Formation of M-C≡C-Cl (M = Ag or Cu) and Characterization by
Rotational Spectroscopy
Daniel P. Zaleski and Nick R. Walker
School of Chemistry, Bedson Building, Newcastle University, Newcastle upon
Tyne, NE1 7RU, UK.
David P. Tew and Anthony C. Legon
School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
The 70th International Symposium on Molecular Spectroscopy, June 25th, 2015.
Chemical Themes
The Basic Chemistry of
Life Emerges from the
Cold and the Dust
Interstellar Chemistry and the
Chemistry of Harsh Environments
The carbon-rich chemistry of the interstellar
medium has direct connections to many
technologically important areas of chemistry
Combustion
chemical intermediates
in flames
ESO
Despite inhospitable conditions,
the full range of organic
chemistry functional groups
are produced in the places
where planets form
Orion Horsehead Nebula
Electrical Discharge
lightning
planetary atmospheres

Organic chemistry is prevalent in the hot core regions
of star and planet formation

Molecule formation requires a combination of gasphase, surface, and ice chemistry

Unusual energy sources drive these chemical transformations (cosmic rays, EUV radiation, outflows)
Nanotechnology
fullerenes
carbon nanotubes
Discharge and Ablation
Phys. Chem. Chem. Phys., 2014, 16, 25221-25228.
 Well known that DC electric
discharges
can
produce
small
(un)stable molecules and hitherto
unknown species
 Laser ablation of solids is another
convenient method of producing
plasmas
 Nd:YAG operating at 532 nm (pulse
duration ~ 900 μs) is about 25
mJ/pulse: enough to ablate common
metals
If this plume immediately interacts with a gas of neutral molecules in
its vicinity, fragmentation of the molecules can occur and the
fragments can then undergo reactions.
Chirped Pulse FTMW Spectroscopy
Broadband spectrometers with instantaneous
frequency coverage from 2-8 GHz, 6.5-18.5 GHz,
18.5-26 GHz, and 25 – 40 GHz have been
constructed.
Current Technology:
AWG
Digital Oscilloscope
24 Gs/s (12 GHz)
100 Gs/s (33 GHz)
Phys. Chem. Chem. Phys., 2014, 16, 25221-25228.
1000x
1% CCl4
6 bar Ar
3M FIDs (100 hr) for normal species
Weaker signals due
to Cu/Cl hyperfine
1% CCl4
6 bar Ar
3M FIDs (100 hr) for the normal species
X-AgCl Trends
Species
χaa (MHz)
r(Ag-Cl) (Å)
AgCl
-36.4
2.281
-Ar
-34.5
2.285
-Kr
-33.8
2.277
Theory:
-Xe
-32.2
2.271
χaa = -31 MHz
-H2O
-32.3
2.272
-NH3
-29.8
2.263
-H2S
-29.4
2.255
-C2H2
-28.9
2.266
-OC
-28.2
2.255
-C2H4
-27.9
2.272
-C6H6
-24.1
2.240
r(Ag-Cl) = 2.218 Å
χaa = -76.93(26) MHz
rs(Ag-Cl) = 4.8729(12) Å
Z. Naturforsch., 1978, 33a, 156-163.
J. Chem. Phys., 2011, 135, 024315.
Structure Determination
Isotopic substitution produces small (and
predictable) shifts in the rotational constants
that are site-specific.
(A,B,C) = (IA,IB,IC)
(Aˊ,Bˊ,Cˊ) = (IAˊ,IBˊ,ICˊ)
I = Σ mi∙ri2
|ra|,|rb|,|rc|
Free from other assumptions about the
molecular structure
MP2/aug-cc-pVTZ-PP
Am. J. Phys., 1953, 21, 17.
Isotopologues
M = Ag
M = Cu
Species
Calc.
Exp.
Calc.
Exp.
nM12C12C35Cl
742.6 (n=107)
747.45619(16)
974.0 (n=63)
989.14990(73)
nM12C12C35Cl
738.3 (n=109)
743.16060(19)
961.7 (n=65)
976.72539(78)
nM12C12C37Cl
717.4 (n=107)
722.13078(21)
944.4 (n=63)
959.04302(38)
nM12C12C37Cl
713.2 (n=109)
717.88218(28)
932.3 (n=65)
-
nM13C13C35Cl
738.6 (n=107)
743.37328(30)
971.2 (n=63)
986.25614(29)
nM13C13C35Cl
734.3 (n=109)
739.03637(10)
958.9 (n=65)
-
Ag, Cu, C: CCSD(T)/aug-cc-pV5Z
Cl:
CCSD(T)/aug-cc-pV(5+d)
J. Chem. Phys., 2010, 133, 174301.
Properties
M = Ag
M = Cu
Calc.
r0
Calc.
r0
r(M-C) (Å)
2.0187
2.015(14)
1.8383
1.812(16)
r(C≡C) (Å)
1.2219
[1.2219]
1.2233
[1.2233]
r(C-Cl) (Å)
1.6491
1.635(6)
1.6479
1.639(6)
r(M∙∙∙Cl) (Å)
4.8897
4.8722(2)
4.7095
4.6736(6)
difference between r0 and re for the triple bond in
acetylene is 0.003 Å
Ag, Cu, C: CCSD(T)/aug-cc-pV5Z
Cl:
CCSD(T)/aug-cc-pV(5+d)
J. Chem. Phys., 2011, 134, 064119.
Population Analysis
It is difficult to discuss the precise mechanism by
which these slightly exotic substances are formed,
but it is well known that CCl, CCCl and CCl2 are
among the products when a thermal plasma is
sustained in CCl4/Ar mixtures.
AgCCCl: CCl2: CCCl
1 : 1 : 0.1
The geometry of the 2Σ ground state of the CCCl radical has r(C‒C) = 1.267 Å,
r(C‒Cl) = 1.634 Å and ∠ CCCl = 156.9°.
The first and third of these lie midway between the corresponding values in ethyne
and ethane, while r(C‒Cl) = 1.634 Å is very similar to the corresponding distance
determined here for both Ag‒C≡C‒Cl and Cu‒C≡C‒Cl.
J. Chem. Phys., 2003, 119, 1426-1432.
J. Mol. Spectrosc., 2005, 232, 375-379.
Plasma Chem. Plasma Proc., 2005, 109-119.
Conclusions
 Demonstrated the usefulness of unbiased broadband survey
spectra
 Identified a “pathway” for synthesizing MCCCl
- M = Ag or Cu
 Would be interesting to further investigate the MCCCl binding
properties
- look at gas phase clusters coordinating to either side
- M or Cl
 Look to synthesize longer chains
Acknowledgments
Engineering and Physical
Sciences Research Council
AWE
(Aldermaston)