Moderate Two-photon Absorption Cross-section Research Articles

Synthesis, spectroscopic characterization, one and two-photon absorption properties of β-β linked BODIPY dimers

Five β-β linked BODIPY dimers (d1-d5) with different electron-donating/withdrawing groups at the meso-position were synthesized through improved synthetic methods. All compounds were characterized by 1H and 13C NMR and HRMS. The single crystal X-ray analyses indicate that d4 and d5 display a linear coplanar conformation with two linked BODIPY moiety. Their photophysical and electrochemical properties have been investigated by UV–vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy, two-photon excited spectroscopy and cyclic voltammetry. The β-β linked BODIPY dimers exhibit a prominent red shift from the visible region to the red/near-infrared region of their absorption and emission spectra, large Stokes shifts and moderate two-photon absorption cross section σ2 with different groups at the meso-position.

Organotin(IV) carboxylate complexes containing polyether oxygen chains with two-photon absorption in the near infrared region and their anticancer activity

Two novel organo tin carboxylate complexes (BuSnO)6L6 and Bu3SnOL, where L = a cinnamic acid unit containing polyether chains, were rationally designed for two-photon fluorescent imaging and anticancer purpose. The organotin (IV) complex (BuSnO)6L6 possessed strong one-photon exited fluorescence (1PF) intensity and moderate two-photon absorption cross-section in the near infrared region. Living cell evaluation revealed that (BuSnO)6L6 exhibited good bio-compatibility and outstanding selectivity in the selected tumor cell lines as well as in the normal cells. Furthermore, the anti-tumor activity and mechanism of (BuSnO)6L6 have been investigated systematically. The results indicated that (BuSnO)6L6 could induce apoptotic cell death through a mitochondrial dysfunction, ROS (Reactive oxygen species produced by cell during metabolism) and Cytochrome c elevation pathway. This work provides a novel strategy for rationally designing carboxylate organotin complex with two-photon activity and anti-tumor activity.

Indolo[2,3-b]carbazoles with tunable ground states: how Clar's aromatic sextet determines the singlet biradical character

Polycyclic hydrocarbons (PHs) with a singlet biradical ground state have recently attracted extensive interest in physical organic chemistry and materials science. Replacing the carbon radical center in the open-shell PHs with a more electronegative nitrogen atom is expected to result in the more stable aminyl radical. In this work, two kinetically blocked stable/persistent derivatives (1 and 2) of indolo[2,3-b]carbazole, an isoelectronic structure of the known indeno[2,1-b]fluorene, were synthesized and showed different ground states. Based on variable-temperature NMR/ESR measurements and density functional theory calculations, it was found that the indolo[2,3-b]carbazole derivative 1 is a persistent singlet biradical in the ground state with a moderate biradical character (y0 = 0.269) and a small singlet–triplet energy gap (ΔES–T ≅ −1.78 kcal mol−1), while the more extended dibenzo-indolo[2,3-b]carbazole 2 exhibits a quinoidal closed-shell ground state. The difference can be explained by considering the number of aromatic sextet rings gained from the closed-shell to the open-shell biradical resonance form, that is to say, two for compound 1 and one for compound 2, which determines their different biradical characters. The optical and electronic properties of 2 and the corresponding aromatic precursors were investigated by one-photon absorption, transient absorption and two-photon absorption (TPA) spectroscopies and electrochemistry. Amphoteric redox behaviour, a short excited lifetime and a moderate TPA cross section were observed for 2, which can be correlated to its antiaromaticity and small biradical character. Compound 2 showed high reactivity to protic solvents due to its extremely low-lying LUMO energy level. Unusual oxidative dimerization was also observed for the unblocked dihydro-indolo[2,3-b]carbazole precursors 6 and 11. Our studies shed light on the rational design of persistent aminyl biradicals with tunable properties in the future.

Two-photon excited fluorescent chemosensor for homogeneous determination of copper(ii) in aqueous media and complicated biological matrix

In the present work, a two-photon excited fluorescent chemosensor for Cu(2+) was prepared. The probe was constructed on the basis of internal charge transfer (ICT) principle with macrocyclic dioxotetraamine as the Cu(2+) receptor. The good water-solubility of the molecule enabled recognition and assay of Cu(2+) ions in biological media. The photophysical properties of the chemosensor were investigated in detail, exhibiting favorable fluorescence quantum yield and moderate two-photon absorption cross-section. The studies on binding thermodynamics demonstrated the formation of 1 : 1 complex between the chemosensor and Cu(2+) and an association constant of ca. 1.04 × 10(5) M(-1). Due to the rational design of the molecular structure, the sensor was highly specific to Cu(2+), which ensured high selectivity in Cu(2+) determination. Upon Cu(2+) binding, the intramolecular charge-transfer extent within the chromophore was weakened resulting in a remarkable quenching of fluorescence, based on which quantitative determination of Cu(2+) was performed. Good linearity was obtained between the fluorescence quenching value and Cu(2+) concentration ranging from 0.04 to 2.0 μM in aqueous solution. Benefiting from the merits of two-photon excitation, the chemosensor was free of interference from background luminescence in serum. A homogeneous quantitative determination of Cu(2+) was achieved in the serum medium with a linear range of 0.04 to 2.0 μM. Considering the structural flexibility of the sensor, this work also opens up the possibility to construct other two-photon excited chemosensors for direct homogeneous assay of various molecules/ions in complicated biological sample matrices.

