Supplementary Information
Figure S1. Product ion spectrum of m/z 268 (a), and that of m/z 303 (b) recorded by tandem mass spectrometry. A sample of HgCl2 was placed in the source and m/z 268 and 303 ions were mass isolated and subjected to collision-induced dissociation. The relative abundances of the observed fragments are in excellent agreement with the theoretically predicted fragmentation pathways.
Figure S2: A HePI mass spectrum recorded from a deposit of pure HgI2 (a), and that obtained from a HgI2 sample exposed to HCl vapor emanating from TiCl3 (b).
Figure S3: A time versus absolute intensity plot recorded under negative-ion generating conditions (m/z 20 to 350), upon exposure of a deposit of Hg(NO3)2 to a HePI source. The sample was inserted at the beginning of the experiment, and at 0.9 min it was exposed to HCl vapor emanating from a TiCl3 vial. The insert shows a mass spectrum obtained by summation of mass spectral data between 0.9 to 1.3 min, and subtracting background data obtained before the exposure to HCl vapor.
Figure S4: (a) Time versus absolute intensity plot recorded under negative-ion generating conditions upon exposure of a deposit of HgSO4 to a HePI source. After recording background spectra (m/z 50 to 400) for 2.0 min, a sample of HgSO4 was introduced to the source. At 5.0 min, an aqueous solution of NaCl was added to the dry deposit. At 6.50 min sample deposit plate was withdrawn from the source. (b) A mass spectrum obtained by summation of mass spectral data between 3.0 to 5.0 min and subtraction of background data recorded before 2.0 min. (c) A mass spectrum obtained by summation of mass spectral data between 5.0 to 6.5 min and subtraction of background data recorded before 2.0 min.
Figure S5: A mass spectrum recorded from a deposit of pure HgS sample exposed to HCl vapor emanating from TiCl3.
Figure S6. HePI mass spectra recorded from solid deposits of Hg(II) acetate (a) and Hg(II) trifluoroacetate (b) exposed to HCl vapor emanating from solid TiCl3.
Figure S7. (a) A time versus absolute intensity plot recorded under negative-ion generating conditions upon exposure of deposit of HgO to a HePI source. After recording spectra for 1.0 min from HgO, an open vial of TiCl3 was introduced to the source and withdrawn after about 1.8 min. The insertion and withdrawal of the TiCl3 vial were repeated three more times and spectra were recorded from m/z 20 to 450. (b) A mass spectrum obtained by summation of mass spectral data between 3.0 to 3.4 min, and subtraction of background data recorded before the exposure to HCl vapor emanating from solid TiCl3.
Figure S8. A mass spectrum recorded from a deposit of pure calomel (Hg2Cl2) under a stream of
desolvation gas at 400°C. A very low signal for HgCl2-• was generated from the pristine sample
(blackened area and inset); however, upon addition of a drop of H2O2, the HgCl2-• signal intensity increased dramatically, and the HgCl3- signals appeared prominently as well (red).
Table S1. Theoretical predictions of Hg-Cl bond length using various basis sets.
Method / Cl basis / RHgCl (Å) / Error (Å)Experimental / 2.252
B3LYP / aug-cc-pvtz / 2.298 / 0.046
M06 / aug-cc-pvtz / 2.291 / 0.039
B97D / aug-cc-pvtz / 2.306 / 0.054
wB97XD / aug-cc-pvtz / 2.272 / 0.020
mPW1PW91 / aug-cc-pvtz / 2.271 / 0.019
mPW1PW91 / 6-311+G(3df) / 2.273 / 0.021
mPW1PW91 / aug-cc-pv5z / 2.261 / 0.009
CCSD(T) / aug-cc-pvtz / 2.274 / 0.022
CCSD(T) / aug-cc-pvqz / 2.237 / -0.015
Table S2. Geometric and electronic properties of HgCl2 and HgCl2-•
Species / RHgCl (Å) / ÐClHgCl (°) / ChargeQHg (e) / Charge
QCl (e) / Spin density
rHg (e) / Spin density
rCl (e) / Electronic configuration
HgCl2 / 2.261 / 180.0 / 1.138 / -0.569 / 0.000 / 0.000 / Hg: 6s0.75d9.96p0.2; Cl: 3s1.93p5.6
HgCl2-• (I) / 2.628 / 180.0 / 0.610 / -0.805 / 0.920 / 0.040 / Hg: 6s1.35d106p0.1; Cl: 3s2.03p5.8
HgCl2-• (II) / 2.581 / 140.2 / 0.590 / -0.795 / 0.972 / 0.014 / Hg: 6s1.25d106p0.3; Cl: 3s2.03p5.8
HgCl2-• (III) / 3.369 / 45.8 / -0.013 / -0.493 / 0.000 / 0.500 / Hg: 6s2.05d10; Cl: 3s2.03p5.5
All calculations were done using Gaussian 09 [1]. Geometries of all species were optimized by using the mPW1PW91 method, with SDD for Hg [2], and the largest available Dunning’s correlation consistent basis aug-cc-pv5z for Cl. This is based on the methodological studies showing in Table S1, evaluating B3LYP [3, 4] and mPW1PW91 [5] based on their good performance in previous investigations of metal complexes [6-12] and three more recently developed methods: M06 [13], B97D [14], and wB97xd [15]. Consistent with our previous reports for transition metal complexes [7, 9-12], the best result is from using mPW1PW91 (Table S1).
Frequency calculations were done to verify the nature of respective species in their potential energy surfaces, with all positive frequencies found for minimal energy states and only one imaginary frequency found for the transition state. Gibbs free energies were calculated from using the mPW1PW91 method, with the CCSD(T) energy correction by adding the difference of CCSD(T) and mPW1PW91 electronic energies for each species.
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