1. Microwave Spectra and Structures of H4C2CuCl and H4C2AgCl1
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

2. 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.

3. 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

4. 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

5. 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 averaging cycles
Frequency / MHz

6. 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

7. 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
(34)
(24)
(31)
(39)
C0/MHz
(34)
(24)
(31)
(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 MHz.

8. 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= (14) Å
rCH= (13) Å
CCH=121.16(11)
a) N. C. Craig, P. Gröner and D. C. McKean, J. Phys. Chem. A 110, (2006).
b) T. C. Tan, K. I. Goh, P. P. Ong and H. H. Tro, J Mol. Spectrosc. 307, (2001).
r0 bond length of AgCl= 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.

9. H4C2CuCl
Spectroscopic constant
12C2H463Cu35Cl
12C2H465Cu35Cl
12C2H463Cu37Cl
A0/ MHz
24076(42)
24076*
B0 / MHz
(30)
(28)
(20)
C0 / MHz
(30)
(28)
(20
ΔJ / kHz
0.281(26)
0.281*
ΔJK / kHz
18.89(63)
18.89*
χaa(Cu) / MHz
(76)
59.046(30)
(39)
{ χbb(Cu) χcc(Cu)}/MHz
44.55(28)
41.15*
44.54*
χaa(Cl) /MHz
 (95)
 (88)
 (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 MHz; N. C. Craig, P. Gröner and D. C. McKean, J. Phys. Chem. A 110, (2006).

10. 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.

11. 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
(6)
(6)
113.48(2)
H2SAgCl
rAgS / Å
2.2835
2.4049
76.2
2.2777
2.3875
(13)
(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.

12. 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
<
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