Crystal structure of Al(tBu)3(NH2CH2CH2Ph): A molecular “slinky”

Aitken, Candice L.; Barron, Andrew R.

doi:10.1007/bf01677785

Cited by 12 publications

(8 citation statements)

References 9 publications

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“…In contrast, this signal could not be clearly detected in either the standard CPMAS or dipolar dephasing spectra of DOD-GLY-SWNT (1) or GLY-SWNT, even though the C SWNT :substituent ratio is similar for GLY-SWNT, AHA-SWNT, and AUDA-SWNT. The diffi culty in CPMAS NMR detection of the sidewall sp 3 C N site in the amino acid-functionalized SWNTs is similar to the situation encountered with C 60 bound to a polystyrene derivative through its pendant primary amines: for this polymer-bound C 60 , the analogous C 60 sp 3 C N site was not detected by CPMAS NMR [53].…”

Section: Nano Researchmentioning

confidence: 81%

“…AFM, TEM, and Raman suggest that the amino acid (and hence ester) moieties are distributed along the sidewall, we propose that void spaces are present between the SWNTs in the solid state. Thus, the freedom of movement of the chain will be greater for longer functional groups, and the relaxation of the aliphatic carbon atoms would approach that of the "liquid" or "molten" state [60], resulting in a more slowly decaying aliphatic signal in the dipolar dephasing experiment. Such a trend is indeed observed.…”

Section: Nano Researchmentioning

confidence: 99%

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Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

et al. 2008

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Carboxylic acid-functionalized single walled carbon nanotubes (SWNTs) prepared via the reaction of an amino acid, NH 2 (CH 2 ) n CO 2 H where n = 1 (glycine, GLY), 5 (6-aminohexanoic acid, AHA), 10 (11-aminoundecanoic acid, AUDA), with fl uorinated single walled carbon nanotubes (F-SWNTs) have been characterized by MAS 13 C NMR spectroscopy. The ease of observing the aliphatic CH 2 groups and the resolution of the signal are dependent on the length of the amino acid's aliphatic chain. We have proposed that where substituent chains are short (making NMR data collection difficult) chemical modification to extend the chain length should alleviate analysis problems. In this regard, we have investigated the esterifi cation of the carboxylic acid termini. The amino acid-functionalized SWNTs were esterified with an appropriate alcohol to ensure parity of the overall substituent length, i.e., GLY-SWNT (C 1 ) + 1-dodecanol (C 12 ) = DOD-GLY-SWNT (1), AHA-SWNT (C 5 ) + 1-octanol (C 8 ) = OCT-AHA-SWNT (2), and AUDA-SWNT (C 10 ) + 1-propanol (C 3 ) = PRO-AUDA-SWNT (3). The 13 C NMR shift for the sp 3 nitrogen-substituted carbon atoms of the SWNT sidewall is observed at ≈ 75 ppm. Increasing the length of SWNT sidewall functional groups enhances the ability to observe the sidewall sp 3 carbon. The methylene carbon signal intensity is less attenuated in the dipolar dephasing spectrum of the ester-functionalized SWNTs than their associated amino acid derivatives, suggesting more motional freedom of the side chain in the solid state. The confi rmation of the dipolar dephasing spectral effects was assisted by the characterization of the ester of AUDA-SWNT with 1,3-propanediol: PPD-AUDA-SWNT (4).

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Section: Nano Researchmentioning

confidence: 81%

Section: Nano Researchmentioning

confidence: 99%

Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

et al. 2008

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“…In compounds 12 and 21 , the thermal parameters and electron density maps indicated possible disorder; this could not be resolved, however. The side chains in compound 18 exhibited static disorder resulting from two different chain conformations (the so-called “slinky effect”) and the disorder of the carbons attached to nitrogen.…”

Section: Methodsmentioning

confidence: 99%

Steric Effects in Aluminum Compounds Containing Monoanionic Potentially Bidentate Ligands: Toward a Quantitative Measure of Steric Bulk

et al. 1999

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To develop an understanding of the factors that control the strength of the Lewis acidbase interactions in five-coordinate compounds of aluminum, dimeric dialkylaluminum compounds [R 2 Al{µ-O(CH 2 ) n ER′ x }] 2 (n ) 2, 3; ER′ x ) OR′, SR′, NR′ 2 ) have been prepared from AlR 3 and the appropriate substituted alcohol, thiol, or amine: [R The molecular structures of compounds 1, 2, 6, 7, 12, 13, 16, 18-22, and [Me 2 Al(µ-OCH 2 -CH 2 NMe 2 )] 2 have been determined by X-ray crystallography. The solution structures have been probed by 13 C NMR spectroscopy using the alkoxide derivatives, [R 2 Al(µ-O n Bu)] 2 , R ) t Bu (8), i Bu (9), and Et (10), as a comparison, which show that compounds 1-7 and 11-23 exist as an equilibrium mixture between the four-coordinate isomer and its five-coordinate isomer, where K eq ) [4-coord]/ [5-coord]. Factors that control the extent of this equilibrium and hence the coordination about aluminum include the steric bulk of the substituents at aluminum (R) and the Lewis base donor (R′), the basicity of the neutral donor group (ER′ x ), and the chelate ring size (as determined by n). The intramolecular bond dissociation energies (BDEs) of the Lewis base donor (ER′ x ), as determined by variable-temperature NMR spectroscopy, for compounds 1, 12, 15, 16, [Me 2 Al(µ-OCH 2 CH 2 OMe)] 2 , and [R 2 Al(µ-OCH 2 -CH 2 NMe 2 )] 2 (2.3-13.2 kJ‚mol -1 ) are significantly lower than observed for their fourcoordinate analogues, R 3 Al(ER′ x+1 ) (63.8-125.5 kJ‚mol -1 ). In addition, the relative donor ability (thioether > ether > amine) is the opposite of that expected. The similarity in BDE between compound 1 and 11 suggests that no cooperative effects are present. Ab initio calculations on the four-and five-coordinate isomers of the model compound [H 2 Al(µ-OCH 2 -CH 2 OH)] 2 indicate that the surprisingly weak fifth coordination ligation in [R 2 Al{µ-O(CH 2 ) n -ER′ x }] 2 is a consequence of significant steric hindrance between the aluminum alkyl groups (R) and the Lewis base donor group. A quantitative measure of the thermodynamic destabilization that occurs upon substitution of H with Me or t Bu is proposed on the basis of the derivation of the Lennard-Jones (12,6) potential from solution thermodynamic and X-ray structural data.

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“…The methyl groups occupy fixed places in the lattice, while the S and O reside in two positions each in a "slinky-esque" disorder. 22 Refinement of positional and anisotropic thermal parameters led to convergence (see Table 4).…”

Section: Crystallographic Studiesmentioning

confidence: 99%

Structural characterization of borate esters in which sodium acts as a support to the structural framework

Bishop

Bott

Barron

2000

J. Chem. Soc., Dalton Trans.

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Crystal structure of Al(tBu)3(NH2CH2CH2Ph): A molecular “slinky”

Cited by 12 publications

References 9 publications

Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

Steric Effects in Aluminum Compounds Containing Monoanionic Potentially Bidentate Ligands: Toward a Quantitative Measure of Steric Bulk

Structural characterization of borate esters in which sodium acts as a support to the structural framework

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