Galan Jhenny F, Germany Edward, Pawlowski Amanda, Strickland Lynette, Galinato Mary Grace I
Department of Marine Sciences, Texas A&M University at Galveston , 200 Seawolf Parkway, Galveston, Texas 77553, United States.
J Phys Chem A. 2014 Jul 17;118(28):5304-15. doi: 10.1021/jp503539m. Epub 2014 Jul 8.
Structural organization of macromolecules is highly dependent on the conformational propensity of the monomer units. Our goal is to systematically quantify differences in the conformational propensities of aromatic oligourea foldamer units. Specifically, we investigate the conformational propensities of N,N'-diphenylurea and N,N'-dimethyl-N,N'-diphenylurea in different media using a combination of theoretical methods, and infrared and nuclear magnetic resonance spectroscopies. Our results show variation in the conformational behavior upon adding methyl substituents on N,N'-diphenylurea, and varying the environments surrounding the compounds. Our energetic analyses and conformational distributions in the gas phase show predominance of the cis-trans and trans-trans conformations for N,N'-diphenylurea, while cis-cis conformation is favored for N,N'-dimethyl-N,N'-diphenylurea. In solution, our results support the trans-trans conformer as the predominant conformer for N,N'-diphenylurea, whereas the cis-cis and cis-trans forms are favored in N,N'-dimethyl-N,N'-diphenylurea. N,N'-Dimethyl-N,N'-diphenylurea also exhibits a more dynamic conformational behavior in solution, with constant fluctuations between cis-cis and cis-trans conformations. Our detailed quantitative analyses are an important aspect in fine-tuning desired conformations and dynamic properties of this class of oligomers by providing a molecular basis for the behavior at the monomeric level.
大分子的结构组织高度依赖于单体单元的构象倾向。我们的目标是系统地量化芳香族低聚脲折叠体单元构象倾向的差异。具体而言，我们使用理论方法、红外光谱和核磁共振光谱相结合的方式，研究了N,N'-二苯基脲和N,N'-二甲基-N,N'-二苯基脲在不同介质中的构象倾向。我们的结果表明，在N,N'-二苯基脲上添加甲基取代基以及改变化合物周围的环境时，构象行为会发生变化。我们在气相中的能量分析和构象分布表明，N,N'-二苯基脲的顺式-反式和反式-反式构象占主导，而N,N'-二甲基-N,N'-二苯基脲则有利于顺式-顺式构象。在溶液中，我们的结果支持反式-反式构象是N,N'-二苯基脲的主要构象，而在N,N'-二甲基-N,N'-二苯基脲中，顺式-顺式和顺式-反式构象更受青睐。N,N'-二甲基-N,N'-二苯基脲在溶液中也表现出更动态的构象行为，顺式-顺式和顺式-反式构象之间不断波动。我们详细的定量分析通过提供单体水平行为的分子基础，为微调这类低聚物的理想构象和动态性质提供了一个重要方面。
