Investigation of crystalline naphthazarin B by carbon-13 NMR spectroscopy using "magic angle" spinning techniques and by x-ray diffraction: evidence for a dynamic disordered structure

Shiau, Wen-I; Duesler, Eileen N.; Paul, Iain C.; Curtin, David Y.; Blann, William G.; Fyfe, C. A.

doi:10.1021/ja00533a054

Cited by 89 publications

(34 citation statements)

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“…20 , 21 The components of the chemical shift tensor describing this anisotropy are found to be 220, 186 and 40 ppm, consistent with expectations for an aromatic molecule. 14 , 20, 21 The narrowing of the powder pattern as the sample is warmed to 295 K shows that the molecule reorients rapidly at 295 K. The correlation time for molecular motion is -10-9 s at 233 K, as deduced from the observation of a minimum in the spin relaxation time in a 7.04 T field, indicating rotational correlation times < 10-s at 295 K. At intermediate temperatures the spectrum appears to be a superposition of a narrow and a broad line, suggesting the possibility that two phases with different barriers to rotation may coexist, 22 or that there may be a distribution of barriers to rotation in the sample. 23 Although the icosahedral symmetry of C6 0 is now established with reasonable certainty, the detailed electronic and geometric structure of this molecule are of considerable interest.…”

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confidence: 86%

Solution and Solid State NMR Studies of the Structure and Dynamics of C₆₀ and C₇₀

et al. 1990

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We have Investigated the structure and dynamics of C 60 and C 7 0 with 13 C NMR spectroscopy. In solution, high-resolution spectra reveal that Co 0 has a single resonance at 143 ppm, Indicating a strained, aromatic system with high symmetry. This is strong evidence for a Co 0 "soccer ball" geometry. A 2D NMR INADEQUATE experIment on 13 C-enriched C 70 reveals the bonding connectivity to be a linear string, in firm support of the proposed "rugby ball" structure with D5h symmetry, and furnishes resonance assignments. Solid state NMR spectra of Co 0 at ambient temperatures yield a narrow resonance, Indicative of rapid molecular reorientation. Variable temperature T 1 measurements show that the rotational correlation time is -10-9s at 230 K. At 77 K, this time Increases to more than I ms, and the 13 C NMR spectrum of Co 0 is a powder pattern due to chemical shift anisotropy (tensor components 220, 186, 40 ppm). At intermediate temperatures a narrow peak is superimposed on the powder pattern, suggesting a distribution of barriers to molecular motion in the sample, or the presence of an additional phase in the solid state. A Carr-Purcell dipolar experiment on Co 0 in the solid state allows the first precise determination of the C 60 bond lengths: 1.45 and 1.40A.The architect and visionary R. Buckminster Fuller developed the concept of synergy, where parts combine to form a system whose effects are greater than those of the mere sum of the pads. 2 He later applied these ideas to develop geodesic structures, which distribute strain efficiently, and hence possess great structural strength. It is therefore not surprising that these ideas found expression in chemistry. In 1985 Smalley, Kroto, and co-workers ascribed a closed-shell, "soccer ball" structure to an observed 60-atom pure-carbon cluster. 3 The great stability of this structure was established five years later by the production of significant amounts of fullerenes. 4-7 The proposed structures 3 , 8 for C 60 and C 70 shown in Figure 1 are carbon shells consisting of hexagons and pentagons; the 12 pentagons in each structure produce torsional strain, creating curvature that leads to closure. Figure 1. The struc_b tures of C 6 o (a) and C 70 (b). All carbons in Co 0 are chemically equivalent, but C 70 consists of five kinds of carbons, labelled a-e in the figure.

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confidence: 86%

Solution and Solid State NMR Studies of the Structure and Dynamics of C₆₀ and C₇₀

et al. 1990

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“…1) having different point group symmetry. The X-ray results [4], combined with NMR spectroscopy data of the solid [9], indicate that there is a rapid proton exchange between the adjacent oxygen atoms at room temperature in all three polymorphs and the resulting structures are centrosymmetrical. At low temperature, naphthazarin undergoes a phase modification caused by changes in the hydrogen bond, and the molecular structure determined from 60 K neutron diffraction data shows C2v symmetry (Fig.…”

