Infrared evidence of NO linkage photoisomerization in Na2[Fe(CN)5NO].2H2O at low temperature: experimental and theoretical (DFT) isotopic shifts from 15n(O), 18O and 54Fe species.

Infrared spectra of the metastable state I (MSI) of normal and 15NO, N18O and 54Fe isotopically substituted sodium nitroprusside dihydrate (Na2[Fe(CN)5NO].2H2O) have been obtained at 77 K. A comparison of the isotopic shifts measured for the vibrational modes of the FeXY (XY = NO or ON) moiety with those calculated by means of quantum chemistry (DFT) procedures supports the linear Fe-O = N arrangement for the MSI state.