A Host-Guest Electron Transfer Mechanism for Magnetic and Electronic Modifications in a Redox-Active Metal-Organic Framework.

Host-guest electron transfer (HGET) in molecular framework systems is a critical trigger for drastic functional changes in both host framework and guest. A reversible magnetic phase transition was achieved via HGET in a layered framework, [{Ru 2 (2,6-F 2 PhCO 2 ) 4 } 2 (BTDA-TCNQ)] (1), where 2,6-F 2 PhCO 2 - and BTDA-TCNQ represent 2,6-difluorobenzoate and bis[1,2,5]dithiazolotetracyanoquinodimethane, respectively. The guest-free 1 with an antiferromagnetic ground state transformed into a paramagnet, [{Ru 2 (2,6-F 2 PhCO 2 ) 4 } 2 (BTDA-TCNQ)]I 3 (1-I 3 ), by adsorbing iodine (I 2 ). The local charge distribution of [{Ru 2 II,III } + -(BTDA-TCNQ) .- -{Ru 2 II,II }] in 1 was reversibly modified to [{Ru 2 II,III } + -(BTDA-TCNQ) 0 -{Ru 2 II,II }](I 3 - ) in 1-I 3 through HGET. Theoretical calculations of 1-I 3 indicated a partial charge delocalization as [{Ru 2 } (1-δ)+ -(BTDA-TCNQ) 0 -{Ru 2 } δ+ ](I 3 - ) with δ≈0.2, aided by weak ferromagnetic coupling. 1-I 3 exhibited a hundred-fold enhancement in electrical conductivity compared to that of 1.