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

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.