Microwave Spectra and Structures of H4C2CuCl and H4C2AgCl 1 Microwave Spectra and Structures of H4C2CuCl and H4C2AgCl by Nicholas R. Walker, Susanna L. Stephens, Victor A. Mikhailov and Anthony C. Legon Rod rotator Laser arm Gas line attached to solenoid valve Microwave emission antenna

Objectives Apply microwave spectroscopy to study interactions of the broadest significance in inorganic chemistry. Examples include complexes formed between CO, H2S, N2, H2O, NH3 and the noble metal atoms Cu and Ag. Establish laser ablation as a general method for the production of metal-ligand complexes for study by microwave spectroscopy. Compare units such as H4C2CuCl, H4C2AgCl with hydrogen-bonded analogues, e.g. H4C2HCl, to identify common trends. Previous works include studies of OCMX by Gerry and co-workers. Also N2MX and H2SMX by Walker, Legon and co-workers.

Balle-Flygare FTMW spectrometer Rod rotater Laser arm 532 nm Nd:YAG laser Focusing lens Solenoid valve Adiabatic expansion of CCl4 / C2H4 / Ar Gas line Copper or silver rod and rod rotater Connections to microwave emission and detection circuits Fixed mirror To vacuum Adjustable mirror

H4C2CuCl and H4C2AgCl X Asymmetric tops of C2v symmetry. Dipole moment on a axis, Expect a-type transitions. Determine B0, C0, and possibly A0? Sensitive to rMCl, rMX and maybe rCC. M

H4C2AgCl F′-F′′ = Frequency / MHz JK-1 K+1 JK-1 K+1 = 313  414 Silver rod, natural isotope abundances. 3000 averaging cycles Isotopically-enriched 107Ag rod. 3000 averaging cycles Frequency / MHz

H4C263Cu35Cl Frequency / MHz F′′-F′ = JK-1 K+1 JK-1 K+1 = 202  303 F′′-F′ = , 23 , 45 , 56 1000 averaging cycles Frequency / MHz

H4C2AgCl Spectroscopic constant 12C2H4107Ag35Cl 12C2H4109Ag35Cl 12C2H4107Ag37Cl 12C2H4109Ag37Cl A0/ MHz 24301(47)a,b 24427(33) 24236(57) 24329(62) B0/MHz 1602.15391(34) 1602.04542(24) 1556.60563(31) 1556.44731(39) C0/MHz 1533.53207(34) 1533.43255(24) 1491.74602(31) 1491.59972(39) ΔJ/kHz 0.2198(84) 0.2295(64) 0.191(11) 0.202(11) ΔJK/kHz 13.59(41) 12.33(29) 13.75(48) 12.84(39) χaa(Cl)/MHz 27.856(25) 27.850(18) 22.026(28) 21.962(29) { χbb(Cl) χcc(Cl)}/MHz 2.75(10) 2.719(91) 1.91(12) 2.02(15) N 31 28 25 26 σr.m.s /kHz 2.7 1.8 2.3 3.0 Pb / u Å2 17.46(2) 17.40(2) 17.48(2) 17.44(2) Pc / u Å2 3.34(2) 3.29(2) 3.37(2) 3.33(2) a Numbers in parentheses are one standard deviation in units of the last significant figure. b The C0 rotational constant of 12C2H4 is 24824.20 MHz.

Dihedral angle(AgCCH) (94.51)c 6 isotopologues Distances and angles rs-geometry r0-geometry r(XAg)/Ǻ 2.1697(4)a 2.1719(9) r(Ag–Cl)/Ǻ 2.2701(2) 2.2724(8) r(C–C)/Ǻ 1.354(40) 1.3518(4) r(C–H)/Ǻ  (1.0853)b Angle(CCH) /deg. 123.02(6) Dihedral angle(AgCCH) (94.51)c 6 isotopologues X r0 Geometrya,b of isolated C2H4 rCC= 1.3386(14) Å rCH= 1.0849(13) Å CCH=121.16(11) a) N. C. Craig, P. Gröner and D. C. McKean, J. Phys. Chem. A 110, 7461-7469 (2006). b) T. C. Tan, K. I. Goh, P. P. Ong and H. H. Tro, J Mol. Spectrosc. 307, 189-192 (2001). r0 bond length of AgCl= 2.2836 Å; K. D. Hensel, C. Styger, W. Jäeger, A.J. Merer and M.C.L. Gerry; J. Chem. Phys. 99, 3320 (1993). a Small rs coordinate for silver calculated using the first moment condition. b Assumed from ab initio value corrected for the difference between re and r0 for C2H4. cAssumed unchanged from ab initio re value.

