Assembling silver(i) coordination polymers of an NS4-macrocycle via an endo/exocyclic coordination mode

Abstract

Networking of molecular hosts via non-covalent interactions has become one of the central topics in crystal engineering. We herein report the self-assembly of silver(I) coordination polymers with an NS₄-macrocycle (L) whose connectivity patterns depend on anion types. First, a one-pot reaction of L with AgPF₆ yielded an endo/exocyclic one-dimensional (1D) coordination polymer {[Ag₃L₂](PF₆)₃·2CH₂Cl₂}_n (1) in which two silver(I) atoms (^endoAg)₂ are sandwiched by two L ligands to form an L(^endoAg)₂L unit. Further, the disilver(I) sandwich units are linked by one exocyclic silver(I) atom (^exoAg), giving rise to a polymeric loop chain array of 1 without anion coordination. When L was reacted with AgCF₃SO₃ and AgCF₃CO₂, again, endo/exocyclic 1D coordination polymers {[Ag₄L₂(CF₃SO₃)₂](CF₃SO₃)₂·CH₂Cl₂}_n (2) and {[Ag₄L₂(CF₃CO₂)₂](CF₃CO₂)₂·4CH₃OH}_n (3) with a similar connectivity pattern were obtained, respectively. In both 2 and 3, one ^endoAg atom and one ^exoAg atom link three L ligands to form a double-stranded array with one anion coordinated to the ^exoAg atom. In the anion exchange experiments, the formation of 2 (CF₃SO₃⁻ form) is relatively favourable over 1 (PF₆⁻ form) or 3 (CF₃CO₂⁻ form) mainly due to the anion access-friendly conformation and moderate binding affinity of CF₃SO₃⁻ which can easily gain entry.