A Diruthenium‐Based Mixed Spin Complex Ru 2 5+ ( S =1/2)‐CN‐Ru 2 5+ ( S =3/2)

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The synthesis and characterization of Class II-III mixed valence complexes have been an interesting topic due to their special intermediate behaviour between localized and delocalized mixed valence complexes. To investigate the influence of the isocyanidometal bridge on metal-to-metal charge transfer (MMCT) properties, a family of new isocyanidometal-bridged complexes and their one-electron oxidation products cis-2'-bipyridyl (5,5'-dmbpy, 2[PF 6 ] n ) and 4,4'dimethyl-2,2'-bipyridyl (4,4'-dmbpy, 3[PF 6 ] n )) have been synthesized and fully characterized. The experimental resultssuggest that all the one-electron oxidation products may belong to Class II-III mixed valence complexes, supported by TDDFT calculations. With the change of the substituents of the bipyridyl ligand on the Ru centre from H, 5,5'-dimethyl to 4,4'-dimethyl, the energy of MMCT for the one-electron oxidation complexes changes in the order: 1 3 + < 2 3 + < 3 3 + , and that for the two-electron oxidation complexes decreases in the order 1 4 + > 3 4 + > 2 4 + . The potential splitting (ΔE 1/2 (2)) between the two terminal Fe centres for N[PF 6 ] 2 are the largest potential splitting for the cyanido-bridged complexes reported so far. This work shows that the smaller potential difference between the bridging and the terminal metal centres would result in the more delocalized mixed valence complex.

Influence of Fine Ligand Substitution Modification of the Isocyanidometal Bridge on Metal‐to‐Metal Charge Transfer Properties in Class II–III Mixed Valence Complexes

Zhang

Zeng

et al. 2021

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Effects of cis/trans‐Configuration and Ligand Substitution of the Cyanidometal Bridge on Metal to Metal Charge Transfer Properties in Mixed Valence Complexes

Zeng

et al. 2022

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To investigate the effects of cis/trans-configuration of the cyanidometal bridge and the electron donating ability of the auxiliary ligand on the cyanidometal bridge on metal to metal charge transfer (MMCT) in cyanidometal-bridged mixed valence compounds, two groups of trinuclear cyanidometal-bridged compounds cis/trans-(cis/trans-2[PF 6 ] 3 ) were synthesized and fully characterized. The exper-imental results indicate that for these one-and two-electron oxidation mixed valence compounds, the trans-configuration compounds are more beneficial for MMCT than the cisconfiguration compounds, and increasing the electron donating ability of the auxiliary ligand on the cyanidometal bridge is also conductive to MMCT. Moreover, compounds cis/trans-1[PF 6 ] n (n = 3, 4) and cis/trans-2[PF 6 ] 3 belong to localized compounds by analyzing the experimental characterization results, supported by the TDDFT calculations.

Coexistence of Three Different Spin States in a Cyanido‐Bridged Trinuclear Iron(III) Complex with an Unusual Fe^III to Ligand Charge Transfer

Huang

Zhu

et al. 2023

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We report a trinuclear iron(III) cyanido‐bridged complex trans‐[CpMe3FeIII(dppe)(CN)]2[FeIII(LN4)][PF6]4 (2[PF6]4) as the oxidation product of binuclear complex [CpMe3(dppe)FeIICN‐FeIII(LN4)][PF6] (1[PF6]) (CpMe3=1, 2, 4‐trimethyl‐1,3‐cyclo‐pentadienyl, dppe=1,2‐bis(diphenylphosphino)ethane, LN4=pentane‐2,4‐dione‐bis(S‐methylisothiosemicarbazonato). Complex 1[PF6] possesses an intermediate‐spin five‐coordinated FeIII (S=3/2) which couples antiferromagnetically to the π‐radical ligand (L⋅N4)2− and shows a LMCT (ligand to metal charge transfer) transition from (L⋅N4)2− to FeIII and the FeII→FeIII MMCT transition. Upon oxidation of 1[PF6], (L⋅N4)2− loses one electron to be the strong electron‐attracting ligand (LOxN4)− and the intermediate‐spin five‐coordinated FeIII (S=3/2) becomes a low‐spin six‐coordinated FeIII (S=1/2) in 2[PF6]4. Also interestingly, 2[PF6]4 presents the coexistence of three different spin states (one S=3/2 and two S=1/2) and an uncommon FeIII→(LOxN4)− MLCT transition, confirmed by the experimental results and supported by the TDDFT calculations.