title: Ultrafast Dynamics of Manganese(III), Manganese(II), and Free-Base Bacteriochlorin: Is There Time for Photochemistry?
abstract: Manganese(III) and manganese(II) complexes of halogenated sulfonamide tetraphenylbacteriochlorins were prepared for the first time via a transmetalation reaction and shown to be stable at room temperature. The behavior of the electronic states of the paramagnetic complexes is remarkably different from those of the metal-free bacteriochlorins or diamagnetic metallobacteriochlorins. The Mn3+complex exhibits eight electronic transitions between different states from 300 to 1100 nm, with a very prominent band (molar absorption coefficient of ca. 50000 M-1cm-1) at 829 nm. Ultrafast transient absorption showed the formation of an excited singquintet state that decays to a tripquintet state with a femtosecond lifetime. The tripquintet state decays in 5 ps, yielding a tripseptet state with a 570 ps lifetime. The electronic absorption of the Mn2+complex more closely resembles those of diamagnetic metallobacteriochlorins, but the longest decay lifetime is only ca. 8 ps. The intense photoacoustic waves generated with near-infrared excitation suggest the use of these complexes in photoacoustic tomography.
authors.affiliation: Luzitin SA, Ed. Bluepharma , S. Martinho do Bispo, 3045-016 Coimbra, Portugal.|Chemistry Department, University of Coimbra , 3004-535 Coimbra, Portugal.
authors.forename: Fabio A
authors.identifier: http://orcid.org/0000-0002-9339-7259
authors.initials: FA
authors.lastname: Schaberle
authors.affiliation: Luzitin SA, Ed. Bluepharma , S. Martinho do Bispo, 3045-016 Coimbra, Portugal.
authors.forename: Artur R
authors.initials: AR
authors.lastname: Abreu
authors.affiliation: Luzitin SA, Ed. Bluepharma , S. Martinho do Bispo, 3045-016 Coimbra, Portugal.
authors.forename: Nuno P F
authors.initials: NP
authors.lastname: Gonçalves
authors.affiliation: LaserLeap SA, IPN , R. Pedro Nunes, 3030-199 Coimbra, Portugal.
authors.forename: Gonçalo F F
authors.initials: GF
authors.lastname: Sá
authors.affiliation: Chemistry Department, University of Coimbra , 3004-535 Coimbra, Portugal.
authors.forename: Mariette M
authors.initials: MM
authors.lastname: Pereira
authors.affiliation: Chemistry Department, University of Coimbra , 3004-535 Coimbra, Portugal.
authors.forename: Luís G
authors.initials: LG
authors.lastname: Arnaut
mesh_terms: D002151:Calorimetry; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D013997:Time Factors
chemical_list: D056831:Coordination Complexes; D011166:Porphyrins; C452433:bacteriochlorin; D008345:Manganese