Theoretical and Experimental Study of Medium Effects on the Structure and Spectroscopy of the [Fe(CN)₅NO]^2- Ion

Abstract

The influence of the solvent on the structure and IR spectrum of the [Fe(CN)(5)NO](2)(-) ion is investigated by using gradient corrected density functional theory. IR spectra are also measured on different solvents and the results obtained are compared with the predicted ones. We have treated the solvent effects with a continuum model, based on the Onsager's reaction field approach; in order to mimic strong specific interactions, calculations were also performed on the complex protonated at the cyanide trans to the nitrosyl group. The reaction field calculations predict only qualitatively the most important observed trends, e.g., the shifts in the nitrosyl stretching wavenumber, but fail in accounting quantitatively for the differences between the spectra in water and acetonitrile. The possible role of specific interactions is consistently accounted for by interpreting the experimental shifts of the NO stretching wavenumber nu(NO), as well as the visible absorption energies, when changing the Lewis acidity of the solvent, as measured by the Gutmann's acceptor number. Ligand population analysis was performed to relate the solvent effects with the sigma donor and pi acceptor behavior of cyanide and nitrosyl ligands. The significance of nu(NO) shifts as a result of changes in the medium is discussed in view of the physiological relevance of transition-metal nitrosyl chemistry.

A HF/CI-SD study of the low-lying states of nitroprusside ion

“…We also expect that in acetonitrile medium, the composition of the HOMO will change, with a greater participation of p-donnor contributions of cyanides. In fact, the calculations in vacuum may be ascribed to a solvent of negligible acceptor character; thus, the presently reported results on the composition of the HOMO are in agreement with the strong intramolecular electron shifts detected in SNP when dissolved in different solvents 10 .…”

“…Both calculations, MNSL and DZSL, generated similar orbital ordering with the metal d orbitals deep in core and • 20 and confirm our results. The Mulliken atomic charges confirmed well known tendencies 10 showing the cyano nitrogens negatively charged and the nitrosyl nitrogen largely positively charged. It is believed these charges are responsible for the intense solvatochromic effects observed in many bands of SNP, thus influencing the nitrosyl electrophilic reactivity.…”

“…This results can be interpreted on the basis of the interactions of the cations with the free electron pairs of the cyanides. The stabilization of the electron density at cyanides makes energetically more costly the onset of reaction 3, a similar explanation as previosly given for the changes in absorption energies and redox potentials upon the change of solvent 10 .…”

Ab initio study of magnetic property of BEST2 [Fe(CN)5NO] charge-transfer salt

“…Also the design and synthesis of molecular materials combining two or more physical properties as conducting, magnetic, and optical ones have become one of the most appealing challenges in the chemistry of materials in the past few years. In this field, the efforts have been centered, on the one hand, on the use of magnetic polyoxometalates [3], and on the other hand, on the use of tetrahedral metal halide anions [4] and octahedral anions such as ½FeðCNÞ 6 3À ; ½FeðCNÞ 5 NOÞ 2À or ½FeðC 2 O 4 Þ 3 3À which have been well studied, since they are used in connection with optical storage media using holography [5][6][7]. And the reason for choosing magnetic radical anion lies in the probability to prepare molecular metals having two types of open-shell electron orbitals.…”

On the ability of metal-nitroprusside complexes as electrode modifiers: Characterization and electrochemical study of palladized aluminum electrode modified with iron pentacyanonitrosylferrate

“…8, the FT-IR spectrum of the FePCNF precipitate is dominated by CN and NO stretching vibrations, which fall at 2182 and 1945 cm -1 respectively. These absorptions are assigned exclusively to the stretching band of NO and CN of nitroprusside anion as formulated by [Fe II (CN) 5 NO + ] 2- [28][29][30]. According to this formulation, the v(NO)…”