Semiempirical calculation of 29Si NMR chemical shifts and 29Si-13C spin-spin coupling constants in some substituted bridgehead polycycloalkanes

Kovaček, Damir; Maksić, Zvonimir B.; Elbel, Susanne; Kudnig, J.

doi:10.1016/0166-1280(94)80021-9

Cited by 11 publications

(24 citation statements)

References 32 publications

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“…The 29 Si resonances were assigned following previous reports in the literature, 8,39,40 while those of 13 C were referred to the solution spectra of the corresponding unbound precursors. In the case of the T_Si-8C(F) derivative, the structure is also confirmed by the correct integral ratio between hydrogen and fluorine carbons.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Here, 13 C and 29 Si solid-state CP/MAS NMR are used to investigate the different behavior and reactivity toward the nano-TiO 2 surface of siloxanes with different organic chains. The 29 Si resonances were assigned following previous reports in the literature, ,, while those of 13 C were referred to the solution spectra of the corresponding unbound precursors. In the case of the T_Si-8C(F) derivative, the structure is also confirmed by the correct integral ratio between hydrogen and fluorine carbons.…”

Section: Resultsmentioning

confidence: 99%

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Multiscale Rough Titania Films with Patterned Hydrophobic/Oleophobic Features

et al. 2012

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Oxide-based hybrids are promising systems to modulate the surface properties and impart different functionalities. Here, the wettability features of rough titanium dioxide (TiO2) layers derivatized by siloxanes are tailored with respect to both water and nonaqueous solvents. The adopted synthetic procedure is very simple and may be extended to different substrates, as it is based on the direct functionalization of homemade, tailored, TiO2 nanoparticles by different siloxanes, both fluorinated and nonfluorinated. Nanotitania provides a multiscale roughness able to impart superhydrophobicity and its photocatalytic activity can be exploited to obtain surfaces with patterned wettability by photocatalytic lithography. The behavior of the different siloxanes (oleophobicity degree, self-cleaning properties, and kinetics of ultraviolet degradation) is related to the surface energy components of the bare siloxane films, evaluated by Owens–Wendt classical model, and to the structure of the siloxane monolayer at the TiO2 surface, as determined by 13C and 29Si solid-state nuclear magnetic resonance. Finally, patterned structures with tunable hydrophobic and oleophobic patches are obtained by using the photocatalytic activity of the oxide. The siloxane photodegradation process is analyzed by Fourier transform infrared spectroscopy. The resulting wetting contrast is exploited to obtain a site selective adsorption of a dye molecule. The presented procedure can be applied to obtain the site selective deposition or growth of a large variety of materials, such as semiconductor quantum dots, polymers, or biological molecules.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Multiscale Rough Titania Films with Patterned Hydrophobic/Oleophobic Features

et al. 2012

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“…In previous studies of empirical relationships between 1 J 13 C - 1 H and hybridization or bond angles, summarized in Table , the choice of compounds was arbitrary and those with large deviations of calculated vs experimental 1 J 13 C - 1 H couplings, such as strained polycyclics, were generally excluded, obviating meaningful comparisons between different correlations. Most studies used both experimental and calculated geometries (employing INDO, −,, AM1, CNDO/2, , or MM 24a,25 methods), which could be a source of systematic deviations, too, while conformational averaging was ignored in most cases. Hybridization parameters were extracted with different methods; most gave the same general picture, but some give unsatisfactory results for highly strained cyclopropane ring compounds.…”

Section: Resultsmentioning

confidence: 99%

“…The MP relationship has been widely used in its original form or in modified versions to make quantitative predictions for nuclear spin couplings and to test theoretical models of molecular systems. Numerous linear correlations dealing with hybridization have been proposed in the literature. − Maksić et al introduced a modified relationship of the 1 J 13 C - 1 H dependence on % s C with inclusion of C−H bond overlap, and Hu and Zhan 18 suggested an analogous relationship where bond overlap is replaced with bond order. Subsequently, starting from a theoretical analysis of the Fermi contact coupling interaction with inclusion of ionic terms to the C−H bond, Zhan and Hu proposed a relationship for calculation of 1 J 13 C - 1 H that includes contributions from both hybrid orbitals and net atomic charges.…”

