Microsolvation of -propiolactone as revealed by
Chirped-Pulse Fourier Transform Microwave Spectroscopy
Justin L. Neill, Matt T. Muckle, Daniel P. Zaleski, Brooks H. Pate Department
of Chemistry, University of Virginia, McCormick Rd, P.O. Box 400319, Charlottesville,
VA 22904
I. Peña, C. Perez, J.L. Alonso Grupo de Espectroscopía Molecular (GEM),
Departamento de Química Física y Química Inorgánica, Facultad de Ciencias,
Universidad de Valladolid, E-47005 Valladolid, Spain
High-Resolution Spectroscopy of Solvated Organic Molecules
Water cubes:
-benzene-(H2O)8: Gruenloeh et al.
-phenol-(H2O)7,8: Janzen et al.
(UV/IR)
Microwave studies:
-trifluoroacetic acid-(H2O)3: Ouyang et al.
-formic acid-(H2O)2 : Priem et al.
(H2O)3-6: Saykally group (THz tunneling)
C.J. Gruenloeh et al., Science 276, 1678 (1997).
Ch. Janzen et al., J. Chem. Phys. 110, 9898 (1999).
B. Ouyang, T.G. Starkley, B.J. Howard, J. Phys. Chem. A 111, 6165 (2007).
D. Priem, T.-K. Ha, A. Bauder, J. Chem. Phys. 113, 169 (2000).
S. E. Novick, Bibliography of Rotational Spectra of Weakly Bound Complexes, (2010). Electronic updates are available on the web
at http://www.wesleyan.edu/chem/faculty/novick/vdw.html.
Experimental Methods:
Chirped-Pulse FTMW Spectrometer
Tools for structural analysis:
-10% H218O sample to observe isotopically
substituted species
-CP-FTMW Stark effect measurement (60 V/cm)
calibrated with trifluoropropyne 1st-order shifts
1.23 million averages (59 h), 300 W TWTA
2 nozzles, 10 FIDs per valve injection
He or Ne backing gas (4 atm)
G.G. Brown, B.C. Dian, K.O. Douglass, S.M. Geyer, S.T. Shipman, and B.H. Pate, Rev. Sci. Instrum. 79 (2008) 053103
L. Alvarez-Valtierra, S.T. Shipman, J.L. Neill, B.H. Pate, A. Lesarri, ISMS 2008, WF12.
T. Emilsson, H.S. Gutowsky, G. de Oliveira, C.E. Dykstra, J. Chem. Phys. 112, 1287 (2000).
CP-FTMW Spectrum
x50
x500
x5000
Dense spectrum—microwave-microwave double resonance spectroscopy used extensively
CP-FTMW Spectrum
1966 lines detected with signal to noise > 3:1
x230
1197 lines (61%) still unassigned
-propiolactone
Experimental
Ab Initio
Pct. Error
A (MHz)
12405.9884(13)
12372.59
-0.27%
B (MHz)
5244.4548(5)
5240.17
-0.08%
C (MHz)
3869.1913(4)
3864.47
-0.12%
A (D)
3.675(10)
3.74
1.8%
B (D)
2.01(5)
2.07
2.9%
C (D)
---
0.00
---
total (D)
4.19
4.28
2.1%
CP-FTMW
Kwak et al.
A (D)
3.675(10)
3.67(4)
B (D)
2.01(5)
2.00(2)
Large circles: ab initio structures
Small circles: substitution coordinates
Avg. deviation: 0.011 Å
Ab Initio calculations: Gaussian 03W, mp2/6-311++g(d,p) (all structures)
Spectral fits: SPFIT/SPCAT, PIFORM (PROSPE, Z. Kisiel, http://www.ifpan.edu.pl/~kisiel/prospe.htm), QSTARK (PROSPE)
Figures: PMIFST (PROSPE)
N. Kwak, J.H. Goldstein, J.W. Simmons, J. Chem. Phys. 25, 1203 (1956).
Z. Chen and J. van Wijngaarden, J. Mol. Spectrosc. 257, 164 (2009).
-propiolactone-H2O
Experimental
Ab Initio
Pct. Error
A (MHz)
6792.8734(20)
6721.55
-1.05%
B (MHz)
2056.4976(5)
2091.08
1.68%
C (MHz)
1613.5724(5)
1631.76
1.13%
A (D)
0.9964(11)
0.74
-25.7%
B (D)
2.543(23)
2.45
-3.47%
C (D)
[0] (fixed)
0.63
---
total (D)
2.73
2.64
-3.30%
No c-type transitions observed; searched for tunneling gap
<500 MHz
O deviation: 0.071 Å
-propiolactone-(H2O)2
Experimental
Ab Initio
Pct. Error
A (MHz)
2856.852(3)
2938.33
2.85%
B (MHz)
1730.192(4)
1763.43
1.92%
C (MHz)
1377.649(3)
1417.81
2.92%
A (D)
2.160(10)
2.03
-6.02%
B (D)
1.544(23)
1.36
-11.9%
C (D)
0.330(3)
0.32
-3.03%
total (D)
2.676(25)
2.46
-8.07%
average O deviation: 0.106 Å
-propiolactone-(H2O)3
Experimental
Ab Initio
Pct. Error
A (MHz)
1861.023(6)
1915.73
2.94%
B (MHz)
1165.9916(6)
1157.19
-0.76%
C (MHz)
883.9891(5)
873.67
-1.17%
A (D)
2.357(5)
1.98
-16.0%
B (D)
0.60(13)
0.36
-40%
C (D)
0.12(8)
0.31
158%
total (D)
2.44(15)
2.03
-16.8%

