Durães Jussara A, da Silva Filho Demétrio A, Ceschin Artemis M, Sales Maria J A, Martins João B L
Institute of Chemistry, University of Brasília, P.O. Box 04478, 70904-970, Brasília, Brazil.
J Mol Model. 2014 Aug;20(8):2405. doi: 10.1007/s00894-014-2405-3. Epub 2014 Aug 13.
When heterocyclic monomers are polymerized by electrochemical or chemical methods, they form fully conjugated polymers which have a wide range of applications due to their outstanding electronic properties. Among this class of compounds, thiophene derivatives are widely used due to their chemical stability and synthesis flexibility. With the goal to investigate the torsion barrier of polymer chains, a few units of 3,4-ethylenedioxythiophene (EDOT) were chosen and submitted to molecular mechanics (MM), density functional theory (DFT) and coupled cluster CCSD(T) calculations. This study helps to understand the performance and transferability of force fields used in molecular mechanics and molecular dynamics simulations often used to describe structure-property relationships of those systems. Determination of inter-ring torsion angle was performed in a comparative study using both force field, DFT and CCSD(T) methods. A good agreement was noticed between MM and QC results and highlights the importance of the description of the interactions involving the oxygen atoms present in the structure of EDOT. These observations are related to the α,α-coupling that occurs between the monomer units and yields a linear polymer. DFT HOMO and LUMO orbitals were also presented. Finally, UV-vis spectra of EDOT units were obtained using several levels of theory by means of time-dependent DFT calculations (TD-DFT).
当杂环单体通过电化学或化学方法聚合时，它们会形成完全共轭的聚合物，由于其出色的电子性能，这类聚合物有着广泛的应用。在这类化合物中，噻吩衍生物因其化学稳定性和合成灵活性而被广泛使用。为了研究聚合物链的扭转势垒，选取了几个3,4-亚乙基二氧噻吩（EDOT）单元，并进行了分子力学（MM）、密度泛函理论（DFT）和耦合簇CCSD(T)计算。这项研究有助于理解分子力学和分子动力学模拟中常用的力场的性能和可转移性，这些模拟常用于描述那些体系的结构-性质关系。使用力场、DFT和CCSD(T)方法在一项比较研究中进行了环间扭转角的测定。MM和量子化学计算结果之间观察到了良好的一致性，并突出了描述EDOT结构中存在的氧原子相关相互作用的重要性。这些观察结果与单体单元之间发生的α,α-偶联有关，从而产生线性聚合物。还给出了DFT的最高已占分子轨道（HOMO）和最低未占分子轨道（LUMO）。最后，通过含时密度泛函理论计算（TD-DFT），使用几种理论水平获得了EDOT单元的紫外-可见光谱。
