Limits in Proton Nuclear Singlet‐State Lifetimes Measured with
<i>para</i>
‐Hydrogen‐Induced Polarization
作者:Yuning Zhang、Xueyou Duan、Pei Che Soon、Vladimír Sychrovský、James W. Canary、Alexej Jerschow
DOI:10.1002/cphc.201600663
日期:2016.10.5
molecule was developed, where the polarization and the singlet state were preserved over two controlled chemical steps. Nuclear singlet‐state lifetimes close to 6 min for protons are reported in dimethyl fumarate. Owing to the high symmetry (AA′X3X3′ and A2 systems), the singlet‐state readout requires either a chemical desymmetrization or a long and repeated spin lock. Using DFT calculations and relaxation
开发了超极化分子的合成,其中在两个受控化学步骤中保留了极化和单重态。据报道,富马酸二甲酯的质子核单重态寿命接近6分钟。由于具有高对称性(AA'X 3 X 3 '和A 2系统),单重态读数需要化学去对称或长时间重复的自旋锁定。使用DFT计算和弛豫模型,我们进一步确定核自旋单重态寿命的限制因素,包括分子内偶极耦合机制(质子-质子和质子-氘),化学位移各向异性机制(对称和反对称)以及分子间偶极耦合机理(氧和氘)。如果可以消除由残余氧引起的顺磁弛豫的限制,则分子内偶极与氘的偶合将成为限制弛豫机制,并且此处考虑的分子(马来酸二甲酯和富马酸二甲酯)的质子寿命可以达到26分钟。