Gizatullin Bulat, Gafurov Marat, Murzakhanov Fadis, Vakhin Alexey, Mattea Carlos, Stapf Siegfried
Institute of Physics, Technische Universität Ilmenau, Ilmenau 98693, Germany.
Kazan Federal University, Kremlevskaya, 18, Kazan 420008, Russia.
Langmuir. 2021 Jun 8;37(22):6783-6791. doi: 10.1021/acs.langmuir.1c00882. Epub 2021 May 27.
The use of vanadyl porphyrins either in synthetic compounds or naturally occurring in asphaltenes is investigated as a source of proton hyperpolarization via dynamic nuclear polarization (DNP) in nuclear magnetic resonance (NMR) experiments. The features of dynamics and location of the vanadyl VO complex in aggregates within the oil asphaltene molecules are studied by means of DNP, electron paramagnetic resonance (EPR), and NMR field cycling relaxometry. Both the solid effect and Overhauser DNP were observed for the asphaltene solution in benzene, as well as in the solution and solid states for synthetic compounds. By comparison with a solution of synthetic vanadyl porphyrins, it is shown that vanadyl porphyrins in asphaltene aggregates are localized outside of the interface of the asphaltene aggregates and more exposed to the maltene molecules than "free" carbon-centered radicals associated with the core of asphaltene molecules. The perceptible contribution of scalar interaction is observed in solutions for both synthetic and asphaltene vanadyl porphyrins.
研究了钒基卟啉在合成化合物中或天然存在于沥青质中的情况，将其作为核磁共振（NMR）实验中通过动态核极化（DNP）实现质子超极化的来源。借助DNP、电子顺磁共振（EPR）和NMR场循环弛豫测量法，研究了油沥青质分子聚集体中钒氧基VO配合物的动力学特征和位置。在苯中的沥青质溶液以及合成化合物的溶液和固态中，均观察到了固体效应和奥弗豪泽DNP。通过与合成钒基卟啉溶液进行比较，结果表明，沥青质聚集体中的钒基卟啉位于沥青质聚集体界面之外，并且比与沥青质分子核心相关的“游离”碳中心自由基更易暴露于软沥青分子中。在合成和沥青质钒基卟啉的溶液中均观察到了标量相互作用的明显贡献。
