1Kanagawa Institute of Technology 3Georgia Southern University The differences in the role of O and S atoms in the molecular structure and dynamics of some complexes Yoshiyuki Kawashima,1 Akinori Sato,1 Yoshio Tatamitani,1 Nobuyuki Ohashi,2 James M. Lobue,3 and Eizi Hirota4 1Kanagawa Institute of Technology 2Kanazawa University 3Georgia Southern University 4The Graduate University for Advanced Studies

Ar–dimethyl sulfide (DMS) CO–ethylene oxide (EO) Purpose We have investigated van der Waals complexes containing of either one of a rare gas atom, CO, N2, or CO2 combined with one of the two pair molecules: DME/DMS and EO/ES by using a FTMW spectrometer, 　　in order to examine how different the role of the O and S atoms is in molecular properties of the complex. The present talk reports the results on Ar-DMS and CO-EO, in comparison with those on Ar-DME and CO-ES, respectively. Ar–dimethyl sulfide (DMS) CO–ethylene oxide (EO)

Potential of the tunneling motion for Rg-DME complexes；Rg = Ne, Ar and Kr The large amplitude motion is expected in the weak van der Waals complex. Rg C2v a Rc.m. E / cm–1 Ne–DME: 16 cm–1 Ar–DME: 58 cm–1 Kr–DME: 112 cm–1 Binv 1– v = 1+ Binv: Barrier to inversion 807.2(9) MHz 0.9980(6) MHz 0.26 (5) MHz 0– v = DE 0+ a / deg

CO-dimethyl ether (DME) complex1) Heavy-atom skeleton of CO-DME was essentially planar. The carbon atom of CO is closer to DME than the O atom. The splitting between the two sets of the same transition varied from 2 to 15 MHz, and the two components were assigned to the two lowest states of the internal rotation of CO with respect to DME governed by a twofold potential. The bond distance between the center of mass is 3.68 Å. The van der Waals bonding of CO- DME is weak and is between those of Ne- DME and Ar-DME. 75.7° Rc.m. = 3.68 Å 1) Y. Kawashima et al, J. Chem. Phys. 127, 194302 (2007)

Instrument: Fourier transform microwave spectrometer Experimental Instrument: Fourier transform microwave spectrometer Sample : 1% DMS diluted with Ar or 0.5% EO and 1.5% CO diluted with Ar Backing pressure : 1.0 atm Shots : 20 Frequency region : 3.7~25 GHz Step : 0.25 MHz Vacuum chamber Mirror (fixed) Supersonic molecular beam injection Molecular beam injection nozzle MW Mirror (mobile) sample Diffusion pump Rotary pump

Observed spectra of Ar-DMS Ar–DMS (normal) 221 – 111 a(vdW) c(vdW) b(DMS) 7050 7100 7150 7200 7250 7300 7350 Spectrum of Ar–DME 212(+) – 202(–) 212(–) – 202(+) 111(+) – 101(–) 111(–) – 101(+) DE ≈ 1 MHz 18000 18200 18400 18600 18800 19000 220 – 110 No splitting due to the large amplitude motion is found! Ar–DMS (34S) Ar–DMS (13C) 220 – 110 221 – 111 220 – 110 221 – 111 Frequency / MHz

Observed spectra of the a-type and c-type transitions of Ar-DMS a-type transition 505–404 EE c-type transition 211–101 AA EE AE EA AE EA 9823.9 9824.4 AA 12665.3 12665.8 Frequency / MHz Frequency / MHz V3 = 736.17 (32) cm-1 (V3 = 752.7 cm-1 for DMS monomer)

Observed spectra of the forbidden transitions of Ar-DMS

Phenomenological Hamiltonian The first-order Coriolis term where

Molecular constants and the substituted coordinates of the S and C atoms in Ar-DMS Ar–DMS (normal) Ar–(CH3)234S Ar–13CH3SCH3 A / MHz 5819.71216(22) 5778.88622(20) 5677.33741(42) B / MHz 1334.991997(71) 1315.99190(11) 1327.59112(24) C / MHz 1209.047917(10) 1195.23069(12) 1198.51825(27) DJ / kHz 5.80475(46) 5.67154(48) 5.6862(11) DJK / kHz 40.9120(45) 39.210(7) 40.275(15) DK / kHz –39.911(19) –38.075(24) –39.77(8) dJ / kHz 0.52885(16) 0.50346(17) 0.53750(32) dK / kHz 25.669(24) 24.52(5) 25.15(12) FK / kHz 0.0962(24) – <1|q|2> / MHz 0.03556(11) Na-type / - 43 16 Nc-type / - 79 39 25 s / kHz 3.8 0.6 rs coordinates as (S or C) / Å 1.5713 1.3420 bs (S or C) / Å 0.0715 i ±1.3707 cs (S or C) / Å 0.5684 0.5713

