Pyrrolo[3,2-b]pyrroles-From Unprecedented Solvatofluorochromism to Two-Photon Absorption.
A combined experimental and theoretical study of the two-photon absorption (2PA) properties of a series of quadrupolar molecules possessing a highly electron-rich heterocyclic core, pyrrolo[3,2-b]pyrrole, is presented. In agreement with quantum-chemical calculations, large 2PA cross-section values, σ2PA ≈10(2) -10(3)  GM (1 GM=10(50)  cm(4)  s photon(-1) ), are observed at wavelengths of 650-700 nm, which correspond to the two-photon allowed but one-photon forbidden transitions. The calculations also predict that increased planarity of this molecule through removal of two N-substituents leads to further increase in the σ2PA values. Surprisingly, the most quadrupolar pyrrolo[3,2-b]pyrrole derivative, containing two 4-nitrophenyl substituents at positions 2 and 5, demonstrates a very strong solvatofluorochromic effect, with a fluorescence quantum yield as high as 0.96 in cyclohexane, whereas the fluorescence vanishes in DMSO.
Universitetet i Tromsø-Norges Arktiske Universitet, Centre for Theoretical and Computational Chemistry Tromsø, 9037 Tromsø (Norway).
Daniel H
DH
Friese
Department of Physics, Montana State University, Bozeman, MT 59717 (USA).
Alexander
A
Mikhaylov
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland).
Maciej
M
Krzeszewski
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland).
Yevgen M
YM
Poronik
Department of Physics, Montana State University, Bozeman, MT 59717 (USA). rebane@physics.montana.edu.|National Institute of Chemical Physics and Biophysics, Akadeemia Tee 23, 12618 Tallinn (Estonia). rebane@physics.montana.edu.
Aleksander
A
Rebane
Universitetet i Tromsø-Norges Arktiske Universitet, Centre for Theoretical and Computational Chemistry Tromsø, 9037 Tromsø (Norway). kenneth.ruud@uit.no.
Kenneth
K
Ruud
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland). dtgryko@icho.edu.pl.
Daniel T
DT
Gryko
D004583:Electrons; D005456:Fluorescent Dyes / Q000737:chemistry*; D015394:Molecular Structure; D009596:Nitrophenols / Q000737:chemistry*; D017785:Photons; D011758:Pyrroles / Q000737:chemistry*; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence
D005456:Fluorescent Dyes; D009596:Nitrophenols; D011758:Pyrroles; C024719:4-nitrophenyl
absorption; fluorescence; heterocycles; solvatochromism; structure-activity relationships