OD(H)…S hydrogen bonds in crystalline hydrates: survey and correlation of vibrational spectroscopic and structural data

Abstract

Structural and vibrational spectroscopic data of O w-D(H)…S H-bonds in crystalline hydrates are discussed. The compilation includes 85 O w-D(H)… S groups in 16 different compounds, for which accurate structural data (from neutron and/or X-ray diffraction measurements), as well as high quality v OD stretching frequency data (from low temperature Raman and/or IR measurements of isotopically dilute samples) are available. The data are discussed with respect to accuracy of neutron and X-ray data, temperature effects, different types of water molecules with approximately linear H-bonds, bifurcated H-bonds and ‘free’ OD(H) groups, and reliability of assignments of frequencies to O-D(H) groups. From the correlation between v OD frequencies and R o…s bond distances the existence of significant and systematic differences between different kinds of sulfur acceptors becomes evident. It is shown in particular that at comparable bond distances the v OD stretching frequencies of OD..S H-bonds in different compounds significantly increase within the series S″ ⪡ SnS 4″″ < XCS 2′ (XRO, R 2N) ⩽ XS 4‴ (XP, As, Sb) < S 2O 3″ < SCN′, from about 2380 to 2530 cm −1 at R o…s=3.3 Å. The observed differences may reasonably well be interpreted in terms of different mean net charges of the different kinds of sulfur acceptors, which systematically decrease within this series.