¹H NMR study of internal motions and quantum rotational tunneling in (CH₃)₄NGeCl₃

Abstract

(CH 3 ) 4 NGeCl 3 is prepared, characterized and studied using 1 H NMR spin lattice relaxation time and second moment to understand the internal motions and quantum rotational tunneling. Proton second moment is measured at 7 MHz as function of temperature in the range 300-77 K and spin lattice relaxation time (T 1 ) is measured at two Larmor frequencies, as a function of temperature in the range 270-17 K employing a homemade wide-line/pulsed NMR spectrometers. T 1 data are analyzed in two temperature regions using relevant theoretical models. The relaxation in the higher temperatures (270-115 K) is attributed to the hindered reorientations of symmetric groups (CH 3 and (CH 3 ) 4 N). Broad asymmetric T 1 minima observed below 115 K down to 17 K are attributed to quantum rotational tunneling of the inequivalent methyl groups.

Quantum Rotations and Chiral Polarization of Qubit Prototype Molecules in a Highly Porous Metal–Organic Framework:1H NMRT1Study

“…However, the real V act ( D 3 ) value in this case cannot be determined directly because the spin–lattice relaxation time T 1 _2 of the twisted ( D 3 ) dabco molecules is almost temperature-independent between 165 and ∼130 K. In parallel with the above consideration of the spin–lattice relaxation time T 1 _1 of the untwisted ( D 3 h ) dabco molecules, the similar behavior of T 1 _2 definitely indicates the quantum tunneling mechanism of rotations of the twisted ( D 3 ) dabco molecules. Such a conclusion is independently supported by the fact that the spin–lattice relaxation times T 1 _1 and T 1 _2 do not depend on the Larmor frequency ν L (Figure ), as expected according to the quantum theory of NMR spin–lattice relaxation. − The noticeable difference in the temperature dependences of the spin–lattice relaxation times T 1 _1 and T 1 _2 can be related to the increased hindering barrier V act ( D 3 ) for rotations of the twisted dabco molecules, resulting in a more complicated spectrum of tunnelling states for the twisted ( D 3 ) dabco molecules with respect to the untwisted ones.…”

Study of molecular dynamics and cross relaxation in tetramethylammonium hexafluorophosphate (CH3)4NPF6 by 1H and 19F NMR

“…This investigation shows a single plateau in second moment indicating that the correlation frequencies for the two motions are quite close to each other [22]. [29]. H NMR second moment data for TMA-HFP at 7 MHz in the temperature region 300-155 K; the line is a guide to the eye.…”

Complex dynamics of 1.3.5-trimethylbenzene-2.4.6-D3 studied by proton spin–lattice NMR relaxation and second moment of NMR line

“…The tunnelling correlation time is independent on temperature therefore, T 1 here is also constant value. Such an effect, a constant value of T 1 has been detected at low temperatures for a number of methyl bearing solids [22,23,[27][28][29][30][31][32][33][34][35][36]. The low temperature flattening of T 1 is not visible for the significant values of 1/T 1(inter) (1/T 1EE contribution) [13,[38][39][40][41][42].…”