Two-photon Absorption Chromophores Research Articles

Unity fluorescent carbene–gold(i)–acetylide complexes with two-photon absorption and energy-efficient blue FOLEDs

Two-photon absorption chromophores suitable for the construction of energy-efficient blue fluorescent OLEDs.

The design strategies and applications for organic multi-branched two-photon absorption chromophores with novel cores and branches: a recent review

This review provides a timely summary of recent advances in the construction of OMBCs with novel cores and branches. Their structure–property relationships and applications are also summarized.

Synthesis and structural study of organic two-photon-absorbing cycloalkanone chromophores.

The three organic two-photon-absorbing cycloalkanone chromophores 2,4-bis[4-(diethylamino)benzylidene]cyclobutanone, C26H32N2O (I), 2,5-bis[4-(diethylamino)benzylidene]cyclopentanone, C27H34N2O (II), and 2,6-bis[4-(diethylamino)benzylidene]cyclohexanone, C28H36N2O (III), were obtained by a reaction between 4-(diethylamino)benzaldehyde and the corresponding cycloalkanone and were characterized by single-crystal X-ray diffraction studies, as well as density functional theory (DFT) quantum-chemical calculations. Molecules of this series have three main fragments, i.e. central acceptor (A) and two terminal donors (D1 and D2) and represent examples of the D1-π-A-π-D2 molecular design. All three compounds crystallize with two crystallographically independent molecules in the asymmetric unit (A and B) and are distinguished by the conformations of both the molecular Et2N-C6H4-C=C-C(=O)-C=C-C6H4-NEt2 backbone (arcuate or linear) and the terminal diethylamino substituents (syn- or antiperiplanar to the plane of the molecule). The central four- and five-membered rings in I and II are almost planar, and the six-membered ring in III adopts a sofa conformation. In the crystals of I-III, the two independent molecules A and B form hydrogen-bonded [A...B] dimers via intermolecular C-H...O hydrogen bonds. Furthermore, the [A...B] dimers in I are bound by intermolecular C-H...O hydrogen bonds into two-tier puckered layers, whereas in the crystals of II and III, the [A...B] dimers are stacked along the c and a axes, respectively. Taking into account the decreasing steric strain upon expanding the central ring, compound I might be more efficient as a two-photon absorption chromophore than compounds II and III, which corresponds to the results of spectroscopic studies.

Synthesis, photophysical properties, and DNA-binding of novel A-π-D-π-A' two-photon absorption chromophores

Three novel two-photon absorption chromophores (1BI, 2TAZ, and 3PyB), which have trans-1,4-divinylbenzene π-bridge, methoxy donors, and different acceptors, were synthesized. Their structures were elucidated by means of hydrogen-1 nuclear magnetic resonance, carbon-13 nuclear magnetic resonance, Fourier transform infrared spectroscopy, and high-resolution mass spectrometry. Their photophysical properties, including linear absorption, single-photon excited fluorescence, two-photon absorption, and two-photon excited fluorescence, were systematically investigated in various solvents. The structure-property relationships were studied aided with the density functional theory calculations. In addition, the absorption, single- and two-photon fluorescence spectra of 3PyB-ctDNA were examined to evaluate whether 3PyB could be used as a DNA stain. The possible interaction mechanism of 3PyB-ctDNA was also studied by the NaCl titration and the viscosity experiment. The results indicate that 3PyB may serve as a potential DNA fluorescent probe.

Three new water-soluble fluorescent organic nanoparticles with embedded structure: Structure-activity relationship and two-photon bio-imaging application

Three benzothiazole-based two-photon absorption (2PA) chromophores (B1-3) were synthesized and the optical properties were investigated. The results illustrated the largest fluorescence quantum yield and effective 2PA cross-sections reached to 0.81 for compound B1 and 1013 GM for compound B3 in tetrahydrofuran solutions, respectively. Furthermore, the water-soluble fluorescent organic nanoparticles (FONs) possessing an embedded structure were prepared from the three compounds and Pluronic F127, which were successfully applied on two-photon nuclear envelope imaging.

Light-induced self-written waveguide fabrication using 1550 nm laser light.

Light-induced self-written (LISW) optical waveguides were fabricated for the first time, to the best of our knowledge, using a photopolymerizable resin system formed by 1550nm pulse laser light. A two-photon absorption (TPA) chromophore with a TPA cross section of several hundred Goeppert-Mayer (GM) at 1550nm was used. Furthermore, the optical interconnection between a single-mode fiber and a fiber Bragg grating was demonstrated by the present technique, using one-way irradiation of 1550nm laser light through the single-mode fiber. The LISW waveguide formation using 1550nm laser light offers a new and promising alternative route for optical interconnection in silicon photonics technology.

