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Strongly Coupled Cyclometalated Ruthenium–Triarylamine Hybrids: Tuning Electrochemical Properties, Intervalence Charge Transfer, and Spin Distribution by Substituent Effects
Author(s) -
Yao ChangJiang,
Nie HaiJing,
Yang WenWen,
Shao JiangYang,
Yao Jiannian,
Zhong YuWu
Publication year - 2014
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.201404549
Subject(s) - terpyridine , diphenylamine , ruthenium , chemistry , ligand (biochemistry) , photochemistry , electron paramagnetic resonance , substituent , crystallography , pyridine , stereochemistry , metal , nuclear magnetic resonance , medicinal chemistry , biochemistry , physics , receptor , organic chemistry , catalysis
Nine cyclometalated ruthenium complexes with a redox‐active diphenylamine unit in the para position to the RuC bond were prepared. MeO, Me, and Cl substituents on the diphenylamine unit and three types of auxiliary ligands—bis( N ‐methylbenzimidazolyl)pyridine (Mebip), 2,2′:6′,2′′‐terpyridine (tpy), and trimethyl‐4,4′,4′′‐tricarboxylate‐2,2′:6′,2′′‐terpyridine (Me 3 tctpy)—were used to vary the electronic properties of these complexes. The derivative with an MeO‐substituted amine unit and Me 3 tctpy ligand was studied by single‐crystal X‐ray analysis. All complexes display two well‐separated redox waves in the potential region of +0.1 to +1.0 V versus Ag/AgCl, and the potential splitting ranges from 360 to 510 mV. Spectroelectrochemical measurements show that these complexes display electrochromism at low potentials and intense near‐infrared (NIR) absorptions. In the one‐electron oxidized form, the complex with the Cl‐substituted amine unit and Mebip ligand shows a moderate ligand‐to‐metal charge transfer at 800 nm. The other eight complexes show asymmetric, narrow, and intense intervalence charge‐transfer transitions in the NIR region, which are independent of the polarity of the solvent. The Mebip‐containing complexes display rhombic or broad isotropic EPR signals, whereas the other seven complexes show relatively narrow isotropic EPR signals. In addition, DFT and time‐dependent DFT studies were performed to gain insights into the spin distributions and NIR absorptions.