ja6b02485_si_001.pdf (1.53 MB)
Solid-State Redox Switching of Magnetic Exchange and Electronic Conductivity in a Benzoquinoid-Bridged MnII Chain Compound
journal contribution
posted on 2016-04-26, 00:00 authored by Ie-Rang Jeon, Lei Sun, Bogdan Negru, Richard
P. Van Duyne, Mircea Dincă, T. David HarrisWe
demonstrate that incorporation of a redox-active benzoquinoid ligand
into a one-dimensional chain compound can give rise to a material
that exhibits simultaneous solid-state redox switching of optical,
magnetic, and electronic properties. Metalation of the ligand 4,5-bis(pyridine-2-carboxamido)-1,2-catechol
(N,OLH4) with MnIII affords the chain
compound Mn(N,OL)(DMSO). Structural and spectroscopic analysis
of this compound show the presence of MnII centers bridged
by N,OL2– ligands, resulting partially
from a spontaneous ligand-to-metal electron transfer. Upon soaking
in a solution of the reductant Cp2Co, Mn(N,OL)(DMSO) undergoes a ligand-centered solid-state reduction to [Mn(N,OL)]−, as revealed by a suite of techniques,
including Raman and X-ray absorption spectroscopy. The ligand-based
reduction engenders a dramatic modulation of the physical properties
of the chain compound. An electrochromic response, evidenced by a
color change from dark green to dark purple is accompanied by a nearly
40-fold increase in magnetic coupling strength, from J = −0.38(1) to −15.6(2) cm–1, and
a 10,000-fold increase in electronic conductivity, from σ =
2.33(1) × 10–12 S/cm (Ea = 0.64(1) eV) to 8.61(1) × 10–8 S/cm
(Ea = 0.39(1) eV). Importantly, the chemical
reduction is reversible: treatment of the reduced compound with [Cp2Fe]+ regenerates the oxidized chain. Taken together,
these results highlight the ability of benzoquinoid ligands to facilitate
solid-state ligand-based redox reactions in nonporous coordination
solids, giving rise to reversible switching of optical properties,
magnetic exchange interactions, and electronic conductivity.