Photochemistry of Complex Ions. III. Absolute Quantum Yields for the Photolysis of Some Aqueous Chromium(III) Complexes. Chemical Actinometry in the Long Wavelength Visible Region

Abstract

Absolute quantum yields are reported for the photoaquation of aqueous Reinecke´s salt, KCr(NH3)2-(NCS), and of Cr(urea)6Cl3 at 230 for a number of wavelengths between 316 and 750 Mμ and between 452 and 735 ntyi, respectively. Detailed procedures are given so that these systems may be used for chemical actinometry. The respective apparent activation energies are 1.3 and 3.0 kcal/mole. In addition, pH-dependence studies on the first system indicated that while only one thiocyanate is released per primary act, in alkaline solutions the remaining three are rapidly hydrolyzed off. Less complete data are reported for aqueous K3Cr(NCS)6. Again, only one thiocyanate is released in the primary act, but the remaining five are hydrolyzed off rapidly in alkaline solution. Some photoaquation quantum yields are also reported for aqueous Cr(NH3)6(N03)3. The data include a number of quantum yield determinations in the region of the doublet absorption bands. © 1966, American Chemical Society. All rights reserved.