex [Pb-2(o-L)(2)(CH3OH)(2)(mu(2)-ClO4)(2)](ClO4)(2) (7), adopting a monocapped trigonal prismatic geometry. In all cases, the pyridine arms with the different nitrogen positions have an important role in their three dimensional coordination behaviours via the strong N-py-M bonds. Also their coordination patterns depend markedly on the variation of the pyridyl nitrogen positions especially for m-L and p-L due to the preference of the network formation with discrete or continuous structures.