Electronic Structures of the Electron Transfer Series [M(bpy)3]n, [M(tpy)2]n, and [Fe(tbpy)3]n(M = Fe, Ru;n= 3+, 2+, 1+, 0, 1-): A Mössbauer Spectroscopic and DFT Study

England, J., Scarborough, C. C., Weyhermüller, T., Sproules, S. and Wieghardt, K. (2012) Electronic Structures of the Electron Transfer Series [M(bpy)3]n, [M(tpy)2]n, and [Fe(tbpy)3]n(M = Fe, Ru;n= 3+, 2+, 1+, 0, 1-): A Mössbauer Spectroscopic and DFT Study. European Journal of Inorganic Chemistry, 2012(29), pp. 4605-4621. (doi: 10.1002/ejic.201200232)

Abstract

The five-membered electron-transfer series [M(bpy)3]n and [M(tpy)2]n (M = Fe, Ru; bpy = 2,2′-bipyridine, tpy = 2,2′:6′,2″-terpyridine) and [Fe(tbpy)3]n (tbpy = 4,4′-di-tert-butyl-2,2′-bipyridine; n = 3+, 2+, 1+, 0, 1–) have been investigated and the electronic structure of the so called “low-valent” complexes (n = 1+, 0, 1–) have been established by a combination of electro- and magnetochemistry, electron paramagnetic resonance (EPR) and Mössbauer spectroscopy, X-ray crystallography, and DFT calculations. These complexes are accessed by reduction of the d6 S = 0 dicationic starting materials [M(bpy)3]2+ and [M(tpy)2]2+ (M = Fe, Ru) and [Fe(tbpy)3]2+. The monocations [M(bpy·)(bpy0)2]1+ (S = 1/2) and [M(tpy·)(tpy0)]1+ (S = 1/2) (M = FeII, RuII) also contain a low-spin (t2g)6 divalent metal center, plus a single radical monoanion (bpy·)1– or (tpy·)1–, and two or one neutral (bpy0) or (tpy0) ligands, respectively. The unpaired electron resides in a ligand π* orbital. The neutral complexes [FeII(bpy·)2(bpy0)]0 and [RuII(tpy·)2]0 were found, by DFT calculations, to possess an S = 1 ground state that is attained by weak intramolecular ferromagnetic coupling between two ligand radical anions and a singlet excited state (S = 0). In contrast, the neutral species [RuII(bpy·)2(bpy0)]0 possesses an S = 0 ground state. The metal centers of these neutral complexes retain a low-spin (t2g)6 configuration. Remarkably, the corresponding neutral complex [FeII(tpy·)2]0 contains high-spin FeII (SFe = 2). Strong intramolecular antiferromagnetic metal–radical coupling yields an experimentally observed S = 1 ground state. The monoanions [MII(bpy·)3]1– (M = Fe, Ru) are composed of a low-spin metal ion [Fe, Ru; (t2g)6; SM = 0] and three (bpy·)1– radical anions.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Sproules, Dr Stephen
• Authors: England, J., Scarborough, C. C., Weyhermüller, T., Sproules, S., and Wieghardt, K.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: European Journal of Inorganic Chemistry
• Publisher: Wiley-VCH Verlag
• ISSN: 1434-1948
• ISSN (Online): 1099-0682