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AffiliationN.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry of Siberian Branch of Russian Academy of Sciences,

Research area 03 - CHEMISTRY AND MATERIAL SCIENCES, 03-602 - Chemistry of new organic and hybrid functional materials

Annotation
Graphene is a two-dimensional crystal demonstrating a unique set of optical, electrical and mechanical properties (Rev. Mod. Phys. 2009b 81, 109). Recently, graphene magnetism associated with the ferromagnetic state of its zigzag edges has attracted interest (Nanotechnology, 2010, 21, 302001, Review of Modern Physics 2016, 88, 025005). Researchers agree that the realization of processes of coherent manipulation of edge state graphene spins can become an important milestone in the creation of working devices for spintronics and quantum computers (Nature Materials 2012, 11, 409; Nature Physics 2007, 3, 192). However, there is a serious problem impeding the practical implementation of these ideas. It is connected with the fact that each time the nanocarbons studied are single objects characterized by the shape of the edges and the length of magnetically active zigzag fragments, which, moreover, are also chemically extremely unstable (Physical Review B, 2011, 83, 045414; Nano Letters 2006, 6, 2748). The solution consists in developing a directed synthesis of stable molecular graphene nanocarbon structures bearing stable radical groups. Similar works performed at the junction of two directions: the chemistry and physics of organic high-spin systems and nanocarbon materials are not available in the literature. On this topic there is only one work done with the direct participation of the author of the project, which was accepted for publication shortly before the project was written (M. Slota, A. Keerthi, WK Myers, E. Tretyakov, M. Baumgarten, A. Ardavan, H. Sadeghi , CJ Lambert, A. Narita, K. Müllen, L. Bogani, Nature, 2017, accepted). The first example of obtaining a spin-labeled graphene nanocarbon with atomic and magnetic accuracy using the "bottom-up" technology is described. The synthesized magnetically active graphene is stable under ordinary conditions, and, at the same time, contains two ensembles of spin systems: edge delocalized spins of the actual nanografen and localized spins of the radical groups. Using the time-resolved ESR, it was shown that in the resulting compound, the spin relaxation time is 1.1 μs at 85 K and 0.55 μs at 300 K. Since the observed reversal times of the edge spins turned out to be much shorter, ~ 300 ns, this allowed us to realize for the first time in coherent manipulations state of the spins of different carriers. The result is outstanding, but obviously requires a systematic study aimed at revealing the magnetic-structural correlations of a wide range of spin-labeled graphene nanocarbons with subsequent optimization of their structure. For this purpose it is proposed to found a new direction of research, namely, molecular design for graphene magnets with an output in the future on materials suitable for their electronic and magnetic characteristics for solving actual problems of spintronics, such as electronic detection of spin states and realization of quantum operations by means of a single conducting electron (Reviews of Modern Physics 2007, 79 , 1217, Science 2005, 309, 2180).

Expected results
The project will result in the creation of a new direction of research - the design of magnetic graphene materials, by successively assembling graphene-like structures carrying alkyl or polyfluoroalkyl groups and stable organic paramagnetic groups. The synthesis of "bottom-up" spin-labeled graphenes with atomic and magnetic accuracy will open unprecedented opportunities for obtaining magnetically active graphene materials with two or more types of spin-oriented spin carriers. Unlike classical methods involving the separation of graphene layers, cutting it into fragments (Physica E 2007, 40, 228), unfolding carbon nanotubes (Nature 2009, 458, 872), providing a random configuration of the edges and magnetic states, a new approach makes it possible to obtain long (up to 700 nm) graphene structures with a width of 1-2 nm with a given periphery. In the course of the project, we plan to reach a wide range of magnetic graphene materials, identify their inherent magneto-structural correlations, study them using stationary, pulsed and time-resolved EPR methods, as well as scanning electron spectroscopy.

