1. Pure Rotational and Ultraviolet-Microwave Double Resonance Spectroscopy of Two Water Complexes of para-methoxyphenylethylamine (pMPEA) Justin L. Neill, Matt T. Muckle and Brooks H. Pate, Department of Chemistry, University of Virginia Ryan G. Bird, David W. Pratt, Department of Chemistry, University of Pittsburgh

2. Spectroscopy of pMPEA and pMPEA-water pMPEA Seven conformers reported: Martinez et al, J. Mol. Spectrosc. 158 (1993) 82-92. Complete (correct) structural assignment: Robertson, Simons, and Mons, J. Phys. Chem. A 105 (2001) 9990. Yi, Robertson, and Pratt, Phys. Chem. Chem. Phys. 4 (2002) 5244-5248. (rotationally resolved LIF) Douglass et al., MF02, ISMS (2006) (CP-FTMW and UV-MW) Cortijo, Alonso, and López, Chem. Phys. Lett. 466 (2008) 214-218. (MW) pMPEA-water Two clusters found, binding energies measured, assigned to structures: Unamuno et al, Chem. Phys. 271 (2001) 55-69. Unamuno et al.

3. Conformational Landscape of pMPEA ConformerE (cm -1 ) E-80 D-534 C-738 A-454 B-1351 F-2489 G-3498 6675 9678 Yi, Robertson, and Pratt, Phys. Chem. Chem. Phys. 4 (2002) 5244-5248. mp2/6-31g** A B C D E F G B FG A D E C

4. New CP-FTMW Measurements Sample acquired from Aldrich (98%); placed in reservoir within nozzle, heated to approximately 100°C, seeded in He/Ne supersonic expansion. (No water added) CP-FTMW sample reduction techniques: 3 nozzles 10 FIDs per valve pulse Collected 995,000 FIDs, using 298,500 valve pulses, equivalent sensitivity to 8.955 million pulses with a single nozzle! Measurement time: 48 hours (consecutive) G.G. Brown, B.C. Dian, K.O. Douglass, S.M. Geyer, S.T. Shipman, and B.H. Pate, Rev. Sci. Instrum. 79 (2008) 53103-1-13.

5. New CP-FTMW Measurements 3 nozzles, 995,000 FIDs (298,500 pulses) versus 1 nozzle, 80,000 FIDs (80,000 pulses) Scaled to match signal heights on strongest transitions

6. New CP-FTMW Measurements 2008 spectrum much richer than 2006…(used same bottle) 3 nozzles, 995,000 FIDs (298,500 pulses) versus 1 nozzle, 80,000 FIDs (80,000 pulses) Scaled to match signal heights on strongest transitions

7. New Transitions Several unassigned Q-branches observed. For near-prolate top, b/c-type Q-branches are located at approximately (A-(B+C)/2)*(2K-1), so the ratio between two Q-branches gives you their K assignments and A-(B+C)/2. Pattern of the Q-branches gives (B-C), then (A+B+C) can be varied until the strong b/c-type R-branches are fit. Two new spectra were assigned this way.

8. New Transitions

9. pMPEA-water Fit Parameters Conformer D-waterExperimentTheory A/MHz1740.6781(7)1769.85 B/MHz430.5044(4)426.01 C/MHz380.0915(4)376.65 χ aa /MHz0.20(6)0.41 χ bb -χ cc /MHz-2.419(26)-2.19 N lines 224 rms error/kHz24.2 µ a /D0.64 µ b /Db ≈ c2.84 µ c /D2.60 Conformer E-waterExperimentTheory A/MHz1533.8873(10)1552.23 B/MHz457.8598(5)452.47 C/MHz398.9191(9)383.61 χ aa /MHz0.785(47)0.97 χ bb -χ cc /MHz-2.31(44)-2.04 N lines 137 rms error/kHz12.7 µ a /D0.47 µ b /Dc only0.49 µ c /D2.32 Observed structures are analogous to those of other similar structures: tryptamine (Felker, J. Phys. Chem. 96 (1992) 7844); 2-phenylethylamine (Melandri, et al, RC13) Ab initio: b3pw91/6-311+g(df,pd), using effective Q and recommended basis set of W.C. Bailey (http://homepage.mac.com/wcbailey/nqcc/) All fits performed using SPFIT (Pickett), with standard errors determined by PIFORM (Kisiel). (Quartic distortion parameters not listed)

