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Molecular Insights into the Ligand‐Based Six‐Proton‐ and Six‐Electron‐Transfer Processes Between Tris‐ ortho ‐Phenylenediamines and Tris‐ ortho ‐Benzoquinodiimines
Author(s) -
Matsumoto Takeshi,
Yamamoto Risa,
Wakizaka Masanori,
Nakada Akinobu,
Chang HoChol
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202001873
Subject(s) - chemistry , ligand (biochemistry) , proton , tris , electron transfer , redox , molecule , stereochemistry , crystallography , photochemistry , inorganic chemistry , organic chemistry , receptor , biochemistry , physics , quantum mechanics
The global demand for energy and the concerns over climate issues renders the development of alternative renewable energy sources such as hydrogen (H 2 ) important. A high‐spin ( hs ) Fe II complex with o ‐phenylenediamine (opda) ligands, [Fe II (opda) 3 ] 2+ ( hs ‐ [6R] 2+ ), was reported showing photochemical H 2 evolution. In addition, a low‐spin ( ls ) [Fe II (bqdi) 3 ] 2+ (bqdi: o ‐benzoquinodiimine) ( ls ‐ [0R] 2+ ) formation by O 2 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] [PF 6 ] 2 can be reduced by hydrazine giving ls ‐[Fe II (opda)(bqdi) 2 ][PF 6 ] 2 ( ls ‐ [2R] [PF 6 ] 2 ) and ls ‐[Fe II (opda) 2 (bqdi)][PF 6 ] 2 ( ls ‐ [4R] [PF 6 ] 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.