CFA-1: the first chiral metal-organic framework containing Kuratowski-type secondary building units

The novel homochiral metal-organic framework CFA-1 (Coordination Framework Augsburg-1), [Zn-5(OAc) 4(bibta)(3)], containing the achiral linker {H-2-bibta = 1H, 1' H-5,5'-bibenzo[d][1,2,3] triazole}, has been synthesised. The reaction of H-2-bibta and Zn(OAc)(2)center dot 2H(2)O in N-methylformamide (NMF) (90 degrees C, 3 d) yields CFA-1 as trigonal prismatic single crystals. CFA-1 serves as a convenient precursor for the synthesis of isostructural frameworks with redox-active metal centres, which is demonstrated by the postsynthetic exchange of Zn2+ by Co2+ ions. The framework is robust to solvent removal and has been structurally characterized by synchrotron single-crystal X-ray diffraction and solid state NMR measurements (C-13 MAS-and H-1 MAS-NMR at 10 kHz). Results from MAS-NMR and IR spectroscopy studies are corroborated by cluster and periodic DFT calculations performed on CFA-1 cluster fragments.