Molecular Insights into the Ligand-Based Six-Proton- and Six-Electron-Transfer Processes Between Tris-ortho-Phenylenediamines and Tris-ortho-Benzoquinodiimines |
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| Authors: | Dr Takeshi Matsumoto Risa Yamamoto Dr Masanori Wakizaka Dr Akinobu Nakada Prof Dr Ho-Chol Chang |
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| Institution: | Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga Bunkyo-ku, Tokyo 112–8551, Japan |
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| Abstract: | The global demand for energy and the concerns over climate issues renders the development of alternative renewable energy sources such as hydrogen (H2) important. A high-spin (hs) FeII complex with o-phenylenediamine (opda) ligands, FeII(opda)3]2+ (hs- 6R] 2+), was reported showing photochemical H2 evolution. In addition, a low-spin (ls) FeII(bqdi)3]2+ (bqdi: o-benzoquinodiimine) (ls- 0R] 2+) formation by O2 oxidation of hs- 6R] 2+, accompanied by ligand-based six-proton and six-electron transfer, revealed the potential of the complex with redox-active ligands as a novel multiple-proton and -electron storage material, albeit that the mechanism has not yet been understood. This paper reports that the oxidized ls- 0R] PF6]2 can be reduced by hydrazine giving ls-FeII(opda)(bqdi)2]PF6]2 (ls- 2R] PF6]2) and ls-FeII(opda)2(bqdi)]PF6]2 (ls- 4R] PF6]2) with localized ligand-based proton-coupled mixed-valence (LPMV) states. The first isolation and characterization of the key intermediates with LPMV states offer unprecedented molecular insights into the design of photoresponsive molecule-based hydrogen-storage materials. |
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| Keywords: | iron N ligands oxidation reduction valency |
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