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: 44-89-160

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).

Instrumentation 2-8 GHz Chirped pulse Fourier transform microwave spectrometer Nozzle heated to between ~100-115 External water reservoir 1:1 water mixtures for 16O:18O mixtures Brown, G. G. et al. Rev. Sci. Instrum. 79, 53103 (2008). Schmitz, D., Alvin Shubert, V., Betz, T. & Schnell, M. J. Mol. Spectrosc. 280, 77–84 (2012).

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

Acenaphthene – water complexes 2.5 million acquisitions 3 bar neon

Acenaphthene – water complexes 2.5 million acquisitions 3 bar neon

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

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

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).

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).

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

(Ace)2 – H2O complex 18O

ΔE between rank 227 and rank 399 (Ace)2 – H2O complex Constrained Experimental M062x/ 6-31++G** 6-311++G** MP2/ aug-cc-pVDZ   2A1W 2A1W_18O hf3c rank 227 rank 399 A (MHz) 365.12749(22) 362.68191(18) 355 349 B (MHz) 204.00890(17) 200.12250(16) 215 217 245 C (MHz) 181.69642(17) 179.14017(17) 194 196 236 ΔJ (kHz) 0.0130(12) 0.0139(11) ΔJK (kHz) 0.9645(54) 1.3173(51) ΔK (kHz) -0.9213(46) -1.2583(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

(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) 365.12749(22) 362.68191(18) 355 349 B (MHz) 204.00890(17) 200.12250(16) 215 217 245 C (MHz) 181.69642(17) 179.14017(17) 194 196 236 hf3c Rank 227 Rank 399

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

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

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