title: Nonlinear absorption properties of 5,10-A2B2 porphyrins--correlation of molecular structure with the nonlinear responses.
abstract: The nonlinear absorption properties of two series of novel free base and metalated meso 5,10-A2B2 substituted porphyrins, both bearing p-tolyl as an A substituent and TMS-ethynyl or bromine as a B substituent, were investigated with the open Z-scan technique at 532 nm in the ns time regime. Most of the compounds exhibited a transmission drop with increasing input fluence. This behavior is desirable for their applications in optical limiting. More complex responses: a drop in transmission followed by an increase in transmission or an increase in transmission followed by a transmission drop, with increasing input fluence, were detected for certain compounds. All of the recorded responses were successfully fitted with a four-level model with simultaneous two-photon absorption arising from the higher excited states (consecutive one- + one- + two-photon absorption). The TMS-ethynyl group was found to be a more efficient meso substituent in optical limiting than the bromine atom. Indium, lead and zinc complexes with TMS-ethynyl substituents were the strongest positive nonlinear absorbers amongst compounds studied which makes them the most interesting candidates for optical limiting application.
authors.affiliation: School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Monika
authors.initials: M
authors.lastname: Zawadzka
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Werner J
authors.initials: WJ
authors.lastname: Blau
authors.forename: Mathias O
authors.initials: MO
authors.lastname: Senge
mesh_terms: D054879:Halogenation; D008670:Metals / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D013053:Spectrophotometry; D014297:Trimethylsilyl Compounds / Q000737:chemistry
chemical_list: D008670:Metals; D009942:Organometallic Compounds; D011166:Porphyrins; D014297:Trimethylsilyl Compounds