Ionothermal syntheses and crystal structures of two cobalt(II)–carboxylate compounds with different topology

Two cobalt–carboxylate compounds, namely, {[PMIM]2[Co2(BTC)2(H2O)2]}n (1) (PMIM = 1-propyl-3-methylimidazolium and H3BTC = 1,3,5-benzenetricarboxylic acid) and [Co3(BDC)3(IM)2]n (2) (H2BDC = 1,4-benzenedicarboxylic acid and IM = imidazole) have been synthesized under ionothermal reactions. Compound 1 has a 3D anionic framework with (4.62)2(42.610.83) topology based on dinuclear cobalt(II) as a secondary building unit. The imidazolium cation [PMIM]+ of the ionic liquid acting as extraframework charge-balancing species occupies the channels of the 3D anionic framework. Complex 2 features a 3D neutral framework with (412.63) topology constructed of unusual linear trinuclear cobalt(II) as a secondary building unit. The rich ionic environments of the ionic liquid may be particularly helpful in the formation of the frameworks of 1 and 2. The roles of the ionic liquid in ionothermal syntheses and crystallizations of compounds are briefly discussed.