Density functional study of nitroprusside: Mechanism of the photochemical formation and deactivation of the metastable states

Abstract

ABSTRACT:In this article, we present a theoretical investigation about the mechanism of the photochemical formation and deactivation of the metastable states observed in nitroprusside ions. The quantum chemical calculations are based on density functional theory. The peculiar photochemical and photophysical behavior of this molecule has attracted chemists' interest for a while. Due to this interest, many details on the nature of nitroprusside's ground state and its two metastable states were known. However, a clear picture of the reaction pathways between the three minima on the ground-state potential energy curve was still missing. By studying the excited states corresponding to all three minima, we could set up, in this work, a model explaining the photochemistry and photophysics responsible for the population of the three different states on the ground-state potential energy curve.

Ferric and Ferrous Iron in Nitroso‐Myoglobin: Computer Simulations of Stable and Metastable States and Their Infrared Spectra

“…This finding is in good agreement with qualitative data from model compounds such as the nitroprusside ion [Fe(CN) 5 (NO)] 3À [25,26] and recent theoretical work on metalloporphyrin NO complexes. [27] The PES was used in molecular dynamics simulations to investigate the relative stability of the three minima.…”

“…To facilitate comparison, the energy of the global minimum was set to the same value as in Figure 2. [28,26] and excited states. [29] The behaviour of the energies of the frontier molecular orbitals (HOMOs and LUMOs) in nitroprusside can be expected to be similar to those of the orbitals in ferric nitrosyl heme and were not investigated further here.…”

“…For the two remaining minima, the porphyrin and imidazole units were held fixed in the configuration of the global minimum and the position and orientation of NO was optimized. 2À [25,26] and in theoretical studies on metalloporphyrin complexes, [27] although the relative energies of the minima are different. The minima found on the fitted PES are not in exact agreement with the optimized ab initio minima.…”

Direct Observation of Photoinduced Bent Nitrosyl Excited-State Complexes

“…This is consistent with previous studies that have shown that multiple photons are needed to form iso-S 0 from S 0 and that the formation of iso-S 0 relies upon the presence of a stable, photochemically accessible η 2 -S 0 intermediate. 8,21,22 Since neither species B nor C can be assigned to η 2 -S 0 or iso-S 0 , the unassigned peaks must be due to excited state bent-NO complexes. The calculated NO stretching frequencies for both T 1 (1664 cm -1 ) and Since the calculated NO stretching frequencies of S 1 and T 1 are indistinguishable given the accuracy of DFT calculations, 36 we have used the calculated potentials in Figures 10b and 10c to further differentiate between them.…”

One- and two-dimensional infrared spectroscopic studies of solution-phase homogeneous catalysis and spin-forbidden reactions

“…This is consistent with previous studies that have shown that multiple photons are needed to form iso-S 0 from S 0 and that the formation of iso-S 0 relies upon the presence of a stable, photochemically accessible η 2 -S 0 intermediate. [19,109,110] Since neither species B nor C can be assigned to η 2 -S 0 or iso-S 0 , the unassigned peaks must be due to excited state bent-NO complexes. The calculated NO stretching frequencies for both T 1 (1664 cm −1 ) and S 1 (1659 cm −1 ) agree best with the NO stretching mode of C (1685 cm −1 ).…”