Matrix-Isolation Study of the Vacuum-Ultraviolet Photolysis of Chloroform. Infrared Spectra of the CCl3+, HCCl2+, and HCCl2− Molecular Ions

Abstract

Photolysis of samples of HCCla isolated in an argon matrix at 14°K using 1216-A. radiation leads not only to the isolation of a high yield of CCla, but also to the photoionization of CCla, resulting in the stabilization of a sufficient concentration of CCl 3 + for direct infrared spectroscopic identification. The assignment of still other infrared absorptions which appear in this system to negatively charged species has been confirmed by experiments in which a small concentration of an alkali metal atom is also present in the matrix, providing a photoelectron source. When matrix-isolated HCCl3 is subjected to photolysis by 1067-A. argon resonance radiation, very little CCla is produced, but HCCb, HCCb+, and the same negatively charged species are stabilized in significant concentration. Studies of chloroform samples enriched in carbon-13 and of DCCla samples have provided support for these identifications and have yielded data necessary for obtaining several of the force constants of these species. The infrared spectrum of the negatively charged species can most satisfactorily be explained by postulating that dissociative electron attachment to chloroform occurs, resulting in the stabilization of HCCb-in the matrix environment.

Energetics of hydride and electron pair attachment to EX30/+ (E=B, C, Al, Si and X=F, Cl, Br, I) and the study of bonding trends among EX30/+, EX32−/−, and EX3H−/0 by use of ELF and NBO analyses

“…Results abound for species where X = F [1,2,7,[9][10][11][14][15][16][17][18][19][20][21] or Cl [1,2,6,7,[12][13][14][15][16][17][18][19][21][22][23], but are relatively sparse for X = Br [1,2,4,6,7] and I [1,2,4,6]. The bonding and relative stabilities of the trihalomethyl cations have been assessed in terms of relative degrees of s and p donation from the halogen atom to the carbon center [1,2,4,5,[24][25][26][27]. The s effect, from the perspective of the halogen atoms of CX 3 + , has been found to be strongly withdrawing in the case of fluorine and weakly donating in the case of chlorine, bromine, and iodine (I > Br > Cl).…”

The use of threshold photoelectron–photoion coincidence spectroscopy to probe the spectroscopic and dynamic properties of the valence states of CCl3F+, CCl3H+ and CCl3Br+

“…[46] Values for the other modes are unknown, hence vibrational frequencies of the isoelectronic BFCl 2 molecule are used. [33] For CCl 3 + , the value of the degenerate ν 3 (e') mode, 1037 cm -1 , is taken from Jacox and Milligan, [47] otherwise vibrational frequencies of the isoelectronic BCl 3 molecule are used. [33] The maximum values of <KE> t and hence <f> t determined for the modified-impulsive model were calculated assuming that the polyatomic fragment initially has a regular tetrahedral geometry with bond angles of 109. .…”

A Transient Ion Pair (CCl · Cl−) in Irradiated Liquid CCl4: Evidence for a ‘delayed’ geminate ion neutralisation. (Preliminary communication)

“…There must be a reason for the stability of such ion pairs. Only brief mentioning of two types of possible arguments will follow here: 1) CCl: is a planar cation [14]. On neutralisation with C1-the structure has to change to tetraedric symmetry.…”