An Unusual Stable Mononuclear Mn<sup>III</sup> Bis-terpyridine Complex Exhibiting Jahn-Teller Compression: Electrochemical Synthesis, Physical Characterisation and Theoretical Study - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Chemistry - A European Journal Année : 2009

An Unusual Stable Mononuclear MnIII Bis-terpyridine Complex Exhibiting Jahn-Teller Compression: Electrochemical Synthesis, Physical Characterisation and Theoretical Study

Résumé

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 13+ ion is a rare example of a mononuclear MnIII complex stabilised solely by neutral N ligands. Complex 13+ is obtained by electrochemical oxidation of the corresponding MnII compound 12+ in anhydrous acetonitrile. Under these conditions the cyclic voltammogram of 12+ 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 13+ 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.

Dates et versions

hal-00417307 , version 1 (15-09-2009)

Identifiants

Citer

Sophie Romain, Carole Duboc, Franck Neese, Eric Rivière, Lyall R. Hanton, et al.. An Unusual Stable Mononuclear MnIII Bis-terpyridine Complex Exhibiting Jahn-Teller Compression: Electrochemical Synthesis, Physical Characterisation and Theoretical Study. Chemistry - A European Journal, 2009, 15 (4), pp. 980-988. ⟨10.1002/chem.200801442⟩. ⟨hal-00417307⟩
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