Time-Resolved Infrared Absorption Studies of the Solvent-Dependent Photochemistry of ClNO

Abstract

The photochemistry of nitrosyl chloride (ClNO) dissolved in cyclohexane is investigated using ultrafast time-resolved infrared (TRIR) spectroscopy. Following 266 nm photolysis, the photochemistry is measured by following changes in optical density at frequencies spanning the N═O stretch fundamental transition. A photoinduced depletion in optical density is observed consistent with the depletion of ground-state ClNO. The depletion in optical density remains constant out to ∼50 ps demonstrating that ClNO photodissociation is not followed by recombination of the Cl and NO photofragments. In addition, no evidence for the formation of the ClON photoisomer is observed. These results stand in contrast to previous studies in acetonitrile where ClNO photolysis is followed by geminate recombination of Cl and NO, and by the production of ClON. These differences in ClNO photochemistry are proposed to arise from the population of different excited-states caused by solvent dependence of the ground-state potential energy surface minimum along the Cl-N stretch coordinate. Solvent-dependent vibrational relaxation and differences in strength of the solvent cage are also proposed to contribute to the solvent-dependent photochemistry. Finally, these results are placed in the context of recent models of ClNO photochemistry and role of this compound in tropospheric ozone production.

Comparing molecular photofragmentation dynamics in the gas and liquid phases

“…23 The recent literature contains many studies of the UV photofragmentation of prototypical small molecules, e.g. I 2 , [24][25][26][27][28][29] HgI 2 , 30-37 I 3 À , 19,[38][39][40][41][42] ICN, 11,[43][44][45][46][47] ClNO, [48][49][50] OClO, [51][52][53][54][55][56][57][58][59][60] HOCl 61,62 and CH 3 OCl, 63 and haloalkanes like CF 2 I 2 , 64-66 CH 2 I 2 , [67][68][69][70][71][72] and CH 2 Br 2 , 73,74 that seek more quantitative insights into VET and/or recombination mechanisms and, more generally, to explore the synergies and the obvious differences between molecular photofragmentations occurring in the gas and condensed phases. 13,75 The present perspective article seeks to explore such issues by comparing and contrasting the UV photofragmentation behaviour of a limited family of molecules -phenols, thiophenols and selected ether/thi...…”

Resonance Raman Intensity Analysis of ClNO2 Dissolved in Methanol

“…A similar vibrational shift is not observed in the neat ClNO 2 liquid, which can be attributed to the different intermolecular interactions operant between two weakly dipolar solute molecules (0.44–0.52 D), which must be mainly of the form of induced dipole-induced dipole (van der Waals), versus the interactions of the solute with a protic polar solvent. In the thorough work of Reid and co-workers on ClNO, another dissociative molecule along the Cl–N coordinate, a very strong dependence of the N–O stretch frequency on the polarity of the solvent was clearly demonstrated. − Particularly, the frequency increased with increased polarity of the solvent. This was attributed to a long Cl–N bond (1.973 Å) that leads to poor overlap between the p orbital of Cl and the 2π antibonding orbital of NO and consequently to a partial charge transfer from NO to the more electronegative Cl, comprising thus NO ionic-like with a stronger bond that further decreases in length with increasing polarity of the solvent.…”

Double Photoionization of Nitrosyl Chloride by Synchrotron Radiation in the 24–70 eV Photon Energy Range

“…Despite various studies already conducted concerning photo-induced processes on ClNO using photons in the ultraviolet (UV)-visible [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ] and infrared [ 15 , 16 , 17 ] energy range, no data on its double photoionization by direct ejection of two valence electrons are available.…”