Annotation of the results obtained in 2020
Some of the most significant results include the following: 1. An approach to the production of nanocarbon magnetic materials based on the functionalization of the edges of graphene nanostructures by radical groups is analyzed for the first time. The result is presented in the review “From spin-labeled condensed polyaromatic compounds to magnetically active graphene nanostructures” published in the journal Uspekhi Khimii (Russ. Chem. Rev., 2020, 89, 693-712). The review considers the synthesis and properties of the closest precursors of spin-labeled graphene structures - condensed polycyclic aromatic hydrocarbons and heteroatomic analogs carrying nitroxyl groups, and an analysis of their inherent magneto-structural correlations. This view of the problem of obtaining magnetically active graphene nanostructures is presented in the literature for the first time, and it allows rational use of the achievements of the chemistry of organic paramagnets in the molecular design of magnetic graphene nanostructures. 2. A series of paramagnetic blocks with a localized or delocalized spin density or their diamagnetic precursors, including previously unknown ones, have been obtained and fully characterized. For the first time, polyfluorinated iodo- and acetylenyl-substituted nitroxyl radicals were obtained and isolated in free form using the reaction of nucleophilic substitution of a fluorine atom. Their molecular and crystal structures have been established, and the possibility of their introduction into the hexabenzooronene backbone has been shown. 3. Methods for obtaining fluorinated hexaphenylbenzenes and hexabenzocoronenes have been developed. A multistage assembly of hexabenzocoronenes with phenoxyl, hybrid phenoxyl-nitroxyl and nitroxyl spin labels (12-15 stages!), Representing the first high-spin systems with a hexabenzocoronene backbone, has been proposed and implemented. The synthesized spin-labeled hexabenzocoronenes have been fully characterized by EPR, IR, UV, and mass spectroscopy. It was found that the obtained high-spin molecules are prone to aggregation, and, depending on the structure, strong or weak intramolecular exchange interactions on the EPR scale are realized. 4. Various approaches to the synthesis of magnetically active graphene nanostructures have been studied. Model experiments have been carried out, including those that showed the introduction of spin labels into the peri-positions of graphene structures to be unlikely. Taking into account the accumulated experience, the multistage synthesis (14-17 stages!) Of graphene nanoribbons with a high content of spin labels (~ 90%) has been successfully implemented for the first time. The acetylene derivative of pyrroline-1-oxyl radical and phenyl-substituted 3-imidazoline-1-oxyl radicals were used as such. The resulting graphene spin-labeled nanoribbons are fully characterized by EPR, IR and UV spectroscopy. According to EPR monitoring data, the synthesized paramagnetic graphene nanoribbons are stable under normal conditions and long-term storage. When a graphene nanoribbon molecule, carrying pyrroline-1-oxyl radicals along the edges, is deposited onto the gold surface, they tend to parallel packing, the periodicity of which is ~ 5.1 nm, which corresponds to the nanoribbon width.

Publications

1. E. Tretyakov, A. Tkacheva, G. Romanenko, A. Bogomyakov, D. Stass, A. Maryasov, E. Zueva, B. Trofimov, V. Ovcharenko. (Pyrrole-2,5-Diyl)-Bis(Nitronyl Nitroxide) andBis(Iminonitroxide): Specific Features of the Synthesis, Structure, and Magnetic Properties. Molecules, 25, 1503 (year - 2020) https://doi.org/10.3390/molecules25071503

2. E.V. Tretyakov, S.I. Zhivetyeva, P.V. Petunin, D.E. Gorbunov, N.P. Gritsan, I.Yu. Bagryanskaya, A.S. Bogomyakov, P.S. Postnikov, M.S. Kazantsev, M.E. Trusova, I.K. Shundrina, E.V. Zaytseva, D.A. Parkhomenko, E.G. Bagryanskaya, V.I. Ovcharenko Ferromagnetically Coupled S = 1 Chains in Crystals of Verdazyl-Nitronyl Nitroxide Diradicals Angewandte Chemie International Edition, 59, 20704–20710 (year - 2020) https://doi.org/10.1002/anie.202010041

3. L.V. Politanskaya, P.A. Fedyushin, T.V. Rybalova, A.S. Bogomyakov N.B. Asanbaeva, E.V. Tretyakov Fluorinated Organic Paramagnetic Building Blocks for Cross-Coupling Reactions. Molecules, 25, 5427 (year - 2020) https://doi.org/10.3390/molecules25225427

