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-F2PhCO2)(4)}(2)(BTDA-TCNQ)] (1), where 2,6-F2PhCO2- 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-F2PhCO2)(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-delta)+)-(BTDA-TCNQ)(0)-{Ru-2}(delta+)](I-3(-)) with delta approximate to 0.2, aided by weak ferromagnetic coupling. 1-I-3 exhibited a hundred-fold enhancement in electrical conductivity compared to that of 1.

Automated summary

Host-guest electron transfer is a critical factor for functional changes in molecular framework systems. This study achieved reversible magnetic phase transition by adsorbing iodine and demonstrated a significant enhancement in electrical conductivity.