ffective pi-electron number and symmetry perturbation effect on the two-photon absorption of oligofluorene

Author(s)

Abegao, Luis M. G. ^{[1, 2]} ; Cocca, Leandro H. Z. ^[1] ; Mulatier, Jean-Christophe ^[3] ; Pitrat, Delphine ^[3] ; Andraud, Chantal ^[3] ; Misoguti, Lino ^[1] ; Mendonca, Cleber R. ^[1] ; Vivas, Marcelo G. ^[4] ; De Boni, Leonardo ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Fis Sao Carlos, Photon Grp, CP 369, BR-13560970 Sao Carlos, SP - Brazil

^[2] Univ Fed Goias, Inst Fis, Grp Foton, BR-74690900 Goiania, Go - Brazil

^[3] Univ Lyon, Ens Lyon, CNRS UMR 5182, Lab Chim, F-69342 Lyon - France

^[4] Univ Fed Alfenas, Lab Espectroscopia Otica & Foton, BR-37715400 Pocos De Caldas, MG - Brazil

• Document type: Journal article
• Source: Physical Chemistry Chemical Physics; v. 23, n. 34 AUG 2021.
• Web of Science Citations: 0

Abstract

Fluorene-based molecules exhibit significant nonlinear optical responses and multiphoton absorption in the visible region, which, combined with the high fluorescence quantum yield in organic solvents, could make this class of materials potentially engaging in diverse photonics applications. Thus, herein, we have determined the two-photon absorption (2PA) of oligofluorenes containing three, five, and seven repetitive units by employing the wavelength-tunable femtosecond Z-scan technique. Our outcomes have shown that the 2PA cross-section in oligofluorenes presents an enhanced value of around 18 GM per N-eff, in which N-eff is the effective number of pi-electrons, for the pure 2PA allowed transition (1(1)A(g)-like -> 2(1)A(g)-like). Furthermore, a weak 2PA transition was observed in the same spectral region strongly allowed by one-photon absorption (1(1)A(g)-like -> 1(1)B(u)-like). This last result suggests a molecular symmetry perturbation, probably induced by the molecular disorder triggered by the increase of moieties in the oligofluorene structure. We have calculated the permanent dipole moment difference related to the lowest-energy transition using the Lippert-Matagaformalism and the 2PA sum-over-states approach to confirm this assumption. Moreover, we have estimated the fundamental limits for the 2PA cross-section in oligofluorenes. (AU)

• FAPESP's process: 15/20032-0 - Study on Nonlinear and Charge Transport Properties of Multi-branched Molecules via Quantum Chemical Methods.
• Grantee: Daniel Luiz da Silva
• Support Opportunities: Regular Research Grants
• FAPESP's process: 11/12399-0 - Femtosecond pulses applied to nonlinear optics: spectroscopy, pulse shaping and microfabrication
• Grantee: Cleber Renato Mendonça
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 18/11283-7 - Nonlinear photonics: spectroscopy and advanced processing of materials
• Grantee: Cleber Renato Mendonça
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 16/20886-1 - Ultrafast nonlinear optical spectroscopy: Transient Absorption and optical Kerr Gate with polarization control
• Grantee: Leonardo de Boni
• Support Opportunities: Regular Research Grants