How many molecular layers of polar solvent molecules control chemistry? The concept of compensating dipoles.
The extension of the solvent influence of the shell into the volume of a polar medium was examined by means of anti-collinear dipoles on the basis of the E(T)(30) solvent polarity scale (i.e., the molar energy of excitation of a pyridinium-N-phenolatebetaine dye; generally: E(T) =28,591 nm kcal mol(-1)/λmax) where no compensation effects were found. As a consequence, solvent polarity effects are concentrated to a very thin layer of a few thousand picometres around the solute where extensions into the bulk solvent become unimportant. A parallelism to the thin surface layer of water to the gas phase is discussed.
Department of Chemistry, LMU University of Munich, Butenandtstrasse 13, 81377 Munich (Germany), Fax: (+49) 89-2180-77640. Langhals@lrz.uni-muenchen.de.
Heinz
H
Langhals
Patricia
P
Braun
Christian
C
Dietl
Peter
P
Mayer
dipoles; polarity; solvatochromism; solvent shells