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首页> 外文期刊>International Journal of Quantum Chemistry >Layered alkyltrimethylammonium chromates: Thermal and structural investigations and crystal structure of the anhydrous bisoctyltrimethylammonium dichromate
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Layered alkyltrimethylammonium chromates: Thermal and structural investigations and crystal structure of the anhydrous bisoctyltrimethylammonium dichromate

机译：层状烷基三甲基铬酸铬：无水双辛基三甲基铵重铬酸的热和结构研究及晶体结构

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摘要

New mesostructured bisalkyltrimethylammonium dichromates of formula (CnH2n+1(CH3)(3)N)(2)Cr2O7.xH(2)O (n = 12, 14, 16, 18; 0 less than or equal to x less than or equal to 2) were prepared at 80 degrees C from an aqueous solution of alkyltrimethylammonium salt and K2Cr2O7. The chemical composition and phase transitions have beers determined by thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) and mass spectrometry (MS). As suggested by X-ray diffraction and transmission electron microscopy studies, the lamellar hydrated and anhydrous bisalkyltrimethylammonium dichromates crystallize in the triclinic system, with space group P-1. The structure of the anhydrous bisoctyltrimethylammonium dichromate, (C18H37(CH3)(3)N)(2) Cr2O7, was determined from single-crystal X-ray diffraction data. The compound crystallizes in the triclinic system, space group P-1, with 2 formula units in a cell a = 7.197(1)Angstrom, b = 8.816(2)Angstrom, c = 43.400(9)Angstrom, alpha = 93.43(3)degrees, beta = 90.00(3)degrees, gamma = 113,98(3)degrees. The structure consists of discrete dichromate anions stacking up in a layer, separated by a double layer of octyltrimethylammonium surfactant chains lying in parallel. The interlayer spacing of 43.4 Angstrom, smaller than the expected value far the fully extended molecular model, is achieved through a tilting of the surfactant chains of about 37.5 degrees from the normal to the (Cr2O7)(2-) plane. (C) 1998 Academic Press. [References: 24]
机译：分子式为（CnH2n + 1（CH3）（3）N）（2）Cr2O7.xH（2）O的新的介孔双烷基三甲基重铬酸铵（n = 12，14，16，18; 0小于或等于x小于或等于至2）是在80℃下由烷基三甲基铵盐和K 2 Cr 2 O 7的水溶液制备的。通过热重分析（TGA）结合差示扫描量热法（DSC）和质谱（MS）确定了化学成分和相变。正如X射线衍射和透射电子显微镜研究所表明的那样，层状水合和无水双烷基三甲基铵重铬酸盐在三斜晶系体系中结晶，空间群为P-1。从单晶X射线衍射数据确定无水双辛基三甲基重铬酸铵（C18H37（CH3）（3）N）（2）Cr2O7的结构。该化合物在三斜晶系系统P-1空间群中结晶，在一个单元中具有2个公式单元a = 7.197（1）埃，b = 8.816（2）埃，c = 43.400（9）埃，alpha = 93.43（3 ）度，β= 90.00（3）度，伽马= 113,98（3）度。该结构由堆积成一层的离散重铬酸盐阴离子组成，并由平行的双层辛基三甲基铵表面活性剂链隔开。通过使表面活性剂链从法线向（Cr2O7）（2-）平面倾斜大约37.5度，可以达到43.4埃的层间距，该距离比完全扩展的分子模型的预期值还小。 （C）1998年学术出版社。 [参考：24]

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