Lande Dipali N, Shewale Maneesha N, Gejji Shridhar P
Department of Chemistry, Savitribai Phule Pune University , Pune 411 007, India.
J Phys Chem A. 2017 May 18;121(19):3792-3802. doi: 10.1021/acs.jpca.7b02238. Epub 2017 May 8.
The binding of novel endofunctionalized bis-urea/thiourea molecular receptors toward neutral 1,4-diazabicyclo[2.2.2]octane (DABCO) demonstrates stronger binding of the bis-thiourea macrocycles than for their urea analogues by employing M06-2X/6-31+G(d,p)-based density functional theory. The formation of such inclusion complexes is spontaneous, thermodynamically favorable, and facilitated via bifurcated N-H···N···H-N hydrogen bonding and C-H···π, dipole-dipole, and other noncovalent interactions, which are reflected in the frequency shift of their characteristic N-H vibrations in the calculated vibrational spectra of these complexes. The underlying noncovalent interactions are analyzed using the molecular electrostatic potential topography and quantum theory of atoms in molecules in conjunction with the noncovalent interactions reduced density gradient method. It has also been shown that the encapsulation of DABCO within the π-electron-rich cavity of such hosts brings about shielding of the guest protons confined within the host cavity whereas those facilitating hydrogen bonding engender the downfield signals in their calculated H NMR spectra.
通过基于M06 - 2X/6 - 31 + G(d,p)的密度泛函理论，新型末端官能化双脲/硫脲分子受体与中性1,4 - 二氮杂双环[2.2.2]辛烷（DABCO）的结合表明，双硫脲大环的结合比其脲类似物更强。这种包合物的形成是自发的，在热力学上是有利的，并且通过分叉的N - H···N···H - N氢键以及C - H···π、偶极 - 偶极和其他非共价相互作用得以促进，这在这些配合物的计算振动光谱中其特征N - H振动的频率偏移中得到体现。使用分子静电势拓扑图和分子中的原子量子理论并结合非共价相互作用密度降低梯度方法对潜在的非共价相互作用进行了分析。研究还表明，将DABCO封装在这种主体的富π电子腔内会导致主体腔内受限客体质子的屏蔽，而那些促进氢键形成的作用则在其计算的H NMR光谱中产生低场信号。
