Rostock 2019 – scientific programme

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MO: Fachverband Molekülphysik

MO 12: High Resolution Spectroscopy and Precision Experiments

MO 12.4: Talk

Wednesday, March 13, 2019, 11:15–11:30, S HS 002 Biologie

Triphenylmethane and all-meta tert-butyl triphenylmethane dimers: Observation of an unusual C-H⋯H-C distance in the gas phase via stimulated Raman spectroscopy — •Dominique Maué¹, Dominic Bernhard¹, Patrick H. Strebert¹, Sören Rösel², Peter R. Schreiner², and Markus Gerhards¹ — ¹Physical Chemistry, TU Kaiserslautern, Germany — ²Organic Chemistry, JLU Gießen, Germany

Recently a dimerization of triphenylmethane (TPM) and all-meta tert-butyl triphenylmethane (T^tBuPM) has been observed in crystals which leads in the case of T^tBuPM to an unusually short C-H⋯H-C contact. In order to find out if this is a pure intrinsic behavior of the molecules, we report here on molecular beam investigations on isolated dimers by applying stimulated Raman spectroscopy with our new Raman set-up. In combination with DFT calculations (including dispersion corrections) the formation of the head-to-head motif in T^tBuPM under isolated conditions has been proven by selectively probing the Raman-active central aliphatic C-D vibration within the dimer of the singly deuterated monomers. This arrangement is driven by London dispersion involving the tert-butyl groups which outbalances their steric repulsion. It is a first example of this binding motif investigated in an isolated dimer in the gas phase. In the unsubstituted TPM dimer no such dispersion interaction is possible, thus a tail-to-tail structure is identified as the most stable arrangement.