Recent progress on intramolecular charge-transfer compounds as photoelectric active materials

This article summarized the recent advance on the structural design and synthetic strategies of intramolecular charge-transfer compounds as well as their potential applications in two-photon absorption chromophores, organic photovoltaics and organic light-emitting diodes.

Fluorescent phenanthroimidazoles functionalized with heterocyclic spacers: synthesis, optical chemosensory ability and two-photon absorption (TPA) properties

Fluorescent phenanthroimidazoles bearing heterocyclic spacers as novel optical chemosensors and two-photon absorption chromophores.

Ruthenium(II)–terpyridine complexes-containing glyconanoparticles for one- and two-photon excited fluorescence imaging

The synthesis of ruthenium(II)–terpyridine complexes-containing glyconanoparticles (Ru–GNPs) for one- and two-photon excited fluorescence imaging was described. Ru–GNPs were built from diblock copolymers of pentafluorophenyl acrylate (PFA) and 2-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucosyloxy)ethyl methacryalte (AcGlcEMA), prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. The pendant reactive pentafluorophenyl ester groups were substituted and the copolymer cross-linked by the two-photon absorption (TPA) chromophore, bis[4′-(4-aminophenyl)-2,2′:6′,2″-terpyridyl]ruthenium(II) hexafluorophosphate. After deacetylation of the acetyl-protecting groups in the AcGlcEMA block, TPA nanoparticles with cross-linked ruthenium(II)–terpyridine complexes as the core and glycopolymers as the corona were obtained. The resulting Ru–GNPs exhibit good water dispersity, one-photon absorption and emission and low cytotoxicity towards KB cell line. Ru–GNPs also undergo two-photon excitation when excited in the near-infrared (NIR, 720–880nm) in water, with TPA cross-sections in the range of 0.2–22 Göppert–Mayer (GM, 1 GM=10−50cm4s1photon−1). Ru–GNPs are thus potentially useful as effective cellular labeling agents for one- and two-photon excited fluorescence imaging.

Molybdenum(vi) tris(dithiolene) complexes as a new class of three-dimensional two-photon absorption chromophores at telecommunications wavelengths

Two molybdenum(VI) tris(dithiolene) complexes with phenyl or naphthyl substituents were synthesized and their two-photon absorption properties were investigated by an open-aperture Z-scan technique using near-infrared femtosecond laser pulses. Both of these complexes exhibited significant two-photon cross sections around the wavelength of 1.3 μm, with the naphthyl substituted complex showing a two-photon cross section of 660 × 10−50 cm4 s−1 photon−1, suggesting a new class of three-dimensional chromophore for use at telecommunications wavelengths.

Divinyl sulfides/sulfones-based D–π–A–π–D dyes as efficient non-aromatic bridges for π-conjugated compounds

Novel photoactive divinyl sulfides and sulfones have been obtained by a straightforward approach using a Wittig–Horner reaction. These compounds behave as quadrupolar chromophores and show absorption in the UV region and fluorescence emission tailored by the solvent polarity due to an intramolecular charge transfer mechanism in the excited state, confirmed by the large Stokes' shift and the positive solvatochromism exhibited by their fluorescence spectra. In particular, a large Stokes' shift has been achieved for the sulfone containing the carbazole moiety, which behaves like a “push–pull” architecture. These new molecules represent an efficient alternative as stable non-heterocyclic π-conjugated compounds for potential applications as photoactive or two-photon absorption chromophores.

A p‐Quinodimethane‐Bridged Porphyrin Dimer

A p-quinodimethane (p-QDM)-bridged porphyrin dimer 1 has been prepared for the first time. An unexpected Michael addition reaction took place when we attempted to synthesize compound 1 by reaction of the cross-conjugated keto-linked porphyrin dimers 8a and 8b with alkynyl/aryl Grignard reagents. Alternatively, compound 1 could be successfully prepared by intramolecular Friedel-Crafts alkylation of the diol-linked porphyrin dimer 14 with concomitant oxidation in air. Compound 1 shows intense one-photon absorption (OPA, λ(max)=955 nm, ε=45400 M(-1) cm(-1)) and a large two-photon absorption (TPA) cross-section (σ((2))(max)=2080 GM at 1800 nm) in the near-infrared (NIR) region due to its extended π-conjugation and quinoidal character. It also exhibits a short singlet excited-state lifetime of 25 ps. The cyclic voltammogram of 1 displays multiple redox waves with a small electrochemical energy gap of 0.86 eV. The ground-state geometry, electronic structure, and optical properties of 1 have been further studied by density functional theory (DFT) calculations and compared with those of the keto-linked dimer 8b. This research has revealed that incorporation of a p-QDM unit into the porphyrin framework had a significant impact on its optical and electronic properties, leading to a novel NIR OPA and TPA chromophore.

