磁几何阻挫材料羟基氯化钴的中红外光谱特征

使用3种光谱仪测量了磁几何阻挫材料羟基氯化钴Co₂(OH)₃Cl的中红外(4000—400 cm^-1)吸收光谱,筛选出确信为Co₂(OH)₃Cl的本征吸收峰数据,结合已知的晶体结构参数,指认了官能团和指纹区相应谱峰的来源.在指认中着重探讨了羟基伸缩振动基频模vOH的具体实验数据,根据固体中氢键的特点,以Co₃—O平均距离为基准,推算了本样品 关键词： 红外光谱 几何阻挫 羟基氯化钴 三聚氢键

Mid-infrared spectroscopic properties of geometrically frustrated basic cobalt chlorides

Three types of FTIR spectrometers were employed to measure the mid-infrared (4000—400 cm^-1) absorption spectra of geometrically frustrated hydroxyl cobalt chloride Co₂(OH)₃Cl, and the intrinsic absorption peaks in the functional group region and fingerprint region were selected and assigned to corresponding vibrational modes according to its known crystal structure. In the assigning process, great emphasis was laid on analyzing the exact experimental data of hydroxyl stretching vibration mode vOH, that is, estimating the free vOH of the Co₃—OH group without any hydrogen bond (H-bond), to obtain the red-shift which reflects the formation of an H-band in Co₂(OH)₃Cl. A 156 cm^-1 red-shift is obtained theoretically which demonstrates the presence of non-negligible weak H-bonds, and eventually result in the discovery of the rarely reported trimeric H-bond in the field of crystalline materials, which consists of three independent hydroxyl donors and only one Cl^- acceptor. We explained the relative weakness of this kind of hydrogen bond which may have a critical effect on the lattice symmetry and magnetic structure.