1. BROADBAND MICROWAVE SPECTROSCOPY AS A TOOL TO STUDY DISPERSION INTERACTIONS IN CAMPHOR-ALCOHOL SYSTEMS
MARIYAM FATIMA, CRISTÓBAL PÉREZ, MELANIE SCHNELL, Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany

2. Non-Covalent Interactions
Water
Amino Acid
Guanine
Cytosine

3. Molecule of Interest : Camphor-Alcohol System
Z. Kisiel et al., Phys. Chem. Chem. Phys. 5(2003), 820
Side view:
Camphor
Camphor
Methanol
Ethanol

4. Camphor-Water System
2 isomers for camphor-water were observed using rotational spectroscopy 3 1 2
3 possibilities where water can form a complex with camphor.
Isomer 1
Isomer 2
Camphor-(H2O)
C.Pérez et al., J. Phys. Chem. Lett., 7 (1) (2016), 154–160

5. Chirped Pulse Microwave Spectroscopy in Hamburg
Sample introduction
2-8 GHz
20 kHz linewidth
Microwave Horn Antenna (Receiver)
Supersonic Expansions
Microwave Horn Antenna (Emitter)
Backing pressure of neon: 3.2 bar
Temperature for camphor: 100 ° C

6. PART 1: CAMPHOR-METHANOL

7. Camphor-Methanol: Ab initio Results
∆E = 0 kJ/mol
∆E ≈ 1 kJ/mol
Level of theory:
B3LYP-D3/aug-cc-pvtz

8. Camphor-Methanol: Experimental Spectrum
Isomer 1

9. Camphor-Methanol: Rotational Constants
Isomer 1
∆E=0 kJ/mol
B3LYP-D3
Dipole Moment (D)
A (MHz)
3.3
B (MHz)
441.38
0.4
C (MHz)
429.50
-0.1
Isomer 2
B3LYP-D3
Dipole Moment (D)
A (MHz)
-4.0
B (MHz)
450.59
1.0
C (MHz)
434.39
0.2
∆E=1 kJ/mol

10. Camphor-Methanol: Splitting Patterns

11. Internal Rotation in Methanol
Internal rotation barrier height E
Internal rotation barrier = 3.2 kJ/mol A A E E A

12. Internal Axis Method x Internal rotation axis z y XIAM Program:
uses internal axis method
predict and fits the rotational spectrum of an asymmetric molecule having internal rotors
Internal rotation barrier = (21) kJ/mol
  H.Hartwig et al., Z. Naturforsch 51a (1996),

13. Camphor-Methanol: Results
606←505
66 a-type transitions assigned
606←505 E
624←523
606←505 A
625←524 A A E
Isomer 1

14. Camphor-Methanol: Results
Internal rotation barrier = (21) kJ/mol
Isomer 1

15. PART 2: CAMPHOR-ETHANOL

16. Camphor-Ethanol 3 conformations of ethanol Gauche ∆E=0.5 kJ/mol Trans
Z. Kisiel et al., Phys. Chem. Chem. Phys. 5(2003), 820
Hearn et al., J. Chem. Phys. 123 (2005),

17. Camphor-Ethanol: Ab initio Results
Level of theory:
B3LYP-D3/aug-cc-pvtz
∆E≈ 0.6 kJ/mol
∆E≈ 0.7 kJ/mol
Isomer 3
Isomer 2
∆E=0 kJ/mol
Isomer 1

18. Camphor-Ethanol: Experimental Spectrum
Ethanol dimer 1, Ethanol dimer 2, Ethanol dimer 3
Isomer 1, Isomer 2, Isomer 3, Isomer 4

19. Camphor-Ethanol: Experimental Spectrum
Isomer 1, Isomer 2, Isomer 3, Isomer 4

20. Camphor-Ethanol: Results
Isomer 1

21. Camphor-Ethanol: Results
Isomer 2

22. Camphor-Alcohol: Summary
Camphor-methanol
Camphor-ethanol
Isomer 1
Isomer 1
Isomer 2
Only gauche conformation of ethanol was found.
No internal rotation in camphor-ethanol. 3 1 2
ROLE OF DISPERSION INTERACTION???

23. Camphor-Ethanol (Isomer 1) Camphor-Ethanol (Isomer 2)
Symmetry Adapted Perturbation Theory
Eint = EAB - EA - EB
Energy Decompositions (kJ/mol ) from a SAPT(0)/jun-cc-pVDZ
(Water)2
Camphor-Water
Camphor-Methanol
(Isomer 1)
Camphor-Ethanol (Isomer 1)
Camphor-Ethanol (Isomer 2)
∆Eelst
-8.90
-49.2
-49.4
-46.79
-46.6
∆Eind
-2.40
-14.6
-13.3
-13.2
∆Edisp
-1.35
-11.6
-19.6
-20.4
∆Eexch
8.17
43.6
43.7
47.4
48.7
∆Etot
-4.47
-31.8
-31.9
-32.4
-31.6

24. Conclusion and Outlook
The extent of hydrogen bonding is decreasing while the dispersion interaction is increasing.
To identify complexes of camphor ethanol.
Further work on camphor-propanol
complexes will be done to see
the effect of dispersion interactions.

25. Acknowledgements

26. THANK YOU