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2‐(8‐Iodonaphthalen‐1‐yl)‐Substituted Nitronyl Nitroxide: Suppressed Reactivity of Iodine Atom and Unusual Temperature Dynamics of the EPR Spectrum
Author(s) -
Tretyakov Evgeny V.,
Lomanovich Konstantin A.,
Bagryanskaya Elena G.,
Romanenko Galina V.,
Bogomyakov Artem S.,
Zueva Ekaterina M.,
Petrova Maria M.,
Dmitriev Alexey A.,
Gritsan Nina P.
Publication year - 2021
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.202100138
Subject(s) - chemistry , diradical , electron paramagnetic resonance , nitroxide mediated radical polymerization , paramagnetism , computational chemistry , atom (system on chip) , basis set , crystallography , moiety , stereochemistry , density functional theory , nuclear magnetic resonance , condensed matter physics , atomic physics , organic chemistry , polymerization , physics , singlet state , computer science , embedded system , excited state , polymer , radical polymerization
Abstract While developing methods for obtaining high‐spin graphene nanostructures, we carried out a model cross‐coupling reaction between 1,8‐diiodonaphthalene and an organogold derivative of a nitronyl nitroxide. It was found that only one iodine atom reacted, leading to the corresponding 8‐iodonaphthalen‐1‐yl‐substituted nitronyl nitroxide. The latter was successfully isolated as two polymorphic modifications, whose X‐ray structural analysis revealed a strong distortion of the paramagnet's geometry in comparison with a noniodinated analog. Moreover, the spatial proximity of the heavy iodine atom and the paramagnetic moiety resulted in unprecedented temperature dynamics of the EPR spectrum. To clarify these dynamics, quantum chemical calculations were performed using the exact two‐component relativistic X2C method with the self‐consistent account of spin‐orbit coupling in conjunction with the B3LYP functional and relativistic STO‐type basis set. These computations predicted a reasonable a iso ( 127 I) value that can affect the EPR spectrum. Substitution of the second iodine atom would lead to the formation of a diradical with a 1,8‐naphthalenediyl bridge, whose structure and magnetic properties were analyzed at the DFT level. Two stable conformations of the diradical with strongly distorted geometry were identified. In both conformations, calculations predict a ferromagnetic exchange between the paramagnetic centers with J =8 and 14 cm −1 ( H=−2 J⋅S 1 S 2 ).