Effects of Polymorphism on Functional Group Dynamics: Solid State 2H NMR Studies of the Dynamic Properties of the α and β Phases of l-Glutamic Acid Export

@article{citeulike:4071372, abstract = {doi: 10.1021/jp020064r l-Glutamic acid (LGA) exists as two polymorphic solid phases (denoted the alpha and beta phases) with different molecular conformations. This paper investigates the contrasting dynamic properties of the alpha and beta phases of LGA, from measurements of solid state 2H NMR line shapes and spinlattice relaxation times for the ND3+ groups in selectively deuterated samples. For both phases, the 2H NMR line shapes have been simulated successfully in terms of a three-site 120o jump motion of the ND3+ group, with the jump frequency varying from 1.5 107 to 1.5 103 s-1 within the temperature range 373 to 198 K. The activation energy for the reorientation of the ND3+ group is higher for the alpha phase [(47 +- 2) kJ mol-1] than for the beta phase [(34 +- 3) kJ mol-1]. The 2H NMR spinlattice relaxation time data are also consistent with the three-site 120o jump motion of the ND3+ group and are in good agreement with the activation energies [alpha phase, (48 +- 1) kJ mol-1; beta phase, (39 +- 2) kJ mol-1] determined from our 2H NMR line shape studies. The differences in the dynamic properties of the ND3+ groups between the two polymorphs can be rationalized directly in terms of different local environments in the crystal structures, particularly concerning the different hydrogen bonding geometries involving the ND3+ groups.}, author = {Kitchin, Simon J. and Ahn, Shinbyoung and Harris, Kenneth D.}, citeulike-article-id = {4071372}, citeulike-linkout-0 = {http://dx.doi.org/10.1021/jp020064r}, citeulike-linkout-1 = {http://pubs.acs.org/doi/abs/10.1021/jp020064r}, day = {1}, doi = {10.1021/jp020064r}, journal = {The Journal of Physical Chemistry A}, keywords = {2h-nmr, glutamic\_acid, ssnmr}, number = {31}, pages = {7228--7234}, posted-at = {2009-02-19 15:48:11}, priority = {2}, title = {Effects of Polymorphism on Functional Group Dynamics: Solid State 2H NMR Studies of the Dynamic Properties of the α and β Phases of l-Glutamic Acid}, url = {http://dx.doi.org/10.1021/jp020064r}, volume = {106}, year = {2002} }

TY - JOUR ID - citeulike:4071372 L3 - citeulike-article-id:4071372 N2 - doi: 10.1021/jp020064r l-Glutamic acid (LGA) exists as two polymorphic solid phases (denoted the alpha and beta phases) with different molecular conformations. This paper investigates the contrasting dynamic properties of the alpha and beta phases of LGA, from measurements of solid state 2H NMR line shapes and spinlattice relaxation times for the ND3+ groups in selectively deuterated samples. For both phases, the 2H NMR line shapes have been simulated successfully in terms of a three-site 120o jump motion of the ND3+ group, with the jump frequency varying from 1.5 107 to 1.5 103 s-1 within the temperature range 373 to 198 K. The activation energy for the reorientation of the ND3+ group is higher for the alpha phase [(47 +- 2) kJ mol-1] than for the beta phase [(34 +- 3) kJ mol-1]. The 2H NMR spinlattice relaxation time data are also consistent with the three-site 120o jump motion of the ND3+ group and are in good agreement with the activation energies [alpha phase, (48 +- 1) kJ mol-1; beta phase, (39 +- 2) kJ mol-1] determined from our 2H NMR line shape studies. The differences in the dynamic properties of the ND3+ groups between the two polymorphs can be rationalized directly in terms of different local environments in the crystal structures, particularly concerning the different hydrogen bonding geometries involving the ND3+ groups. IS - 31 JF - The Journal of Physical Chemistry A EP - 7234 TI - Effects of Polymorphism on Functional Group Dynamics: Solid State 2H NMR Studies of the Dynamic Properties of the α and β Phases of l-Glutamic Acid VL - 106 SP - 7228 KW - 2h-nmr KW - glutamic_acid KW - ssnmr AU - Kitchin, Simon AU - Ahn, Shinbyoung AU - Harris, Kenneth PY - 2002//01/ UR - http://dx.doi.org/10.1021/jp020064r ER -