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

CrystEngComm Pub Date: 2012-07-02 DOI: 10.1039/C2CE25708D

Abstract

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 AgI, HgII, PbII and CuII 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 AgI 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, [Ag2(m-L)2]2(ClO4)4 (2), the cyclic dimer complex [Ag2(p-L)2](ClO4)2·CH3CN (3) and the unique poly(cyclic dimer) network complex {[Ag2(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 [Pb2(o-L)2(CH3OH)2(μ2-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 Npy-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.

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