# $^{35}Cl NQR$ studies of 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-3-nitrobenzene as a function of pressure and temperature

Srinivas, Jandhyala and Subramanian, Raman K and Ramesh, Keralapura P and Ramakrishna, Jandhyala and Suresh, Kalkunte S and Rao, Chdaghatta Raghavendra (2002) $^{35}Cl NQR$ studies of 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-3-nitrobenzene as a function of pressure and temperature. In: Magnetic Resonance in Chemistry, 40 (5). pp. 337-345.

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## Abstract

The temperature and pressure dependences of $^{35}Cl$ nuclear quadrupole resonance (NQR) frequency and spin–lattice relaxation time $(T_1)$ were investigated for 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-3-nitrobenzene. $(T_1)$ was measured in the temperature range 77–300 K. Furthermore, the NQR frequency (n) and $(T_1)$ for these compounds were measured as a function of pressure up to 5.1 kbar at 300 K. Relaxationwas found to be due to the torsional motion of the molecule and the reorientation motion of the nitro group. By analysing the temperature dependence of $(T_1)$, the activation energy for the reorientation motion of the nitro group was obtained. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities W1 and W2 for the \bigtriangleup m = \pm 1 and \bigtriangleup m = \pm 2 transitions, were also obtained. Both compounds showed a non-linear variation of NQR frequencywith pressure. The pressure coefficients were observed to be positive. A thermodynamic analysis of the data was carried out to determine the constant-volume temperature coefficients of the NQR frequency. The spin–lattice relaxation time $(T_1)$ for both the compounds was found to be weakly dependent on pressure, showing that the relaxation is mainly due to the torsional motions.

Item Type: Journal Article The copyright belongs to John Wiley & Sons, Ltd. nqr;35Cl;frequency;spin lattice relaxation time;reorientation;torsional motion;pressure dependence;temperature dependence;1-chloro-2,4-dinitrobenzene;1,2-dichloro-3-nitrobenzene Division of Physical & Mathematical Sciences > Physics 06 Mar 2006 19 Sep 2010 04:23 http://eprints.iisc.ernet.in/id/eprint/5603