1. THE STUDY OF ACENAPHTHENE AND ITS COMPLEXATION WITH WATER
AMANDA L. STEBER, CRISTOBAL PEREZ, BERHANE TEMELSO, GEORGE C. SHIELDS, ANOUK M. RIJS, ZBIGNIEW KISIEL, and MELANIE SCHNELL
Styling: MPSD color:

2. Introduction PAH Hypothesis: No identification of an individual PAH
Used to explain UIR bands in the mid IR from 3.3 – 12.7 microns
Postulates PAHs are the most abundant molecules in space after H2 and CO
An estimated 20% of the total galactic carbon is locked in PAHs1
Believed to help form ice grains
No identification of an individual PAH
Cyclic water trimer has only been observed once in microwave spectroscopy2 due to tunneling effects
1 Joblin, C. & Mulas, G. EAS Publ. Ser. 35, 133–152 (2009).
2 Arunan, E., Emilsson, T. & Gutowsky, H. S. J. Am. Chem. Soc. 116, 8418–8419 (1994).

3. Instrumentation
2-8 GHz Chirped pulse Fourier transform microwave spectrometer
Nozzle heated to between ~
External water reservoir
1:1 water mixtures for 16O:18O mixtures
Brown, G. G. et al. Rev. Sci. Instrum. 79, (2008).
Schmitz, D., Alvin Shubert, V., Betz, T. & Schnell, M. J. Mol. Spectrosc. 280, 77–84 (2012).

4. Acenaphthene Monomer 800,000 acquisitions 2.5 bar neon
S. Thorwirth et al. Astrophys. J., 662, 1309 (2007).

5. Acenaphthene – water complexes
2.5 million acquisitions
3 bar neon

6. Acenaphthene – water complexes
2.5 million acquisitions
3 bar neon

7. Acenaphthene – water structures
Calculations: MP2/aug-cc-pVTZ

8. Acenaphthene – water structures
r0 vs rs structures
r0 vs ab initio:
RMSD = 0.12Å

9. 3water complexes Arunan, E., Emilsson, T. & Gutowsky, H. S.
J. Am. Chem. Soc. 116, 8418–8419 (1994).
Keutsch, F. N., Cruzan, J. D. & Saykally, R. J.
Chem. Rev. 103, 2533–2578 (2003).
Ouyang, B., Starkey, T. G. & Howard, B. J.
J. Phys. Chem. A 111, 6165–6175 (2007).
Pérez, C. et al.
Angew. Chem. Int. Ed. 54, 979–982 (2015).
Pérez, C. et al.
J. Phys. Chem. Lett. 7, 154–160 (2016).

10. Cyclic (H2O)3 comparison
Ace - (H2O)3 Complex
Ab initio
r0 structure
rs structure
O-O distance (Å)
A-B
2.782
2.790
2.810 (10)
2.812 (30)
B-C
2.766
2.856 (9)
2.851 (11)
A-C
2.891
2.953 (10)
2.942 (28)
Keutsch, F. N., Cruzan, J. D. & Saykally, R. J.
Chem. Rev. 103, 2533–2578 (2003).

11. Binding Energies SAPT2+3/6-311++G** MP2 ΔEelst ΔEexch ΔEind ΔEdisp
ΔEtot
(H2O)2
-8.90
8.17
-2.40
-1.35
-4.47
Benzene-H2O
-2.98
3.87
-1.04
-2.34
-2.49
-3.28
Ace-H2O
-4.81
6.62
-1.22
-4.23
-3.64
-4.32
Ace-(H2O)2
---
-13.29
Ace-(H2O)3
-24.99

12. (Ace)2 – H2O complex
18O

13. ΔE between rank 227 and rank 399
(Ace)2 – H2O complex
Constrained
Experimental
M062x/
6-31++G**
G**
MP2/
aug-cc-pVDZ
2A1W
2A1W_18O
hf3c
rank 227
rank 399
A (MHz)
(22)
(18)
355
349
B (MHz)
(17)
(16)
215
217
245
C (MHz)
(17)
(17)
194
196
236
ΔJ (kHz)
0.0130(12)
0.0139(11)
ΔJK (kHz)
0.9645(54)
1.3173(51)
ΔK (kHz)
(46)
(46)
δJ (kHz)
---
δK (kHz)
-1.129(23)
-1.505(25)
# lines 83 88
σ (kHz)
4.44
4.29
ΔE between rank 227 and rank 399
M062x: ΔE = 0.46 kcal/mol
MP2: ΔE = 2.84 kcal/mol

14. (Ace)2 – H2O complex Experimental M062x/ 6-31++G** 6-311++G**
Constrained
MP2/
aug-cc-pVDZ
2A1W
2A1W_18O
hf3c
rank 227
rank 399
A (MHz)
(22)
(18)
355
349
B (MHz)
(17)
(16)
215
217
245
C (MHz)
(17)
(17)
194
196
236
hf3c
Rank 227
Rank 399

15. (Ace)2 – H2O complex
Calculations: M062x/6-31++G**

16. Conclusions Acenaphthene KRA structure determined
Ace – (H2O)n complexes observed and structure determined
(Ace)2 – H2O observed
Distorted cyclic water trimer observed for the three water complex
Implications for ice grain formation

17. Thank you for your attention!
Acknowledgement
Thank you for your attention!
Funding:
CUI – Louise Johnson Fellowship