4. Yury Ten, Konstantin Lomanovich, Dmitrii Mazhukin, Nadezhda Troshkova, Elena Bagryanskaya, Evgeny Tretyakov A Biradical with a Hexa-peri-Hexabenzocoronene Core Molecules, - (year - 2021)

Annotation of the results obtained in 2018
Graphene is a two-dimensional crystal that exhibits a unique set of optical, electrical, and mechanical properties [Rev. Mod. Phys. 2009, 81, 109]. Recently, magnetism of graphene fragments with zigzag edges has attracted interest [Nanotechnology 2010, 21, 302001; Review of Modern Physics 2016, 88, 025005], since such fragments can serve as working elements of spintronics and quantum computers [Nature Materials 2012, 11, 409; Nature Physics 2007, 3, 192]. The molecular design of magnetically active graphene materials is designed to solve the problem of assembling them with atomic and magnetic precision [Nature, 2018, 557, 691], which is unavailable in the framework of “top-down” technologies and is necessary for solving such urgent spintronics problems as, for example, electronic detection of spin states and the implementation of quantum operations through a single conducting electron [Reviews of Modern Physics 2007, 79, 1217; Science 2005, 309, 2180]. The project is aimed to perform molecular design of various magnetically active, stable graphene systems, based on the functionalization of the edges of graphene nanostructures by radical groups. The first steps were the synthesis of key halogen-substituted graphene nanostructures (Hal-GNS) of cyclic and linear structure, capable of entering into cross-coupling reactions with paramagnetic reagents (FG-N–O•) with the formation of high-spin systems. In order to assess the degree of radicalization of the graphene nanoribbling and polymer precursor, as well as optimize the reaction of cross-combination of bromine derivatives with NN – Au – PPh3, samples of NN-GNR were synthesized. Using quantitative EPR, Cu(acac)2 and DPPH as standards, precision and independent measurements of the degree of radicalization of the polymer and graphene nanotape were first carried out. It is shown that the use of the cross-coupling reaction gives products with a low radicalization value, about 1.3% for the NN-GNR. To estimate the expected values of J1 and J2, quantum-chemical calculations of flat fragments of nanoribbons were carried out up to the maximum possible fragments for the selected computational approaches (GGA + U). It is shown that the exchange interaction between the paramagnetic centers across the ribbon is antiferromagnetic in nature, its parameter is 0.2–0.4 cm–1, while the value of the exchange parameter along the ribbon is an order of magnitude smaller, J = ~ 0.06 cm–1. The parameters of J1 and J2 measured by us in the synthesized NN-GNR samples were much lower than the calculated ones and were J1 = –8.3∙10–4 cm–1 and J2 = 4.0∙10–4 cm–1. The difference between the calculated and experimental values of J is related to the low degree of radicalization of GNR, which according to quantitative EPR is close to 1%, which, with an average length of graphene nano tape of about 100 nm, gives from two to three radical groups distributed randomly within the nano tape. The obtained data on the low efficiency of cross-coupling with NN–Au–PPh3 required the search for conditions for this reaction. It was found that the gold complex is significantly more stable in DMF; it can be heated to 80–85 oC, and at the same time it reacts with aryl halides in the presence of Pd(PPh3)4. This allows us to consider the reaction of cross-combination as the main approach to the chemical assembly of magnets based on graphene systems.

Publications

1. Morozov V., Tretyakov E. Spin injection on the edge of graphene nano-ribbons Journal of Molecular Modeling, - (year - 2019)

2. Stass D.V., Tretyakov E.V. Estimation of absolute spin counts in nitronyl nitroxide-bearing graphene nanoribbons Applied Magnetic Resonance, - (year - 2019)

3. Politanskaya L.V, Selivanova G.A., Panteleeva E.V., Tretyakov E.V., et al. Современная фторорганическая химия в России Успехи химии, - (year - 2019)

4. Tretyakov E. Графеновые наноструктуры, несущие стабильные радикальные группировки Молодёжная научная школа-конференция "Актуальные проблемы органической химии", - (year - 2018)

