Synthesis and NMR studies of silver complexes with octaaza Schiff-base cryptands and the structure of a polymeric silver cryptate

Four binuclear and one polymeric silver complex of octaaza Schiff-base cryptands were synthesized by [2 + 3] condensation of tris(3-aminopropyl)amine (trpn) or tris(2-aminoethyl)amine (tren) with 5-R-2-methoxy-1,3-benzenedicarboxaldehyde (R = OCH₃, CH₃, Br or Ph) in the presence of excess of Ag¹ ion. The polynucleating and extended coordination nature of the trpn-derived cryptand L¹ (R = OCH₃) was established by X-ray structure of [{Ag(Ag₂L¹)}n][(ClO₄) ₃·2CH₃CN·CH₃OH·2H ₂O]_n. The polymeric cation [{Ag (Ag₂L¹)}_n] can be described as the bridge-twisted binuclear (Ag₂L¹) units linked together by silver atoms via a linear N - Ag - N bridging bonding mode in alternate (inward, outward) conformations relative to the benzene rings, resulting in an infinite single helical chain. The benzene rings in the helix chain are almost parallel to each other, with a π - π stacking distance of 3.84 Å. The coordination behaviour of cryptands have also been studied by NMR spectroscopy in solution.