Section: Introductionmentioning

confidence: 95%

“…The crystal structure of naphthazarin has been the subject of numerous X-ray and neutron diffraction [4], spectroscopic [8], and NMR [9] investigations (for a summary of the structural work see ReL 4). Naphthazarin crystallizes in three polymorphic forms at room temperature, and there is a phase change at lower temperature [4].…”

Section: Introductionmentioning

confidence: 99%

Ab initio HF-SCF study of naphthazarin: Geometries, isomerism, hydrogen bonding, and vibrational spectrum

Ramondo¹,

Bencivenni²

1994

Struct Chem

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The structural properties and intmmolecular hydrogen bonding of a series of structures of naphthazarin molecule were investigated by ab initio HF-SCF methods. The geometries of the C2~,, C2h, D2h, and Cs symmetry structures were optimized using split-valence basis sets. MP2/6-31G*// HF/6-31G single-point energy calculations indicate that the C2,, isomer (5,8-dihydroxy-l,4-naphthoquinone) is the lowest energy structure of the molecule and that the C2h symmetry one (4,8-dihydroxy-l,5-naphthoquinone), lying 37 kJ/mol above the C2,, form, is the other stable isomer of naphthazarin. At the HF/6-31G level, the intramolecular proton exchange between two equivalent C2v structures is a two-step process where each proton can be independently transferred through an unsymmetrical potential having a 1,5-quinone intermediate, the C2h symmetry structure, and two equivalent transition states of Cs symmetry, with a barrier height equal to 38 kJ/ tool (MP2/6-31G*//HF/6-31G). The study of naphthazarin molecule is flanked by a theoretical investigation on the C2v and C2h isomers of the parent naphthoquinone and dihydroxynaphthalene molecules. The SCF vibrational spectrum of the ground state of naphthazarin, harmonic frequencies, and infrared and Raman band intensities were computed at the HF/6-3 IG level. The results of the calculations are compared with the matrix isolation FT-IR spectroscopy measurements and with the infrared and Raman spectra of the crystal molecule.KEY WORDS: Naphthazarin; intramolecular hydrogen bonding; internal proton exchange; ab initio calculations, vibrational spectrum.

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“…Picosecond spectros copy has been used to study the mech anisms of radiationless decay from ex cited states of several molecules. Re cently, Bondybey et al (5) investi gated naphthazarin (5,8-dihydroxy-1,4-naphthoquinone) spectroscopically in a neon matrix at 4 K. Besides in vestigating the ground-state structure of naphthazarin, which has been pre viously studied (6)(7)(8)(9)(10)(11)(12), they studied vibrational relaxation of this relatively large molecule while it was matrix-iso lated in neon at 4 K. Vibrational and electronic relaxation of excited mole cules in condensed media has received much attention, particularly with re gard to understanding the mechanism of energy dissipation in larger poly atomic molecules. Unrelaxed fluores cence frequently is observed from ex cited vibrational levels of diatomic and even triatomic molecules.…”

Section: Applications Of Picosecond Spectroscopymentioning

confidence: 99%

Picosecond Spectroscopy: Methods and Recent Applications

Hilinski¹,

Rentzepis²

1983

Anal. Chem.

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Investigation of crystalline naphthazarin B by carbon-13 NMR spectroscopy using "magic angle" spinning techniques and by x-ray diffraction: evidence for a dynamic disordered structure

Cited by 89 publications

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Solution and Solid State NMR Studies of the Structure and Dynamics of C₆₀ and C₇₀

Solution and Solid State NMR Studies of the Structure and Dynamics of C₆₀ and C₇₀

Ab initio HF-SCF study of naphthazarin: Geometries, isomerism, hydrogen bonding, and vibrational spectrum

Picosecond Spectroscopy: Methods and Recent Applications

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Investigation of crystalline naphthazarin B by carbon-13 NMR spectroscopy using "magic angle" spinning techniques and by x-ray diffraction: evidence for a dynamic disordered structure

Cited by 89 publications

References 0 publications

Solution and Solid State NMR Studies of the Structure and Dynamics of C60 and C70

Solution and Solid State NMR Studies of the Structure and Dynamics of C60 and C70

Ab initio HF-SCF study of naphthazarin: Geometries, isomerism, hydrogen bonding, and vibrational spectrum

Picosecond Spectroscopy: Methods and Recent Applications

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Solution and Solid State NMR Studies of the Structure and Dynamics of C₆₀ and C₇₀

Solution and Solid State NMR Studies of the Structure and Dynamics of C₆₀ and C₇₀