H4C2CuCl Spectroscopic constant 12C2H463Cu35Cl 12C2H465Cu35Cl 12C2H463Cu37Cl A0/ MHz 24076(42) 24076* B0 / MHz 1988.92787(30) 1988.625649(28) 1933.68868(20) C0 / MHz 1882.69407(30) 1882.41064(28) 1833.15068(20 ΔJ / kHz 0.281(26) 0.281* ΔJK / kHz 18.89(63) 18.89* χaa(Cu) / MHz 63.8102(76) 59.046(30) 63.8125(39) { χbb(Cu) χcc(Cu)}/MHz 44.55(28) 41.15* 44.54* χaa(Cl) /MHz 20.9974(95) 20.9906(88) 16.5534(52) { χbb(Cl) χcc(Cl)} /MHz 5.657(55) 5.659* 4.46* (Cbb + Ccc) / kHz 12.38(77) 13.58(45) 12.38 N 56 13 24 σr.m.s / kHz 3.5 1.0 1.3 a Numbers in parentheses are one standard deviation in units of the last significant figure. b The C0 rotational constant of 12C2H4 is 24824.20 MHz; N. C. Craig, P. Gröner and D. C. McKean, J. Phys. Chem. A 110, 7461-7469 (2006).

Nuclear Quadrupole Coupling Constants / MHz Ionicity, ic M=Cu M=Ag MCla 16.2 32.1 36.4 0.71 0.67 ArMCla 33.2 28.0 34.5 0.74 0.69 KrMCla 36.5 27.3 33.8 0.75 H2OMClb 50.3 25.5 32.3 0.77 H3NMClb  29.8 0.73 H2SMClc 61.8 23.0 29.4 0.79 OCMClb 70.8 21.5 28.1 0.80 H4C2MCl 63.8 21.0 27.9 0.81 NaCld 5.7 0.95 ArNaCld 5.8 Intense signals. Nuclear quadrupole coupling constants and force constants (calculated from (B0+C0)/2 and DJ) indicate strong interactions between the metal and C2H4.

Theory Dr. David Tew, University of Bristol CCSD(T) calculations. H2OAgCl rAgCl / Å rAgO / Å  / ˚ cc-pVTZa 2.280 45.0 cc-pVQZb 2.272 2.209 43.7 r0 2.273(6) 2.198(10) 37.4(16) H3NAgCl rAgN / Å AgNH cc-pVTZ 2.2783 2.1619 111.87 cc-pVQZ 2.2714 2.1530 111.68 2.26333(6) 2.15444(6) 113.48(2) H2SAgCl rAgS / Å 2.2835 2.4049 76.2 2.2777 2.3875 2.26882(13) 2.38384(12) 78.052(6) H4C2AgCl rAgX / Å CCH 2.2837 2.1975 121.46 2.2771 2.1945 2.2724(8) 2.1719(9) 123.02(6) Dr. David Tew, University of Bristol CCSD(T) calculations. cc-pVTZ basis sets for H, O. cc-pV(T+d)Z basis set for Cl. cc-pVTZ-PP for Ag.

Engineering and Physical Sciences Research Council Acknowledgments and Advertisements Susanna L. Stephens Colin M. Western – for adapting and developing PGOPHER for microwave spectroscopy. Anthony C. Legon Victor A. Mikhailov <http://pgopher.chm.bris.ac.uk/> Theory David P. Tew Jeremy N. Harvey MH02, now follows – CP-FTMW Spectroscopy of CF3ICO, Susanna Stephens. WH04, (Wed. 2:21) – Microwave Spectrum and Structure of H2O AgF, Susanna Stephens. WH05, (Wed. 2.38) – Internal Rotation in CF3INH3 and CF3IN(CH3)3 Probed by CP-FTMW Spectroscopy , Nick Walker. Financial Support Engineering and Physical Sciences Research Council