Anion ZEKE-Spectroscopy of the Weakly Bound Iodine Water Complex

Abstract

Zero kinetic electron energy photodetachment spectroscopy of I(-)·H(2)O and I(-)·D(2)O has been performed from 27 660 to 28 500 cm(-1) and from 27 660 to 35 900 cm(-1), respectively. The I(-)·D(2)O spectral data and theoretical studies resulted in a reassignment of earlier anion-ZEKE spectra of iodide water ( Bässmann , C. ; et al. Int. J. Mass Spectrom. Ion Processes 1996 , 159 , 153 ). In opposite to the I(-)·H(2)O, the I(-)·D(2)O spectrum reveals a regular progression of the iodine-water van der Waals stretching mode and a short progression of even quanta of the van der Waals rocking mode. A rough estimation delivers dissociation thresholds of the anionic and of the lower and the upper spin-orbit component of the neutral van der Waals complex. A high resolution ZEKE spectrum of the van der Waals stretching mode (v = 1) reveals significant fine structure, which is found again in a former photodissociation spectrum of the anionic complex ( Ayotte , P. ; et al. J. Phys. Chem. A 1998 , 102 , 3067 ). Our assignments are supported by theoretical calculations of molecular structures and vibrational motions. Vibrational frequencies and isotope effects are reproduced very satisfyingly by these calculations.

Spectroscopic Signatures of Mode-Dependent Tunnel Splitting in the Iodide–Water Binary Complex

“…For example, the bend overtone mode near 3200 cm –1 is missing in the low-power, linear predissociation (PD) spectrum (complete trace in Figure B) but can be observed using Ar-tagging methods (gray inset in Figure B); this observation establishes that the effective dissociation energy at the experimental temperature lies between 3200 and 3400 cm –1 . As discussed below, the discrepancy between these values and the previously reported dissociation energy is likely due to the fact that the excited states accessed in the transitions shown in Figure near 3400 cm –1 (β 13–16 ) are situated just above dissociation threshold but are surprisingly long-lived . Steps taken to confirm that the spectrum shown in Figure results from the absorption of a single photon are discussed in the Supporting Information (S2).…”

“…Experimentally, the I – ·H 2 O cluster was prepared with electrospray ionization and cooled in a temperature-controlled ion trap that has been described previously, , and its vibrational spectrum was recorded by infrared photodissociation with several complementary laser configurations. , The dissociation energy of this complex has been reported to be in the range of 3410–3510 cm –1 using threshold electron photodetachment of the anion, which lies in middle of the OH stretching range. As such, a changeover from one- to two-photon dissociation will occur, depending on whether the upper state in the transition lies above or below the dissociation energy and, in the case of the former, the dissociation lifetime of the metastable state.…”

Electrostatics, Charge Transfer, and the Nature of the Halide–Water Hydrogen Bond

“…Although some systematic errors in CCSD(T)-F12b basis-set extrapolations have been noted, 79−81 the binding energies computed in ref 77 are more consistent with the experimental dissociation energy of I − (H 2 O), estimated at 3200−3500 cm −1 (9.1−10.0 kcal/ mol). 37,82 This minor discrepancy poses no serious problem, as the present work is focused on understanding the physical nature of the halide−water interaction, for which we rely on SAPT calculations.…”

Electronic Structure Theory Study of the Microsolvated F–(H2O) + CH3I SN2 Reaction

“…The geometry of product I − (H 2 O) was obtained by the MP2/aug-cc-pVTZ/AVTZ+ECP46MWB and B3LYP/6-311++G(3df,3pd)/Lanl2DZ+diff calculations. 59 2. Vibrational Frequencies.…”