School of Chemistry, Southampton University, SO17 1BJ Southampton, UK.
J Am Chem Soc. 2013 Feb 13;135(6):2120-3. doi: 10.1021/ja312227h. Epub 2013 Feb 5.
Nuclear singlet states are nonmagnetic states of nuclear spin-1/2 pairs that may exhibit lifetimes much slower than the relaxation of the component spins in isolation. This feature makes them attractive vehicles for conveying nuclear hyperpolarization in NMR spectroscopy and magnetic resonance imaging experiments and for reducing signal losses in other NMR experiments caused by undesirably fast nuclear spin relaxation. Here we show access to (13)C(2) singlet states in a symmetrical oxalate molecule by substituting one or more (16)O nuclei by the stable nonmagnetic isotope (18)O. The singlet relaxation time of the (13)C(2) pair in [1-(18)O,(13)C(2)]-oxalate is 2-3 times longer than the spin-lattice relaxation time T(1).
核单重态是核自旋为 1/2 的偶极子的非磁性状态，其寿命可能比孤立的组成自旋的弛豫时间长得多。这一特性使它们成为在 NMR 光谱学和磁共振成像实验中传递核超极化以及减少其他 NMR 实验中由于不希望的快速核自旋弛豫而导致的信号损失的有吸引力的载体。在这里，我们通过用稳定的非磁性同位素 (18)O 取代一个或多个 (16)O 核，从而实现了对称草酸盐分子中 (13)C(2) 单重态的进入。[1-(18)O，(13)C(2)]-草酸盐中 (13)C(2) 偶极子的单重态弛豫时间比自旋晶格弛豫时间 T(1)长 2-3 倍。
