69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 HIGH-RESOLUTION INFRARED SPECTROSCOPY OF CUBANE, C 8 H 8 M. LAMY, F. DUGUE-BOYER, V. BOUDON, Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9. Av. A. Savary, BP 47870, F Dijon Cedex, France O. PIRALI, S. GRUET, Ligne AILES – Synchrotron SOLEIL, L’Orme des Merisiers, F Gif-sur-Yvette, France and Institut des Sciences Moléculaires d’Orsay, UMR 8214 CNRS-Université Paris-Sud, Orsay Cedex, France L. D’ACCOLTI, C. FUSCO, C. ANNESE, Dipartimento di Chimica, Universita` di Bari A. Moro and CNR-ICCOM-UOS Bari,, Via E. Orabona, 4, I Bari, Italy E. ALIKHANI, Sorbonne Universités, UPMC Université Paris 06, UMR 8233, MONARIS, Paris, France and CNRS, UMR 8233, MONARIS, Paris, France MONARIS

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 Contents I.The cubane molecule II.Experiment at SOLEIL III.The ν 11 and ν 12 fundamental bands IV.Other bands V.Conclusion and perspectives

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 I. The cubane molecule

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 A very unusual hydrocarbon molecule Methane, CH 4 (sp 3 hydridized) Bond angle 109.8° Cubane, C 8 H 8 Bond angle 90° Huge strain! « Platonic » hydrocarbon Highest density of all hydrocarbons : 1.29 g/cm 3 Stores a lot of energy Octahedral symmetry (spherical-top), point group O h 18 normal modes of vibration (including degeneracies), 3 being IR-active: ν1ν1 ν2ν2 ν3ν3 ν4ν4 ν5ν5 ν6ν6 ν7ν7 ν8ν8 ν9ν9 ν 10 ν 11 ν 12 ν 13 ν 14 ν 15 ν 16 ν 17 ν 18 A1gA1g A1gA1g A2uA2u A2uA2u EgEg EgEg EuEu EuEu F1gF1g F1uF1u F1uF1u F1uF1u F2gF2g F2gF2g F2gF2g F2gF2g F2uF2u F2uF2u 2995 cm – cm – cm –1 839 cm – cm –1 912 cm – cm –1 617 cm – cm – cm – cm –1 852 cm – cm – cm –1 821 cm –1 665 cm – cm –1 829 cm –1 C–HC–CC–HCCH C–CCCHCCCCCHC–HCCHC–CC–HCCHC–CCCCCCHC–C RR––RR–––IR RRRR–– (Approximate wavenumbers from A. S. Pine et al., J. Am. Chem. Soc. 106, 891–897 (1991) – R = Raman, IR = Infrared)

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 P. E. Eaton, et al., Synthesis, 1995, 501–502 (1995) P. E. Eaton, et al., Synthesis, 1995, 501–502 (1995) C. Annese, L. D’Accolti, C. Fusco et al., Organic Lett, 11, 3574–3577 (2009) C. Annese, L. D’Accolti, C. Fusco et al., Organic Lett, 11, 3574–3577 (2009) Cubane synthesis in Bari 150 mg sample

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 II. Experiment at SOLEIL

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 AILES beamline at SOLEIL High Resolution Absorption Spectroscopy in the Far-IR Synchrotron beam entrance Interferometer Multiple pass cell: L max = 200 m Detectors (bolometer, MCT, InSb) Maximum spectral resolution = cm -1 Spectral range= cm -1 Multiple pass White cell: L = 150 m Ambiant temperature (T = 296 K)

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 Low-resolution overview Combination bands C–C H / C–C C–H ν 11 ν 12 ν 10

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 Experimental conditions PressureResol. / cm –1 Nb. scansIris / mm SeparatrixWindowsDetectorFilter low-pass cm –1 Source 2 µbar KBrZnSeMCTNoSynchrotron 3 µbar KBrZnSeMCTNoSynchrotron 0.7 µbar KBrZnSeInSb3200NIR 16 µbar KBrZnSeMCTNoGlobar 16 µbar KBrZnSbInSb2400Globar 49 µbar KBrPolyproyleneMCT2400Globar Optical path length = 150 m for all spectra

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 III. The ν 11 and ν 12 fundamental bands

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 ν 11 and ν 12 fundamental bands: fit statistics BandCenter / cm -1 # assigned lines J max d RMS / cm -1 # param. H Devel. order ν (46) ν (69)

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 ν 11 fundamental band: Overview ν 11

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 ν 11 fundamental band: R branch detail

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 ν 11 fundamental band: Q branch detail

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 ν 12 fundamental band: Overview ν 12

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 ν 12 fundamental band: P branch detail C 4 clusters C 3 clusters

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 ν 12 fundamental band: Q branch detail (Transmission was used here because of saturated lines)

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 IV. Other bands

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 ν 10 fundamental band region This band appears highly perturbed A Coriolis interaction with ν 3 (A 2u ) is very likely A dyad treatment is under investigation ν 3 /ν 10

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 Ab initio calculations Quantum Chemistry Program: Gaussian 09 - RevA.02 Basis set: Pop = G(2d,2p) Methods: Optimization and harmonic frequency calculations: CCSD(T): Coupled-cluster approach with single and double substitutions and including triple excitations non-iteratively MP2: Møller-Plesset correlation energy correction truncated at second-order B3LYP: The Becke Three Parameter Hybrid Functional Anharmonic frequency and vibrational-rotational coupling calculations: PT2: Second-order perturbative approach i.Fundamental Bands ii.Overtones iii.Combination Bands iv.Vibrational-rotational coupling v.IR. Int. (beyond Gaussian 09 - RevD.01)

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 Some combination bands (I) A lot of combination bands! (plus some « forbidden bands » through couplings) Clear octahedral structure Complex polyads Assignment to be confirmed ν 8 +ν 16 ν 7 +ν 14 ν 18

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 Some combination bands (II) ν 15 +ν 18 ν 16 +ν 17 / ν 6 +ν 18 / ν 6 +ν 12 / ν 8 +ν 9 ν 8 +ν 14 / ν 3 +ν 15 / ν 7 +ν 16 / ν 2 +ν 18 / ν 15 +ν 17 ν 2 +ν 12 / ν 5 +ν 18 / ν 3 +ν 15 / ν 5 +ν 12 / ν 7 +ν 15

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 V. Conclusions and perspectives

69 th International Symposium on Molecular Spectroscopy / Champaign-Urbana, Illinois, USA, June 16–20, 2014 Next analyses & cage-molecule investigations Dyad treatment for the ν 3 / ν 10 C–H stretching region Combination bands ν 18 “forbidden band” This study is part of a series of cage-molecule investigations: Adamantane (C 10 H 16 ) Hexamethylenetetramine (C 6 N 4 H 10 ) New project: 1-aza-adamantanone (C 9 H 13 NO)