Nuclear resonance vibrational spectroscopy (NRVS) is a relatively new addition to the vibrational spectroscopy toolbox that allows for a more robust vibrational evaluation of biologically important heme complexes. In previous work, our group have explored NRVS spectra in which spectra are taken in three orthogonal directions on [Fe(OEP)(NO)] complex, and vibrational anisotropy was observed as the axial nitrosyl ligand controls the direction of the in-plane iron motion[1]. We had performed user-friendly scripts to simulate NRVS, especially for anisotropic vibration, from DFT calculation for mode assignments [2]. The method has been applied to a few iron porphrinates in our group at vibrational level, shown in figure. Recently, we has extended our computational prediction to {Fe(NO)}6 [3] and {Fe(NO)}7 [4]. Important vibrations involving the axial NO group are the Fe-NO stretch and the Fe-N-O bend. The modes were assigned by the calculations combined with oriented single-crystal nuclear resonance vibrational spectra in experiment. The featured/mixing modes and ligand effect in vibration have been discussed to understand the control factor in coordination of small molecular (NO), porphyrin or axil ligand (imidazole). The results clearly further confirm the nature of the top most MO’s of the isoelectronic CO and NO complexes are decidedly different and that the classical π backbonding model is not applicable in {Fe(NO)}6, while in {Fe(NO)}7 the mixing iron modes must be related to the differing peripheral phenyl substituents. [1] Pavlik, J. W.; Barabanchikov, A.;. Oliver, A. G; Alp, E. E.; Sturhahn, W.; Zhao, J.; Sage, J. T.; Scheidt, W. R. Angew. Chem., Int. Ed. 2010, 49, 4400–4404. [2] Peng, Q.; Pavlik, J. W.; Scheidt, W. R.; Wiest, O. J. Chem. Theory Comput. 2012, 8, 214. [3] Li, J.; Peng, Q.; Oliver, A. G.; Alp, E. E.; Hu, M. Y.; Zhao, J.; Sage, J. T.; Scheidt, W. R. J. Am. Chem. Soc. 2014, 136, 18100. [4] Peng, Q.; Pavlik, J. W.; Alp, E. E.; Hu, M. Y.; Zhao, J.; Sage, J. T.; Scheidt, W. R. will submit in 2015

Computational prediction on nuclear resonance vibrational anisotropy applied to Iron porphrinates

251st National Meeting (2016)

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