Tuning intramolecular electron transfer of cyanide bridged [CoFe] squares through chemical modifications in solid and solution

Cyanide bridged heterometallic complexes exhibiting intramolecular electron transfer associated with a spin conversion (so-called electron-transfer-coupled spin transition, ETCST) have attracted considerable attention for future applications in new generation molecular switching devices. Yet, the ra...

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Veröffentlicht in:Inorganic chemistry frontiers 2022-12, Vol.1 (1), p.288-295
Hauptverfasser: You, Pei-Ye, Wei, Rong-Jia, Xie, Mo, Ning, Guo-Hong, Oshio, Hiroki
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Sprache:eng
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Zusammenfassung:Cyanide bridged heterometallic complexes exhibiting intramolecular electron transfer associated with a spin conversion (so-called electron-transfer-coupled spin transition, ETCST) have attracted considerable attention for future applications in new generation molecular switching devices. Yet, the rational control of intermetallic electron transfer, especially in bistable molecules in solid and solution, remains challenging. In this work, we report three structurally related [Co 2 Fe 2 ] molecular square complexes, {[Co(bpy) 2 ] 2 [Fe(tp′)(CN) 3 ] 2 }(PF 6 ) 2 ( 1 ), {[Co(dmbpy) 2 ] 2 [Fe(tp′)(CN) 3 ] 2 }(PF 6 )(OTf)·2MeOH ( 2 ), and {[Co(dtbbpy) 2 ] 2 [Fe(tp′)(CN) 3 ] 2 }(PF 6 )·2MeOH·3EtOH ( 3 ), (tp′ = hydrotris(3-methylpyrazol-1-yl)borate, bpy = 2,2′-bipyridine, dmbpy = 4,4′-dimethyl-2,2′-bipyridine, and dtbbpy = 4,4′-di- tert -butyl-2,2′-bipyridine, OTf = trifluoromethanesulfonate), which showed different ETCST behavior with electronic configurations in the high-spin (HS: [(Co II HS ) 2 (Fe III LS ) 2 ]) and low-spin (LS: [(Co III LS ) 2 (Fe II LS ) 2 ]) states in solid. Solution experiments revealed that the substituents of the bipyridyl ligand lead to different ETCST behavior, which was caused by the changes in Co II/III redox potentials. Moreover, hydrogen bonding interactions of the terminal cyanide group on the Fe sites with solvent molecules of MeOH, EtOH, and n -PrOH shifted the equilibrium temperature between the HS and LS states in the square molecules. We report three cyanide-bridged [Co 2 Fe 2 ] molecular squares by systematic ligand substitution and their tunable electron-transfer-coupled spin transition (ETCST) behaviors in solid and solution.
ISSN:2052-1553
2052-1545
2052-1553
DOI:10.1039/d2qi02108k