Montejo Manuel, Navarro Amparo, Kearley Gordon J, Vázquez Juana, López-González Juan Jesús
Department of Physical and Analytical Chemistry, University of Jaén, 23071 Jaén, Spain.
J Am Chem Soc. 2004 Nov 24;126(46):15087-95. doi: 10.1021/ja040130y.
The calculated structures of furan as a monomer, a dimer that was isolated from the crystal structure, and the full crystal structure have been thoroughly investigated by a combination of density functional theory (DFT) calculations and inelastic neutron scattering (INS) measurements. To improve our understanding of the nature and magnitude of the intermolecular interactions in the solid, the atoms in molecules (AIM) theory has been applied to the dimer and a cluster of eight monomers. After a careful topological study of the theoretical charge density and of its Laplacian, we have established the existence of C-H...pi, C-H...O, and H...H interactions between adjacent molecules in solid furan. The electron distribution has also been analyzed by performing natural bond orbital (NBO) calculations for the monomer and a H-bonded dimer. When the hydrogen bond is established between two adjacent furan rings, some electron charge is transferred from the pi electronic system of one furan ring to the other molecule in the dimer. This result provides a model of the interaction between end groups of neighboring chains of polyfuran and could be applicable to other conjugated polymers where the pi system is responsible for their conducting properties. To determine how the intermolecular bonds in the solid affect the vibrational dynamics in the periodic system, INS data were analyzed by performing molecular and periodic density functional calculations. Reasonable agreement is achieved, although we note that the poorest agreement is for modes involving hydrogen atoms.
通过密度泛函理论（DFT）计算和非弹性中子散射（INS）测量相结合的方法，对呋喃作为单体、从晶体结构中分离出的二聚体以及完整晶体结构的计算结构进行了深入研究。为了增进我们对固体中分子间相互作用的性质和强度的理解，分子中的原子（AIM）理论已应用于二聚体和由八个单体组成的簇。在对理论电荷密度及其拉普拉斯算子进行仔细的拓扑研究之后，我们确定了固态呋喃中相邻分子之间存在C-H...π、C-H...O和H...H相互作用。还通过对单体和氢键二聚体进行自然键轨道（NBO）计算来分析电子分布。当两个相邻的呋喃环之间形成氢键时，一些电子电荷从一个呋喃环的π电子体系转移到二聚体中的另一个分子上。这一结果提供了聚呋喃相邻链端基之间相互作用的模型，并且可能适用于其他共轭聚合物，其中π体系决定了它们的导电性能。为了确定固体中的分子间键如何影响周期系统中的振动动力学，通过进行分子和周期密度泛函计算来分析INS数据。尽管我们注意到与涉及氢原子的模式的一致性最差，但仍取得了合理的一致性。
