Rational Assembly of d10 Metal-Organic Frameworks with Helical Nanochannels Based on Flexible V-Shaped Ligand

Solvothermal reactions of Zn(II) or Cd(II) nitrates and V-shaped ligand of 4,4'-(hexafluoroisopropylidene)bis-(benzoic acid) (H(2)hfipbb) in the presence or absence of 4,4'-bipy afforded four interesting d(10) metal-organic frameworks with helical nanochannels, namely, Zn(hfipbb)center dot 0.5H(2)O center dot 0.5DMF enantiorners (P6(2)22, 1a, and P6(4)22, 1b), Zn(hfipbb)(4,4'-bipy)center dot DMF (2), and Cd(hfipbb)(DMF)center dot 0.5DMF (3). The enantiomeric la and 1b exhibit similarly a (4,4)-connected 3D network with two types of helically 2-fold and 8-fold nanochannels along the c-axis, in which ultralong helical pitches are found in the 8-fold helical channels. Compound 2 features a 2D layered structure based on dizinc(II) paddle-wheel clusters with the appearance of left- and right-hand helical channels alternatively, while ID double helical channels exist in the complicated structure of compound 3. The luminescent properties of all the compounds have also been studied.