ANHARMONIC VIBRATIONAL SPECTROSCOPY FOR TRANSITION METAL COMPLEXES Camille Latouche Julien Bloino Vincenzo Barone Dimitrios Skouteris Federico Palazzetti Alberto Baiardi

Outline Introduction I – Computed Resonance Raman Spectra of Metal Complexes including Anharmonic and Solvent Effects II – Benchmark on Frequencies of Metal Complexes including Anharmonic Corrections Perspectives

Introduction Ru derivatives are used in many industrial fields: Solar Cells Sensors … In order to characterize the targeted compounds  Multi-Frequency analyses Vibrational contributions to electronic transition are rarely taken into account. Vibronic spectra are still rare, especially on metal complexes Need data at the anharmonic level for many types of compounds, including complexes

I- Resonance Raman on [Ru(bpy)3]2+ Our target: [Ru(bpy)3]2+ This compound has been extensively studied both experimentally and theoretically B3PW91/LANL2DZ + pol./PCM(CH3CN) Minimum requisite for vibronic spectroscopy Further refinement What is mandatory: DFT Frequency calculation on the optimized Ground State TD-DFT calculation of Excited State energies and gradients on the optimized Ground State What is better: TD-DFT Optimization of the Excited State TD-DFT Harmonic Frequency calculation on the optimized Excited State DFT Anharmonic frequency calculation on the optimized Ground State Scaling of Harmonic Frequencies of the Excited State

Toward quantitative accuracy Inclusion of solvent effects Inclusion of anharmonic effects and of the correct excited-state PES

First Conclusions It is possible to reproduce resonance Raman spectra of Metal Complexes accurately To do so, it is necessary to go beyond the harmonic level and to get more information from the Exc. State. DFT has become a crucial and effective tool thanks to intensive developments to improve its reliability and efficiency The anharmonic effects have critical impact on the accuracy To go further and with other molecules, it is necessary to have more data but beyond the Harmonic level  Need for a comprehensive Benchmark of frequencies at the Anharmonic level

II- Anharmonic Benchmark of Metal Complexes Need simple molecules Need well-characterized molecules Need molecules well studied at both experimental and theoretical levels Metallocenes seem to be the best candidates to do so First, we study the C-H vibrations and, in the case of Ferrocene, metal vibration will be discussed Acronyms used: CAM = CAM-B3LYP Def2 = DefTZVP Def2s = Def2SVP LAN = LANL2DZ + polarization

Harmonic vs Anharmonic frequencies, the case of Ferrocene PBE0/# B3PW91/# # = m6-31g*/SNSD B3LYP/# PBE0/§ B3PW91/§ B3LYP/§ PBE0/* § = m6-31g*/6-31g** B3PW91/* B3LYP/* * = Stuttgart/6-311g** CAM/Def2 CAM/Lan PBE0/Def2 PBE0/Lan B3PW91/Def2 B3PW91/Lan B3LYP/Def2 B3LYP/Lan BP86/Def2 BP86/Lan

Harmonic vs Anharmonic frequencies, the case of Ruthenocene Preliminary results CAM/Def2 CAM/Lan PBE0/Def2 PBE0/Lan B3PW91/Def2 B3PW91/Lan B3LYP/Def2 B3LYP/Lan BP86/Def2 BP86/Lan

Harmonic vs Anharmonic frequencies, the case of Osmocene (I) CAM/Def2s PBE0/Def2s B3PW91/Def2s B3LYP/Def2s BP86/Def2s PBE0/* B3PW91/* B3LYP/* * = Stuttgart/6-311g** CAM/Def2 CAM/Lan PBE0/Def2 PBE0/Lan B3PW91/Def2 B3PW91/Lan B3LYP/Def2 B3LYP/Lan BP86/Def2 BP86/Lan

Harmonic vs Anharmonic, the case of Osmocene (II) CAM/Def2s PBE0/Def2s B3PW91/Def2s B3LYP/Def2s BP86/Def2s PBE0/* B3PW91/* * = Stuttgart/6-311g** B3LYP/* CAM/Def2 CAM/Lan PBE0/Def2 PBE0/Lan B3PW91/Def2 B3PW91/Lan B3LYP/Def2 B3LYP/Lan BP86/Def2 BP86/Lan

The Case of Ferrocene in detail |Difference vs. Experiment (cm-1)| CAM/Def2 PBE0/Lan PBE0/Def2 CAM/Lan B3PW91/Lan B3PW91/Def2 BP86/Lan BP86/Def2 B3LYP/Lan B3LYP/Def2 B3LYP/* B3PW91/* B3LYP/§ B3PW91/§ PBE0/§ B3LYP/# B3PW91/# PBE0/* PBE0/# * = Stuttgart/6-311g** § = m6-31g*/6-31g** # = m6-31g*/SNSD

Conclusion and Perspectives DFT and TD-DFT calculations are efficient tools for the rationalization of spectroscopic properties. Second order vibrational perturbation theory (VPT2) has been used to compute anharmonic IR and Raman spectra. Next, a complete vibronic treatment has been introduced for Resonance Raman spectra. Solvent effects and anharmonic corrections are mandatory to reach quantitative agreement with experiment concerning both positions (IR, Raman, RR) and intensities (RR) of all peaks Concerning ligand vibrations, the computational models validated for organic molecules perform a good job also in metallo-organic systems Vibrations directly involving the metal are more sensitive to the choice of the correlation functional: PW91 seems much better than LYP B3PW91, associated to a triple-ζ basis set seems to give the best results for the whole spectra

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