Tuning Electrical- and Photo-Conductivity by Cation Exchange within a Redox-Active Tetrathiafulvalene-Based Metal-Organic Framework.

To activate electronic and optical functions of the redox-active metal-organic framework, (Me2 NH2 )[InIII (TTFTB)]⋅0.7 C2 H5 OH⋅DMF (Me2 NH2 @1, TTFTB=tetrathiafulvalene-tetrabenzoate, DMF=N,N-dimethylformamide), has been exchanged by tetrathiafulvalenium (TTF.+ ) and N,N'-dimethyl-4,4'-bipyridinium (MV2+ ). These cations provide electron carriers and photosensitivity. The exchange retains the crystallinity allowing single-crystal to single-crystal post-synthetic transformation to TTF@1 and MV@1. Both TTF.+ and MV2+ enhance the electrical conductivity by a factor of 102 and the visible light induced photocurrent by 4 and 28 times, respectively. EPR evidences synergetic effect involving charge transfer between the framework redox-active TTFTB bridges and MV2+ . The results demonstrate that functionalization of MOF by cation exchange without perturbing the crystallinity extends possibilities to achieve switchable materials.