Molecular motions of [Beta]-carotene and a carotenoporphyrin dyad in solution. A carbon-13 NMR spin-lattice relaxation time study

Journal Article · Wed Mar 08 23:00:00 EST 1995 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100010a056· OSTI ID:6455563

Li, S; Swindle, S L; Smith, S K; Nieman, R A; Moore, A L; Moore, T A; Gust, D ^[1]

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1. Arizona State Univ., Tempe, AZ (United States)

Analysis of [sup 13]C NMR spin-lattice relaxation times (T[sub 1]) yields information concerning both overall tumbling of molecules in solution and internal rotations about single bonds. Relaxation time and nuclear Overhauser effect data have been obtained for [Beta]-carotene and two related molecules, squalane and squalene, for zinc meso-tetraphenylporphyrin, and for a dyad consisting of a porphyrin covalently linked to a carotenoid polyene through a trimethylene bridge. Squalane and squalene, which lack conjugated double bonds, behave essentially as limp string, with internal rotations at least as rapid as overall isotropic tumbling motions. In contrast, [Beta]-carotene reorients as a rigid rod, with internal motions which are too slow to affect relaxation times. Modeling it as an anisotropic rotor yields a rotational diffusion coefficient for motion about the major axis which is 14 times larger than that for rotation about axes perpendicular to that axis. The porphyrin reorients more nearly isotropically and features internal librational motions about the single bonds to the phenyl groups. The relaxation time data for the carotenoporphyrin are consistent with internal motions similar to those of a medieval military flail. 31 refs., 3 figs., 5 tabs.

• DOE Contract Number: FG02-88ER13969
• OSTI ID: 6455563
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 99:10; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
664100 -- Theory of Electronic Structure of Atoms & Molecules-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
ALKANES
CARBOXYLIC ACIDS
CAROTENOIDS
CHEMICAL SHIFT
DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
INFORMATION
MAGNETIC RESONANCE
MATHEMATICAL MODELS
MOLECULAR MODELS
NUCLEAR MAGNETIC RESONANCE
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOMETALLIC COMPOUNDS
OVERHAUSER EFFECT
PIGMENTS
POLYENES
PORPHYRINS
RELAXATION
RESONANCE
SPIN-LATTICE RELAXATION
SQUALANE
SQUALENE
TERPENES