Towards the complete analysis of the rotational spectrum of (CH3)3SnCl

Abstract

The rotational spectrum of the symmetric top trimethyl tin chloride (CH 3 ) 3 SnCl has been studied using a pulsed molecular beam Fourier transform microwave spectrometer in the frequency range from 3 to 24 GHz. The spectrum is exceedingly complicated by the internal rotation motions of the three equivalent methyl tops, the high number of Sn-and Cl-isotopes and the quadrupole hyperfine structure of the chlorine nucleus. In this paper, we present the microwave spectrum, ab initio calculations, permutation inversion (PI) group-theoretical considerations, Starkeffect measurements and finally the assignments and fits of the different torsionrotation species. Based on the Stark-effect measurements, the dipole moment is µ = 3.4980(30) D. Due to ∆K = ±1-mixing effects we observe linear Stark-effect behavior and additional quadrupole splitting for some K = 0 torsion-rotation transitions in (CH 3 ) 3 SnCl, which can be group-theoretically explained. The symmetric rotor fit of A 1 states leads to an effective B-constant of 1680.040124(50) MHz for the main isotopologue (CH 3 ) 3 120 Sn 35 Cl. A global fit of 182 K = 0 torsion-rotation transitions yields a V 3 torsional barrier of 148.299(54) cm −1 .

Three-dimensional intramolecular dynamics: Internal rotation of (CH3)3GeBr

“…1-8 of Ref. [17]), by replacing the Sn atom with the Ge atom, and using the appropriate bond lengths. Here, we only give the resulting transformation properties of the nine independent variables R, α 0 , α 1 , α 2 , χ, θ, and φ (Table 2).…”

Multidimensional Large‐Amplitude Motion: Revealing Concurrent Tunneling Pathways in Molecules with Several Internal Rotors

“…The appropriate PI group for the molecules of the series (CH 3 ) 3 XCl (X = Si, Ge, Sn) is G 162 , [12][13][14] which consists of 162 elements and is not isomorphic with any point group. Generally, these PI groups can become quite large (for a more detailed description of the molecular symmetry group G 162 , see reference [15]). …”

“…Furthermore, the splitting patterns appear far more complicated, and to facilitate the assignments of the torsion-rotation transitions we employed Stark-effect measurements [19] to differentiate between the different torsionrotation transitions by their Stark effect (linear or quadratic). [15] At the low barriers encountered for the tin compound, all five tunneling pathways must be considered to be feasible. The theoretical results are displayed in Figure 3 together with the measured J + 1 [15] The contributions from H L and H E (tunneling pathways describe the concerted internal rotation of three methyl tops) are of the order of several hundred kHz (see the Supporting Information) and are thus important in reproducing the measured transition frequencies with experimental accuracy (1-4 kHz).…”

“…[15] At the low barriers encountered for the tin compound, all five tunneling pathways must be considered to be feasible. The theoretical results are displayed in Figure 3 together with the measured J + 1 [15] The contributions from H L and H E (tunneling pathways describe the concerted internal rotation of three methyl tops) are of the order of several hundred kHz (see the Supporting Information) and are thus important in reproducing the measured transition frequencies with experimental accuracy (1-4 kHz). The contributions of H R , H A , and H G are all of the same order of magnitude in (CH 3 ) 3 SnCl, which results in large changes in the relative ordering of the torsional energy levels compared with (CH 3 ) 3 SiCl and (CH 3 ) 3 GeCl.…”

Mehrdimensionale Bewegungen mit großer Amplitude: Aufdeckung simultaner Tunnelpfade in Molekülen mit mehreren internen Rotoren

“…Um die Zuordnung der Torsionsrotationsübergänge zu ermöglichen, wurden Messungen des Stark-Effekts ausgeführt [19] (hierbei lassen sich die Torsionsrotationsübergänge anhand ihres Stark-Effekts (linear oder quadratisch) unterscheiden; siehe Lit. [15]). Bei den niedrigen Torsionsbarrieren der Zinnverbindung müssen alle fünf Tunnelpfade auf der Zeitskala des Experiments als durchführbar ("feasible") angenommen werden.…”