# Study of dynamics in pentachlorophenol in the solid state by 1D Nuclear Quadrupole Resonance exchange spectroscopy

TL;DR: In this paper, the dynamic process in pentachlorophenol (PCP) in the solid state by one-dimensional Nuclear Quadrupole Resonance (NQR) exchange spectroscopy employing shaped rf pulses was studied.

Abstract: The paper reports studies of the dynamic process in pentachlorophenol (PCP) in the solid state by one-dimensional Nuclear Quadrupole Resonance (NQR) exchange spectroscopy employing shaped rf pulses. Pentachlorophenol exhibits intramolecular hydrogen bonding between the hydroxyl proton and one of the o-chlorines. Reorientation of the hydrogen bond with migration of the hydroxyl proton from one o-chlorine to the other is possible in a wide temperature range. In this process the two o-chlorines are exchanged; at the same time this implies the exchange of the two m-chlorines as well, which we have chosen to monitor, modeling it as a two-site exchange process. A detailed analysis of the appropriate Bloch-McConnell equation is performed to formulate the relevant kinetic matrix. The exchange pulse sequence implemented by us involves suitably modulated shaped RF pulses to achieve simultaneous on-resonance excitation of the two exchanging sites. This approach results in a clear definition of the exchange time wind...

##### References

More filters

••

TL;DR: In this paper, a general technique for the investigation of exchange processes in molecular systems is proposed and demonstrated and applications include the study of chemical exchange, of magnetization transfer by inter-and intramolecular relaxation in liquids, and of spin diffusion and cross-relaxation processes in solids.

Abstract: A new general technique for the investigation of exchange processes in molecular systems is proposed and demonstrated. Applications comprise the study of chemical exchange, of magnetization transfer by inter‐ and intramolecular relaxation in liquids, and of spin diffusion and cross‐relaxation processes in solids.

4,534 citations

••

TL;DR: In this paper, the modified Bloch equations for nuclear magnetic resonance are modified to describe the magnetic resonance of a single nuclear species X which is transferred back and forth between two (or more) magnetic environments (A,B) by kinetic molecular processes.

Abstract: The Bloch equations for nuclear magnetic resonance are modified to describe the magnetic resonance of a single nuclear species X which is transferred back and forth between two (or more) magnetic environments (A,B) by kinetic molecular processes. The modified Bloch equations involve the usual assumptions of the Bloch theory and, in addition, require (a) that the X nuclear relaxation times be independent of the molecular exchange rates, and (b) that the X nuclear magnetization in A relax independently of the X magnetization in B, and vice versa. The modified Bloch equations are easily solved in the slow passage case, with arbitrary rf saturation. Earlier relations between reaction rates, and resonance line shapes, which were developed by Gutowsky, McCall, and Slichter, and extended by a number of other investigators, are easily derived using the modified Bloch equations. In the present work the modified equations are used to show how rapid exchange rates can sometimes be measured in solutions where the X r...

1,453 citations

•

01 Jan 1974

164 citations

### "Study of dynamics in pentachlorophe..." refers methods in this paper

...Molecular dynamics involving quadrupolar nuclei in the solid state may be studied by 1D Nuclear Quadrupole Resonance (NQR) measurements of the temperature dependence of spectral frequencies and T1s [1,2]....

[...]

...This is unlike the case of chloral hydrate [9] where the reduction factors and T1s are equal at all the sites involved....

[...]

••

TL;DR: In this paper, a theory of the direct effect of molecular rotations on longitudinal spin relaxation in pure quadrupole resonance is described and applied to the hexamethylene tetramine.

Abstract: Slow motional processes for which there is no motional narrowing can be important in spin-lattice relaxation. These relaxation mechanisms cannot be treated by perturbation theory. It is shown that the relaxation times are directly proportional to the motional correlation times. It is suggested that they can be used very effectively to measure the rate of motional processes in solids. A theory of the direct effect of molecular rotations on longitudinal spin relaxation in pure quadrupole resonance is described. The theory is applied to the ${\mathrm{N}}^{14}$ resonance in hexamethylene tetramine. Measurement of the longitudinal relaxation times in this molecule were carried out by a steady-state pulse method, and the rotational correlation times were determined. The results are in agreement with previous nmr measurements.

138 citations