Amplified Two‐Photon Absorption in Trans‐A₂B₂‐Porphyrins Bearing Nitrophenylethynyl Substituents

Abstract

We show that peripheral nitro groups enhance the maximum two-photon absorption cross-section of trans-A2B2-porphyrins bearing two phenylethynyl substituents by more than one order of magnitude. Maximum values as high as 1000 GM result from realization of suitable conditions for effective resonance enhancement along with a lowering of the energy and intensification of the two-photon allowed transitions in the Soret region.

Symmetry Breaking in Pyrrolo[3,2‐b]pyrroles: Synthesis, Solvatofluorochromism and Two‐photon Absorption

“…The fact that no distinct 0–0 2PA peak is observed may be related to the amplification of the 0–1 band, which, along with inhomogeneous broadening, is able to mask a relatively weaker 0–0 component. For example, for 4‐nitrophenyl‐substituted nominally centrosymmetric porphyrins, where inhomogenous broadening is relatively small, the 0–0 component is clearly detected in the 2PA spectrum, even though its relative amplitude can be 10–20 times less compared to the adjacent 0–1 . Nevertheless, the fact that 2PA did not completely vanish in the 0–0 region allowed us to assume that despite the structure being nominally centrosymmetric, the chromophores in solution may become slightly distorted, for example, due to interaction with the solvent molecules, thus rendering the two‐photon transition partially allowed.…”

Near-infrared dyes for two-photon absorption in the short-wavelength infrared: strategies towards optical power limiting

“…[287][288][289][290] These concepts are illustrated by the tetrasubstituted porphyrin base 121 incorporating ethynyl-linked peripheral nitrophenyl moieties as acceptors and mild alkoxy donors, which exhibits a 2PA cross-section of 70 GM at 1240 nm. [291][292][293] Following this approach, Osuka and co-workers developed a series of azulene-based porphyrins 122-125 enabling a strong ICT between donor and acceptor extremities. 286 The most efficient chromophore was the dipolar Zn(II) porphyrin 125 with a 2PA cross-section of 8030 GM at 1400 nm.…”

Ground‐ and Excited‐State Symmetry Breaking and Solvatofluorochromism in Centrosymmetric Pyrrolo[3,2‐b]pyrroles Possessing two Nitro Groups

“…They tend to possess cyanoaryl or pentafluorophenyl substituents as flanking substituents and either dialkoxybenzene as central electron-rich core. [17] More structurally advanced dyes bearing such units as dimesitylboronthiophene [18] or pyridinium salts [19] as acceptors and pyrrole, [20] carbazole, [21] porphyrin, [22] bisthiophene [23] or fluorene [24] as donors have been reported as well. Femtosecond 2PA spectra were measured in the excitation wavelength range of 2PA = 600-1050 nm by using a two-photon excited fluorescence (2PEF) method (see Experimental Section) and are presented in Figure 5.…”