Brown S, Cao J, Musfeldt J L, Conner M M, McConnell A C, Southerland H I, Manson J L, Schlueter J A, Phillips M D, Turnbull M M, Landee C P
Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
Inorg Chem. 2007 Oct 15;46(21):8577-83. doi: 10.1021/ic070122t. Epub 2007 Sep 11.
We report a systematic investigation of the temperature-dependent infrared vibrational spectra of a family of chemically related coordination polymer magnets based upon bridging bifluoride (HF(2)-) and terminal fluoride (F-) ligands in copper pyrazine complexes including Cu(HF(2))(pyz)(2)BF(4), Cu(HF(2))(pyz)(2)ClO(4), and CuF(2)(H(2)O)(2)(pyz). We compare our results with several one- and two-dimensional prototype materials including Cu(pyz)(NO(3))(2) and Cu(pyz)(2)(ClO(4))(2). Unusual low-temperature hydrogen bonding, local structural transitions associated with stronger low-temperature hydrogen bonding, and striking multiphonon effects that derive from coupling of an infrared-active fundamental with strong Raman-active modes of the pyrazine building-block molecule are observed. On the basis of the spectroscopic evidence, these interactions are ubiquitous to this family of coordination polymers and may work to stabilize long-range magnetic ordering at low temperature. Similar interactions are likely to be present in other molecule-based magnets.
我们报道了对一类基于桥联双氟化物（HF₂⁻）和末端氟化物（F⁻）配体的化学相关配位聚合物磁体的温度依赖红外振动光谱的系统研究，这些配体存在于铜吡嗪配合物中，包括Cu(HF₂)(pyz)₂BF₄、Cu(HF₂)(pyz)₂ClO₄和CuF₂(H₂O)₂(pyz)。我们将结果与几种一维和二维原型材料进行比较，包括Cu(pyz)(NO₃)₂和Cu(pyz)₂(ClO₄)₂。观察到异常的低温氢键、与更强低温氢键相关的局部结构转变，以及源于红外活性基频与吡嗪结构单元分子的强拉曼活性模式耦合的显著多声子效应。基于光谱证据，这些相互作用在这类配位聚合物中普遍存在，并且可能有助于在低温下稳定长程磁有序。类似的相互作用可能存在于其他分子基磁体中。
