Achieving Multiway Switching in 2D Hexagonal Networks: A Molecular Engineering Strategy to Design Ambient Temperature Bistable Materials

Magnetic materials exhibiting bistability at ambient condition are appealing for application in high-density memory, data storage, sensing and switches devices. Octacyanometallates have been extensively studied as building blocks for constructing novel molecular magnetic materials with exciting physical properties. Here, we have designed and synthesized two cyanide bridged 2D hexagonal networks using octacyanotungstate(V) building block where {[W(CN)8]2[Co(V-im)4]3}n(1) undergoes a single-crystal to single-crystal (SC-SC) structural transformation to form {[W(CN)8]2[Co(V-im)4]2[Co(V-im)2(DMF)2].4H2O}n (2). Complex 1 exhibits reversible thermo-induced metal-to-metal electron transfer (MMET) (T1/2 = 176 K) with a 12 K thermal hysteresis width while complex 2 exhibits near ambient temperature two-step MMET (heating: T1/2(1) 324 K, T1/2(2) 340 K; cooling: T1/2(1) 286 K, T1/2(2) 232 K) with a hysteresis width of 4 and 15 K respectively. Interestingly, light-induced reversible ON/OFF MMET has also been observed for both complexes (1 and 2) using 808 nm and 900 nm lights (ON mode) and 405 and 635 (OFF mode) respectively, converting the low-temperature diamagnetic {WIVLS-CN-CoIIILS} ground-state into the metastable paramagnetic {WVLS-CN-CoIIHS} phase and vice-versa . X-ray absorption spectroscopy was performed in order to investigate the local electronic structure and magnetization associated with the MMET between the W and Co metal centres.