Identification and quantification of cis and trans isomers in aminophenyl double‐decker silsesquioxanes using ¹H–²⁹Si gHMBC NMR

Abstract

Cis and trans isomers of a series of double-decker silsesquioxanes (DDSQ) were characterized by two-dimensional NMR techniques. The (1)H NMR spectra of these species have not previously been assigned to a degree that allows for quantification. Thus, (1)H-(29) Si HMBC correlations were applied to facilitate (1)H spectral assignment and also to confirm previous (29)Si assignments for this class of silsesquioxanes. With the ability to identify all the pertinent resonances of the (1)H NMR spectrum, (29)Si NMR is no longer required for quantification and required only for characterization. This not only saves time and material but also provides a more accurate quantification, thus allowing for the ratio of cis and trans isomers present in each compound to be determined. A more accurate measure of the cis/trans ratio enables the investigation of its influence on the physical and chemical properties of DDSQ nanostructured materials.

Bis-phenylethynyl polyhedral oligomeric silsesquioxanes: new high-temperature, processable thermosetting materials

“…The cis isomer's central silicon atoms are in differing chemical environments, with the shis from the two atoms opposite the phenylethynyl groups at À79.6 ppm (green), and the shis from the atoms between the phenylethynyl groups appearing at À79.1 ppm (orange). 24 Single crystals suitable for X-ray diffraction were grown from concentrated solutions of benzene containing either cis or trans bis-PE-POSS. The crystal structures, presented in Fig.…”

Chlorine‐Free Catalytic Formation of Silsesquioxanes with Si‐OH and Si‐OR Functional Groups

“…Results obtained for 3k and 3m allowed for quantitative integration of corresponding signals for diverse Si atoms, showing the obtained composition of cis and trans products mixture to be in equimolar ratio (see Supporting Information, section 5). The analysis was performed on the basis of Lee's report and it is consistent with our previous observations , …”

“…The analysis was performed on the basis of Lee's report and it is consistent with our previous observations. [69,72]…”

Modern concepts and methods in the chemistry of polyhedral metallasiloxanes

“…1), but only a few previous studies have described cage molecules containing 4, 6, 10, or 12 silsesquioxane fragments. By contrast, over 1000 previous studies have reported octameric cage molecules [RSiO 1.5 ] 8 (cubic structures) with different organic groups at the silicon atom [2,[11][12][13][14][15][16][17][18][19][20][21][22] (see Table 1). M a n u s c r i p t 3 This prevalence of octameric structures among structures with the same composition but different sizes is not accidental, and there are several possible explanations.…”

“…Thus, the association of two (17) or three (18) siloxane cubic structures occurs during the interaction with AlMe 3 [47]. It should be noted that the introduction of a cerium atom into this structure is accompanied by the oxidation of Ce(III) to Ce(IV) ( [47] 18 [47] 19 [51] Scheme 4.…”