An electron transfer driven magnetic switch: ferromagnetic exchange and spin delocalization in iron verdazyl complexes

Abstract

The verdazyl 'pincer' ligand, 1-isopropyl-3,5-dipyridyl-6-oxoverdazyl (dipyvd), coordinates iron to form a series of pseudooctahedral coordination compounds [Fe(dipyvd)2]n+ (n = 0-3). In the case where n = 2, the molecular geometry and physical and spectral properties are consistent with a low spin (S = 0) iron(ii) ion coordinated by two ferromagnetically coupled radical ligands. Upon one electron reduction, the room temperature effective magnetic moment of the complex jumps from μeff = 2.64 to μeff = 5.86 as a result of spin crossover of the iron atom combined with very strong ferromagnetic coupling of the remaining ligand centered unpaired electron with the metal center. The sign of the exchange is opposite to that observed in other high spin iron/radical ligand systems and appears to be a result of delocalization of the ligand unpaired electron across the whole molecule. The large change in magnetic properties, combined with a delocalized electronic structure and accessible redox potentials, suggests the utility of this and related systems in the development of novel molecular spintronic devices.

Redox-Controlled and Reversible N–N Bond Forming and Splitting with an IronIV Terminal Imido Ligand

“…The trivalent complex 2 OAc · C 7 H 8 features Fe1–N1 pyrr and Fe1–N2 pyr bond lengths of 1.988(1) and 2.057(1) Å which are indistinguishable and elongated in comparison to the ones for [{( t Bu pyrr) 2 py}­FeCl] (Fe1–N1 pyrr = 1.991(2) Å and Fe1–N2 pyr = 1.981(2) Å), respectively . The iron–hydrazine interatomic distance (Fe1–N3 hydz = 1.909(1) Å) is notably shorter than the one for benzoylacetone S - n -propylisothiosemicarbazonato- O , N 1 , N 4 )­dichloroiron­(III) ethanol solvate (Fe–N hydz = 2.102(2) Å) whose geometry is best described as distorted square pyramidal, as well as the octahedral complexes [Fe III (PLTSC)­Cl 2 (H 2 O)]Cl (Fe–N hydz = 2.220(2) Å) (PLTSC = pyridoxal thiosemicarbazone), and [Fe­(dipyvd) 2 ]­[PF 6 ] (Fe–N hydz = 1.986(2) Å) (dipyvd – = 1-isopropyl-3,5-dipyridyl-6-oxoverdazyl) . The acetate ligand in 2 OAc · C 7 H 8 binds the iron center through localized Fe–O1/O2 bonds of 2.075(2) and 2.102(2) Å with a bite angle of O1–Fe1–O2 = 117.6(1)°.…”

Magnetic couplings and applied electric field regulation in diradical SiC defect diamond-like nanoclusters

“…20 Moreover, molecules with spin state or magnetic switch properties have been widely used in spintronic devices, magnetic shapememory materials and data storage. [21][22][23][24] The spin crossover phenomenon in molecular inorganic compounds is one of the most striking examples of bistability. It can switch between high and low spin states through temperature, pressure, light or magnetic field.…”

Two state “ON–OFF” NLO switch based on coordination complexes of iron and cobalt containing isomeric ligand: a DFT study

“…Coordination complexes are useful for optical applications due to the presence of an electron donor and acceptor moieties connected via a p-conjugate link. 12,[42][43][44] Using metal-ligand frameworks in these compounds, the NLO response can be enhanced. This strategy induces metal to ligand charge transfer (MLCT).…”