Abstract: Long lived spin states (LLS) find various applications in magnetic resonance, namely in the study of slow dynamical processes [1], ligand-protein screening by NMR [2] and nuclear hyperpolarization storage [3]. In trans-azobenzene LLS corresponds to singlet spin state of 15N nuclei pair. This state demonstrates lifetime about 2 minutes at the field 16.4 T, which can be enhanced up to 20 minutes by applying spin-locking [4]. Furthermore, hyperpolarization of 15N nuclei can be achieved by photo-SABRE [5]. Detailed theoretical description of the LLS relaxation may bring new ideas on extending its lifetime even more. Dipole-dipole (DD) interaction and chemical shift anisotropy (CSA) don’t lead to singlet-triplet transitions of 15N nuclei spin pair and consider the closest to the pair protons is necessary. Four the closest protons were considered. To calculate relaxation, J-couplings, and DD interactions between all spin pairs, and also CSA of 15N nuclei were taken into account. Moreover, cross-correlation between all DD interactions, containing at least one nitrogen nucleus, and between these interactions and CSA were considered. To compute relaxation, Redfield theory was used with approach described in [6]. Dependence of the LLS lifetime on external magnetic field was calculated and compared to experimental data. This work was supported by the Russian Science Foundation (project #23-73-10103).

Cite: Vopilovskiy A.M. , Kiryutin A.S. , Yurkovskaya A.V. , Lukzen N.N.
Theoretical study of long-lived state relaxation in transazobenzene with two 15N nuclear isotopes
23rd International School-Conference Magnetic resonance and its applications 30 Mar - 3 Apr 2026