Reversible single crystal to single crystal transformation with anion exchange-induced weak Cu2+center dot center dot center dot I- interactions and modification of the structures and properties of MOFs

{[Cu-6(TTTMB)(8)(OH)(4)(H2O)(6)]center dot 8(NO3)center dot 34.5H(2)O}(n) can reversibly transform to {[Cu-6(TTTMB)(8)I-3]center dot 9I center dot 26H(2)O}(n) upon a single crystal to single crystal process. The transformation is accompanied by the formation of weak Cu2+center dot center dot center dot I- interactions and changes in the coordination numbers, as well as modulation in their properties.