Cationic dimers

Petrenko, A., K. Redding et al. (2005). The influence of the structure of the radical cation dimer pair of aromatic molecules on the principal values of a g-tensor DFT predictions. Chem. Phys. Lett. 406 327-331. 

A second example has been addressed in which the synthesis and potential application of a series of neutral O-glycosylated porphyrin dimers and two original O-glycosyl cationic dimers were examined in PDT. In order to understand the influence of the number of glycosyl moieties, the spatial geometry and the ionic character on their photodynamic activity was evaluated.144 The in vitro results... 

An elegant synthesis of a monomeric porphyrin intermediate bearing one pyridyl and three glycosyl units, precursor of cationic dimers, has also been described (Scheme 18).153 Thus pyrrole, p-formylphenyl 2,3,4,6-tetra-<9-acetyl-/i-D-... 

The lattice-stabilization effects allow the isolation of [MF6]- salts (M=As, Sb) of [S3N2]2+ in the solid state from the cycloaddition of [SN]+ and [S2N]+ cations in S02.66 The S-S and S-N bond distances in the planar, monomeric dication are shorter than those in the dimeric radical cation dimer, as anticipated for the removal of an electron from a n orbital. 

A similar concave-to-convex arrangement was recently proposed for the adduct of the radical cation dimer of corannulene with neutral corannulene, formed in a gas-phase. Becker, H. Javabery, G. Petrie, S. Cheng, P-C. Schwartz, H. Scott, L. T. Bohme, D. K. J. Am. Chem. Soc. 1993,115, 11636. 

The tetranuclear sulfur and selenium derivatives [E(AuPPh3)4]2+ show a square pyramidal geometry with the chalcogen atom in the apical position [241]. These cations dimerize in the solid state through Au-E interactions (Figure 1.40). Further auration of sulfur and selenium to give the penta- and hexa-nudear species has been achieved and trigonal bipyramidal and octahedral structures have been proposed [242]. 

In anodic oxidation of 2,3-diphenylindole (139) in CH3CN-Et4NC104, the initially formed radical-cation dimerizes to a product identified, primarily on the basis of 13C-NMR, as a 3-(5-indolyl)indolenine (140), which is formed in 90-95% yield203 [Eq. (93)]. 

The primarily formed radical-cation dimerizes at C-3 to bis(l-phenyl-A2-pyrazolin-3-yl) if C-3 is unsubstituted.281 By-products include biphenyl derivatives formed by an alternative dimerization of the parent radical-cation. The major product is further oxidized under the reaction conditions to stable cations. By blocking the para position of the phenyl ring in the 1-position, a persistent radical would be expected, and in the presence of a base, e.g., pyridine, the corresponding pyrazole was obtained.284,285 The anodic oxidation of 1,5-diphenyl-3-(4-hydroxycoumarinyl)-A2-pyrazoline in CH3CN-Et4NC104 solution, containing pyridine, resulted in the isolation of l,5-diphenyl-3-(4-hydroxycoumarinyl)pyrazole in 95% yield when the para position was not blocked.290... 

Bond Dissociation Energy of the Radical Cation Dimers of Diethyl Sulfide, Di-n-propyl Sulfide and Di-n-butyl Sulfide. 

As a result, it could be shown that both in the solid state and in solution the [ R2P(CH2)nPR2-K2P XRu=CHR]+cation dimerizes to form dicationic, dinuclear complexes [ R2P(CH2)nPR2-/c2P XRu=CHR 2]2+. In different crossover and trapping experiments, monomeric species could be found in solution. During the next pre-equilibrium step these monomeric complexes should form an olefin jt-complex. The product formation presumably proceeds via a metallacyclobutane according to the Chauvin metathesis mechanism (Figure 3.17) [48],... 

Figure 3.11 Schematic of the formation of ITQ-29, a purely siliceous version of the widely used zeolite A, using a large cationic dimer as a template [55],...

S. Scheiner, Proton transfers in hydrogen-bonded systems. 4. cationic dimers of NH3 and O H2 3. J. Phys. Chem. 86, 376-382 (1982)... 

Both the styrene monomer and the neutral dimer can trap a migrating positive hole or positive charge from solvent radical-cations (solventt) or related cationic species, which leads to the formation of radical cations, dimer cations, and bonded dimer cations. 

So as to get the strongest possible basicity, these biguanides were prepared with the highest possible degree of N-alkylation. However, no satisfactory precedure was described in the literature. So original synthetic methods were devised for this purpose. These rely essentially on the addition of guanidines to carbodiimides or of amines to cationic dimeric carbodiimides.18... 

In addition to UV/visible flash photolysis and TRIR spectroscopy, other techniques have been used for the detection of transition metal-noble gas interactions in the gas phase. The interaction of noble gases with transition metal ions has been studied in detail. A series of cationic dimeric species, ML" " (M = V, Cr, Fe, Co, Ni L = Ar, Kr, or Xe), have been detected by mass-spectroscopic methods (55-58). It should be noted that noble gas cations L+ are isoelectronic with halogen atoms, therefore, this series of complexes is not entirely unexpected. The bond dissociation energies of these unstable complexes (Table IV) were determined either from the observed diabatic dissociation thresholds obtained from their visible photodissociation spectra or from the threshold energy for collision-induced dissociation. The bond energies are found to increase linearly with the polarizability of the noble gas. 

S8 can undergo a SET oxidation by either 357 or Fe3 + to form a dimeric dication, 359, which upon the elimination of two protons results in the formation of the neutral dimer 362. Alternatively, 358 loses one proton, resulting in the formation of radical dimer 360, which is then oxidized to cation dimer 361. Deprotonation of 361 yields 362 [213],... 

Ronlin et al., 1973). A recent kinetic investigation produced a number of interesting results (Aalstad et al., 1981b). A nearly complete changeover in mechanism, from radical cation dimerization at high concentrations to radical... 

Surface Analysis Using Neutral Radicals as Probe Molecules 5.2.4. Metal-related Signals in Supported Catalysts Cation Dimers... 

DF. With large ( medium-sized) cations dimers and trimers of edge-sharing octahedra... 

P. M. S. Monk, R. D. Fairweather, M. D. Ingram, and J. A. Duffy, Evidence for the product of the viologen comproportionation reaction being a spin-paired radical cation dimer, J. Chem. Soc.,... 

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