TY - JOUR
T1 - 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)
AU - Brewer, Cynthia T.
AU - Brewer, Greg
AU - Butcher, Ray J.
AU - Carpenter, Everett E.
AU - Schmiedekamp, Ann M.
AU - Schmiedekamp, Carl
AU - Straka, Alison
AU - Viragh, Carol
AU - Yuzefpolskiy, Yevgeniy
AU - Zavalij, Peter
PY - 2011/1/7
Y1 - 2011/1/7
N2 - 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 [CoH3L 1]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 {[FeH1.5L 1](BF4)}2 or by the metathesis reaction of [FeH2L1][FeHL1](ClO4)2 with sodium hexafluorophosphate to give [FeH3L1][FeL 1](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 [CoL 1]. [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.
AB - 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 [CoH3L 1]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 {[FeH1.5L 1](BF4)}2 or by the metathesis reaction of [FeH2L1][FeHL1](ClO4)2 with sodium hexafluorophosphate to give [FeH3L1][FeL 1](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 [CoL 1]. [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.
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U2 - 10.1039/c0dt01098g
DO - 10.1039/c0dt01098g
M3 - Article
C2 - 21103467
AN - SCOPUS:78650141069
SN - 1477-9226
VL - 40
SP - 181
EP - 194
JO - Dalton Transactions
JF - Dalton Transactions
IS - 1
ER -