Reply to a ''Comment on 'IR-spectroscopic study of isotope effects on the NH/ND stretching bands of meso-tetraphenylporphine and vibrational hydrogen tunneling'''

Journal Article · Tue May 15 00:00:00 EDT 1984 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.446569· OSTI ID:7119250

Limbach, H H

In a comment, Sarai has suggested that the observation of a sharp NH stretching band in meso-tetraphenylporphine (TPP) may not be relevant to the proton-skeleton coupling problem of the hydrogen tunneling process in TPP, as was proposed by us previously. In this reply we point out that Sarais comment refers to the case where the top of the barrier is far above the first excited NH stretching level, as predicted by CNDO calculations, whereas our still valid statement refers to the low barrier case which is observed experimentally. The result of recent NMR experiments on the hydrogen migration in solid state porphines are discussed. It is shown that the asymmetry of the proton potential in triclinic TPP is caused by crystal packing forces and not by the pseudo-Jahn--Teller effect. The consequence is that there is, for the moment, no experimental evidence for a coupling of a heavy atom motion to proton tunneling in porphines.

• Research Organization: Institut fuer Physikalische Chemie der Universitaet Freiburg i. Br., Albertstr. 21, D 7800 Freiburg i. Br., West Germany
• OSTI ID: 7119250
• Journal Information: J. Chem. Phys.; (United States), Vol. 80:10
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
DEUTERIUM
ISOTOPE EFFECTS
ORGANIC NITROGEN COMPOUNDS
INFRARED SPECTRA
LINE WIDTHS
OSCILLATION MODES
VIBRATIONAL STATES
ENERGY LEVELS
EXCITED STATES
HYDROGEN ISOTOPES
ISOTOPES
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
SPECTRA
STABLE ISOTOPES
400302* - Organic Chemistry- Isotope Effects- (-1987)