Vibrational spectra, theoretical calculations, and structure of 4-silaspiro(3,3)heptane

•The four-membered rings of the title molecule are puckered with dihedral angles of 34°.•The two rings are tilted relative to each other by 9°.•The molecule has C2 symmetry but its vibrations follow D2d selection rules closely.•DFT calculations do an excellent job of predicting the vibrational spectra.

Theoretical computations have been carried out for 4-silaspiro(3,3)heptane (SSH) in order to calculate its structure and vibrational spectra. SSH was found to have two puckered four-membered rings with dihedral angles of 34.2° and a tilt angle of 9.4° between the two rings. The puckering and tilting reduce the D2d symmetry to C2. Nonetheless, the vibrational assignments can be done quite well on the basis of D2d symmetry. This is confirmed by the fact that all but the lowest E vibrations show insignificant splitting into A and B modes of C2 symmetry. However, the observed splittings of the lowest frequency modes do confirm the lower conformational symmetry. The calculated infrared and Raman spectra were compared to the experimental spectra collected for the vapor, liquid, and solid states, and the agreement is excellent.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide