Anthracene Chromophore Research Articles

100 μs Luminescence Lifetime Boosts the Excited State Reactivity of a Ruthenium(II)-Anthracene Complex in Photon Upconversion and Photocatalytic Polymerizations with Red Light.

The triplet excited state lifetime of a photosensitizer is an essential parameter for diffusion-controlled energy- and electron-transfer, which occurs usually in a competitive manner to the intrinsic decay of a triplet excited state. Here we show the decisive role of luminescence lifetime in the triplet excited state reactivity toward energy- and electron transfer. Anchoring two phenyl anthracene chromophores to a ruthenium(II) polypyridyl complex (RuII ref) leads to a RuII triad with a luminescence lifetime above 100 μs, which is more than 40 times longer than that of the prototypical complex. The obtained RuII triad sensitizes energy transfer to anthracene-based annihilators more efficiently than RuII ref and enables red-to-blue photon upconversion with a pseudo anti-Stokes shift of 0.94 eV and a moderate upconversion efficiency near 1 % in aerated solution. Particularly, RuII triad allows rapid photoredox catalytic polymerizations of acrylate and acrylamide monomers under aerobic condition with red light, which are kinetically hindered for RuII ref. Our work shows that excited state lifetime of a photosensitizer governs the dynamics of the excited state reactions, which seems an overlooked but important aspect for photochemistry.

Functionalizing Thiosemicarbazones for Covalent Conjugation.

Thiosemicarbazones (TSCs) with their modular character (thiosemicarbazides + carbonyl compound) allow broad variation of up to four substituents on the main R1R2C=N(1)-NH-C(S)-N(4)R3R4 core and are thus interesting tools for the formation of conjugates or the functionalization of nanoparticles (NPs). In this work, di-2-pyridyl ketone was introduced for the coordination of metals and 9-anthraldehyde for luminescence as R1 and R2 to TSCs. R3 and R4 substituents were varied for the formation of conjugates. Amino acids were introduced at the N4 position to produce [R1R2TSC-spacer-amino acid] conjugates. Further, functions such as phosphonic acid (R-P(O)(OH)2), D-glucose, o-hydroquinone, OH, and thiol (SH) were introduced at the N4 position producing [R1R2TSC-spacer-anchor group] conjugates for direct NP anchoring. Phenyl, cyclohexyl, benzyl, ethyl and methyl were used as spacer units. Both phenyl phosphonic acid TSC derivatives were bound on TiO2 NPs as a first example of direct NP anchoring. [R1R2TSC-spacer-end group] conjugates including OH, S-Bn (Bn = benzyl), NH-Boc (Boc = tert-butyloxycarbonyl), COOtBu, C≡CH, or N3 end groups were synthesized for potential covalent binding to functional molecules or functionalized NPs through amide, ester, or triazole functions. The synthesis of the thiosemicarbazides H2NNH-C(S)-NR3R4 starting from amines, including amino acids, SCCl2 or CS2, and hydrazine and their condensation with dipyridyl ketone and anthraldehyde led to 34 new TSC derivatives. They were synthesized in up to six steps with overall yields ranging from 10 to 85% and were characterized by a combination of nuclear magnetic resonance spectroscopy and mass spectrometry. UV-vis absorption and photoluminescence spectroscopy allowed us to easily trace the dipyridyl imine and anthracene chromophores.

Water-dispersable photoreactors based on core–shell mesoporous silica particles

Robust solid-core silica particles with submicrometer size and anthracene-containing mesoporous shell were obtained and studied as model water-dispersable photoreactors. An anthracene derivative containing a triethoxysilyl group was synthesized and co-condensed with tetraethoxysilane in various ratios to form a photoactive mesoporous shell with a thickness up to approximately 80 nm on previously prepared solid silica particles. Mesopores of as-synthesized particles, without a commonly applied removal of the micellar templates, offered a confined space for solubilization of hydrophobic molecules. Efficient excitation energy transfer from anthracene chromophores to both hydrophobic (perylene) and hydrophilic (fluoresceine) encapsulated acceptors was observed in an aqueous dispersion of the particles. Photosensitized oxidation of encapsulated perylene was shown to proceed efficiently in such systems serving as water-dispersable photoreactors. Importantly, the designed core–shell systems were found to be stable for a long time (at least 24 months) and robust enough, thanks to the presence of solid cores, to be handled by centrifugation in aqueous dispersions. All these features make them promising candidates for reusable systems for the photosensitized degradation of water pollutants, especially hydrophobic pollutants.

