Intrinsic electronic spectra of cryogenically prepared protoporphyrin IX ions - deprotonation-induced Stark shifts

• Published in: Physical chemistry chemical physics : PCCP Vol. 22; no. 36; pp. 2295 - 232
• Main Authors: Zagorec-Marks, Wyatt, Smith, James E. T, Foreman, Madison M, Sharma, Sandeep, Weber, J. Mathias
• Format: Journal Article
• Language: English
• Published: 23.09.2020
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d0cp03614e

We present electronic spectra containing the Q x and Q y absorption bands of singly and doubly deprotonated protoporphyrin IX, prepared as mass selected ions in vacuo at cryogenic temperatures, revealing vibronic structure in both bands. We assign the vibronic progression of the Q x band using a Frank-Condon-Herzberg-Teller simulation based on time-dependent density functional theory, comparing the observed bands with those calculated for porphine. A comparison of the electronic spectra of the two charge states allows investigation of the electronic Stark effect with an electric field strength beyond the capabilities of typical laboratory setups. We analyze the differences in the electronic spectra of the two charge states using n-electron valence perturbation theory (NEVPT2) and simulated charge distributions. We present electronic spectra containing the Q x and Q y absorption bands of singly and doubly deprotonated protoporphyrin IX, prepared as mass selected ions in vacuo at cryogenic temperatures, revealing vibronic structure of both bands.