Premium
Mixed Donor–Acceptor‐Derived N , N′ ‐Diarylpyrazine‐2,5‐dicarboxamido‐Bridged Diruthenium Systems: Structures, Magnetic Properties, and Electronic Forms in Multiredox States
Author(s) -
Khan Farheen Fatima,
Mandal Abhishek,
Klein Johannes,
Priego José Luis,
JiménezAparicio Reyes,
Sarkar Biprajit,
Lahiri Goutam Kumar
Publication year - 2017
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201701009
Subject(s) - chemistry , comproportionation , electron paramagnetic resonance , crystallography , delocalized electron , redox , stereochemistry , deprotonation , intramolecular force , acceptor , electrochemistry , nuclear magnetic resonance , inorganic chemistry , ion , physics , organic chemistry , electrode , condensed matter physics
Herein, we report diruthenium(III) complexes bridged by the deprotonated N , N′ ‐diphenylpyrazine‐2,5‐dicarboxamide (H 2 L 1 ) and N , N′ ‐dimesitylpyrazine‐2,5‐dicarboxamide (H 2 L 2 ) ligands in meso diastereomeric form, namely, (acac) 2 Ru III (µ‐L 1 )Ru III (acac) 2 ( 1 , acac = acetylacetonato) and (acac) 2 Ru III (µ‐L 2 )Ru III (acac) 2 ( 2 ), as well as the monodeprotonated HL 1 ‐derived mononuclear counterpart (acac) 2 Ru III (HL 1 ) ( 3 ). Variable‐temperature magnetic studies of 1 revealed a weak bridge‐mediated intramolecular antiferromagnetic interaction with J = –7.58 cm –1 . The dinuclear complexes exhibited anisotropic electron paramagnetic resonance (EPR) signals at g ≈ 2 along with half‐field signals at g 1/2 ≈ 4, whereas the mononuclear counterpart 3 displayed an EPR signal with rhombic symmetry. Complexes 1 and 2 exhibited two oxidation and reduction steps with comproportionation constants ( K c ) of 10 2 and 10 6 or 10 7 . Complex 3 displayed one oxidation and two reductions steps. The electrogenerated compounds 1 – and 2 – exhibited metal‐based EPR signals and a very weak and broad near‐infrared (NIR) transition at λ ≈ 1200 nm. The C=O bands of the bridge were monitored through IR spectroelectrochemistry, which revealed a shift of these bands to lower energies on reduction. However, the native and reduced states have the same number of bands, which suggests a similar local symmetry for both redox forms and a delocalized electronic situation in the reduced compounds. A combination of electrochemistry and spectroelectrochemistry was used to probe the electronic structures of the various redox states in these complexes.