Correspondence of RuIIIRuII and RuIVRuIII Mixed Valent States in a Small Dinuclear Complex |
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| Authors: | Hemlata Agarwala Dipl‐Chem Thomas Michael Scherer Dr Somnath Maji Dr Tapan Kumar Mondal Dr Shaikh M Mobin Dr Jan Fiedler Prof Dr Reyes Jiménez‐Aparicio Prof Dr Wolfgang Kaim Prof Dr Goutam Kumar Lahiri |
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| Institution: | 1. Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai‐400076 (India), Fax: (+91)?022‐2572‐3480;2. Institut für Anorganische Chemie, Universit?t Stuttgart, Pfaffenwaldring 55, D‐70550 Stuttgart (Germany), Fax: (+49)?711 685‐64165;3. Department of Chemistry, Jadavpur University, Jadavpur, Kolkata‐700032 (India), Fax: (+91)?33‐2414‐6584;4. J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolej?kova 3, CZ‐18223 Prague (Czech Republic), Fax: (+420)?286582307;5. Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense, Ciudad Universitaria, E‐28040 Madrid (Spain), Fax: (+34) 91‐394‐4352 |
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| Abstract: | The diruthenium(III) compound (μ‐oxa){Ru(acac)2}2] 1 , oxa2?=oxamidato(2?), acac?=2,4‐pentanedionato] exhibits an S=1 ground state with antiferromagnetic spin‐spin coupling (J=?40 cm?1). The molecular structure in the crystal of 1? 2 C7H8 revealed an intramolecular metal–metal distance of 5.433 Å and a notable asymmetry within the bridging ligand. Cyclic voltammetry and spectroelectrochemistry (EPR, UV/Vis/NIR) of the two‐step reduction and of the two‐step oxidation (irreversible second step) produced monocation and monoanion intermediates (Kc=105.9) with broad NIR absorption bands (ε ca. 2000 M ?1 cm?1) and maxima at 1800 ( 1 ?) and 1500 nm ( 1 +). TD‐DFT calculations support a RuIIIRuII formulation for 1 ? with a doublet ground state. The 1 + ion (RuIVRuIII) was calculated with an S=3/2 ground state and the doublet state higher in energy (ΔE=694.6 cm?1). The Mulliken spin density calculations showed little participation of the ligand bridge in the spin accommodation for all paramagnetic species (μ‐oxa){Ru(acac)2}2]n, n=+1, 0, ?1, and, accordingly, the NIR absorptions were identified as metal‐to‐metal (intervalence) charge transfers. Whereas only one such NIR band was observed for the RuIIIRuII (4d5/4d6) system 1 ?, the RuIVRuIII (4d4/4d5) form 1 + exhibited extended absorbance over the UV/Vis/NIR range. |
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| Keywords: | density functional calculations EPR spectroscopy magnetic properties mixed‐valent compounds ruthenium spectroelectrochemistry |
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