High Efficiency Platinum Acetylide Nonlinear Absorption Chromophores Covalently Linked to Poly(methyl methacrylate)

We report three platinum acetylide acrylate monomers containing known two-photon absorption (TPA) chromophores and their covalent incorporation into polymers via free radical polymerization with methyl methacrylate. The photophysical properties of the platinum acetylide monomers and resulting poly(methyl methacrylate) (PMMA) copolymers were investigated to determine if the one- and two-photon photophysical properties of the chromophores were maintained in the copolymers. The photophysical properties of the series of copolymers were studied in solution and solid state with minimum shifts exhibited in the ground state absorption, photoluminescence, and triplet-triplet transient absorption spectra. The polymer films displayed markedly stronger phosphorescence and longer triplet excited state lifetimes than the polymers in solution or the monomers. The incorporation of the platinum acetylide chromophores into the PMMA copolymers allows the materials to be cast as thin films or into free-standing monoliths. Films with ~3.6 μm in thickness and monoliths with 1 mm path length were fabricated and examined. The nonlinear absorption responses of the polymers in solution were measured via the nanosecond z-scan method, and the solid state polymer monoliths were measured via nonlinear transmittance. Both measurements indicate that the polymers exhibited strong transmittance attenuation at input pulse energies exceeding 100 μJ.

Two-photon induced emissive thiophene donor–acceptor systems as molecular probes for in vitro bio-imaging: synthesis, crystal structure, and spectroscopic properties

Two new classes of organic two-photon absorption (TPA) chromophores, D–π–A (Bt11/Tt11) and D–π–A–π–D (Bt22/Tt22), were designed and synthesized using a Sonogashira coupling reaction between 4-ethynyl-N,N-dimethylaniline and 5′-bromo-2,2′-bithiophene/2,2′:5′,2′′-terthiophene or 5,5′-dibromo-2,2′-bithiophene/2,2′:5′,2′′-terthiophene, respectively. At room temperature, all of the compounds had single-photon fluorescent and solvatochromatic properties, and could produce two-photon-induced luminescence upon excitation at 700 nm (Ti:sapphire femtosecond laser, 150 fs pulses). The corresponding TPA cross-section values ranged from 81 to 563 GM (10−50 cm4 s photon−1 molecule−1). The quadrupolar-type (D–π–A–π–D) chromophores, Bt22 and Tt22, exhibited a larger TPA cross-section (σ2) value than their dipolar analogues (D–π–A), Bt11 and Tt11, whereas the bithiophene chromophores, Bt11 and Bt22, exhibited a larger σ2 value than their terthiophene counterparts, Tt11 and Tt22. All of the compounds were used for bio-imaging in living human cervical carcinomas (HeLa). We found that Bt11 and Tt11 were able to pass through the cell membrane and to selectively stain the cell cytoplasm and lysosome, respectively. The results of these studies could provide new molecular-design strategies for two-photon imaging in vitro.

Optical Properties of a Two-Photon Chromophore in a Polymeric Nanostructure

Optical properties of a cationic two-photon absorption (TPA) chromophore, 1,4-bis{4′-[N,N-bis(6″-trimethylammoniumhexyl)amino]styryl}benzene tetrabromide (C1) upon complexation with an anionic diblock copolymer, poly[(ethylene oxide)-block-(sodium 2-acrylamido-2-methyl-1-propane sulfonate)] (Em -An ) and a cationic surfactant, cetyltrimethylammonium bromide (CTAB) have been studied. Electrostatic interaction among C1, cationic CTAB and anionic (Em -An ) forms a vesicular polymeric nanostructure (containing C1 in a core), which is soluble in water. Incorporation of C1 into the nonpolar microenvironment inside the nanostructure successfully modulated its optical properties in aqueous medium. In water, fluorescence quantum yield (η) of C1 (0.32) was increased up to 0.55 accompanied with 30∼40 nm PL photoluminescence (PL) spectral shifts by forming the self-assembled nanostructure. This vesicular nanostructure may have a potential application as a two-photon molecular tag for biological imaging by two-photon microscopy.

