Polyradical

In molecules with more than one unpaired electron, electron-electron interactions can have a significant role in the stabilization of the system. Bond formation that results from direct overlap is highly favorable and, thus is an overriding consideration in all low-spin polyradicals, even to the extent that the system sometimes adopts a strained, closed-shell state as opposed to a polyradical. In cases in which bonding cannot occur, indirect interactions that are usually insignificant, such as electron exchange and spin-polarization, can have significant impact. The presence of these interactions is often reflected in the thermochemical properties. 

The spiro polymerization is a novel reaction type that uses the spiro dimerization of o-QMs to build up linear oligomers and polymers. The basic properties of the spiro dimer of a-tocopherol, that is, its fluxional structure and its ready reduction to the ethano-dimer, remain also active when such structural units are bound in the polymer. The products of the reaction, both in its poly(spiro dimeric) form (41) and in the form of the reduced polytocopherols (42), are interesting materials for application as high-capacity antioxidants, polyradical precursors, or organic metals, to name but a few. 

For a recent theoretical investigation on the energy, spectra and magnetic properties of polymers derived from the polyradical ions of infinite radialenes, see N. Tyutyulkov, F. Dietz, K. Mullen, M. Baumgarten and S. Karabunarliev, Chem. Phys., 189, 83 (1994). 

The physical organic chemistry of very high-spin polyradicals, 40, 153 Thermodynamic stabilities of carbocations, 37, 57 Topochemical phenomena in solid-slate chemistry, 15, 63 Transition state analysis using multiple kinetic isotope effects, 37, 239 Transition state structure, crystallographic approaches to, 29, 87 Transition state structure, in solution, effective charge and 27, 1... 

Rajca, A. Wongsriratanakul, J. Rajca, S. Cemy, R. A Dendritic Macrocyclic Organic Polyradical With a Very High Spin of S = 10. Angew. Chem., Int. Ed. 1998, 37, 1229-1232. 

All the theories predict that polyradicals [14] consisting of w-diphenylmethyl units connected at w-positions should have S = mil and spin multiplicities of w + 1. The exchange interactions between the radical centres in [14] are estimated to be 0.2055 and 0.0012 eV for the first and second neighbours, respectively (Tyutyulkov and Karabunarliev, 1986). 

While rather lengthy synthetic efforts may be necessary for constructing high-spin polyradicals, samples having intermolecular spin order can be prepared by a combination of rather simple components like appropriate donors and acceptors. 

Uses Chemical intermediate in numerous applications and in the formation of polyradicals for resins insecticides and dyestuffs. Derived from industrial and experimental coal gasification operations where the maximum concentrations detected in gas, liquid, and coal tar streams were 9.1, 0.057, and 8.0 mg/m, respectively (Cleland, 1981). 

In principle, an organic molecule can accept as many electron pairs as it has low-lying vacant orbitals. In the same way, high-lying occupied orbitals can release not a single, but several electrons. Such multielectron processes can result in the formation of polyion-polyradicals. As will be seen from this section, the main topic of interest in poly(ion-radicals) consists of their spin multiplicity. 

From the materials just mentioned earlier, one can conclude that mutual meta orientation (meta through a benzene) of the spin-bearing moieties is an indispensable condition for the existence of triplet states in aromatic di- or tri-(cation-radical)s. However, in fact, these systems have both singlet and triplet forms, and the questions are about what is the difference in the corresponding energy and which state is more stable. Stability of the polyion-polyradicals is also a very important factor, especially in the sense of practical application. Let us consider several relevant examples. 

The catalyst thus acts as a sort of polyradical influencing the course of the reaction in the same manner in which the introduction of free radicals into a homogeneous medium affects the course of a homogeneous reaction. In both cases, the reaction is accelerated because of the participation of the free valencies. In the case of heterogeneous catalysis, these free valencies are introduced by the catalyst itself. In the final account, it is they who sustain and regulate the process. 

Our choice was the two series of dendritic polymers 5 and 6, depicted in Figure 4, which have all their open-shell centers (or trivalent carbon atoms) sterically shielded by an encapsulation with six bulky chlorine atoms in order to increase their life expectancies and thermal and chemical stabilities. Indeed, it is very well known that the monoradical counterpart of both series of polyradicals, the perchlo-rotriphenyl methyl radical, shows an astonishing thermal and chemical stability for which the term of inert free radical was coined. The series of dendrimer polymers 5 and 6 differ in the nature and multiplicity (or branching) of their central core unit, N, as well as in their branch-juncture multiplicities, N Thus, series 5 has a hyperbranched topology with = 3 and = 4, while dendrimer series 6 has a lower level of branching with = 3 and = 2, and the topology of a three-coordinated Cayley tree. 

Rajca and co-workers have studied star-branched and dendritic high-spin polyradicals which are potential organic magnets. Representative data were obtained for the model tetra-anionic compound 55. Three redox waves were observed by cyclic voltammetry and differential pulse voltammetry for a four-electron process between the potentials of -2.00 and -1.20 V (vs. SCE). Electrochemical experiments with these materials have usually been performed at 200 K. The polyradicals, which are less stable for systems with more unpaired electrons, have been characterized by spectroscopic studies, ESR data, and SQUID magnetometiy. 

R. A. Forrester, K. Ishizu, G. Kothe, S. F. Nelson, H. Ohya-Nishiguchi, K. Watanabe, and W. Wilker, Organic Cation Radicals and Polyradicals, in Landolt Bornstein, Numerical Data and Functional Relationships in Science and Technology, Vol. IX, Part d2. Springer-Verlag, Heidelberg, 1980. 

Title Method for Manufacturing Polyradical Compound and Battery... 

Research Focus Identification of polyradicals having a high capacity density from which a large current can be extracted for use as components in secondary... 

Originality Six-year ongoing investigation using polyradicals in secondary battery... 

Graft copolymers were prepared by polymerizing ethylene oxide onto the PVN polyradical anion (10), The latter was obtained by reaction of PVN with cesium in tetrahydrofuran solution. The copolymers were extracted with water to remove the PEO homopolymer which was formed as a byproduct. Experimental details and evidence for bond formation between ethylene oxide and the aromatic moiety were presented elsewhere (//). 

Only Kekulean benzenoid and coronoid hydrocarbons are known to exist. Non-Kekulean benzenoid and coronoid systems have never been synthesized [2-6], they should be polyradicals and have very low chemical stability. 

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