1. NON COVALENT INTERACTIONS IN LARGE DIAMONDOID DIMERS IN THE GAS PHASE - A MICROWAVE STUDY
CRISTOBAL PEREZ, MARINA SEKUTOR, ANDREY A. FOKIN, SEBASTIAN BLOMEYER, YURY V. VISHNEVSKIY, NORBERT W. MITZEL, PETER R. SCHREINER, MELANIE SCHNELL
Styling: MPSD color:

2. Motivation
C26H34O2
Need of accurate structural information of large molecules.
Benchmarking experimental and theoretical methods.
The longest C-C bond in an alkane reported to date stabilized by long range dispersive interactions.
GED, XRD and CP-FTMW as spectroscopic techniques.

3. Chirped Pulse Spectrometer in Hamburg
Experimental Technique
1. Generation of a chirped microwave pulse (4 µs, 2-8 GHz, eight frames at 9 Hz) and excitation of a molecular ensemble.
Polarization starts to decay after the pulse.
3. Recording of the Free Induction Decay (FID).
Low noise amplifier
Horn antenna
Oscilloscope
Horn antenna
Power amplifier
Fourier
transformation
Arbitrary waveform
generator
G. G. Brown, B. C. Dian, K. O. Douglass, S. M. Geyer, S. T. Shipman, B. H. Pate, Rev. Sci. Instrum. 79, (2008)

4. Oxygen-substituted diamondoid dimers
Coupling of a racemic
mixture
M06-2X/cc-pVDZ full rotation potential of 2a
Inversion of the
absolute configuration
Enantiomers

5. Oxygen-substituted diamondoid dimers
Coupling of a racemic
mixture
M06-2X/cc-pVDZ full rotation potential of 2b

6. Broadband Spectrum of Oxy-diamondoid dimers
10 mg sample
1 Million acq
4h measurement
2 bar
200 C
SCS-MP2/def2-QZVP
2a_1
2b_1
2b_4
A (MHz)
393.35
393.23
393.54
B (MHz)
159.46
159.74
159.60
C (MHz)
159.45
159.24
159.18
ma (D)
0.2
mb (D)
1.2
mc (D)
1.5
2.75
0.38 1 2
A (MHz)
(96)
(70)
B (MHz)
(79)
(60)
C (MHz)
(76)
(54)
Observed
b and c-type
c-type
σ (kHz)
7.78
3.77
Nlines 78 56

7. Broadband Spectrum of Oxy-diamondoid dimers
No b-type
spectrum

8. Structure of Oxy-diamondoid dimers
Benchmarking of theoretical and experimental structure determination methods.

9. Diadamantyl ether C20H30O1 Diphenyl Ether
C. Medcraft et al. Phys. Chem. Chem. Phys., 2016, 18, 25975

10. Diadamantyl ether
C20H30O1
MIN (C2)
TS (C2v)

11. Broadband Spectrum of Diadamantyl ether
1.6 Million acq
6h measurement
2 bar
185 C
SNR 700:1
EXP
THR
A (MHz)
(11)
825.91
B (MHz)
(22)
189.04
C (MHz)
(23)
187.96
ma (D) -
mb (D)
Observed
1.09
mc (D)
s (kHz)
5.7 N
143
10 distinct spectra from single 13C substitution

12. Isotopic Measurements
C2 Symmetry confirmed from isotopic measurements in natural abundance
B3LYP-D3(BJ)-cc-pVTZ vs Kraitchman

13. Summary
Rotational spectroscopy as a tool for structural studies of molecules of increasing size.
Oxadiamondoid Dimers (C26H34O2).
Diamantyl Ether (C20H30O1).
Benchmarking of theoretical and experimental structure determination methods.
Accuracy of theory to predict unusually long range contacts
Diadamantyl ether structure confirmed from single 13C substitution
Only one conformed observed.
No internal dynamics

14. Thank you for your attention!
Acknowledgement
Thank you for your attention!