cis Versus trans-Azobenzene: Precise Determination of NMR Parameters and Analysis of Long-Lived States of 15N Spin Pairs

• Published in: Applied magnetic resonance 2018-03, Vol.49 (3), p.293-307
• Main Authors: Sheberstov, Kirill F., Vieth, Hans-Martin, Zimmermann, Herbert, Ivanov, Konstantin L., Kiryutin, Alexey S., Yurkovskaya, Alexandra V.
• Format: Article
• Language: English
• Subjects: Atoms and Molecules in Strong Fields; Azo compounds; Chemical reactions; Couplings; Deuteration; Laser Matter Interaction; Lifetime; Magnetic fields; Magnetization; Molecular dynamics; Nitrogen isotopes; NMR; Nuclear magnetic resonance; Optimization; Organic Chemistry; Original Paper; Parameters; Physical Chemistry; Physics; Physics and Astronomy; Protons; Solid State Physics; Spectra; Spectroscopy/Spectrometry; Spectrum analysis; Spin dynamics
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/s00723-017-0968-8

We provide a detailed evaluation of nuclear magnetic resonance (NMR) parameters of the cis - and trans -isomers of azobenzene (AB). For determining the NMR parameters, such as proton–proton and proton–nitrogen J -couplings and chemical shifts, we compared NMR spectra of three different isotopomers of AB: the doubly 15 N labeled azobenzene, 15 N, 15 N′-AB, and two partially deuterated AB isotopomers with a single 15 N atom. For the total lineshape analysis of NMR spectra, we used the recently developed ANATOLIA software package. The determined NMR parameters allowed us to optimize experiments for investigating singlet long-lived spin states (LLSs) of 15 N spin pairs and to measure LLS lifetimes in cis -AB and trans -AB. Magnetization-to-singlet-to-magnetization conversion has been performed using the SLIC and APSOC techniques, providing a degree of conversion up to 17 and 24% of the initial magnetization, respectively. Our approach is useful for optimizing the performance of experiments with singlet LLSs; such LLSs can be exploited for preserving spin hyperpolarization, for probing slow molecular dynamics, slow chemical processes and also slow transport processes.