CP-FTMW Spectroscopy of Metal-containing Complexes Nicholas R. Walker, Susanna L. Stephens, Anthony C. Legon Max-Planck Advanced Study Group at the Center for Free Electron Laser Science 1 22 nd September, Engineering and Physical Sciences Research Council

Introduction 1)Microwave spectroscopy provides high precision in the determination of molecular geometries and hyperfine parameters. Can also provide insight into barriers to internal rotation and internal dynamics. 2)Recently completed construction of a chirped pulse Fourier transform microwave (CP-FTMW) spectrometer at the University of Bristol. The instrument benefits from recent advances in electronics that allow direct digitisation of waves at GHz frequencies. 3)Present results from complexes of CF 3 I that illustrate the capabilities of the spectrometer. 4) Show how the CP-FTMW spectrometer is being applied to the study of metal-containing complexes.

Animation : Prof. Wolfgang Jäger, Dept. of Chemistry, University of Alberta, Edmonton, AB, CANADA, T6G 2G2. 7

Power divider SPST switch Mixer Low noise amplifier Pin diode limiter Adjustable attenuator 300 W Power amplifier AWG ( GHz) Oscilloscope (0-12 GHz) 10 MHz reference frequency PDRO (19.00 GHz) GHz GHz 12.2 GHz Low-pass band filter CP-FTMW Spectrometer

Multiple Free Induction Decay Acquisition per Valve Pulse Faraday Discuss., 2011, 150, 284–285 Small percentage of OCS in 2 bar of helium.

Faraday Discuss., 2011, 150, 284–285

V. Amico, S. V. Meille, E. Corradi, M. T. Messina and G. Resnati, J. Am. Chem. Soc. 1998, 120, E. Corradi, S. V. Meille, M. T. Messina, P. Metrangolo and G. Resnati, Tetrahedron Lett. 1999, 40, Crystal Engineering with Halogen Bonds

CF 3 I CF 3 I  NH 3 ?? CF 3 I  NH 3

[1] G. T. Fraser, F. J. Lovas, R. D. Suenram, D. D. Nelson, Jr. and W. Klemperer, J. Chem. Phys. 1986, 84, [2] G. Valerio, G. Raos, S. V. Meille, P. Metrangolo and G. Resnati, J. Phys. Chem. A, 2000, 104, C 3v Symmetric top ? Internal rotation? The Hamiltonian

Energy/MHz Exp. Sim. [80 kHz FWHM] Energy/MHz A species sim. E species sim. Total (A and E) sim. Simulation and fitting using PGOPHER (2010, version ), a Program for Simulating Rotational Structure, C. M. Western, University of Bristol, CF 3 I  14 NH 3

Energy/MHz Exp. Sim. CF 3 I  15 NH 3

CF 3 I  14 N(CH 3 ) 3 CF 3 I Energy/MHz Exp. A and E species sim. CF 3 I  14 N(CH 3 ) 3

3.054 Å > r N  I > Å for CF 3 I  NH 3 where 30  >  >0  and 8  >  >0  Å > r N  I > Å for CF 3 I  N(CH 3 ) 3 where 30  >  >0  and 8  >  >0  Structure implies  = 20.5(12)  for CF 3 I  NH 3 and  = 16.2(20)  for CF 3 I  N(CH 3 )

V. Amico, S. V. Meille, E. Corradi, M. T. Messina and G. Resnati, J. Am. Chem. Soc. 1998, 120, E. Corradi, S. V. Meille, M. T. Messina, P. Metrangolo and G. Resnati, Tetrahedron Lett. 1999, 40, r N  I =2.84(3) Å. r N  I close to 2.80 Å Å > r N  I > Å for CF 3 I  N(CH 3 ) 3 where 30  >  >0  and 8  >  >0  Å > r N  I > Å for CF 3 I  NH 3 where 30  >  >0  and 8  >  >0  Correspondence with solid state

H 2 S  ICF 3 Spectrum assigned using a symmetric top Hamiltonian. H 2 O  C 6 H 6 and H 2 S  C 6 H 6 [1] E. Arunan et al. J. Chem. Phys., 2002, 117, [2] S. Suzuki et al. Science, 1992, 257, [3] H. S. Gutowsky et al. J. Chem. Phys., 1993, 99, [4] H. Ram Prasad et al. J. Mol. Spectrosc. 2005, 232, H 2 O  CF 3 Cl and H 2 O  CF 4 [5] W. Caminati, A. Maris, A. Dell’Erba and P. G. Favero, Angew. Chem. Int. Ed. 2006, 45, 6711 – [6] L. Evangelisti, G. Feng, P. Écija, E. J. Cocinero, F. Castaño and W. Caminati, Angew. Chem. Int. Ed., (in press). Exp. Sim.

H 2 O  ICF 3 Superposition of spectra assigned using symmetric and asymmetric top Hamiltonian’s, respectively. Sym. Asym. Total sim. Exp. Total sim.

