Infrared spectroscopy studies of platinum salts containing tetracyanoplatinate(II). Evidence for strong hydrogen-bonding interactions in "vapochromic" environmental sensor materials

We have studied the sorption of volatile organic compounds (VOCs) by [(n-C4H9)(4)N](2)[Pt(CN)(4)] and [Pt(p-CN-C6H4-C10H21)(4)][Pt(CN)(4)] with FTIR spectroscopy. The data indicate a strong correlation exists between nu(CN) stretching frequencies in the [Pt(CN)(4)](2-) ions and the hydrogen bonding ability of the VOC (as expressed by Abraham's alpha values). The nu(CN) stretching frequencies for each salt with sorbed VOC indicate that similar VOC-material interactions are present in both. The correlation of the IR data for [Pt(p-CN-C6H4-C10H21)(4)][Pt(CN)(4)] with the previously reported NIR data was only successful for solvents with alpha > 0.15. These results suggest that vapochromic shifts in the electronic transitions of [Pt(p-CN-C6H4-C10H21)(4)][Pt(CN)(4)] result not only from H-bonds between the VOC and [Pt(CN)(4)](2-) but also from one or more additional mechanisms that are most important for solvents with low H-bond donor character (alpha < 0.15).