Collision-induced dissociation and laser photodissociation spectroscopy of N-aromatic metalloporphyrin complexes Kelechi Uleanya, Edward Mathews, Derek Wann and Caroline E.H Dessent Department of Chemistry, University of York, UK Laser photodissociation spectroscopy is applied to iron centred metalloporphyrin complexing with N-aromatics (pyridine, quinoline, isoquinoline). The clusters (FeTPP + · py, FeTPP + · iQ and FeTPP + · Q) are produced in the gas-phase using electrospray ionization mass spectrometry. Our results reveal that the photodepletion and higher-collisional dissociation (HCD) produced same fragments with m/z 668 = FeTPP + as the most intense fragment followed by sequential loss of the substituent groups of the FeTPP + moiety, respectively. Photodepletion spectra of the clusters show that the extinction coefficient of the metalloporphyrins studied does not reduce on ligation. The excited state of the clusters is suggested to decay by one and two photon absorption processes in the Soret band region and only one photon process in the Q-band region. The spectra difference between the photofragment m/z 668 and other photofragments in the Soret band region are attributed to contributions from the ultrafast decay of S 1 state through internal conversion followed by ergodic dissociation of the ground state cluster in the production of all the photofragments while intersystem crossing to a lower lying triplet state which is longer lived, decay results only in the production of m/z 668. Computational results have been used to assign the bands to our experimental results. The experimental results are hence discussed with regard to the contributions of ligation and the intrinsic properties of the N-aromatics to the binding preferences, binding energies, spin states and photochemistry of the clusters compared to the uncomplexed FeTPP + . These are the first experiments to characterize all the photofragments produced from the photodepletion of the clusters therefore giving a full picture of the effect of ligation on the photochemistry of iron centred metalloporphyrins. References 1. B Nielsen, J. S Forster, P.R Ogilby, and S. B Nielsen, J. Phys. Chem. A, 2005, 109 , 3875-3879. 2. C. Durrant, Dalton Trans., 2014, 43 , 9754–9765. 3. Manna, R. Lo and P. Hobza, Dalton Trans., 2020, 49 , 164-170. 4. T. F. M. Luxford, E. M. Milner, N. Yoshikawa, C. Bullivant and C. E. H. Dessent, Chem. Phys. Lett., 2013, 577 , 1-5.
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