Conductive Molecular Crystals. Structural, Magnetic, and Charge-Transport Properties of (5,10,15,20-Tetramethylporphyrinato)nickel(II) Iodide
Conductive Molecular Crystals. Structural, Magnetic, and Charge-Transport Properties of (5,10,15,20-Tetramethylporphyrinato)nickel(II) Iodide
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导电分子晶体。
DOI：
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发表时间：
1983
期刊：
影响因子：
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通讯作者：
J. Ibers
中科院分区：
文献类型：
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作者：
L. Pace;J. Martinsen;Abraham Ulman;B. Hoffman;J. Ibers
(5，10，15，20-Tetramethylporphyrinato)nickel(II)，镍(TMP)与碘反应被部分氧化。我们报道了所得化合物Ni(TMP)I的单晶的结构、磁性和电荷输运性质。该化合物属于四方晶系的D/sup 4//sub4h/-P4/nnc空间群，在114K时，以a=16.610埃和c=6.932埃为一个晶胞，有四个公式单位。对69个变量的全矩阵最小二乘修正给出了1418K下F/sup 2/0.079的R指数的最终值。其结构由S/亚4/-褶皱镍(TMP)分子组成，堆积在金属上，沿堆叠的Ni-Ni间距为3,466埃。单位电池中相邻的Ni(TMP)单位交错37/sup 0/。严重无序的碘链位于镍(TMP)堆栈周围的通道中。根据漫反射X射线散射和共振拉曼光谱确定碘为I/sub3//sup-/。在低温下，共振拉曼光谱中的I/sub3//sup-/带的分裂变得明显。单晶室温沿针轴方向的电导率平均为110欧米伽/sup~(-1)/cm/sup~(-1)/，略低于大环卟啉导体。Ni(TMP)I的电导率随温度的变化在115K以上类似金属，在较低温度下被激活。更多的单晶EPR研究表明，Ni(TMP)I的氧化是以配体为中心的。磁化率类似金属，在28K以上与温度无关，但反常的高表明库仑关联增强。这种磁化率的增强可能是由于小的卟啉大环的电子结构而产生的磁性三重态的混合。当温度降低到28K以下时，磁化率急剧下降。
(5,10,15,20-Tetramethylporphyrinato)nickel(II), Ni(tmp), has been partially oxidized by reaction with iodine. We report structural, magnetic, and charge-transport properties of single crystals of the resulting compound, Ni(tmp)I. The compound crystallizes in space group D/sup 4//sub 4h/-P4/nnc of the tetragonal system with four formula units in a cell of dimensions a = 16.610 angstrom and c = 6.932 angstrom at 114 K. Full-matrix least-squares refinement of 69 variables gives gives a final value for the R index on F/sup 2/ of 0.079 for 1418 observations. The structure consists of S/sub 4/-ruffled Ni(tmp) molecules, stacked metal-over-metal, with a Ni-Ni spacing along the stack of 3,466 angstrom. Adjacent Ni(tmp) units in the unit cell are staggered by 37/sup 0/. Severely disordered chains of iodine are located in channels surrounding the Ni(tmp) stacks. The iodine is identified as I/sub 3//sup -/ from diffuse X-ray scattering and resonance Raman spectroscopy. Splitting of the I/sub 3//sup -/ bands in the resonance Raman spectrum becomes evident at low temperature. Single-crystal room-temperature conductivity along the needle axis averages 110 ..cap omega../sup -1/ cm/sup -1/, slightly less than that of large-ring porphyrinic conductors. The temperature dependence of the conductivity of Ni(tmp)I is metal-like above 115 K and activated at lower temperatures.more » Single-crystal EPR studies indicate that the oxidation of the Ni(tmp) moiety is ligand centered. The magnetic susceptibility is metal-like, being temperature independent above 28 K but anomalously high indicative of enhanced Coulomb correlations. This susceptibility enhancement may arise from the mixing in of a magnetic triplet state that is available because of the electronic structure of small porphyrinic macrocycles. The susceptibility decreases sharply as the temperature is lowered below 28K.« less