A major challenge is the development of multifunctional metal-organic frameworks (MOFs), wherein magnetic and electronic functionality can be controlled simultaneously. Herein, we rationally construct two 3D MOFs by introducing the redox active ligand tetra(4-pyridyl)tetrathiafulvalene (TTF(py) ) and spin-crossover Fe centers. The materials exhibit redox activity, in addition to thermally and photo-induced spin crossover (SCO). A crystal-to-crystal transformation induced by I doping has also been observed and the resulting intercalated structure determined. The conductivity could be significantly enhanced (up to 3 orders of magnitude) by modulating the electronic state of the framework via oxidative doping; SCO behavior was also modified and the photo-magnetic behavior was switched off. This work provides a new strategy to tune the spin state and conductivity of framework materials through guest-induced redox-state switching.

Understanding the effects of intermolecular interactions on metal-to-metal charge transfer (MMCT) is crucial to develop molecular devices by grafting MMCT-based molecular arrays.H erein, we report as eries of solvent-free {Fe 2 Co 2 } compounds sharing the same cationic tetranuclear {[Fe(PzTp)-(CN) 3 ] 2 [Co(dpq) 2 ] 2 } 2+ (PzTp À = tetrakis(pyrazolyl)borate, dpq = dipyrido[3,2-d:2',3'-f]quinoxaline) square units but having anions with different size, including BF 4 À ,PF 6 À ,OTf À ,and [Fe(PzTp)(CN) 3 ] À .I ntermolecular p···p interactions between dpq ligands,w hichc oordinate to cobalt ions in the {[Fe-(PzTp)(CN) 3 ] 2 [Co(dpq) 2 ] 2 } 2+ units,c an be modulated by introducing different counterions,r egulating the distortion of the CoN 6 octahedron and ligand field around the cobalt ions. This change results in different MMCT behavior.C omputational analyzes reveal the substantial role of the intermolecular interactions tuned by the presence of different counteranions on the MMCT behavior.

The on/off-switching of single-chain magnetic behavior tuned through bidirectional light irradiation.