14.28°
10.3°
-4.0°

87.18°
81.2°
-5.9°
average O deviation: 0.197 Å
Experimental
A (MHz)
1887.1478(18)
B (MHz)
1110.5723(12)
C (MHz)
838.6250(12)
A (D)
0.8690(24)
B (D)
---
C (D)
1.773(8)
total (D)
1.975(8)
~5x weaker than above spectrum
No structural assignment
-propiolactone-(H2O)4
Experimental
Ab Initio
Pct. Error
A (MHz)
1234.1037(7)
1253.26
1.55%
B (MHz)
931.7212(4)
951.05
2.08%
C (MHz)
830.9703(5)
846.04
1.81%
A (D)
0.5026(9)
0.54
7.44%
B (D)
3.785(11)
3.90
3.04%
C (D)
2.667(7)
2.94
10.24%
total (D)
4.657(13)
4.91
5.43%
average O deviation: 0.105 Å
Experimental
Ab Initio
Pct. Error
A (MHz)
1263.5285(10)
1313.81
3.98%
B (MHz)
933.8867(9)
964.39
3.27%
C (MHz)
828.4353(8)
828.80
0.04%
A (D)
0.9848(15)
1.32
34.0%
B (D)
4.215(19)
4.46
4.77%
C (D)
2.009(7)
2.17
8.01%
total (D)
4.772(20)
5.14
7.71%
2:1 intensity ratio
E rel= 70.4 cm-1
-propiolactone-(H2O)4
-(H2O)4 mininum: free protons are “udud”
around the ring
-BPL-(H2O)4: free protons are “uudd”
around the ring--less stable by 325 cm-1
tunneling quenched by complexation
-two structures differ only by the direction of
H-bonding around the ring
J.D. Cruzan, M.R. Viant, M.G. Brown, R.J. Saykally, J. Phys. Chem. A 101, 9022 (1997).
M. Schütz, W. Klopper, H.-P. Lüthi, J. Chem. Phys. 103, 6114 (1995).
-propiolactone-(H2O)5
Experimental
Ab Initio
Pct. Error
A (MHz)
945.8879(8)
936.88
-0.95%
B (MHz)
654.1482(5)
679.85
3.93%
C (MHz)
642.1021(5)
661.64
2.95%
(B/A)2
0.27
0.77
(C/A)2
0.60
0.52
Discrepancy in relative b/c dipoles
Conclusions
All observed structures cool to minimum-energy configurations (rather than
sequential addition)
Competition/compromise between water-molecule and water-water interactions
Importance of isotopic substitution, Stark effect measurements in structure
determination of large water clusters
-substitution structures and dipole moments agree very well with
ab initio values
-Use of isotopic assignments to drive ab initio (rather than
the reverse)
Acknowledgements
Funding
National Science Foundation
Chemistry CHE-0616660
CRIF:ID CHE-0618755
Miniesterio de Ciencia y Tecnología (Grant CTQ2006-05367)
Junta de Castilla y León, Fondo Social Europeo (Grant VA012C05)
Dipole Moment Errors
PL
PL-(H2O)3
Experimental
Ab Initio
Error
Experimental
Ab Initio
Error
 (D)
4.189
4.28
2.05%
 (D)
2.435
2.04
-16.4%

28.7°
29.0°
0.3°

14.28°
10.3°
-4.0°

90°
90°
0°

87.18°
81.2°
-5.9°
PL-H2O
PL-(H2O)4 (stronger)
Experimental
Ab Initio
Error
Experimental
Ab Initio
Error
 (D)
2.727
2.64
-3.33%
 (D)
4.657
4.914
5.5%

68.57°
73.2°
4.6°

82.44°
82.1°
-0.3°

90°
76.2°
-13.8°

55.07°
53.3°
-1.8°
PL-(H2O)2
PL-(H2O)4 (weaker)
Experimental
Ab Initio
Error
Experimental
Ab Initio
Error
 (D)
2.676
2.46
-7.9%
 (D)
4.772
5.133
7.6%

35.56°
33.8°
-1.7°

76.85°
73.5°
-3.3°

82.92°
82.5°
-0.4°

65.10°
65.0°
-0.1°
Experimental Methods:
MW-MW Double Resonance Spectroscopy
CP-FTMW-MW Double Resonance
Cavity FTMW-MW Double Resonance
-propiolactone-(H2O)5
(H2O)5: slightly puckered, has an “uudud” orientation of the water pentamer
BPL-(H2O)5: similar structure; internal tunneling/pseudorotation quenched by
complexation
K. Liu, M.G. Brown, J.D. Cruzan, R.J. Saykally, J. Phys. Chem. A 101, 9011 (1997).