The partial molar volume of the proton in water determined by time-resolved laser-induced optoacoustic studies

C. D. BORSARELLI; S. E. BRASLAVSKY

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 1998 vol. 43 p. 222 - 228

1011-1344

The structural volume change associated with the formation and decay of the metal-to-ligand charge-transfer (MLCT) slate of (2,2'-bipyridine) tetracyanoruthenate(II) complex, Ru(bpy)(CN)(4)(2-), Delta V-MLCT, has been studied as a function of pH in dilute aqueous solutions ( < 0.4 M) using time-resolved laser-induced optoacoustic spectroscopy. The values of Delta V-MLCT, for the MLCT formation of the complex strongly depend on pH, ranging from + 3.0 +/- 0.3 cm(3)/mol at pH = 0.35 to + 15.0 +/- 0.5 cm(3)/mol at pH = 6.63. The reduction of Delta V-MLCT at low pH values is assigned to the fast excited-state proton ejection undergone by monoprotonated Ru(bpy)(CN)(4)(2-). With the Delta V-MLCT, values and the Drude-Nernst equation for the electrostriction effect with an empirically determined constant, a value for the 'absolute' partial molar volume of the hydrated proton in water of V degrees(H+) = ( - 5.5 +/- 0.8) cm(3)/mol is obtained, in good agreement with Literature data