Thermally stable organic diradicals with at riplet ground state along with large singlet-triplet energy gap have significant potential for advanced technological applications.A series of phenylene-bridged diradicals with oxoverdazyla nd nitronyl nitroxide units were synthesized via ap alladiumcatalyzedc ross-coupling reaction of iodoverdazyls with an itronyl nitroxide-2-ide gold(I) complex with high yields.T he diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 8 8C. Fort he diradicals,b oth substantial AF (DE ST %À64 cm À1)a nd FM (DE ST ! 25 and 100 cm À1)intramolecular exchange interactions were observed. The sign of the exchange interaction is determined both by the bridging moiety (para-or meta-phenylene) and by the type of oxoverdazylb lock(C-linked or N-linked). Upon crystallization, diradicals with the triplet ground state form unique onedimensional exchange-coupled chains with strong intra-and weak inter-diradical ferromagnetic coupling.

Thermally resistant air-stable organic triradicals with a quartet ground state and a large energy gap between spin states are still unique compounds. Moreover, stable triradicals with bridging units of the ethylene-1,1-diyl type and ferromagnetic coupling are limited to the family of nitroxides. In this work, for the first time, we designed and prepared the triradical having a quartet ground state based on oxoverdazyl and nitronyl nitroxide radical fragments. The triradical and appropriate triplet diradical precursor were synthesized via a palladium-catalyzed cross-coupling reaction of diiodoverdazyl with nitronyl nitroxide-2-ide gold(I) complex. Both the di-and triradical are air-stable and possess good thermal stability with decomposition onset at ∼160 °C in an inert atmosphere. X-ray diffraction analysis of single crystals confirmed the presence of verdazyl and nitroxide radical centers. In the diradical, the verdazyl and nitronyl nitroxide centers showed fully reversible redox waves. In case of the triradical, the electrochemical processes occur practically at the same redox potentials but become quasi-reversible for the nitroxide moieties. Magnetic properties of the di-and triradical were characterized by a SQUID magnetometry of polycrystalline powders and by EPR spectroscopy in different matrices. Collected data analyzed using of the highlevel quantum chemical calculations confirmed that the di-and triradical have high-spin ground states. Unique high stability of prepared verdazyl-nitronylnitroxyl triradical opens new perspectives for further functionalization and design of high-spin systems with four or more spins.

A general and effective method for the synthesis of 3‐phenylveradzyl radicals bearing a variety of iodophenyl substituents has been developed. The synthesized radicals have been characterized by ESR, UV/Vis spectroscopy, and cyclic voltammetry. Structures of biphenyl‐substituted radicals have been solved by X‐ray crystal structure analysis. The synthesized iodoverdazyls are applicable in the Sonogashira coupling reaction for the preparation of a wide range of ethynyl derivatives. Both N‐2 and C‐6 substituents were functionalized through Sonogashira coupling.

A novel approach to the preparation of stable Pd-substituted verdazyls was developed through the direct oxidative addition of iodoverdazyls to Pd(PPh3)4.

An antiferromagnetically (AFM) coupled biradical based on oxoverdazyl and nitronylnitroxide was synthesized in 46 % yield using Sonogashira coupling. The obtained heterobiradical evidenced distinct properties of both radical entities in solution. Depending on the solvent, the prepared biradical crystallized in two different forms. SQUID magnetization measurements on Form II showed coupling constants J intraII /k B = À 2.1 K and zJ interII / k B = À 11.5 K. Consequently, total intermolecular exchange interactions are five times larger than the intramolecular ones. Further, DFT calculations explained this phenomenon and indicated the advantage of Form I for further in-depth investigations.Weakly antiferromagnetically coupled (AFM) crystalline spin-1 = 2 dimers can serve to investigate critical phenomena such as, the formation of triplon excitations and their interactions in a magnetic field strong enough to close the singlet-triplet gap of the biradicals. Depending on the interdimer exchange interaction (J inter ) relative to the intradimer exchange interaction (J intra ) different dimensionalities of spin systems in a crystalline solid can be observed, such as one-dimensional (1D) spin-ladder systems showing Luttinger-liquid behavior, [1] two-dimensional (2D) Berezinskii-Kosterlitz-Thouless networks, [2] or three-dimensional (3D) Bose-Einstein condensation (BEC) of triplon excitations. [3] Therefore a control of J intra as well as J inter is essential and we have shown earlier that this is possible in organic biradicals, where the intramolecular interactions can be fine-tuned through the applied spacer between the radical units. [4] Besides changing the bridge between the two radical units, two different stable radicals can also be applied for varying the exchange interaction with a given spacer as exhibited for a tetramethoxypyrene with mixed nitronylnitroxide and iminonitroxide. [5] Earlier, we tested two nitronylnitroxides (NN) depicted as A [6,7] in Figure 1 and two iminonitroxides (IN) shown as B [8] with a tolane bridge (1,2-bis(phenyl) acetylene) for achieving 2D and 3D ordering of triplon excitations of these spin dimers in the crystal lattice.. Therefore in the present work, we consider a combination of nitronylnitroxide (NN) and oxoverdazyl radicals (VZ), which is derived from the described homobiradicals A and B (Figure 1). While it is difficult to achieve such a hetero-biradical upon two different kinds of condensation of dialdehyde precursors, Sonogashira [a] Dr.Figure 1. Homobiradicals A and B and the newly designed heterobiradical 1 with tolane bridge.coupling between the two different radical fragments is considered as a prospective pathway.The hetero-biradical 1 was prepared by using a convergent approach that included the reaction between ethynyl-and iodo-substituted radicals (Scheme 1). Both building blocks were synthesized via well-established procedures: verdazyl 2 was prepared from 4-iodobenzaldehyde via published method [9] and the NNR 3 was synthesized according to Klyatskaya et al. [10] Th...