An amphiphilic ruthenium(II)–polypyridyl appended porphyrin as potential bifunctional two-photon tumor-imaging and photodynamic therapeutic agent

An amphiphilic porphyrin appended with a Ru(II)-polypyridyl complex (Ru-P) showing a moderate two-photon absorption cross-section (178.0+/-26.8GM), high singlet oxygen quantum yield and rapid cellular uptake was synthesized. In vitro study using human nasopharyngeal carcinoma cells showed that Ru-P exhibited a strong two-photon induced fluorescence upon uptake, lysosomal localization and potent two-photon induced cytotoxicity. These results show that Ru-P, which was designed to enhance its cellular uptake, can potentially be used as an efficacious bifunctional two-photon tumor-imaging and photodynamic therapeutic agent despite its moderate two-photon absorption cross-section.

Synthesis and Nonlinear Optical Characterization of a New Two‐photon Absorbing Organic Dye: DMAHAS

AbstractTrans‐4‐(N, N'‐dimethyl amino)‐4′‐(N‐hydroxyethyl‐N'‐ethyl amino) stilbene (DMAHAS) has been synthesized and characterized by 1H NMR spectra, ER spectra and elemental analysis. Linear absorption, single‐photon induced fluorescence and two‐photon induced fluorescence were experimentally studied. This new dye has a moderate two‐photon absorption cross‐section of σ 2 = 0.91 × 10–46 cm4 · s/photon at 532 nm by using an open aperture Z‐scan technique. The result indicates that DMAHAS shows a strong two‐photon induced blue fluorescence of 432 nm when pumped with 800 nm laser irradiation.

Synthesis and Nonlinear Optical Characterization of a New Organic Dye DMAHAS

The title compound DMAHAS has been synthesized and characterized by 1 H-NMR spectra, IR spectra, and elemental analyses. Linear absorption, single-photon induced fluorescence and two-photon induced fluorescence are experimentally studied. This new dye has a moderate two-photon absorption cross-section of σ 2 = 0.91 2 10 m 46 cm 4 - s/photon at 532 nm by using an open aperture Z -scan technique. When pumped with 800 nm laser irradiation, DMAHAS shows a strong two-photon induced blue fluorescence of 432 nm.

Synthesis and Properties of a New Two-photon-absorbed Material Heasps

A new dye Trans-4-[p-(N-hydroxyethyl-N-ethyiamino)styryl]-N-methylpyridinium p-toluene sulfonate (HEASPS) was synthesized, and the two-photon absorption (TPA), TPA-induced frequency up-conversion emission, and two-photon pumped (TPP) frequency up-converted lasing properties of this new dye were experimentally studied. This new dye has a moderate TPA cross-section of\\sigma2 = 4.7 × 10−48 cm4 .s/photon at 1064nm, but exhibits a high lasing efficiency. The net conversion efficiency from the absorbed 1064 nm pump pulse energy to the 626 nm up-converted lasing energy is 18.2% at the pump energy level of 1.9 mJ.

Studies on two-photon pumped frequency up-converted lasing properties of a new material HMASPS

A new dye trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium p-toluene sulphonate (abbreviated as HMASPS) was synthesized, the two-photon absorption (TPA), TPA-induced frequency up-conversion emission, and two-photon pumped (TPP) frequency up-converted lasing properties of HMASPS were experimentally studied. This new dye has a moderate TPA cross-section of σ2 = 6.0 × 10−48 cm4 s photon−1, but exhibits a high lasing efficiency. The net conversion efficiency from the absorbed 1064 nm pump pulse energy to the 630 nm up-converted lasing energy is 4% at a pump energy level of 4mJ.

Studies of two-photon pumped frequency-upconverted lasing properties of a new dye material

The two-photon absorption (TPA), TPA-induced frequency upconversion emission, and two-photon-pumped (TPP) lasing properties of a new dye, trans-4[p-(N-hydroxyethylN-methylamino)stryryl]-N-methylpyridinium iodide (abbreviated as ASPI) were experimentally investigated. This new dye has a moderate TPA cross section (σ2≈3.9×20−20 cm4/GW in benzyl alcohol), but exhibits a low lasing threshold and high lasing efficiency when pumped with a 1064 nm pulsed laser beam. Furthermore, the TPA-induced fluorescence yield is strongly dependent on the polarity of the solvent, making it a promising dye for sensing applications. The spectral, temporal, and spatial structures as well as the output/input characteristics of the TPP cavity lasing and the superradiant (cavityless) lasing are systematically measured using a 1 cm path quartz cuvette filled with the ASPI solution or a doped polymer rod. The net conversion efficiency from the absorbed 1064 nm pump pulse energy to the ∼615 nm upconverted cavity lasing energy was found to be as high as ∼17%.