Single-crystal X-ray diffraction and spectroscopic studies on humboldtine and lindbergite: weak Jahn–Teller effect of Fe2+ ion
Single-crystal X-ray diffraction and spectroscopic studies on humboldtine and lindbergite: weak Jahn–Teller effect of Fe2+ ion
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洪堡石和菱镁矿的单晶 X 射线衍射和光谱研究：Fe2+ 离子的弱 Jahn-Teller 效应
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
M. Kimata
中科院分区：
文献类型：
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作者：
T. Echigo;M. Kimata
首次合成了洪堡碱[Fe2+(C2O4)·2H2O]单晶，并对其晶体结构进行了细化。单晶x射线衍射数据采集采用成像板衍射仪系统和石墨单色MoKα辐射。对洪堡丁的晶体结构进行了改进，得到了595个独特反射的一致性指数R1为3.22%。该矿物在单斜晶系C2/c中结晶，晶胞尺寸为a = 12.011 (11), b = 5.557 (5), c = 9.920 (9) Å， β = 128.53(3)˚，V = 518.0 (8) Å3, Z = 4。在该晶体结构中，草酸盐阴离子[(C2O4)2−]和Fe2+离子交替形成与[010]平行的一维链结构；水分子（H2O）产生氢键连接链，其中（H2O）0本质上是晶体结构的一部分。氧原子上有两个孤电子对（LEPs）的水分子被斜绑在链上，因为一个孤电子对被认为参与了与Fe2+离子的化学键。含氢键的洪堡丁与林白石[Mn2+(C2O4)·2H2O]呈等型。洪堡石中氢键的供体-受体分离略短于林白石，说明洪堡石中的氢键比林白石中的氢键强。洪堡石和林白石单晶的红外和拉曼光谱证实了氢键几何结构的差异。此外，由于Fe2+离子的Jahn-Teller效应，洪堡碱的Fe2+ -O拉伸带在观察到的拉曼光谱中发生了分裂和展宽。这些解释也从键价理论的角度进行了讨论。
The single-crystal of humboldtine [Fe2+(C2O4) · 2H2O] was first synthesized and the crystal structure has been refined. Single-crystal X-ray diffraction data were collected using an imaging-plate diffractometer system and graphite-monochromatized MoKα radiation. The crystal structure of humboldtine was refined to an agreement index (R1) of 3.22% calculated for 595 unique observed reflections. The mineral crystallizes in the monoclinic system, space group C2/c, with unit cell dimensions of a = 12.011 (11), b = 5.557 (5), c = 9.920 (9) Å, β = 128.53 (3)˚, V = 518.0 (8) Å3, and Z = 4. In this crystal structure, the alternation of oxalate anions [(C2O4)2−] and Fe2+ ions forms one-dimensional chain structure parallel to [010]; water molecules (H2O)0 create hydrogen bonds to link the chains, where (H2O)0 is essentially part of the crystal structure. The water molecules with the two lone electron pairs (LEPs) on their oxygen atom are tied obliquely to the chains, because the one lone electron pair is considered to participate in the chemical bonds with Fe2+ ions. Humboldtine including hydrogen bonds is isotypic with lindbergite [Mn2+(C2O4) · 2H2O]. The donor–acceptor separations of the hydrogen bonds in humboldtine are slightly shorter than those in lindbergite, which suggests that the hydrogen bonds in the former are stronger than those in the latter. The infrared and Raman spectra of single-crystals of humboldtine and lindbergite confirmed the differences in hydrogen-bond geometry. In addition, Fe2+–O stretching band of humboldtine was split and broadened in the observed Raman spectrum, owing to the Jahn–Teller effect of Fe2+ ion. These interpretations were also discussed in terms of bond-valence theory.