Toward a more general synthetic route to paramagnetic solids containing RCNSSS*+ radical cations. A structure-property correlation for RCNSSS*+ (R = F5C2, Cl3C)

Reaction of Cl3CN and F5C2CN with a 1:1 mixture of S4(AsF6)2 and S8(AsF6)2 affords the paramagnetic solids Cl3CNSSSAsF6 (1CCl3AsF6) and F5C2CNSSSAsF6 (1C2F5AsF6). Isotropic electron paramagnetic resonance spectra of 1CCl3AsF6 and 1C2F5AsF6 in SO2 consist of a single line with g = 2.01675 and 2.01580, respectively. The structure of 1CCl3AsF6 contains chains of radical cations with relatively close interchain interactions. In contrast, chains are isolated in 1C2F5AsF6. The magnetic behavior of both compounds was interpreted as that of 1D Heisenberg antiferromagnetic chains (1CCl3AsF6, J = -34 cm(-1), theta = -9 cm(-1), TIP = 0.00082, rho = 0.012; 1C2F5AsF6, J = -21 cm(-1), theta = -4.2 cm(-1), TIP = 0.00092, rho = 0.065). Density functional theory calculated and experimental magnetic coupling constants were in good agreement. The correlation between intermolecular S...S contacts and the strength of magnetic couplings was established.     

Bonding between Cu(II) complexes with celluloses and related carbohydrates

The electron paramagnetic resonance spectra of cupriethylenediamine dihydroxide and cupriammonium hydroxide when complexed with cellulose, hydrocellulose, maltose, and dextrose at ?160°C and at room temperature are reported. The spectra of the complexes formed indicate that the interaction is not physical but a chemical one, and the covalent character of the copper ligand has become comparatively weaker. The possibility of weak axial interaction for these complexes is shown to be unlikely, and it is proved that the nature of the interaction is a strong chemical bond between the copper and the 2,3-hydroxyl groups of the pyranoside ring of the ligand.     

Evolution of the pseudo-1,3-dipolar cycloaddition chemistry of SNSMF6 (M = As, Sb) leading to 2,5-dihydroxybenzo-1,3,2-dithiazolylium and 2,7-dicarbonylnaphtha-1,3,2-dithiazolylium salts and their corresponding radicals

We report the unprecedented formation of a benzo-fused 1,3,2-dithiazolylium [AsF6-] salt by a one step, quantitative, cycloaddition of SNSAsF6 with 1,4-benzoquinone. In contrast, the reaction of SNSSbF6 with 1,4-naphthaquinone results in 2,7-dicarbonylnaphtha-1,3,2-dithiazolylium [SbF6-]. Both were reduced to the corresponding 7pi radicals.     

Transform-Limited Pulses Are Not Optimal for Resonant Multiphoton Transitions

Maximizing nonlinear light-matter interactions is a primary motive for compressing laser pulses to achieve ultrashort transform limited pulses. Here we show how, by appropriately shaping the pulses, resonant multiphoton transitions can be enhanced significantly beyond the level achieved by maximizing the pulse's peak intensity. We demonstrate the counterintuitive nature of this effect with an experiment in a resonant two-photon absorption, in which, by selectively removing certain spectral bands, the peak intensity of the pulse is reduced by a factor of 40, yet the absorption rate is doubled. Furthermore, by suitably designing the spectral phase of the pulse, we increase the absorption rate by a factor of 7.     

Accurate calculation of the phenyl radical's magnetic inequivalency, relative orientations of its spin hamiltonian tensors, and its electronic spectrum

The phenyl radical's electronic structure, magnetic inequivalency, spin Hamiltonian tensor components, and the relative orientation of their principal axes are computed by Neese's coupled-perturbed Kohn-Sham hybrid density functional (CPKS-HDF) technique in a moderate amount of time without resorting to expensive post-Hartree-Fock techniques. The g tensor component values are in excellent agreement with those determined experimentally and differ by less than 370 ppm. The computed hydrogen nuclear hyperfine tensors, A(1H), are also found to be in very good agreement with their experimental counterparts. The correlation of the radical's electronic structure with its g and A numerical values corroborates that it has a 2A(1) ground state. In accordance with our previous studies on the equivalency of planar radicals that possess C(2v) symmetry, the in-plane g and A(1H) principal axes should not be parallel to one another. Consequently, the spatially equivalent ortho (1H(2), 1H(6)) and meta (1H(3), 1H(5)) proton pairs should be magnetically inequivalent. This was confirmed in both the present computations and the simulation of the EPR solid-state spectrum. To the best of our knowledge, this is the first aromatic in-plane sigma-type radical whose magnetic inequivalency is studied both computationally and experimentally. To properly interpret the radical's electronic excitation spectra, the spectroscopy-oriented dedicated difference configuration interaction (SORCI) procedure was employed. Aside from a slight overestimation, the method seems to be capable of reproducing the C(6)H(5)* electronic vertical excitation energies in the range of 0-50,000 cm(-1). These vertical excitations, in conjunction with the corresponding orbit and spin orbit matrix elements, were also used to compute the g tensor components, employing the sum-over-states technique. Due to the limited number of computed roots and excited states, the results were marginally inferior to those obtained using the CPKS-HDF method.