1C03
CRDS 法による塩素錯体検出(京大工院) 江波進一、中野幸夫、橋本訓、川崎昌博、(北大工院) 田地川浩人

We have reported the direct observation of the weakly bound Cl-M (M = Cl2, O2, RI, CH3SCH3)
complexes using cavity ring-down spectroscopy (CRDS) in low temperature and moderatepressure conditions. Theoretical calculations confirmed the present experimental results. Thebond lengths and bond energies for Cl-M are summarized in Table 1.

→←

Cl + Cl2 + M
Cl3 + M
Cl3 + Cl → 2Cl2

(1, -1)(2)

1.0

Absorption of Cl3 (arb.unit)[Cl-Cl2] We have firstly reported thebroad absorption of Cl3 radicals in the near
IR region using cavity ring-down
spectroscopy with an OPO laser. The
mechanism for Cl atom reaction with Cl2 is:

0.9
0.8
0.7
0.6
0.5
0.4
1150

1200

1250

1300

Wavelength (nm)The pressure and temperature dependence ofthe formation of Cl3 was experimentally investigated. The rate constants of reaction 2were determined. The equilibrium rate constants of reactions 1, -1 were determinedtheoretically as well as the ground state structure of Cl3. We concluded that the Cl-Cl2complex is of a van der Waals complex type. The Cl-Cl2 bond dissociation energy isdetermined to be 0.9 kcal mol–1１
The equilibrium constants for the formation of ClOO from Cl and O2 are[Cl-O2]experimentally measured at 212 – 245 K.
Cl + O2 →Cl-O2←(3)

A van't Hoff plot analysis yields ∆Hr = 4.8 ± 1.5 kcalmol–1. The bond dissociation energy is determined to be4.67 ± 0.06 kcal mol–1 based on the third-law analysis of the present and previously
reported temperature dependence of the equilibrium constants.２ The reaction of ClOO

1350

with NO was also investigated to determine the reaction branching ratios at T = 213 K.３
Cl-O2 + NO → ClNO + O2→ ClO + NO2(4)(5)[Cl-IR] The visible absorption spectra of RI-Cl (R = CH3, C2H5, C3H7, C4H9, CH2I,CH2Br, CH2Cl, cyclo-C6H11, C6H5, C6F5, p-CH3C6H4) were firstly observed in the gas
phase. Those complexes do not react with O2 at T < 263 K. The complex formation
occurs via the charge transfer mechanism since the absorption intensity is wellcorrelated with the ionization potential of the corresponding RI.４,５
The complex formation of Cl atom with CH3SCH3 was observed in theUV region. The following rate constants and structure of the complex are determined.

[Cl-S(CH3)2]

６

Cl + CH3SCH3 + M → Cl-DMS + M(6a, -6a)

Cl + CH3SCH3 → HCl + CH3SCH2.

(6b)←Acknowledgments:

This work has been performed in collaborations with Dr. Y. Sumiyoshi and Prof. Y. Endo ofUniv. of Tokyo, Prof. S. Aloisio of California State Univ., Prof. J. S. Francisco of Purdue Univ., Prof. T. Ishiwata 0..ofHiroshima Univ., and Dr. S. Nishida and Prof. Y. Matsumi of Nagoya Univ.

Table 1 Summary of Cl-M complexes
Cl-X

Bond length (Å)

Bond energy D0 (kJmol-1)

Cl-Cl2

3.6

3.6 a

Cl-OO

2.1

19.5 b

CH3I-Cl

2.9

59.0 cC6H5I-Cl

2.9

56.5 dCH3S(-Cl)CH3

2.6

74.1 e１ S. Enami, T. Yamanaka, Hashimoto, M. Kawasaki, S. Aloisio, H. Tachikawa, J. Chem. Phys. A. in press
２ K. Suma, Sumiyoshi, Y. Endo, Enami, Aloisio, Hashimoto, Kawasaki, Nishida, Matsumi,. ibid. 2004, 108, 8096
３ S. Enami, Y. Hoshino, Y. Ito, Hashimoto, M. Kawasaki, T. J. Wallington, ibid. 2006, 110, 3546
４ S. Enami, S. Hashimoto, M. Kawasaki, Y. Nakano, T. Ishiwata, T. J. Wallington, ibid. 2005, 109, 1587.
５ S. Enami, T. Yamanaka, S. Hashimoto, M. Kawasaki, K. Tonokura, ibid., 2005, 109, 6066.
６ S. Enami, Y. Nakano, S. Aloisio, S. Hashimoto, M. Kawasaki. J.S. Francisco, ibid. 2004, 108, 7785.