Quantitative Vibrational Dynamics of the Metal Site in a Tin Porphyrin: An IR, NRVS, and DFT Study

Abstract

We used a newer, synchrotron-based, spectroscopic technique (nuclear resonance vibrational spectroscopy, NRVS) in combination with a more traditional one (infrared absorption, IR) to obtain a complete, quantitative picture of the metal center vibrational dynamics in a six-coordinated tin porphyrin. From the NRVS 119Sn site-selectivity and the sensitivity of the IR signal to 112Sn/119Sn isotope substitution, we identified the frequency of the antisymmetric stretching of the axial bonds (290 cm−1) and all the other vibrations involving Sn. Experimentally authenticated density functional theory (DFT) calculations aid the data interpretation by providing detailed normal mode descriptions for each observed vibration. These results may represent a starting point towards the characterization of the local vibrational dynamics of the metallic site in tin porphyrins and compounds with related structures. The quantitative complementariness between IR, NRVS, and DFT is emphasized.

Unraveling the Electronic Structure, Spin States, Optical and Vibrational Spectra of Malaria Pigment

“…The recent development of synchrotronbased NRVS (sometimes called nuclear (resonant) inelastic Xray scattering spectroscopy (NRIXS)) offers ap ossible, albeit not very practical, way.N RVS requires aM çssbauer nucleus ( 57 Fe in b-hematin) and can perform unambiguous mode specification vibrational analysis on oriented single-crystal or textured samples. [68][69][70][71] To our knowledge,a pplication of this technique has not been reported so far in the literature either for natural hemozoin or for b-hematin. In the following section, we provide our calculated results for the NRVS spectra of bhematin.…”