Nonlinear absorption properties of 5,10-A2B2porphyrins—correlation of molecular structure with the nonlinear responses

• Published in: Photochemical & photobiological sciences 2013-06, Vol.12 (6), p.996-1007
• Main Authors: Zawadzka, Monika, Wang, Jun, Blau, Werner J., Senge, Mathias O.
• Format: Article
• Language: English
• Subjects: Biochemistry; Biomaterials; Chemistry; Physical Chemistry; Plant Sciences
• ISSN: 1474-905X; 1474-9092
• DOI: 10.1039/c3pp25410k

The nonlinear absorption properties of two series of novel free base and metalated meso 5,10-A 2 B 2 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.