Section: Introductionmentioning

confidence: 99%

Correlation of ¹³C−H Coupling Constants with Electronic Structure in Bi- and Polycycloalkanes: A PM3 and HF/6-31G* Analysis

Crăciun

Jackson

1998

J. Phys. Chem. A

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Müller−Pritchard-type (1 J 13 C - 1 H = a × % sC) and related expressions are explored for the prediction, from standard quantum chemical models, of one-bond C−H spin−spin coupling constants, in a series of bi- and polycyclics. Correlations of experimental 1 J 13 C - 1 H with quantities computed from NBO analyses of PM3 and HF/6-31G* wave functions//geometries are critically examined for 38 aliphatic hydrocarbons (61 distinct tertiary C−H sites; J range >100 Hz). Experimental vs calculated coupling constants are best fit when the model includes contributions from atomic charges (q H and q C) along with s character at carbon (% sC). Previously used geometrical measures of hybridization are also discussed. The relationships obtained can be employed to easily predict one-bond C−H coupling constants at tertiary sites in polycyclic saturated hydrocarbons with experimentally useful accuracy. By using common computational chemistry methods for a large data set, we offer both a predictive tool for the practicing chemist and insights into the validity of hybridization-based interpretations of coupling.

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“…Regression coefficients in Eq. [22] adapted to 1 J (C b Si) couplings between a bridgehead C b nucleus and a Si one in substituted Si(CH 3 ) 3 ‐polycyclic hydrocarbons were also determined, where the s % character for the SiC bond at each atom were calculated at the AM1 level . When the parent compounds regression analysis for 1 J (C b H) couplings was considered using linear relationships between ( s %) C(b) and net charges on both the Si and C atoms, correlation coefficients of 0.99 and 0.92, respectively, were obtained.…”

Section: Indirect Methodsmentioning

confidence: 99%

From NMR spectra to structure

Facelli

Ferraro

2013

Concepts Magnetic Resonance

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This article discusses the existing methods to correlate NMR parameters describing the high resolution NMR spectra of liquids and solid systems with their structural parameters. Those methods are divided into direct and indirect ones. This article includes two types of direct methods: those based on the Nuclear Overhauser Effect (NOE) contributions to the NMR relaxation and those based on direct measurements of the dipolar couplings using several experimental approaches. Indirect methods are based on the intrinsic dependence of J couplings and shieldings on the atomic coordinates of the atoms in a molecule and its surroundings, requiring complex quantum mechanical calculations to relate NMR spectral properties to molecular and crystal structure. This article discusses how changes in chemical bonding, conformation, and stereo configurations that cause measurable changes in NMR parameters closely related to molecular and crystal structure. The final section provides information about the software and hardware required to perform calculations needed to solve structural problems using high resolution NMR. This article intends to provide molecular structural researchers new to the field of NMR, with an overall panorama of the potential of using high resolution NMR for structure elucidation, when other more traditional techniques are not feasible. To this end and to emphasize the didactic value of this work, after each section a brief conclusion has been added to recap the critical concepts. © 2014 Wiley Periodicals, Inc. Concepts Magn Reson Part A 42A: 261–289, 2013.

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Semiempirical calculation of 29Si NMR chemical shifts and 29Si-13C spin-spin coupling constants in some substituted bridgehead polycycloalkanes

Cited by 11 publications

References 32 publications

Multiscale Rough Titania Films with Patterned Hydrophobic/Oleophobic Features

Multiscale Rough Titania Films with Patterned Hydrophobic/Oleophobic Features

Correlation of ¹³C−H Coupling Constants with Electronic Structure in Bi- and Polycycloalkanes: A PM3 and HF/6-31G* Analysis

From NMR spectra to structure

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Semiempirical calculation of 29Si NMR chemical shifts and 29Si-13C spin-spin coupling constants in some substituted bridgehead polycycloalkanes

Cited by 11 publications

References 32 publications

Multiscale Rough Titania Films with Patterned Hydrophobic/Oleophobic Features

Multiscale Rough Titania Films with Patterned Hydrophobic/Oleophobic Features

Correlation of 13C−H Coupling Constants with Electronic Structure in Bi- and Polycycloalkanes: A PM3 and HF/6-31G* Analysis

From NMR spectra to structure

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Correlation of ¹³C−H Coupling Constants with Electronic Structure in Bi- and Polycycloalkanes: A PM3 and HF/6-31G* Analysis