Thermally stable organic diradicals with at riplet ground state along with large singlet-triplet energy gap have significant potential for advanced technological applications.A series of phenylene-bridged diradicals with oxoverdazyla nd nitronyl nitroxide units were synthesized via ap alladiumcatalyzedc ross-coupling reaction of iodoverdazyls with an itronyl nitroxide-2-ide gold(I) complex with high yields.T he diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 8 8C. Fort he diradicals,b oth substantial AF (DE ST %À64 cm À1)a nd FM (DE ST ! 25 and 100 cm À1)intramolecular exchange interactions were observed. The sign of the exchange interaction is determined both by the bridging moiety (para-or meta-phenylene) and by the type of oxoverdazylb lock(C-linked or N-linked). Upon crystallization, diradicals with the triplet ground state form unique onedimensional exchange-coupled chains with strong intra-and weak inter-diradical ferromagnetic coupling.

Iodine‐ and ethynyl‐containing 'Kuhn'‐verdazyls, oxoverdazyls, and nitronyl nitroxides were investigated as building blocks for the preparation of multi‐spin systems via the Sonogashira reaction, and, as a result, eleven diradicals were prepared with fair yields. The reactivity of the building blocks indicates that oxoverdazyl iodides are effective starting components for the synthesis of diradicals via the Sonogashira coupling. The described one‐step protocol allows combining different spin units, thereby facilitating the design of tolane‐bridged diradicals and screening of their properties. The novel compounds were characterized by cyclic voltammetry, UV/Vis and electron spin resonance (ESR) spectroscopy. Although the electrochemical investigation and electronic spectra showed a negligible influence of radical moieties on each other, ESR data revealed a strong exchange interaction between two unpaired electrons. The prepared verdazyl‐nitronylnitroxide diradicals have high stability at storage and hold promise for further investigation and application.

The local surface plasmon resonances of gold nanoparticles have the potential to create alternative pathways for organic chemical reactions. These transformations depend on various physical factors, such as the temperature, illumination regime, and nanoparticle type. However, the role of chemical factors associated with organic reactants, including the molecular structure, electronic effects, and bonding with the metal surface, is often underestimated. To explore the role of these chemical factors, we synthesized five alkoxyamines (AAs) with different chemical and electronic structures and used electron paramagnetic resonance spectroscopy to study the kinetics of plasmon-induced homolysis. The kinetic data revealed that the rate constant (k d) for plasmon-assisted homolysis is dependent on the highest occupied molecular orbital (HOMO) energy of the AAs, which cannot be described by the kinetic parameters or activation energies observed in thermal homolysis experiments. The proximity of the HOMO to the Fermi energy (E f) of Au led to a more active decrease in the energy required to excite the adsorbate. The observed trend in k d indicates that the intramolecular excitation mechanism plays a key role instead of other commonly accepted mechanisms, which is supported by DFT calculations, spectroscopic characterization, and numerous control experiments. The intramolecular excitation mechanism is the most relevant explanation for the plasmon-induced homolysis of AAs. This observation suggests that the electronic structures of the organic molecules may play a key role in other related reactions used to study the mechanisms of plasmon catalysis.