Tuning Symmetry‐Breaking Charge Transfer by Altering Connectivity Between Anthracene Chromophores

AbstractIn this study, we report on the dynamics of symmetry‐breaking charge transfer (SB‐CT) in a specific derivative of bianthracene, 9,9’,10,10’‐tetraphenyl‐2,2’‐bianthracene (TPBA). Unlike the conventional 9,9’‐bianthracene, TPBA exhibits a notably planar structure due to reduced steric hindrance between anthracene chromophores. This structural characteristic results in a pronounced short‐range charge transfer coupling, driven by substantial overlap integrals of hole and electron. This is in contrast to the 9,9’‐bianthracene case, where long‐range Coulombic coupling dominates while minimizing short‐range interactions. Consequently, TPBA reveals an adiabatic mixture between locally‐excited and charge‐transfer diabats, where the extent of their contributions is modulated by the dielectric properties of the surrounding environment. Furthermore, our investigation reveals that the SB‐CT reaction in TPBA is mainly influenced by solvation dynamics, akin to other molecules displaying SB‐CT. Additionally, the dynamics of triplet formation in TPBA vary depending on the solvent polarity. These findings underscore the significance of chromophore connectivity in efficiently manipulating excited‐state potential energy landscapes.

Enhancement in Two-Photon Absorption and Photoluminescence in Single Crystals of Cd(II) Metal Organic Frameworks.

The emergence of metal organic frameworks (MOFs) as advanced photonic materials has placed them at the forefront of exploration. Nonlinear optical (NLO) phenomena such as simultaneous two-photon absorption and consequent upconversion emission have been in demand for promising applications. A rational design approach based on the fundamental structure-property relationship is key for the fabrication of nonlinear optically active MOF materials. Here, we investigate two-photon-absorption (2PA)-induced photoluminescence of four new Cd(II) MOFs based on an acceptor-π-donor-π-acceptor trans, trans-9, 10-bis(4-pyridylethenyl)anthracene chromophore linker. The use of auxiliary carboxylate linkers resulted in the variation of crystal structures, leading to the modulation of NLO properties. On comparison with a standard Zn(II)-MOF, two MOFs showed enhancement in 2PA, while the other two showed a mild decrease. We tried to establish a structural correlation to explain the trend in NLO activity. The interplay of various factors such as chromophore density, degree of interpenetration, chromophore orientation, and π···π interactions between the individual networks affects the NLO activities. These results show the modulation of the optical properties of MOFs based on a combined strategy for the development of tunable single crystal NLO devices.

Effect of Cyano and Tetrazole Side Groups on the Photophysical and Chelating Properties of Anthracene‐Based Polymers

AbstractThis paper covers the conception of new soluble and filmogene conjugated polymers (PAnSCN and PAnSCN‐Tet) for heavy metal sensing application. The prepared materials are based on the highly emissive anthracene chromophore and contain tetrazole and/or cyanide groups in their molecular chain backbones. The effect of the electron withdrawing groups on photophysical properties and the chelating abilities of the elaborated organic materials were investigated. The optical analysis shows that the CN groups reduced slightly the optical band‐gap of the polymer, however the steric hindrance of tetrazole units dominates their electronic effects leading to a blue‐shift of its absorption spectrum. Also, the electrochemical study reveals a considerable electronic affinity increase by 0.84 eV when passing from PAnSCN into PAnSCN‐Tet. DFT calculations has been employed to estimate the optimized macromolecular structure of both polymers and a notable change in geometry in terms of planarity was observed depending on the incorporated withdrawing group. The synthesized polymers were studied as optical sensors. The changes in the photoluminescence intensity were used to evaluate the binding affinity of the two materials to different metal ions. The obtained results showed considerable decrease in photoluminescence (quenching) responses with Mn2+ cations a short time after adding the cations to both polymer solutions with better sensitivity and selectivity in the case of the PAnSCN‐Tet.

Synthesis of Highly Emissive Fluorophores Based on Multiply Stacked Anthracene Arrangement

AbstractNewly designed fluorophore systems with feather‐like structures were constructed by connecting bisanthracene building units via a concise reaction sequence of bromination, etherification, and desilylation. Spectroscopic characterizations revealed that all of the fluorophore systems achieved high light absorptivity and high emission efficiency by preventing closely spaced anthracene chromophores from mutual interactions to reduce concomitant energy loss by fluorescence quenching. The application of fluorophore systems for the preparation of light‐harvesting dyad materials has successfully demonstrated their potential utility as versatile photofunctional tools.

Multistep sequence-controlled supramolecular polymerization by the combination of multiple self-assembly motifs

The precise sequence control of polymer chain is an important research topic of polymer chemistry. Although some methods such as iterative synthesis and supramolecular polymerization have been developed to fabricate sequence-controllable polymer, it is still a great challenge to consecutively prepare multiple supramolecular polymers with different sequence structures. In this work, through the reasonable utilization of assembly motifs, we integrated multiple host-guest recognitions and metal coordination interactions to prepare different sequence-controlled supramolecular polymers by a multistep assembly strategy. This research provides inspiration for the design and preparation of supramolecular polymers with different sequence structures.

