Mixed Donor–Acceptor‐Derived N, N′‐Diarylpyrazine‐2, 5‐dicarboxamido‐Bridged Diruthenium Systems: Structures, Magnetic Properties, and Electronic Forms in Multiredox States. Issue 46 (14th December 2017)

• Record Type: Journal Article
• Authors: Khan, Farheen Fatima; Mandal, Abhishek; Klein, Johannes; Priego, José Luis; Jiménez‐Aparicio, Reyes; Sarkar, Biprajit; Lahiri, Goutam Kumar
• Is Part Of: European journal of inorganic chemistry. Issue 46(2017)
• Page Start: 5497
• Page End: 5506
• Publication Date: 2017-12-14
• Subjects: Redox noninnocence -- Spectroelectrochemistry -- Ruthenium -- Electronic structure -- Electrochemistry; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201701009
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract : Herein, we report diruthenium(III) complexes bridged by the deprotonated N, N′ ‐diphenylpyrazine‐2, 5‐dicarboxamide (H2 L1 ) and N, N′ ‐dimesitylpyrazine‐2, 5‐dicarboxamide (H2 L2 ) ligands in meso diastereomeric form, namely, (acac)2 Ru III (µ‐L1 )Ru III (acac)2 (1, acac = acetylacetonato) and (acac)2 Ru III (µ‐L2 )Ru III (acac)2 (2 ), as well as the monodeprotonated HL1 ‐derived mononuclear counterpart (acac)2 Ru III (HL1 ) (3 ). Variable‐temperature magnetic studies of1 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 counterpart3 displayed an EPR signal with rhombic symmetry. Complexes1 and2 exhibited two oxidation and reduction steps with comproportionation constants ( K c ) of 10 2 and 10 6 or 10 7 . Complex3 displayed one oxidation and two reductions steps. The electrogenerated compounds1 – and2 – 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. Abstract : Mono‐ and diruthenium complexes of the N, N′ ‐diarylpyrazine‐2, 5‐dicarboxamido ligand are presented. The oxidative chemistry of the complexes is dominated by the ligand, and the reductive chemistry is predominantly metal‐centered. Electrochemistry and UV/Vis/NIR, IR, and electron paramagnetic resonance (EPR) spectroelectrochemistry are used to address issues related to the electronic structures.