title: Photophysical behavior of open-shell, first-row transition metal meso-tetraphenyltetrabenzoporphyrins: insights from experimental and theoretical studies.
abstract: The ground and excited state properties of two metallo-tetraphenyltetrabenzoporphyrins (MTPTBP) have been investigated by a combination of DFT/TDDFT and transient absorption spectrometry to draw a complete picture of the excited state deactivation. The Cu(II) and Co(II) complexes were chosen to investigate the impact of the half-filled d orbitals on the photophysical properties of the tetrapyrrole macrocycle. The first observed transient in CuTPTBP was assigned to the triplet state that equilibrated with a ligand-to-metal charge transfer (LMCT) state. Ground state repopulation, completed within 53 ps, occurred via a lower-lying LMCT state. The dependence of the observed lifetime on solvent polarity confirmed the participation of the LMCT state in the overall deactivation process. For CoTPTBP, the first observed transient, a π-localized triplet state, converted to a hot d,d state, wherein intramolecular cooling occurred and completed within 3 ps. The cooled d,d state decayed to the ground state in an exponential manner with a 17 ps lifetime.
authors.affiliation: Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, USA.
authors.forename: G V Nepali
authors.initials: GV
authors.lastname: Rajapakse
authors.forename: Alexandra V
authors.initials: AV
authors.lastname: Soldatova
authors.forename: Michael A J
authors.initials: MA
authors.lastname: Rodgers
mesh_terms: D000042:Absorption; D004583:Electrons; D006586:Hexanes / Q000737:chemistry; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009570:Nitriles / Q000737:chemistry; D011789:Quantum Theory; D013057:Spectrum Analysis; D014050:Toluene / Q000737:chemistry; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D006586:Hexanes; D008665:Metalloporphyrins; D009570:Nitriles; D028561:Transition Elements; D014050:Toluene; C014356:benzonitrile