Experimental and DFT Evidence for the Fractional Non‐Innocence of a β‐Diketonate Ligand |
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| Authors: | Amit Das Dipl.‐Chem. Thomas Michael Scherer Prasenjit Mondal Dr. Shaikh M. Mobin Prof. Dr. Wolfgang Kaim Prof. Dr. Goutam Kumar Lahiri |
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| Affiliation: | 1. Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai‐400076 (India);2. Institut für Anorganische Chemie, Universit?t Stuttgart, Pfaffenwaldring 55, 70550 Stuttgart (Germany) |
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| Abstract: | New compounds [Ru(pap)2(L)](ClO4), [Ru(pap)(L)2], and [Ru(acac)2(L)] (pap=2‐phenylazopyridine, L?=9‐oxidophenalenone, acac?=2,4‐pentanedionate) have been prepared and studied regarding their electron‐transfer behavior, both experimentally and by using DFT calculations. [Ru(pap)2(L)](ClO4) and [Ru(acac)2(L)] were characterized by crystal‐structure analysis. Spectroelectrochemistry (EPR, UV/Vis/NIR), in conjunction with cyclic voltammetry, showed a wide range of about 2 V for the potential of the RuIII/II couple, which was in agreement with the very different characteristics of the strongly π‐accepting pap ligand and the σ‐donating acac? ligand. At the rather high potential of +1.35 V versus SCE, the oxidation of L? into L. could be deduced from the near‐IR absorption of [RuIII(pap)(L.)(L?)]2+. Other intense long‐wavelength transitions, including LMCT (L?→RuIII) and LL/CT (pap.?→L?) processes, were confirmed by TD‐DFT results. DFT calculations and EPR data for the paramagnetic intermediates allowed us to assess the spin densities, which revealed two cases with considerable contributions from L‐radical‐involving forms, that is, [RuIII(pap0)2(L?)]2+?[RuII(pap0)2(L.)]2+ and [RuIII(pap0)(L?)2]+?[RuII(pap0)(L?)(L?)]+. Calculations of electrogenerated complex [RuII(pap.?)(pap0)(L?)] displayed considerable negative spin density (?0.188) at the bridging metal. |
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| Keywords: | density functional calculations EPR spectroscopy non‐innocent ligands ruthenium X‐ray diffraction |
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