An Unusual Stable Mononuclear MnIII Bis‐terpyridine Complex Exhibiting Jahn–Teller Compression: Electrochemical Synthesis,Physical Characterisation and Theoretical Study |
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| Authors: | Sophie Romain Dr Carole Duboc Dr Frank Neese Prof Eric Rivière Dr Lyall?R Hanton Dr Allan?G Blackman Dr Christian Philouze Dr Jean‐Claude Leprêtre Prof Alain Deronzier Dr Marie‐Noëlle Collomb Dr |
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| Institution: | 1. Université Joseph Fourier Grenoble 1/CNRS, Département de Chimie Moléculaire, UMR‐5250, Institut de Chimie Moléculaire de Grenoble FR‐CNRS‐2607, BP‐53, 38041 Grenoble Cedex 9 (France);2. Institut für Physikalische und Theoretische Chemie, University of Bonn, Wegelerstrasse 12, 53115 Bonn (Germany);3. Laboratoire de Chimie Inorganique, UMR CNRS 8613, Institut de Chimie Moléculaire et des Matériaux d'Orsay, Université Paris‐Sud, 91405 Orsay Cedex (France);4. Department of Chemistry, University of Otago, P.O. Box 56, Dunedin (New Zealand);5. Current address : LEPMI/ELSA/ENSEEG, Domaine Universitaire, 1130 rue de la piscine, BP‐75, 38042 Saint Martin d'Hères (France) |
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| Abstract: | The mononuclear manganese bis‐terpyridine complex Mn(tolyl‐terpy)2](X)3 ( 1 (X)3; X=BF4, ClO4, PF6; tolyl‐terpy=4′‐(4‐methylphenyl)‐2,2′:6′,2“‐terpyridine), containing Mn in the unusual +III oxidation state, has been isolated and characterised. The 1 3+ ion is a rare example of a mononuclear MnIII complex stabilised solely by neutral N ligands. Complex 1 3+ is obtained by electrochemical oxidation of the corresponding MnII compound 1 2+ in anhydrous acetonitrile. Under these conditions the cyclic voltammogram of 1 2+ exhibits not only the well‐known MnII/MnIII oxidation at E1/2=+0.91 V versus Ag/Ag+ (+1.21 V vs. SCE) but also a second metal‐based oxidation process corresponding to MnIII/MnIV at E1/2=+1.63 V (+1.93 V vs. SCE). Single crystals of 1 (PF6)3?2 CH3CN were obtained by an electrocrystallisation procedure. X‐ray analysis unambiguously revealed its tetragonally compressed octahedral geometry and high‐spin character. The electronic properties of 1 3+ were investigated in detail by magnetic measurements and theoretical calculations, from which a D value of +4.82 cm?1 was precisely determined. Density functional and complete active space self consistent field ab initio calculations both correctly predict a positive sign of D, in agreement with the compressed tetragonal distortion observed in the X‐ray structure of 1 (PF6)3?2 CH3CN. The different contributions to D were calculated, and the results show that 1) the spin–orbit coupling part (+2.593 cm?1) is predominant compared to the spin–spin interaction (+1.075 cm?1) and 2) the excited triplet states make the dominant contribution to the total D value. |
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| Keywords: | ab initio calculations density functional calculations electrochemistry Jahn– Teller distortion manganese |
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