1 research outputs found
Multiple Bistability in Quinonoid-Bridged Diiron(II) Complexes: Influence of Bridge Symmetry on Bistable Properties
Quinonoid bridges
are well-suited for generating dinuclear assemblies that might display
various bistable properties. In this contribution we present two diironÂ(II)
complexes where the ironÂ(II) centers are either bridged by the doubly
deprotonated form of a symmetrically substituted quinonoid bridge,
2,5-bisÂ[4-(isopropyl)Âanilino]-1,4-benzoquinone (<b>H</b><sub><b>2</b></sub><b>L2′</b>) with a [O,N,O,N] donor
set, or with the doubly deprotonated form of an unsymmetrically substituted
quinonoid bridge, 2-[4-(isopropyl)Âanilino]-5-hydroxy-1,4-benzoquinone
(<b>H</b><sub><b>2</b></sub><b>L5′</b>) with
a [O,O,O,N] donor set. Both complexes display temperature-induced
spin crossover (SCO). The nature of the SCO is strongly dependent
on the bridging ligand, with only the complex with the [O,O,O,N] donor
set displaying a prominent hysteresis loop of about 55 K. Importantly,
only the latter complex also shows a pronounced light-induced spin
state change. Furthermore, both complexes can be oxidized to the mixed-valent
ironÂ(II)–ironÂ(III) form, and the nature of the bridge determines
the Robin and Day classification of these forms. Both complexes have
been probed by a battery of electrochemical, spectroscopic, and magnetic
methods, and this combined approach is used to shed light on the electronic
structures of the complexes and on bistability. The results presented
here thus show the potential of using the relatively new class of
unsymmetrically substituted bridging quinonoid ligands for generating
intriguing bistable properties and for performing site-specific magnetic
switching