Observed rotational spectra of CO-EO in Ar J = 5←4 CO-EO complex a-type R-branch transitons J = 1←0 c-type R-branch transitions EO monomer c-type Q-branch transitions Ar-EO complex J = 4←3 J = 2←1 J = 3←2 8000 20000 10000 12000 14000 16000 18000 11200 11300 11400 11500 11600 J = 1 5 CO-EO complex C-type Q-branch transitions(Ka=1←0) 8000 20000 10000 12000 14000 16000 18000 Frequency / MHz

Observed rotational spectra and obtained molecular constants of CO-EO complex The a-type and strong c-type transitions of CO-EO complex were observed, however, no b-type transition was found. The rotational and centrifugal distortion constants of CO-EO were determined using an asymmetric top Hamiltonian. 16033.2 16034.0 　404–303 (a-type transition) 16033.6379 MHz normal A /MHz 13556.4299(7) B /MHz 2011.19621(8) C /MHz 1997.86910(9) DJ /kHz 9.7986(10) DJK /kHz 44.185(5) DK /kHz 83.41(13) d1 /Hz –3.04(7) d2 /Hz 46.2(7) N (a-type) 33 N (c-type) 34 s /kHz 1.98 Frequency / MHz 110–000 (c-type transition) 15567.0 15567.8 15567.4151 MHz Frequency / MHz

Molecular constants and the substituted coordinates of the O and C atoms of five isotopomers of CO–EO complex normal CO–EO(13C) CO–EO(18O) 13CO–EO C18O–EO A /MHz 13556.4299(7) 13337.9534(4) 13184.7208(26) 13437.5762(11) 13506.9965(4) B /MHz 2011.19621(8) 1990.28772(9) 1989.1126(4) 1984.01857(31) 1917.24067(6) C /MHz 1997.86910(9) 1973.41181(11) 1984.4680(7) 1973.64698(18) 1906.08012(6) DJ /kHz 9.7986(10) 9.5212(16) 9.686(11) 9.4950(24) 9.0345(9) DJK /kHz 44.185(5) 44.183(13) 43.96(14) 40.326(11) 38.9515(33) DK /kHz 83.41(13) [83.41] a 86.76(23) 90.96(9) d1 /Hz –3.04(7) 15.2(5) 20.95(20) 10.01(5) d2 /Hz 46.2(7) 38.8(13) 48.9(12) 40.2(4) Pbb /uÅ2 19.4779 20.0309 19.4627 19.4740 19.4798 N (a-type) 33 16 11 31 N (c-type) 34 14 12 19 21 s /kHz 1.98 1.03 5.59 3.12 1.20 0.057 0.030 rS coordinates |C(a)| or |O(a)/Å 1.613 1.613 1.771 2.498 0.054 i |C(b)| or |O(b)/Å 0.739 0.739 0.584 0.270 |C(c)| or |O(c)/Å 0.280

Observed and ab initio calculated two structural parameters, stretching force constants, and binding energy or Ar-DMS and related molecules [I aa(vdW) and Ibb(vdW)] [Ibb(vdW) and Icc (vdW)] [Iaa(vdW) and Icc(vdW)] Ne a a Ar a Rcm Rcm a Rcm Ar Rcm Ne Ne–DME Ar–DME Ne–DMS Ar–DMS

cm–1 t / degrees Rc.m. a t a / degrees

Summary Ar CO DME DMS EO ES R(O-Ar)=3.382Å R(O-C)=3.047Å 106.8 ° ks=2.30 Nm-1 ks=1.40 Nm-1 R(S-C)=3.49Å R(S-Ar)=3.989Å DMS 66.9 ° 75.7 ° ks=2.00 Nm-1 ks=2.70 Nm-1 R(O-Ar)=3.476Å R(O-C)=3.00Å EO 93.0 ° 97.7 ° ks=2.20 Nm-1 ks=3.30 Nm-1 R(O-Ar)=3.974Å R(S-C)=3.47Å ES 70.7 ° 74.6 ° ks=2.10 Nm-1 ks=3.20 Nm-1

Summary CO HF DME DMS EO ES 7.2 º R(O-C)=3.047Å 137.1 ° ks=1.40 Nm-1 R(S-C)=3.49Å DMS 75.7 ° ks=2.70 Nm-1 16.5 ° R(O-C)=3.00Å EO 108.0 ° 97.7 ° ks=3.30 Nm-1 R(S-C)=3.47Å ES 16.8 ° 86.5 ° 74.6 ° ks=3.20 Nm-1

Conclusion 1) In the case of the CO-DMS and CO-ES, the CO moiety is located closer to the CH3 and CH2 end of DMS and ES, respectively, whereas to the O end in the cases of CO-DME and CO-EO. 2) Similar differences were found for Rg complexes. Because of the larger atomic radius and lower electronegativity of S than those of O, S behaves as a much weaker nucleophile than O. 3) The structures of Rg-DMS and Rg-ES thus considerably deviate from that of the n-type complex proposed by Legon. A.C. Legon, Angew. Chem. Int. Ed. 38 (1999) 2686.