Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada.
J Chem Phys. 2013 Jun 7;138(21):214302. doi: 10.1063/1.4807604.
Thiophenic compounds are major constituents of fossil fuels and pose problems for fuel refinement. The quantification and speciation of these compounds is of great interest in different areas such as biology, fossil fuels studies, geology, and archaeology. Sulfur 1s Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy has emerged as a qualitative and quantitative method for sulfur speciation. A firm understanding of the sulfur 1s NEXAFS spectra of organosulfur species is required for these analytical studies. To support this development, the sulfur 1s NEXAFS spectra of simple thiols and thioethers were previously examined, and are now extended to studies of thiophenic and aromatic thioether compounds, in the gas and condensed phases. High-resolution spectra have been further analyzed with the aid of Improved Virtual Orbital (IVO) and Δ(self-consistent field) ab initio calculations. Experimental sulfur 1s NEXAFS spectra show fine features predicted by calculation, and the combination of experiment and calculation has been used to improve the assignment of spectroscopic features important for the speciation and quantification of sulfur compounds. Systematic differences between gas and condensed phases are also explored; these differences suggest a significant role for conformational effects in the NEXAFS spectra of condensed species.
噻吩类化合物是化石燃料的主要成分，给燃料精炼带来了问题。这些化合物的定量和形态分析在生物学、化石燃料研究、地质学和考古学等不同领域都具有重要意义。硫 1s 近边 X 射线吸收精细结构（NEXAFS）光谱已成为一种定性和定量的硫形态分析方法。为了进行这些分析研究，需要对有机硫化合物的硫 1s NEXAFS 光谱有一个明确的认识。为了支持这一发展，先前已经对简单硫醇和硫醚的硫 1s NEXAFS 光谱进行了研究，现在将其扩展到了气相和凝聚相下噻吩类和芳香硫醚化合物的研究。借助改进的虚拟轨道（IVO）和 Δ（自洽场）从头计算，对高分辨率光谱进行了进一步分析。实验硫 1s NEXAFS 光谱显示出计算预测的精细特征，实验和计算的结合被用于改进对光谱特征的分配，这些特征对硫化合物的形态分析和定量很重要。还探索了气相和凝聚相之间的系统差异；这些差异表明构象效应对凝聚态物种的 NEXAFS 光谱有重要影响。