5. Tretyakov E.V., Troshkova N.M. СБОРКА ГРАФЕНОВЫХ НАНОСТРУКТУР, НЕСУЩИХ СТАБИЛЬНЫЕ РАДИКАЛЬНЫЕ ГРУППИРОВКИ V Всероссийская с международным участием конференция по органической химии, - (year - 2018)

6. - Сибирский ученый нашел ключ к магнетизму нанолент из графена Наука в Сибири, - (year - )

Annotation of the results obtained in 2019
The molecular design of magnetically active graphene nanoscale structures is a new field of research aimed at producing graphene nanoribbons, as well as graphene quantum dots with specified electronic, optical, and magnetic properties. Graphene ribbons with “armchair” type edges are diamagnetic; they exhibit the properties of semiconductors with a band gap that varies depending on the width of the tape. Tapes with zigzag edges are antiferromagnets with spin density concentrated on the edges of nanoribbons and the band gap of <0.1 eV. Such zigzag ribbons can serve as working elements of spintronics, playing the role of spin nanodiodes and transistors. However, due to the fact that ribbons with zigzag edges are radical-like in nature, they have a high reactivity. The research within the framework of the project is unique and aimed at obtaining stable magnetically active graphene nanostructures by functionalizing the edges of graphene nanomolecules by radical groups. The essence of research carried out within the framework of the project is the synthesis of graphene nanostructures from the bottom up, when the required high-spin nanomolecule is assembled from smaller molecular fragments by means of constructive organic reactions. Magnetically active graphene nanostructures obtained in this way are in demand for solving urgent problems of spintronics, for example, implementing electronic detection of spin states and performing quantum operations using a single conducting electron [Reviews of Modern Physics 2007, 79, 1217; Science 2005, 309, 2180]. During the implementation of the project, an approach to obtaining stable magnetically active graphene nanostructures based on the functionalization of the edges of graphene nanostructures by radical groups was further developed. Optimized for the yield of the alkylation stage of the bromo derivatives of arenes with dodecyl magnesium bromide. New high-spin graphene nanoribbons with an average length of ~ 100 nm and a high content of radical groups have been obtained. A multi-stage synthesis of a number of both previously obtained and new halogen derivatives of hexaphenylbenzenes substituted by alkyl groups — precursors of high-spin hexabenzocoronenes — is realized.

Publications

1. Ten Yu.A., Troshkova N.M., Tretyakov E.V. Метод получения алкилированных 1,3-дифенилпропан-2-онов — компонентов сборки графеновых наноструктур Известия Академии наук. Серия химическая, 2020, № 1, 172-175 (year - 2020)

2. Ten Yu.A., Troshkova N.M., Tretyakov E.V. От спин-меченых конденсированных полиароматических соединений к магнитно-активным графеновым наноструктурам Успехи химии, - (year - 2020)

3. Ten Yu., Troshkova N., Tretyakov E. A novel synthetic approach to alkylated 1,3-diphenyl-2-propanones – key building blocks in design of graphene nanostructures International Conference ORGEL-2019, - (year - 2019)

4. Tretyakov E., Troshkova N. Graphene boom, quo vadis? A historical perspective from an organic chemist’s viewpoint Markovnikov Congress on organic chemistry, - (year - 2019)

5. Tretyakov E., Troshkova N., Ten Yu., Keerthi A., Baumgarten M., Narita A., Müllen K., Slota M., Bogani L. Spin-labeled graphene nanoribbons for organic electronics and spintronics International Conference ORGEL-2019, - (year - 2019)

6. Tretyakov E., Troshkova N., Ten Yu., Keerthi A., Baumgarten M., Narita A., Müllen K., Slota M., Bogani L. Design of Magnetic Edge States in Graphene Nanoribbons 2nd Global Conference on Magnetism and Magnetic Materials, - (year - 2019)

7. Tretyakov E.V., Troshkova N.M., Ten Yu.A., Gurskaya L.Yu., Zhivetyeva S.I., Zayakin I.A., Panteleeva E.V., Fedushin P.A. Высокоспиновые органические молекулы Химия и химическая технология в XXI веке, - (year - 2019)