10. Coherence-Converted Population Transfer UV-FTMW Spectroscopy T.J. Balle and W.H. Flygare, Rev. Sci. Instrum. 52, 33 (1981) M. Nakajima, Y. Sumiyoshi, and Y.Endo, Rev. Sci. Instrum. 73, 165 (2002) MW Synthesizer ν0ν0 ν0ν0 Free Induction Decay (30 MHz Carrier) 1 Gs/s Oscilloscope R.D. Suenram, J.U. Grabow, A. Zuban, and I. Leonov, Rev. Sci. Instrum. 70, 2127 (1999) Douglass, Johns, Nair, Brown, Rees, and Pate, J. Mol. Spectrosc. 239, 29 (2006) 2 GS/s AFG v 0 + 30 MHz Single Sideband Pulsed 1 watt amp Nd:YAG Continuum 10 Hz rep. rate 200 mJ/p 532 nm 5 mJ/p UV 0.025 cm -1 bandwidth Dye laser Lambda Physik All spectra are ~0.1 cm -1 blue-shifted due to coaxial arrangement. Rhodamine 6G dye, doubled with BBO SHG crystal

11. pMPEA-water UV-FTMW Flowed He/Ne gas over cooled (0°C) water reservoir before entering chamber; increased signals by around a factor of 5 (as strong as monomer) With the water reservoir at room temperature, signal started to drop again (higher water clusters?)

12. Ab Initio Relative Energies (cm -1 ) ConformerA-4B-1C-7D-5E-8F-2G-369 Monomer5435138340489498675678 Water cluster1023142710054409189461210816 mp2/6-31g** pMPEA(E)-water pMPEA(C)-waterpMPEA(9)-water

13. pMPEA-water UV-FTMW The assignments of Unamuno et al are correct—35670 cm-1 feature is due to water with conformer 5; 35681 cm-1 feature is due to water with conformer 8. Their assignments were based on structural stability—conformer 8+water goes to strongest peak, conformer 5+water to second-strongest—and low-frequency vibrational mode calculations.

14. Residual Spectrum No residual transitions with resolved quadrupole hyperfine splitting—not pMPEA, or simply a function of cluster size? (large number of hyperfine-resolved transitions for assigned pMPEA-H 2 O clusters) Possibilities: Other conformers with water; water molecule on the methoxy group? (Unlikely due to energetics) Two waters or more? (more likely—ab initio calculations needed) Remeasure CP-FTMW spectrum with water added! MW-MW double resonance spectroscopy needed Strongest pMPEA transition intensity 120 µV

15. Acknowledgements Funding: NSF CRIF:ID (CHE-0618755) Jefferson Scholars Foundation (J.Neill) Tektronix

16. pMPEA-water Fit Parameters Conformer D-waterExperimentTheory A/MHz1740.6781(7)1769.85 B/MHz430.5044(4)426.01 C/MHz380.0915(4)376.65 D J /kHz0.0496(13) D JK /kHz-0.223(6) D K /kHz2.586(13) d J /kHz0.0114(5) d K /kHz0.32(5) χ aa /MHz0.20(6)0.41 χ bb -χ cc /MHz-2.419(26)-2.19 N lines 224 rms error/kHz24.2 µ a /D0.64 µ b /Db ≈ c2.84 µ c /D2.60 Conformer E-waterExperimentTheory A/MHz1533.8873(10)1552.23 B/MHz457.8598(5)452.47 C/MHz398.9191(9)383.61 D J /kHz0.0573(35) D JK /kHz-0.063(12) D K /kHz1.468(34) d J /kHz0.0113(20) d K /kHz0.23(8) χ aa /MHz0.785(47)0.97 χ bb -χ cc /MHz-2.31(44)-2.04 N lines 137 rms error/kHz12.7 µ a /D0.47 µ b /Dc only0.49 µ c /D2.32 Observed structures are analogous to those of other similar structures: tryptamine (Felker, J. Phys. Chem. 96 (1992) 7844); 2-phenylethylamine (Melandri, et al, RC13)