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Unexpected Promotional Effects of Alkyl‐Tailed Ligands and Anions on the Electrochemical Generation of Ruthenium(IV)‐Oxo Complexes
Author(s) -
Tsang ChuiShan,
Lee Lawrence Yoon Suk,
Cheung KwongChak,
Chan PakHo,
Wong WingLeung,
Wong KwokYin
Publication year - 2021
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.202100364
Subject(s) - ruthenium , chemistry , alkyl , perchlorate , electrochemistry , electrolysis , medicinal chemistry , aqueous solution , inorganic chemistry , catalysis , ion , organic chemistry , electrode , electrolyte
Electro‐generation of Ru IV =O species from the Ru II ‐aqua complex is a crucial step to excel the electrocatalytic water oxidation performance of ruthenium oxo complexes. We report herein the synthesis and X‐ray crystal structural characterizations of new Ru II ‐aqua complexes containing N ‐substituted 2,2′‐dipyridylamine ligands ( L) tagged with an alkyl chain of various lengths, [Ru(tpy)( L )(OH 2 )] 2+ . Cyclic voltammetric analyses show that the length of the alkyl chain exerts great influence on the electro‐generation of Ru IV =O species. The L with a longer alkyl chain in an acidic aqueous medium promotes the conversion of Ru III −OH to Ru IV =O efficiently. Surprisingly, this conversion can be further enhanced by the presence of perchlorate anions. Chronocoulometric data reveal that the alkyl chain on L promotes the adsorption of the ruthenium complex on the electrode surface. Bulk electrolysis results indicate that the [Ru(tpy)( dppa )(OH 2 )] 2+ ( dppa =(2,2′‐dipyridyl)‐ n ‐propylamine) gives the most active electrocatalytic water oxidation activity among the ruthenium‐aqua complexes investigated in this study.