29Si NMR of five- and six-coordinate organosilicon complexes

Cella, James A.; Cargioli, Joseph D.; Williams, Elizabeth A.

doi:10.1016/s0022-328x(00)93813-0

Cited by 96 publications

(43 citation statements)

References 7 publications

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“…Additionally, the spectrum reveals several new resonances from -40 to -150 ppm. They can be attributed to various Si functional groups (22)(23)(24) that may be present as a consequence of the biodegradation of the material (see 11, 111, and IV-high-coordinated Si-in Fig. 4).…”

Section: Ex Vivo 29si Nmr Spectroscopy Of Tissuesmentioning

confidence: 99%

Migration and biodegradation of free silicone from silicone gel‐filled implants after long‐term implantation

Pfleiderer

Ackerman

Garrido

1993

Magnetic Resonance in Med

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In vivo 1H NMR chemical shift imaging (CSI), 1H NMR localized spectroscopy (STEAM) and multinuclear NMR spectroscopy (29Si, 13C, 1H) were used to characterize the aging process of silicone gel-filled implants in a rat model after long-term implantation. Although no significant changes could be observed in the implants or surrounding tissue by in vivo 1H chemical shift imaging, in vivo 1H localized spectroscopy of the livers from the longer term population revealed the presence of silicone. Ex vivo 29Si spectroscopy of the liver, spleen, and the capsule formed around the 9 and 12 month implants clearly demonstrated and confirmed for the first time that a significant amount of free silicone migrates from silicone gel-filled implants. Also, these results show that silicones are not metabolically inert, and their biodegradation in tissue and within the implant can be monitored after 9 and 12 months by changes in the 29Si chemical shifts seen in corresponding ex vivo spectra. The NMR findings are supported by those obtained by atomic absorption spectroscopy. Silicone aging changes not only the chemical composition of the gel, but also its proton T2 relaxation times, which increase with long implantation times. The three dimensional structure of the gel disintegrates (i.e., polymer chain rupture), increasing the molecular mobility of the polymer and, consequently, its protons T2 values. The relaxation data we obtained reflect this in vivo degradation, especially in the case of implant rupture. Additionally, small concentrations of fat in the silicone gel were found within the implants. The presence of these lipophilic substances also might increase the T2 values (plasticizer effect). These findings may assist in evaluating the implant integrity and disease symptoms related to their presence in humans.

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Section: Ex Vivo 29si Nmr Spectroscopy Of Tissuesmentioning

confidence: 99%

Migration and biodegradation of free silicone from silicone gel‐filled implants after long‐term implantation

Pfleiderer

Ackerman

Garrido

1993

Magnetic Resonance in Med

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“…The report of a transient hexavalent silicon complex in the diatom Navicula pelliculosa [11] is an exception. Silicon complexes of Ent (1) Si NMR spectra of Si-Sal ( Figure 1) and Si-Ent (see the Supporting Information) each exhibit a single peak at À140 ppm which, in the majority of studied cases, is characteristic of hexaoxo silicon complexes, [12][13][14] (d( 29 Si) = À135 to À145 ppm), whereas chemical shifts of d = À71 to À110 ppm are typical for tetraoxo silicon complexes and values of d = À98 to À110 ppm are common for pentaoxo silicon complexes. Accordingly, the NMR data suggest hexaoxo-coordinated silicon in the siderophore complexes.…”

Section: Dedicated To Professor Siegfried Blechert On the Occasion Ofmentioning

confidence: 99%

The E. coli Siderophores Enterobactin and Salmochelin Form Six‐Coordinate Silicon Complexes at Physiological pH

et al. 2011

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“…The chemical shifts for the penta-and/or hexacoordinated silicon atoms are expected to range from d = À127 to À197 ppm for cationic, anionic and neutral compounds in which the silicon atom is directly attached to two, three, four or six oxygen atoms and with the remaining positions occupied by carbon atoms. [22] Although some other systems appear somewhat deshielded, for example, from d = À20 to À70 ppm depending on the molecular structures, for purposes of comparison, we are mainly interested in those that show substantial shielding. From the results of previously published studies, it has been proposed that when two oxygen atoms are replaced by CH 3 or Cl substituents marked deshielding arises.…”

Section: Nmr Trendsmentioning

confidence: 99%

Novel Phthalocyaninatobis(alkylcarboxylato)silicon(IV) Compounds: NMR Data and X‐ray Structures To Study the Spacing Provided by Long Hydrocarbon Tails That Enhance Their Solubility

Sosa-Sánchez

Farfán

Zamudio‐Rivera

et al. 2005

Chemistry A European J

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The reaction between trans-PcSiCl2 (1) and the potassium salts of six fatty acids (2 a-2 f) led to the trans-PcSi[OOC(CH2)nCH3]2 compounds (3 a-3 f), which were characterised by elemental analysis, IR, UV/Vis and 1H, 13C, and 29Si NMR spectroscopy. From a detailed study of the NMR spectra, the strong anisotropic currents of the Pc macrocycle were found to have an effect on up to the sixth methylenic group. As expected, the length of the hydrocarbon tail does not affect the chemical shift of the 29Si nucleus of any of the compounds, appearing at around -222.6. The structures of PcSi[OOC(CH2)nCH3]2, where n = 7, 10, 12, 13 and 20, were determined by X-ray crystallography. All the compounds were found to be triclinic with a P1 space group. In all cases the observed crystallographic pseudosymmetry is Ci and the asymmetric unit consists of half a molecule. The silicon atom is at the centre of a distorted octahedron and hence its coordination number is six. The carboxylate fragments are in a trans configuration with respect to the Pc macrocycle. The supramolecular structures are discussed in detail herein. The correlation between the 1H NMR chemical shifts and the position of the corresponding carbon atoms in the hydrocarbon tail reveals that the dicarboxylate substituents exhibit a spacer-like behaviour that enhances the solubility. A detailed study of the tail variable allowed us to evaluate the loss of radial shielding along the Pc2- ligand.

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29Si NMR of five- and six-coordinate organosilicon complexes

Cited by 96 publications

References 7 publications

Migration and biodegradation of free silicone from silicone gel‐filled implants after long‐term implantation

Migration and biodegradation of free silicone from silicone gel‐filled implants after long‐term implantation

The E. coli Siderophores Enterobactin and Salmochelin Form Six‐Coordinate Silicon Complexes at Physiological pH

Novel Phthalocyaninatobis(alkylcarboxylato)silicon(IV) Compounds: NMR Data and X‐ray Structures To Study the Spacing Provided by Long Hydrocarbon Tails That Enhance Their Solubility

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