Nicholas R. Walker, Susanna L. Stephens, David P. Tew and Anthony C. Legon

1

68th International Symposium on Molecular Spectroscopy, Ohio State University, 2013.

Unexpected Generation and Observation of a T-shaped Complex of C2H2AgCCH

Engineering and Physical Sciences Research Council

MCCH Complexes - A Recent History

AlCCH – M. Sun, D.T. Halfen, J. Min, D.J. Clouthier, L.M. Ziurys, Chem. Phys. Lett. 553, 11-16 (2012).

ZnCCH – J. Min, D.T. Halfen, M. Sun, B. Harris, L.M. Ziurys, J. Chem. Phys. 136, 244310 (2012).

LiCCH, NaCCH, KCCH – P.M. Sheridan, M.K.L. Binns, M. Sun, J. Min, M.P. Bucchino, D.T. Halfen, L.M. Ziurys, J. Mol. Spectrosc. 269, 231-235 (2011)

CuCCH – M. Sun, D.T. Halfen, J. Min, B. Harris, D.J. Clouthier, L.M. Ziurys, J. Chem. Phys. 133, 174301 (2010).

AlCCH, AgCCH – C. Cabezas, S. Mata, A.M. Daly, A. Martin, J.L. Alonso, J. Cernicharo, J. Mol. Spectrosc. 278, 31-34 (2012)

water hydrogen sulphide

etheneacetylene

ammonia

What is the nature of the interaction between each of these molecules and a single metal atom in isolation?

C

C

Cu/Ag ClMH09, 67th International

Symposium on Molecular Spectroscopy, Ohio State

University, 2012.

Power divider

SPST switch

MixerMixer

Low noise amplifier

Pin diode limiter

Adjustable attenuator

300 W Power amplifier

AWG (0.5- 12 GHz)

Oscilloscope (0- 12 GHz)

10 MHz reference frequency

PDRO (19.00 GHz)

7.0 - 18.5 GHz 7.0 - 18.5 GHz

12.2 GHz Low- pass band filter

CP-FTMW Spectrometer

Laser ablation source informed by the designs currently used by Legon and co-workers, Duncan and co-workers, Gerry and co-workers, Ziurys and co-workers.

Laser ablation source

C2H2AgF ???

8000 10000 12000 14000 16000 18000Frequency / MHz

15300 15400 15500 15600Frequency / MHz 15615 15620 15625 15630

Frequency/MHz

K-1 = 0

K-1 = 1 Two spectra almost overlapped. Silver isotopes !

J J = 4 5

C2H2AgF

• Discover rotational constants are much too small to correspond to C2H2AgF in any physically-reasonable geometry.

• But evidence says complex must be T-shaped, contain C2H2 and a silver atom very close to the centre of mass.

C2H2AgCCH • This would require a degree of C2H2

fragmentation within the laser ablation source but also involve formation of a complex.

• We did not expect to see M-CCH complexes. Do we have AgCCH in the spectrum?

12650 12700 12750 12800 12850 12900 12950Frequency / MHz

Yes!

J J = 1 2AgCCH

  12C2H2107Ag12C12CH 12C2H2109Ag12C12CH

A0 / MHz 34936(50) 34953(120)

B0 / MHz 1579.56940(26) 1579.53918(61)

C0 / MHz 1509.70215(26) 1509.67502(60)

J / kHz 0.1711(39) 0.1714(92)

JK / kHz 23.86(28) 23.58(67)

N 14 14

/ kHz 1.5 3.6

  13C2H2107Ag13C13CH 13C2H2109Ag13C13CH

A0 / MHz 33239(41) 32347(433)

B0 / MHz 1468.430876(91) 1468.4033(12)

C0 / MHz 1404.913582(95) 1404.8890(12)

J / kHz 0.1499(43) 0.117(43)

JK / kHz 20.38(17) 22.8(18)

N 6 7

/ kHz 0.4 5.0

A0 / MHz 0 / u Å2 r(Ag*) / Å 12C2H2107Ag12C12CH 34936(50) 0.34(3) 2.2404(5)

12C2H2107AgCl 34904(45) 0.34(4) 2.1841(82)

B0 / MHz

C2H2 35274.9693(54) - -

Ag-C1 bond distance in AgCCH optimised through measurements of transitions of Ag12C12CH, Ag13C13CH.

C1C2 HAg

C2H2

Molecular Geometry of C2H2AgCCH

*

(1) S.L. Stephens, W. Mizukami, D.P. Tew, N.R. Walker and A.C. Legon, J. Chem. Phys. 137 174302 (2012) (2) M. Herman, A. Campargue, M.l. El Idrissi and J. Vander Auwera, J. Phys. Chem. Ref. Data, 32, 921 (2003).

Conclusions

• A new complex of C2H2 and AgCCH has been observed. The molecular geometry is T-shaped and planar.

• The intensities of transitions of this species and also free AgCCH are enhanced by the presence of SF6 in the gas sample! This raises lots of interesting questions about “synthetic” routes to complexes generated through laser ablation.

• Not yet identified transitions of C2H2AgF despite using a broadband spectrometer to search for them. Have previously noticed that some combinations of B and MX are very difficult to observe. For example, H2SAgF.

Acknowledgements

David Tew (Bristol)Susanna Stephens (Bristol)Anthony C. Legon (Bristol)

Financial Support

Engineering and Physical Sciences Research Council

Bristol In transit Newcastle