Influence of Alkali Metal Cation (Li(I), Na(I), K(I)) on the Construction of Chiral and Achiral Heterometallic Coordination Polymers

A series of chiral and achiral lanthanide-alkali coordination polymers, [LnM(INA)3(OAc)] where [M = Li, Ln = Eu (1); M = Li, Ln = Tb (2); M = Na, Ln = Eu (3); M = Na, Ln = Tb (4); INA = isonicotinate; OAc = acetate] and [TbK(INA)2(OAc)2] (5), have been solvothermally synthesized and structurally characterized. The acetate groups were in situ obtained from oxidation of CH3CN during the reaction. Structures with remarkably different connectivities are formed when Li(I), Na(I), and K(I) were introduced into the system. Compounds 1–4 are isostructural three-dimensional (3D) coordination polymers and built up by right-/left-handed Ln-O-M chiral helicals and INA linkers possessing a 3,3,4,7T2 topology. Compound 5 is a 3D pillared coordination polymer constructed from two-dimensional (2D) Tb–O–K layers with INA as connectivities possessing an alb-4,8-P21/c topology. Circular dichroism (CD) measurements confirmed that the resulting crystals of 1, 3, and 4 were racemic mixtures. The photoluminescent properties of compounds 1–5 were investigated, exhibiting intense characteristic emission spectra of lanthanide ions.