Synthesis and characterization of homo- and heterodinuclear M(II)-M′(III) (M(II) = Mn or Fe, M′(III) = Fe or Co) mixed-valence supramolecular pseudo-dimers. The effect of hydrogen bonding on spin state selection of M(II)

Cynthia T. Brewer; Greg Brewer; Ray J. Butcher; Everett E. Carpenter; Ann M. Schmiedekamp; Carl Schmiedekamp; Alison Straka; Carol Viragh; Yevgeniy Yuzefpolskiy; Peter Zavalij

doi:10.1039/C0DT01098G

Synthesis and characterization of homo- and heterodinuclear M(ii)-M′(iii) (M(ii) = Mn or Fe, M′(iii) = Fe or Co) mixed-valence supramolecular pseudo-dimers. The effect of hydrogen bonding on spin state selection of M(ii)†

Cynthia T. Brewer,^a Greg Brewer,*^a Ray J. Butcher,^b Everett E. Carpenter,^c Ann M. Schmiedekamp,^d Carl Schmiedekamp,^d Alison Straka,^e Carol Viragh,^a Yevgeniy Yuzefpolskiy^d and Peter Zavalij^f

Author affiliations

* Corresponding authors

^a The Catholic University, Washington, DC, USA
E-mail: brewer@cua.edu

^b Department of Chemistry, Howard University, Washington, DC, USA

^c Department of Chemistry, Virginia Commonwealth University, Richmond, VA, USA

^d Pennsylvania State University, Abington, Abington, PA, USA

^e Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, PO Box 38, Solomons, MD

^f Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA

Abstract

Reaction of H₃L¹, the Schiff base condensate of tris(2-aminoethyl)amine with three equivalents of 5-methyl-1H-pyrazole-3-carboxaldehyde, with manganese(II)perchlorate or iron(II)tetrafluoroborate results in the isolation of [MH₃L¹]X₂ (M = Mn and X = ClO₄ and M = Fe and X = BF₄). These complexes are high spin d⁵ and d⁶, respectively, as inferred from the long M–N bond distances obtained by single crystal X-ray diffraction for both and variable temperature magnetic susceptibility and Mössbauer spectroscopy for the iron complex. Aerobic treatment of a solution of [CoH₃L¹]²⁺ with three equivalents of potassium hydroxide produced [CoL¹]. Homonuclear pseudo-dimers were prepared by the aerobic reaction of [FeH₃L¹](BF₄)₂ with 1.5 equivalents of potassium hydroxide to give {[FeH_1.5L¹](BF₄)}₂ or by the metathesis reaction of [FeH₂L¹][FeHL¹](ClO₄)₂ with sodium hexafluorophosphate to give [FeH₃L¹][FeL¹](PF₆)₂. The complexes were characterized by EA, IR, ESI-MS, variable temperature single crystal xray diffraction and Mössbauer spectroscopy. The iron(III) atom is low spin while the iron(II) atom is spin crossover. Heteronuclear pseudo-dimers were prepared by the 1 : 1 reaction of [FeH₃L¹](BF₄)₂ or [MnH₃L¹](ClO₄)₂ with [CoL¹]. [MH₃L¹][CoL¹](X)₂ (M = Fe and X = BF₄ or M = Mn and X = ClO₄), were characterized by IR, EA, variable temperature single crystal X-ray diffraction and Mössbauer spectroscopy in the iron case. The data support a spin crossover and high spin assignment for the iron(II) and manganese(II), respectively. DFT calculations demonstrate that the spin state of the iron(II) atom in {[FeH₃L¹][FeL¹]}²⁺ changes from high spin to low spin as the iron(II)-iron(III) distance decreases. This is supported by experimental results and is a result of hydrogen bonding interactions which cause a significant compression of the M(II)-N_pyrazole bond distances.

Dalton Transactions

Synthesis and characterization of homo- and heterodinuclear M(ii)-M′(iii) (M(ii) = Mn or Fe, M′(iii) = Fe or Co) mixed-valence supramolecular pseudo-dimers. The effect of hydrogen bonding on spin state selection of M(ii)†

Abstract

Supplementary files

Article information

Download Citation

Permissions

Synthesis and characterization of homo- and heterodinuclear M(II)-M′(III) (M(II) = Mn or Fe, M′(III) = Fe or Co) mixed-valence supramolecular pseudo-dimers. The effect of hydrogen bonding on spin state selection of M(II)

Social activity

Search articles by author

Spotlight

Advertisements