Published on Web 08/25/2004
Diruthenium Tetraacetate Monocation, [RuII/III2(O2CMe)4]+, Building Blocks for 3-D Molecule-Based Magnets Thomas E. Vos,† Yi Liao,† William W. Shum,† Jae-Hyuk Her,‡ Peter W. Stephens,† William M. Reiff,§ and Joel S. Miller*,† Contribution from the Department of Chemistry, UniVersity of Utah, 315 S. 1400 E. RM 2124, Salt Lake City, Utah 84112-0850; Department Physics and Astronomy, State UniVersity of New York, Stony Brook, New York 11794-3800; and Department of Chemistry and Chemical Biology, Northeastern UniVersity, 360 Huntington AVenue, Boston, Massachusetts 02115 Received March 31, 2004; E-mail:
[email protected] Abstract: Diruthenium tetracarboxylates monocations are utilized as building blocks for cubic 3-D network structured molecule-based magnets. [RuII/III2(O2CMe)4]3[MIII(CN)6] [M ) Cr (1a), Fe (2), Co (3)] were prepared in aqueous solution. Powder X-ray diffraction indicates that they have body-centered cubic structures (space group ) Im3 h m, a ) 13.34, 13.30, and 13.10 Å for 1a, 2, and 3, respectively), which was confirmed for 1a by Reitveld analysis of the synchrotron powder data [a ) 13.3756(5) Å]. [Ru2(O2CMe)4]3[MIII(CN)6]‚xMeCN [M ) Cr, x ) 1.8 (1b); M ) Mn, x ) 3.3 (4)] were prepared from acetonitrile. The magnetic ordering of 1a (33 K), 1b (34.5 K), 2 (2.1 K), and 4 (9.6 K) was determined from the temperature dependencies of the in-phase (χ′) alternating current (AC) susceptibility. The field dependence of the magnetization, M(H), at 2 K for 1a showed an unusual constricted hysteresis loop with a coercive field, Hcr, of 470 Oe while the M(H) data for 1b, 2, and 4 showed a normal hysteresis loop with a coercive field of 1670, 10, and 990 Oe, respectively. The 57Fe Mo¨ssbauer spectrum of 2 is consistent with the presence of low spin FeIII (δ ) -0.05 mm/s; ∆E ) 0.33 mm/s) at room temperature, and the onset of 3-D magnetic ordering at lower temperature ( θ (1) 3 1 + e-2D/kBT
]
χM )
Ng2µ2B
[S(S + 1)]
3kB(T - θ)
χTot ) 3χRu2 + χM
(2) (3)
While the IR spectra of [RuII/III2(O2CMe)4]3[CrIII(CN)6] synJ. AM. CHEM. SOC.
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VOL. 126, NO. 37, 2004 11633
ARTICLES
Vos et al.
Table 2. Summary of the υCN IR Absorptions and Magnetic Properties for [Ru2(O2CMe)4]3[MIII(CN)6]
1a 1b 2 3 4 a
M
υCN cm-1
T c, K
Tb, K
Ms,b emu Oe/mol
Ms (calcd)c FO emu Oe/mol
Ms (calcd)c AF emu Oe/mol
Cr Cr Fe Co Mn
2138 2142 2116 2125 2118
33 34.5 2.1
32 32 3
9.6
10
20 800 ( 300 16 000 ( 700 22 700 ( 400 31 125 20 000 ( 600
67 020 67 020 55 850 50 265 61 435
33 510 33 510 44 680 50 265 39 095
Mr emu Oe/mol
φd
Hcr Oe
3840 8830 40