The impact of charge defects and resonance enhancement on the two-photon absorption activity of spirofluorene and ladder-type pentaphenylene derivatives

Novel two-photon absorption (TPA) chromophores that contain spirofluorene and ladder-type pentaphenylenes (LPPs) as π-centres with diarylamine groups as electron donors (D) in the D–π–D arrangement are prepared. The spirofluorenes with different donors at the both terminals exhibit TPA activity increase as the donor strength increases (from N-ethylcarbazoyl 1, triphenylamino 2, to N,N-dibutylaminophenyl 3). Compared to the spirofluorene derivatives, the LPP derivatives show the larger TPA efficiency due to better coplanarity throughout the molecule. As the LPP unit added from single (4), double (5), to triple (6), the increment of the TPA cross-section exceeds the one-fold of a LPP unit, which can be attributed to the cooperative enhancement of the TPA cross-section (σ2) between the LPP units. We have also explored the effect of introducing charge defects and examined the resonance enhancement by chemical oxidation on the TPA properties of LPP derivatives 4 and 5. Nearly an order of magnitude enhancement was found in the TPA cross-section of dye 4, which was interpreted as the role of charge transfer from LPP π-centre to the cationic diarylamine end groups.

Benzothiazoles with Tunable Electron-Withdrawing Strength and Reverse Polarity: A Route to Triphenylamine-Based Chromophores with Enhanced Two-Photon Absorption

A series of dipolar and octupolar triphenylamine-derived dyes containing a benzothiazole positioned in the matched or mismatched fashion have been designed and synthesized via palladium-catalyzed Sonogashira cross-coupling reactions. Linear and nonlinear optical properties of the designed molecules were tuned by an additional electron-withdrawing group (EWG) and by changing the relative positions of the donor and acceptor substituents on the heterocyclic ring. This allowed us to examine the effect of positional isomerism and extend the structure-property relationships useful in the engineering of novel heteroaromatic-based systems with enhanced two-photon absorption (TPA). The TPA cross-sections (δ(TPA)) in the target compounds dramatically increased with the branching of the triphenylamine core and with the strength of the auxiliary acceptor. In addition, a change from the commonly used polarity in push-pull benzothiazoles to a reverse one has been revealed as a particularly useful strategy (regioisomeric control) for enhancing TPA cross-sections and shifting the absorption and emission maxima to longer wavelengths. The maximum TPA cross-sections of the star-shaped three-branched triphenylamines are ∼500-2300 GM in the near-infrared region (740-810 nm); thereby the molecular weight normalized δ(TPA)/MW values of the best performing dyes within the series (2.0-2.4 GM·g(-1)·mol) are comparable to those of the most efficient TPA chromophores reported to date. The large TPA cross-sections combined with high emission quantum yields and large Stokes shifts make these compounds excellent candidates for various TPA applications, including two-photon fluorescence microscopy.

Synthesis and photophysical properties of novel two-photon absorption chromophores and research on its solid-state device

Three novel distyrylbenzene derivatives have been synthesized and their optical properties have been investigated. All the compounds give large two-photon absorption (TPA) cross sections and their TPA cross sections are significantly enhanced with the temperature decreases. Especially, the compound of TMVDB is highly luminescent as the fluorescence quantum yield of 0.83. TPA cross section of TMVDB is 1164 GM and ratio of TPA cross section divided to molecular weight is as high as 2.08. All the results of TMVDB show its excellent TPA induced emission performance. The TMVDB is doped into the solid matrix and a solid-state film with strong TPA induced emission is obtained.

Octupolar Polycyclic Aromatic Hydrocarbons as New Two-Photon Absorption Chromophores: Synthesis and Application for Optical Power Limiting

Octupolar Polycyclic Aromatic Hydrocarbons as New Two-Photon Absorption Chromophores: Synthesis and Application for Optical Power Limiting

Fluorene as the π–spacer for new two-photon absorption chromophores

We report herein the design and synthesis of two new quadrupolar D–π–A–π–D chromophores containing diphenyl amine and dicyanobenzene or 2,1,3-benzothiadiazole as electron donor (D) and acceptor (A), respectively, which are bridged by fluorene linkage (π). The introduction of coplanar fluorenes is highly beneficial for the enhancement of two-photon absorption (TPA), where 1b displays a TPA cross section ( σ 2) of up to 1975±207 GM.