1. Encapsulation of water molecules by dibenzo- 18-crown-6-ether in a supersonic jet Ryoji Kusaka, Yoshiya Inokuchi, Kenji Kawasaki, Takayuki Ebata* Department of Chemistry, Hiroshima University, Japan

2. OO O O O O K+K+ Introduction (H 2 O) n OO O O O O Dibenzo-18-crown-6-ether (DB18C6) We report how DB18C6 encapsulates water molecules. Crown ethers encapsulate various metal cations and neutral molecules. (H 2 O) n ?

3. Experiment Fluorescence intensity Probe UV h Pump IR IR-UV double resonance spectroscopy ~100 ns Pump UV h ~4  s Probe UV UV-UV hole burning spectroscopy Fluorescence intensity Probe UV LIF spectroscopy Nd YAG Dye SHG PMT chamber Nd YAG OPO Nd YAG Dye SHG sample water vapor and He gas h

4. LIF and hole burning spectra HB m1 3560035700 3580035900 36000 UV wavenumber / cm -1 HB m2 HB a HB c HB d HB e HB f LIF m1 m2 b c f d e a monomers hydrated clusters m1, m2 : monomers a-f : hydrated clusters From IR-UV spectra

5. The conformation of the monomers (m1 and m2) Chair (C i )  E = +542 cm -1 Boat (C 2v )  E = 0 cm -1 (B3LYP/6-31+G*) Optimized structures HB m1 3560035700 UV wavenumber / cm -1 HB m2 LIF m1 m2 5 cm -1 splitting no splitting Energy Chair Boat 0 cm -1 +542 cm -1 m1 m2 LIF intensity smallerlarger The vibronic structures of m1 and m2 are different. The difference comes from the symmetry.

6. Exciton splitting of chair and boat S2S2 S1S1 S0S0 AgAg AgAg AuAu A1A1 A1A1 B1B1 m1 = Chair ( C i ) m2 = Boat ( C 2v ) Transition dipole 3560035700 UV wavenumber / cm -1 m1 m2 exciton splittingno exciton splitting Next, we estimate the splitting energy.

7. Splitting energy E = 2E = 2 A BA B 4  0 R AB 3 (2cos  A cos  B sin  A sin  B cos  ) S2S2 S1S1 EE V di-di = dipole-dipole interaction V di-di 5 cm -1 (Obs.) This value (  E = 70 cm -1 ) is pure electronic splitting energy. Ratio of a vibronic transition = = 2 V di-di = 70 cm -1 exciton vibronic splitting = 70 cm -1 (pure electronic)0.1 (single vibronic) 3560035700 UV wavenumber / cm -1 m1 m2 exciton vibronic splitting ( ~5 cm -1 ) = 7 cm -1  = 5.5 10 -30 C m R = 8.8 A  = 320 and 220  = 0 the vibronic intensity total intensity = roughly about 10%

8. The structure of water clusters (in DB18C6 part) HB m1 3560035700 3580035900 36000 UV wavenumber / cm -1 HB m2 HB a HB c HB d HB e HB f LIF m1 m2(boat) b c f d e a hydrated clusters of m2(boat) The hydrated clusters, a-f show similar splitting to m2. m2 = Boat-DB18C6

9. DB18C6-(H 2 O) 1 3700360035003400 IR wavenumber / cm -1 3700360035003400 IR wavenumber / cm -1 Band a Band b bidentate H-bond O O H O H H-bonded from bottom H-bonded from top 3560035700 3580035900 UV wavenumber / cm -1 m1 m2 b c f d e a A water molecule Sym 3657 Anti-sym 3756

10. DB18C6-(H 2 O) 2 37003600 3500 340033003200 3100 IR wavenumber / cm -1 OH (H-donor) = 3530 cm -1 H-donor OH Free OH Band a Band c stronger hydrogen bond (H 2 O) 2 Electrostatic potential map (-0.1 a.u. (red) to +0.1 a.u. (blue)) Bidentate OH 3560035700 3580035900 UV wavenumber / cm -1 m1 m2 b c f d e a

11. DB18C6-(H 2 O) 3 and DB18C6-(H 2 O) 4 Free OH 370036003500340033003200 IR wavenumber / cm -1 370036003500340033003200 IR wavenumber / cm -1 H-donor OH Band d Band e H-bonded from bottom and top 3560035700 3580035900 UV wavenumber / cm -1 m1 m2 b c f d e a Bidentate OH

12. Another type of DB18C6-(H 2 O) 4 bridging OH 370036003500340033003200 IR wavenumber / cm -1 H-donor OH Free OH Band f Bidentate OH 3560035700 3580035900 UV wavenumber / cm -1 m1 m2 b c f d e a Band e H-donor OH Bidentate OH Free OH

13. Summary (growth of hydrogen bond networks) n = 1n = 2n = 3 n = 4 boat n = 0 LIF m1 m2 b c f d e a a b c d e f

14. The lowest vibration 21 cm -1 in S 0 HB m1 3560035700 3580035900 36000 UV wavenumber / cm -1 HB m2 HB a HB c HB d HB e HB f LIF m1 m2 b c f d e a monomers hydrated clusters 5 5 55 13 20 Boat m23964039722 3960839688 0.09280.0347 0.13820 chair m1 oscillator strength calc. transition energy / cm S 2 S 0 S 1 S 0 S 2 S 0 S 1 S 0 TD-DFT calculation

15. Bottom viewTop view monomer 1:1 cluster Mulliken charge -1.14 -0.98 -0.93