Vibrational dynamics of a trinuclear oxo-bridged iron complex as studied by nuclear inelastic scattering, Mössbauer spectroscopy and DFT calculations

Abstract

Vibrational dynamics of a trinuclear oxo-bridged iron complex as studied by nuclear inelastic scattering, Mössbauer spectroscopy and DFT calculations IntroductionThere is a continuous interest in the search for selective metal complexes which serve as catalysts for the oxygenation of unactivated hydrocarbon substrates via polynuclear non-heme iron catalysts. The understanding on how such activation reactions work relies on the vibrational dynamics of the metal centre in the catalysts. Vibrational spectroscopy provides a sharp and clear probe of the structure, dynamics and reactivity of biological molecules. Identifying the active metal-site vibrations and relating them to the functional dynamics is of particular interest in enzymes. So far the published works by several authors were conducted on the vibrational properties of iron heme porphyrins [1] and non-heme Fe-S hydrogenase [2]. Recently, the mechanisms governing the spin crossover in Fe compounds were also reported in detail [3]. In this work, we report the first information about the vibrational dynamics of a trinuclear oxobridged iron complex (figure 1), investigated by NIS and DFT methods. The inhomogeneity of the iron coordination is determined by Mössbauer spectroscopy.

A Known Iron(II) Complex in Different Nanosized Particles: Variable-Temperature Raman Study of Its Spin-Crossover Behavior

“…Backscattering Raman spectra were collected using the T-64000 model of JobinYvon (Horiba group) excited with either a He–Ne (Optronics Technologies SA Model HLA-20P, 20 mW) or a Cobolt Fandango TM ISO laser, operating at 632.8 and 514.5 nm, respectively. The laser intensity on the samples was kept low and was varied from 0.4 to 0.8 mW in order to avoid any influence from spin distribution due to local heating by the laser excitation . Dispersion and detection of the Raman-scattered photons were performed with either a 600 grooves/mm or an 1800 grooves/mm (high-resolution spectra, <2 cm –1 for the wavelength of 632.8 nm) grating and a Symphony II 2D CCD detector (liquid nitrogen cooled at 140 K), respectively.…”

“…The laser intensity on the samples was kept low and was varied from 0.4 to 0.8 mW in order to avoid any influence from spin distribution due to local heating by the laser excitation. 23 Dispersion and detection of the Raman-scattered photons were performed with either a 600 grooves/mm or an 1800 grooves/mm (high-resolution spectra, <2 cm −1 for the wavelength of 632.8 nm) grating and a Symphony II 2D CCD detector (liquid nitrogen cooled at 140 K), respectively. Instrument calibration was initially carried out by using the standard 520.5 cm −1 Raman peak position of Si and additionally by regularly collecting the Ne lamp spectrum at the spectral windows of interest.…”