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

Abstract

Four binuclear and one polymeric silver 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-methoxyl-1,3-benzenedicarboxaldehyde (R = OCH 3, CH 3, Br or Ph) in the presence of excess of Ag I ion. The polynucleating and extended coordination nature of the trpn-derived cryptand L 1 (R = OCH 3) was established by X-ray structure of [{Ag(Ag 2L 1)} n][(ClO 4) 3·2CH 3CN·CH 3OH·2 H 2O n . The polymeric cation [{Ag(Ag 2L 1)} n ] can be described as the bridge-twisted binuclear (Ag 2L 1) 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.