title: Solvent-free dynamic nuclear polarization of amorphous and crystalline ortho-terphenyl.
abstract: Dynamic nuclear polarization (DNP) of amorphous and crystalline ortho-terphenyl (OTP) in the absence of glass forming agents is presented in order to gauge the feasibility of applying DNP to pharmaceutical solid-state nuclear magnetic resonance experiments and to study the effect of intermolecular structure, or lack thereof, on the DNP enhancement. By way of (1)H-(13)C cross-polarization, we obtained a DNP enhancement (ε) of 58 for 95% deuterated OTP in the amorphous state using the biradical bis-TEMPO terephthalate (bTtereph) and ε of 36 in the crystalline state. Measurements of the (1)H T1 and electron paramagnetic resonance experiments showed the crystallization process led to phase separation of the polarization agent, creating an inhomogeneous distribution of radicals within the sample. Consequently, the effective radical concentration was decreased in the bulk OTP phase, and long-range (1)H-(1)H spin diffusion was the main polarization propagation mechanism. Preliminary DNP experiments with the glass-forming anti-inflammation drug, indomethacin, showed promising results, and further studies are underway to prepare DNP samples using pharmaceutical techniques.
authors: Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: Ta-Chung
authors: TC
authors: Ong
authors: Melody L
authors: ML
authors: Mak-Jurkauskas
authors: Joseph J
authors: JJ
authors: Walish
authors: Vladimir K
authors: VK
authors: Michaelis
authors: Björn
authors: B
authors: Corzilius
authors: Albert A
authors: AA
authors: Smith
authors: Andrew M
authors: AM
authors: Clausen
authors: Janet C
authors: JC
authors: Cheetham
authors: Timothy M
authors: TM
authors: Swager
authors: Robert G
authors: RG
authors: Griffin
mesh_terms: D003460:Crystallization; D004578:Electron Spin Resonance Spectroscopy; D009682:Magnetic Resonance Spectroscopy; D013730:Terphenyl Compounds / Q000737:chemistry*
chemical_list: D013730:Terphenyl Compounds