New molecular assemblies of redox isomers, [CrIII(X4SQ)3-n(X4Cat) n]-n (X = Cl and Br; n = 0, 1, and 2), with metallocenium cations, [MIIICp2]+ (M = Co and Fe): X-ray crystal structures and physical properties

H. C. Chang, H. Miyasaka, S. Kitagawa

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Abstract

A series of redox isomers of [CrIII(X4SQ)(X4Cat)2] 2-, [CrIII(X4SQ)2(X4Cat)]- , and [CrIII(X4SQ)3]0 (X = Cl and Br, SQ = semiquinonate, and Cat = catecholate) have been synthesized and characterized as charge-transfer (CT) compounds with metallocenium cations: (CoIIICp2)2[CrIII(Cl4S Q)(Cl4Cat)2] (1), (CoIIICp2)2[CrIII(Br4S Q)-(Br4Cat)2] (2), (FeIIICp2)[CrIII(Cl4SQ) 2(Cl4Cat)]·C6H6 (4), (FeIIICp2)[CrIII(Br4SQ) 2(Br4Cat)]·CS2 (5), and (FeIIICp2)[CrIII(Cl4SQ) 2(Cl4Cat)][CrIII(Cl4SQ)3] (6). First, the oxidation states of the chromium complexes are strongly dependent on the redox potentials of the metallocenes used. The CoIICp2, exhibiting stronger reduction power than FeIICp2, is useful for two-electron reduction of the [CrIII(X4SQ)3]0, affording [CrIII(X4SQ)(X4Cat)2] 2- (1 and 2), which are first isolated and crystallographically characterized in the solid state. In contrast the reaction with FeIICp2 affords only [CrIII(X4SQ)2(X4Cat)]- (4 and 5). Second, solvents influence crystal structures of these compounds. The solvent set of C6H6/CS2 gives 1:1:C6H6 compound 4 with unique charged anions, [CrIII(Cl4SQ)2(Cl4Cat)] -, while the other set, n-C6H12/CS2, affords 1:2 compound 6 including the two redox isomers, [CrIII(Cl4SQ)2(Cl4Cat)] - and [CrIII(Cl4SQ)3]0. The [CrIII(X4SQ)(X4Cat)2) 2- anions in 1 and 2 show no significant interconnection between them (discrete type), while the [CrIII(X4SQ)2(X4Cat)]- anions in 4-6 show one-dimensional column-type structures with the aid of intermolecular stacking interactions of the ligand moieties. The anions in 4 show additional stacking interaction with the [FeIIICp2]+ to form one-dimensional ···[D][A][S][D][A]··· (D = [FeIIICp2]+, A = [CrIII(Cl4SQ)2(Cl4Cat)] -, and S = C6H6) type mixed-stack arrangements similar to that of previously reported (CoIIICp2)[CrIII(Cl4SQ) 2(Cl4Cat)]·C6H6 (3). Compound 6 forms a two-dimensional sheet structure where the two redox isomers, [CrIII(Cl4SQ)2(Cl4Cat)] - and [CrIII(Cl4SQ)3]0, are included. The sheet is regarded as a mixed-valence molecular assembly. Two types of the anions, [CrIII(X4SQ)(X4Cat)2] 2- (1 and 2) and [CrIII(X4SQ)2(X4Cat)]- (4-6), exhibiting an intramolecular mixed-valence state, show intramolecular intervalence CT transition (IVCT) from the Cat to the SQ at near 5800 and 4300 cm-1, respectively, both in the solution and in the solid states. The intermolecular mixed-valence state of 6 was characterized by absorption spectroscopy, electric conductivity, and SQUID magnetometry. Interestingly, this mixed-valence state of the chromium module is dependent on the redox active nature of the coordinated ligands.

Original languageEnglish
Pages (from-to)146-156
Number of pages11
JournalInorganic chemistry
Volume40
Issue number1
DOIs
Publication statusPublished - 2001 Jan 1
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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Dive into the research topics of 'New molecular assemblies of redox isomers, [Cr<sup>III</sup>(X<sub>4</sub>SQ)<sub>3-n</sub>(X<sub>4</sub>Cat) <sub>n</sub>]<sup>-n</sup> (X = Cl and Br; n = 0, 1, and 2), with metallocenium cations, [M<sup>III</sup>Cp<sub>2</sub>]<sup>+</sup> (M = Co and Fe): X-ray crystal structures and physical properties'. Together they form a unique fingerprint.

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