Solid-State Redox Switching of Magnetic Exchange and Electronic Conductivity in a Benzoquinoid-Bridged MnII Chain Compound

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• 作者：Ie-Rang Jeon ; Lei Sun ; Bogdan Negru ; Richard P. Van Duyne ; Mircea Dincă ; T. David Harris
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：May 25, 2016
• 年：2016
• 卷：138
• 期：20
• 页码：6583-6590
• 全文大小：478K
• 年卷期：0
• ISSN：1520-5126

文摘

We 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 Mn^III affords the chain compound Mn(^N,OL)(DMSO). Structural and spectroscopic analysis of this compound show the presence of Mn^II centers bridged by ^N,OL^2– 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 (E_a = 0.64(1) eV) to 8.61(1) × 10^–8 S/cm (E_a = 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.