TY - JOUR
T1 - A mixed-valence Mn6 cluster capped by nitronyl nitroxide units
AU - Nakata, Kazuya
AU - Miyasaka, Hitoshi
AU - Iwahori, Fumiyasu
AU - Sugiura, Ken Ichi
AU - Yamashita, Masahiro
N1 - Funding Information:
This work was financially supported by PRESTO (H.M.) and CREST (M.Y.) projects, Japan Science and Technology Agency (JST), and in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.
PY - 2005/11/17
Y1 - 2005/11/17
N2 - A mixed-valence Mn6 cluster, [Mn6O 2(t-BuCO2)10(H2O)(NNPy) 2] (2), has been synthesized by the assembly of [Mn6O 2(t-BuCO2)10(THF)4]·THF (1) with a nitronyl nitroxide radical molecule, 2-(p-pyridyl)-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide (NNPy). Complex 2 consists of [Mn 6O2]10+ core and two NNPy radical attachments, where the [Mn6O2]10+ core is composed of two MnIII ions (i.e., the inner Mn ions) bridged by two μ4-O2- and four MnII ions (i.e., the outer Mn ions) surrounding the inner MnIII ions via the two μ4-O2-, forming an edge-shared double-tetrahedral polygon (vertices: Mn ions, centers: μ4-O2-). Bridges by pivalate groups in μ2- and μ3-modes assist the coordination spheres around these Mn ions. Two of the outer MnII ions in trans position are, to the sixth coordination site, occupied by NNPy molecule (pyridine-N coordination). One of the outer MnII ions is occupied by a water molecule to complete octahedral geometry, but the rest of them is vacancy taking a square-pyramidal geometry. The variable-temperature direct current (DC) magnetic susceptibility was collected in the temperature range of 1.81 to 300 K at a 1 kOe appled field. The molar magnetic susceptibility (χM) steadily increases from 0.053 emu mol -1 at 300 K to 0.29 emu mol-1 at 20 K, showing a kink (peak), and then increases rapidly to 0.70 emu mol-1 at 1.81 K. The profile of this magnetic behavior indicates that the intracluster spin cancellation takes place bellow 20 K to derive an SMn6 = 0 by strong antiferromagnetic interaction between Mn ions. This is consequently leading to paramagnetic isolation of only the two nitronyl nitroxide units as if remaining as exchange-uncorrelated spin carriers. The variable-temperature ESR spectra show a sharp signal below 30 K with g = 2.00, proving the presence of free nitronyl nitroxide radical, in which double integral of such signal obeys the Curie-Weiss law that follows the susceptibility result in the low-temperature region.
AB - A mixed-valence Mn6 cluster, [Mn6O 2(t-BuCO2)10(H2O)(NNPy) 2] (2), has been synthesized by the assembly of [Mn6O 2(t-BuCO2)10(THF)4]·THF (1) with a nitronyl nitroxide radical molecule, 2-(p-pyridyl)-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide (NNPy). Complex 2 consists of [Mn 6O2]10+ core and two NNPy radical attachments, where the [Mn6O2]10+ core is composed of two MnIII ions (i.e., the inner Mn ions) bridged by two μ4-O2- and four MnII ions (i.e., the outer Mn ions) surrounding the inner MnIII ions via the two μ4-O2-, forming an edge-shared double-tetrahedral polygon (vertices: Mn ions, centers: μ4-O2-). Bridges by pivalate groups in μ2- and μ3-modes assist the coordination spheres around these Mn ions. Two of the outer MnII ions in trans position are, to the sixth coordination site, occupied by NNPy molecule (pyridine-N coordination). One of the outer MnII ions is occupied by a water molecule to complete octahedral geometry, but the rest of them is vacancy taking a square-pyramidal geometry. The variable-temperature direct current (DC) magnetic susceptibility was collected in the temperature range of 1.81 to 300 K at a 1 kOe appled field. The molar magnetic susceptibility (χM) steadily increases from 0.053 emu mol -1 at 300 K to 0.29 emu mol-1 at 20 K, showing a kink (peak), and then increases rapidly to 0.70 emu mol-1 at 1.81 K. The profile of this magnetic behavior indicates that the intracluster spin cancellation takes place bellow 20 K to derive an SMn6 = 0 by strong antiferromagnetic interaction between Mn ions. This is consequently leading to paramagnetic isolation of only the two nitronyl nitroxide units as if remaining as exchange-uncorrelated spin carriers. The variable-temperature ESR spectra show a sharp signal below 30 K with g = 2.00, proving the presence of free nitronyl nitroxide radical, in which double integral of such signal obeys the Curie-Weiss law that follows the susceptibility result in the low-temperature region.
KW - DC magnetic susceptibility
KW - ESR study
KW - Magnetic properties
KW - Manganese cluster
KW - Nitronyl nitroxide radical
KW - Single-crystal X-ray analysis
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U2 - 10.1016/j.poly.2005.03.086
DO - 10.1016/j.poly.2005.03.086
M3 - Article
AN - SCOPUS:27644458269
SN - 0277-5387
VL - 24
SP - 2250
EP - 2256
JO - Polyhedron
JF - Polyhedron
IS - 16-17
ER -