Ionothermal synthesis of a 3D heterometallic coordination polymer based on the rod shaped copper(II)–sodium(I)-carboxylate secondary building units with a pcu topology

Compound [(EEIM)NaCu(phth)2]n (1) (EEIM = 1,3-diethylimidazolium and phth = terephthalate) was synthesized by using the mixed ionic liquids of 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM]-BF4 and chiral 1-ethyl-3-methylimidazolium l-lactate as solvent. The sodium(I) ion deriving from the [EMIM]-BF4 with a small amount of Na(I) impurity incorporated into the structure is unprecedented. Compound 1 is a 3D anionic framework based on a unique rod shaped heterometallic copper(II)–sodium(I)-carboxylate secondary building unit, exhibiting a distorted pcu-(412 · 63) topology. It is interesting that the organic template of [EEIM]+ cation formed from an in situ reaction acting as extraframework charge-balancing species occupies the 1D rhombic channels of the 3D anionic framework. The roles of the ionic liquid in ionothermal synthesis and crystallization of 1 are briefly discussed.