Nuclear magnetic resonance relaxation and anisotropic reorientation in liquid dimethylmercury

Abstract

Spin-lattice relaxation times of 'H, D, and '9gHg have been measured between 234 and 333 K in liquid dimethylmercury and its isotopic modifications. These measurenlents have allowed the relaxation mechanisms to be separated. It was found that the spin-rotation interaction is the dominating mechanism for the lg9Hg relaxation at 14.1 kG even at low temperatures. We have estimated the spin-rotation constants, C = -120 i-60 kHz and Cl = -23 i-3 kHz along with the chemical shift anisotropy Ao = o -ol = $-4600 k 1000 ppm. It is concluded that reorientation about the symmetry axis is not well described by niolecular diffusion. Reorientaiion of the methyl group about its symmetry axis is found to be approximately forty times faster than the reorientation about the perpendicular axis. que la reorientation autour de I'axe de symetrie n'est pas bien decrite par la diffusion moleculaire. La reorientation du groupe methyle autour de I'axe de syrnetrie est approximativement 40 fois plus rapide que la reorientation autour de l'axe perpendiculaire.[Traduit par le journal]

Mercury-199 nuclear magnetic resonance relaxation in some mercury(II) compounds

“…[ (20) obtained from liquid crystal data. The main source of error in our calculated value of Ao probably results from inaccuracy in .c2 (2). .c2 must be less than 4.7 ps in order for the TI data to be compatible with the liquid crystal data (19,20).…”

“…The errors in all TI values are estimated to be less than 15% unless otherwise indicated. For the lg9Hg spin-lattice relaxation times, the ratio T,(B, = 5.875 T)/T,(B, = 9.40 T) is given in (9 Hg( CN) 2 For a spin 112 nucleus, the Ig9Hg Ti's measured for Hg(CN), are exceedingly short. The T,'s are field dependent; at applied fields of 9.40 T, spinlattice relaxation is more efficient than relaxation at 5.875T by a factor of 2.9 f 0.4.…”

“…(iv> Hg(C6H5) 2 The field dependent 199Hg TI data (Table 2) indicate that the chemical shielding anisotropy mechanism must completely dominate at Bo = 9.40 T. The appropriate correlation time for 199Hg spin-lattice relaxation in diphenylmercury can be obtained from the 13C TI of the carbon para (C4) to mercury (21). This carbon is relaxed entirely by the dipole-dipole mechanism with directly attached protons.…”

Revisiting HgCl2: A solution- and solid-state 199Hg NMR and ZORA–DFT computational study

“…A compilation by Wrackmeyer and Contreras [4] contains a substantial tabulation of solution-state 199 Hg chemical shifts. The 199 Hg relaxation properties of neat mercury-containing liquids and mercury compounds dissolved in solvents ranging from alcohols and water to organic liquids have also been examined [5][6][7][8][9]. For smaller molecules such as dimethylmercury, Hg(CH 3 ) 2 , and for the Hg 2+ ion in aqueous solution investigated at the low resonance frequencies encountered when using electromagnets with fields of 2.35 T or less, spin-lattice relaxation is generally dominated by the spin-rotation interaction [4,5].…”

“…The 199 Hg relaxation properties of neat mercury-containing liquids and mercury compounds dissolved in solvents ranging from alcohols and water to organic liquids have also been examined [5][6][7][8][9]. For smaller molecules such as dimethylmercury, Hg(CH 3 ) 2 , and for the Hg 2+ ion in aqueous solution investigated at the low resonance frequencies encountered when using electromagnets with fields of 2.35 T or less, spin-lattice relaxation is generally dominated by the spin-rotation interaction [4,5]. However, many reports indicate that the chemical-shift-anisotropy (CSA) mechanism dominates the 199 Hg spin-lattice relaxation in mercury compounds in solution at field strengths greater than 4.7 T [4,6].…”