Adolfo R. Gutierrez

Photochemical and kinetic studies of some metal dithizonate complexes

Abstract The kinetics of the approach to photostationary state have been studied for Hg(HDz) 2 in benzene and toluene, and for Ag(HDz)) in tetrahydrofuran, where HDz − is the anion of dithizone (diphenylthiocarbazone). Photolysis converts the normal orange form to an unstable blue form which, while photointert, reverts thermally. Quantum yields are close to unity for 485 nm light, and from the photolysis kinetics, values of the first order thermal return rate constants, k, are obtained which agree well with the directly determined ones. The behavior of Bi(HDz) 3 , Pb(HDz) 2 , Tl(HDz), Cd(HDz) 2 , Zn(HDz) 2 , Cu(HDz) 2 , and Pd(HDz) 2 was also examined in various solvents. The return rates are fast and k values were obtained by means of laser pulse photolyses. The results allow for some differentiation between reaction schemes; it is concluded that for Hg(HDz) 2 , both ligands isomerize following absorption of a light quantum by the complex. The k values for the set of complexes can be correlated approximately by type of solvent and type of central metal ion.

Maximizing light absorption at the bottom of a film

Abstract Assuming only the conditions for the Lambert Law, and from considerations of inner filter effects, we derive an expression which yields the net fraction of light absorbed by the bottom layer of a film having any optical density and divided into any number of hypothetical layers. We show that there is an optimum total optical density at which absorption by the bottom layer is maximized. The optimum optical density is a function of the thickness of the bottom layer probed. For an infinitesimally thin bottom layer, the optimum total optical density is 0·4343.

Optical hole burning and matrix effects in a phthalocyanine complex of ruthenium(II)

Abstract A doubling of the origin is observed in the low-temperature electronic absorption spectrum of the complex carbonyl(pyridine)-phthalocyaninatoruthenium(II) in glassy matrices. The effect is studied by optical hole burning and results suggest a non-degenerate singlet ground state of near C 2v symmetry to be invoked.

SOLUBILITY, DISPERSION AND CARBON ADSORPTION OF A CHROMIUM HYDROXYAZO COMPLEX IN A TONER

In recent years organic salts such as chromium azo dyes have been used as additive to impart desired surface (tribo) charging properties of electrophotographic toners. 1-4 In this study we have prepared solid blends consisting of a chromium hydroxyazoaryl complex salt (T-37 dye), Cr[-0C10H6-NN-C6H3 (Cl)O-]2 [NH4], in a styrene-hutyl methacrylate copolymer containing carbon black powder. We characterized the blends to determine the bulk and interface concentrations of the salt, and relate it to the contact charge. The salt has limited solubility in the copolymer and in organic solvents. It dissolves up to I .7 pmoles/g at a slow rate in the viscous polymer melt at 190 °C. Solid blends with the chromium complex salt in excess of this amount also contain undissolved aggregates of various sizes depending on the preparation conditions. The chromium complex salt also adsorbs on the surface of carbon black up to a monolayer coverage. The carbon efficiently extracts the salt out of THF, and extracts it slowly out of the viscous polymer melt. The toners (10 pm size powder) develop a negative charge on contact. The charge scales with the amount of chromium complex salt in the blend and further varies depending on the proportion of the salt which is soluhilized, exists as undissoled aggregates or is adsorbed on carbon. The chromium complex salt which is adsorbed on carbon is deactivated for charging by the carbon surface.