Ionothermal synthesis of a 3D zinc(II)-carboxylate coordination polymer with bcu topology based on heptanuclear [Zn7(μ4-O)2] cluster

Compound {(EMIM)2[Zn7(μ4-O)2(1,4-ndc)6]}n (1) (EMIM = 1-ethyl-3-methylimidazolium and 1,4-ndc = 1,4-naphthalenedicarboxylate) has been synthesized by using the mixed ionic liquids of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium l-lactate as solvent. Compound 1 has a 3D anionic framework with bcu-(424·64) topology based on a unique heptanuclear [Zn7(μ4-O)(μ2-COO)10] cluster as secondary building unit. The imidazolium cation [EMIM]+ of the ionic liquid acting as extra framework charge-balancing species occupies the channels of the 3D anionic framework. The roles of the ionic liquid in ionothermal synthesis and crystallization of compound 1 are briefly discussed. The thermal and photoluminescent properties of compound 1 have also been investigated.