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

OC  AgI Frequency/MHz CF 3 I 107 AgI 109 AgI AgI

OC  AgI Frequency / MHz 107 AgI 109 AgI OC  ICF 3 Exp. Sim. OC  107 AgI OC  109 AgI

Conclusions CP-FTMW spectroscopy has greatly accelerated the speed at which it is possible to measure and analyse rotational spectra. In the first year of full operation, the spectra of NH 3  ICF 3, N(CH 3 ) 3  ICF 3, H 2 O  ICF 3, H 2 S  ICF 3, OC  ICF 3, Kr  ICF 3 have been analysed and described in a series of papers. (Two papers in press with PCCP, one paper in press with JCP). The spectra of OC  AgI and H 2 S  AgI have been measured and the molecular geometries have been determined. Further analysis and theoretical calculations are in progress. Future applications in molecular dynamics and analytical chemistry seem possible.

Acknowledgements University of Bristol Susanna Stephens Tony C. Legon Colin M. Western David P. Tew University of Virginia Brooks H. Pate Stephen T. Shipman Financial Support Engineering and Physical Sciences Research Council University of Sheffield Michael Hippler University of Oxford Brian Howard

– Invention of the Maser (Gordon, Zeiger and Townes) First high resolution spectroscopic measurements using microwaves (B. Bleaney) – First polyatomic molecule identified in space is NH – rotational spectra of OCS in He droplets 1981 – cavity FT-MW spectroscopy (Balle and Flygare). Pre-reactive complexes Hydrogen and van der Waals bonding. Explore intermolecular potentials. 3

Experimental Ar/H 2 O/CCl 4 6 Pump Nozzle and Cu rod Lens 532 nm Ar/H 2 O/CCl 4 supersonic expansion

MW Amplifier SPDT switch Digitiser and computer MW Signal generator Image rejection mixer Low Band Pass Filter RF Mixer Pre-amp 20 MHz 10 MHz Single Sideband modulator e - 20 MHz Fabry-Perot Resonator Parallel Propagation 350 mm diameter 840 mm curvature radius ~700 mm distance aluminum e e e - 20 MHz ( m - e ) +20 MHz +Δ MW Signal Generator 20 MHz Δ +20 MHz Frequency Doubler Attenuators Adjustable frequency (6 ≤ e ≥ 18 GHz) -20 MHz Low Noise Amplifier m m =Δ +20 MHz Balle-Flygare FTMW Spectrometer

CF 3 I But what’s this stuff ???? 3 hours of averaging, CF 3 I, CO and Ar gas sample

A new complex of CF 3 I and CO

But what’s this stuff ???? CF 3 I 6 hours of averaging, CF 3 I, N(CH 3 ) 3 and Ar gas sample

A new complex of CF 3 I and N(CH 3 ) 3

Energy/MHz Sym. Asym. Total sim. Exp. C 2 H 4  ICF 3 Prof. Brian Howard, University of Oxford

Frequency / MHz 107 AgI 109 AgI. H2SH2S  107 AgI H2SH2S  109 AgI H 2 S  ICF 3 H 2 S  AgI

V( φ)/cm -1 φ/deg 39.1 º V = “Identification and molecular geometry of a weakly bound dimer (H 2 O,HCl) in the gas phase by rotational spectroscopy” A. C. Legon and L. C. Willoughby, Chem. Phys. Letters, 95, , (1983).

/ MHz Ionicity, i c M=Cu M=AgM=CuM=Ag MCl16.2  32.1  Ar  MCl33.2  28.0  Kr  MCl36.5  27.3  H 2 O  MCl50.3  25.5  H 3 N  MCl  29.8  0.73 H 2 S  MCl61.8  23.0  OC  MCl70.8  21.5  H 4 C 2  MCl63.8  21.0  / MHzIonicity, i c NaCl d  Ar  NaCl d  Determination of the molecular geometry of each of the above complexes completed (where possible from isotopic substitution). Nuclear quadrupole coupling constants provide measure of charge redistribution after formation of the complex. Nuclear Quadrupole Coupling Constants

H 2 O  AgCl r AgCl / År AgO / Å  / ˚ cc-pVTZ a cc-pVQZ b r0r (6)2.198(10)37.4(16) H 3 N  AgCl r AgCl / År AgN / Å  AgNH cc-pVTZ cc-pVQZ r0r (6) (6)113.48(2) H 2 S  AgCl r AgCl / År AgS / Å  / ˚ cc-pVTZ cc-pVQZ r0r (13) (12)78.052(6) H 4 C 2  AgCl r AgCl / År AgX / Å  CCH cc-pVTZ cc-pVQZ r0r (8)2.1719(9)123.02(6) CCSD(T) calculations. cc-pVTZ basis sets for H, O. cc-pV(T+d)Z basis set for Cl. cc-pVTZ-PP for Ag. Theory Dr. David Tew, University of Bristol

Endo and co-workers Publications on B  MX Complexes H 3 N...AgCl, V.A. Mikhailov et al., Chem. Phys. Lett. 499, (2010) H 2 O...CuCl and H 2 O...AgCl ; V.A. Mikhailov et al., J. Chem. Phys., 134, (2011) H 2 O...AgF, S.L. Stephens et al., J. Mol. Spectrosc. 267, (2011) H 2 S...CuCl and H 2 S...AgCl; N.R. Walker et al., J. Chem. Phys. 135, (2011) C 2 H 4...Ag-Cl; S.L. Stephens et al., J. Chem. Phys. 135, (2011)