J. Am. Chem. SOC.1980,102,6566-6568
6566
pendent of sample composition. Since these splittings are unaffected by “slow” motions and are reduced by “rapid” motions, the observation is equivalent to the statement that no motion changes from the slow limit to the rapid limit as a function of sample composition. Second, TIBand TIFare also independent of sample composition. This result places a further restriction on the system that the correlation times for motions controlling relaxation in both bound and free sites are independent of sample compositions6 Third, a nonzero splitting is obtained for the free site, and this is indicative of restricted motion.’ Interpretation of TIBand TIFvalues can be done only in terms of the specific motion controlling each relaxation; a procedure similar to that used for D20relaxation in lecithin/D20 systems might be used.8 Our interpretation of the quadrupole splittings (see below) suggests that there are several rapid motions that could contribute to spin-lattice relaxation in this system which will make interpretation of TI values difficult. The magnitude of AvB can be explained in a straightforward manner, using an approach similar to that used for aqueous lecithin phasesS9 If the binding site for EG is taken to be the phosphate group on L, then local rotation of EG while bound to L could result in the P-0 bond axis becoming a symmetry axis. Rapid reorientation of L around an axis parallel to the long chain is also We assume tetrahedral geometry for EG and nonbonding orbitals on 0,and an 0-P-0 bond angleI3 of 121.6’; from these values, assuming the motions above, we calculate a splitting of 2.0 kHz, which agrees with the AvB value given in Table 11. This preliminary study indicates that the EG/L nonaqueous system lends itself to a more straightforward interpretation than does the H20/L system. This is due partly to the fact that in the aqueous system, solvation of the L head group apparently involves a t least five water molec~les.~ We are continuing these studies by investigating other features of the nonaqueous lecithin liquid crystalline phase, including proton relaxation, translational diffusion, and the effect of varying the diol chain length. ~~~~~~
~~~
Table I. 4-21Ga b Initio Optimized Structural Parameters of Glvcinea
I
I1
111
1.001 1.000 1.001 1.457 1.457 1.474 1.081 1.081 1.081 1.522 1.5 35 1.514 1.202 1.204 1.203 1.365 1.345 1.364 0.975 0.966 0.966 113.28 110.19 115.92 125.42 126.41 122.32 113.82 112.18 110.62 111.49 112.28 108.44 113.27 114.49 112.58 107.14 101.87 107.67 110.29 111.36 109.79 106.61 107.04 107.37 110.27 111.87 109.80 180.0 180.0 0.0 0.0 0.0 180.0 180.0 0.0 180.0 62.38 63.29 114.83 57.65 122.96 122.25 -282.15491 -282.15805 -282.15460 2.2 0.0 1.9 1.10 6.54 1.76 3 4 ) were used in the structure solution and refinement which converged to 0.048 and 0.049 for R and R,,, respectively. The final difference Fourier map was featureless with the largest residual electron density only 0.31 16, 235. e/A3. (4) Suitable single crystals were obtained by slow recrystallization of 1 (8) (a) Moriarty, R. E.; Ernst, R. D.; Bau, R. J . Chem. Soc., Chem. from a saturated methylene chloride solution. The dark blue-green solid Commun. 1972, 1242. (b) Hyde, J.; Magin, L.; Zubieta, J. Ibid. 1980,204. exhibits two strong infrared absorptions attributable to cis-carbonyl ligands (c) Diamantis, A. A,; Snow, M. R.; Vanzo, J. A. Ibid. 1976,264. (d) Pierpont at 1934 and 1842 cm-’. Note that a KBr pellet prepared under aerobic C. G.; Buchanan, R. M . J. Am. Chem. SOC.1975, 97,4912. conditions was purple in color and displayed intense infrared absorptions at (9) (a) Gillum, W. 0.;Wentworth, R. A. D.; Childers, R. F. Inorg. Chem. 2015, 1938, and 1900 cm-‘ attributable to Mo(C0)3[S2CN-i-PrZ]2and a very 1970,9, 1825. (b) Gillum, W. 0.;Huffman, J. C.; Streib, W. E.; Wentworth, strong absorption at 968 cm-’ attributable to M O ( O ) [ S ~ C N - ~ - P ~ ~ ] ~ . R. A. D. J. Chem. SOC.,Chem. Commun. 1969, 843. (c) Bertrand, J. A.; ( 5 ) Colton, R.; Scollary, G. R. Aust. J . Chem. 1968, 21, 1427. Kelley, J. A.; Vassian, E. G. J . Am. Chem. Soc. 1%9,91,2394. (d) Churchill, (6) (a) McDonald, J. W.; Newton, W. E.; Creedy, C. T. C.; Corbin, J. L. M. R.; Reis, A. H., Jr. Inorg. Chem. 1972, 11, 1811. J. Organomet. Chem. 1975, 92, C25. (b) McDonald, J. W.; Corbin, J. L.; (10) (a) Eisenberg, R.; Ibers, J. A. Inorg. Chem. 1966,5,411. (b) Smith, Newton, W. E. J. Am. Chem. SOC.1975, 97, 1970. (c) Chen, G. J.-J.; A. E.; Schrauzer, G. N.; Mayweg, V. P.; Heinrich, W. J . Am. Chem. SOC. 1965,87, 5798. (c) Eisenberg, R.; Gray, H. B. Inorg. Chem. 1967,6, 1844. McDonald, J. W.; Newton, W. E. Inorg. Chim. Acto 1976, 19, L67. (d) Addition of PPha to 1 leads to rapid formation of M O ( C O ) ~ ( P P ~ ~ ) ( S ~ C N R ~ )(d) ~ , Bennett, M. J.; Cowie, M.; Martin, J. L.; Takats, J. J . Am. Chem. SOC. 1973, 95,7504. (e) Stiefel, E. I.; Eisenberg, R.; Rosenberg, R. C.; Gray, H. which has been previously prepared and is well-characterized. See: Chen, G. J.-J.; Yelton, R. 0.;McDonald, J. W. Ibid. 1977, 22, 249. Colton, R.; B. Ibid. 1966, 88, 2956. Rose, G. G. Ausr. J . Chem. 1970 23, 1111. (11) Bondi, A. J . Phys. Chem. 1964,68,441.
0002-7863/80/1502-6568$01 .OO/O 0 1980 American Chemical Society