Alkyl-Chain Bridged Acrylonitrile-Appended Anthracene Chromophore toward Mechanically-Induced Bathochromic Shift

Abstract Designing π-conjugated molecules for mechanochromism has attracted much attention. Here, we found an approach toward mechanofluorochromic dyes, which are composed of dimeric 9-(4-methoxyphenyl)acrylonitrile-appended anthracene units bridged by an alkyl chain. The molecule in an amorphous state showed a dramatic bathochromic shift (ΔλPL = 75 nm) after grinding while a crystalline state of the monomer motif showed a small hypsochromic shift (ΔλPL = 2–20 nm).

Optimized triple core blue emitters based on anthracene–pyrene–anthracene chromophores for organic light-emitting diodes

Three new fluorescent triple-core emitters were newly synthesized by attaching an optimized electron-donating group to an anthracene–pyrene–anthracene core moiety, resulting in 1,6-di(anthracen-9-yl)pyrene (DAP), 10,10′-(pyrene-1,6-diyl)bis(N,N-diphenylanthracen-9-amine) (DPA–DAP–DPA), and 4,4′-(pyrene-1,6-diylbis(anthracene-10,9-diyl))bis(N,N-diphenylaniline) (TPA–DAP–TPA). The photophysical, thermal, and electroluminescence properties of these synthesized materials were examined experimentally and theoretically. The triple-core derivatives were found to exhibit high thermal stability, with decomposition temperatures greater than 433 °C. DAP, DPA–DAP–DPA, and TPA–DAP–TPA showed deep-blue, sky-blue, and real blue photoluminescence emission, with maximum wavelengths of 430, 497, and 459 nm, respectively, in the solution state. Among the synthesized materials, TPA–DAP–TPA showed an excellent photoluminescence quantum yield of 77%. The device doped with TPA–DAP–TPA showed a high efficiency of 5.68 cd/A, CIE coordinates of (0.143, 0.151), and an external quantum efficiency of 4.64% at 10 mA/cm2, indicating that the device has potential applications in mobile phones.

Impact of the Anthryl Linking Mode on the Photophysics and Excited-State Dynamics of Re(I) Complexes [ReCl(CO)3(4'-An-terpy-κ2N)

Rhenium(I) complexes with 2,2′:6′,2″-terpyridines (terpy) substituted with 9-anthryl (1) and 2-anthryl (2) were synthesized, and the impact of the anthryl linking mode on the ground- and excited-state properties of resulting complexes [ReCl(CO)3(4′-An-terpy-κ2N)] (An—anthryl) was investigated using a combination of steady-state and time-resolved optical techniques accompanied by theoretical calculations. Different attachment positions of anthracene modify the overlap between the molecular orbitals and thus the electronic coupling of the anthracene and {ReCl(CO)3(terpy-κ2N)} chromophores. Following the femtosecond transient absorption, the lowest triplet excited state of both complexes was found to be localized on the anthracene chromophore. The striking difference between 1 and 2 concerns the triplet-state formation dynamics. A more planar geometry of 2-anthryl-terpy (2), and thus better electronic communication between the anthracene and {ReCl(CO)3(terpy-κ2N)} chromophores, facilitates the formation of the 3An triplet state. In steady-state photoluminescence spectra, the population ratio of 3MLCT and 3An was found to be dependent not only on the anthryl linking mode but also on solvent polarity and excitation wavelengths. In dimethyl sulfoxide (DMSO), compounds 1 and 2 excited with λexc > 410 nm show both 3MLCT and 3An emissions, which are rarely observed. Additionally, the abilities of the designed complexes for 1O2 generation and light emission under the external voltage were preliminary examined.

Investigation of pyrene vs Anthracene-based oxime esters: Role of the excited states on their polymerization initiating abilities

In this work, two series of oxime esters (OXE) based on Pyrene and Anthracene chromophores were synthesized and tested as Type Ⅰ photoinitiators for the Free Radical Photopolymerization (FRP) under visible irradiation at 405 nm using light-emitting diodes (LED) as the irradiation source. Interestingly, the two series of oxime esters only differ by the nature of the substituents connected to the oxime ester functional group. As a result of this modification, the reactivity of the different compounds only depends on the rate of decomposition from their excited states as well as the reactivity of the generated radicals. Remarkably, the 18 Pyrene-based OXEs (Py-OXE) and 17 Anthracene-based OXEs (An-OXE) were never synthesized prior to this work. Pyrene and Anthracene chromophores were selected as benchmark structures reacting mainly from their first excited singlet (S1) and triplet (T1) states, respectively. This will allow to shed some light on the excited states responsible of the cleavage of OXEs. Therefore, originality of this study relies in the difference of the initiation ability between these two families. In fact, the results showed that Py-OXEs (0.5 % w) are the most efficient systems compared to An-OXEs, so that higher final conversions and rates of polymerization could be obtained with Py-OXEs. Influence of the OXE structure (both chromophores and leaving groups) is discussed on the basis of different characterization techniques such as: UV–visible absorption spectroscopy, photolysis experiments, real-time Fourier transform infrared spectroscopy (RT-FTIR), stationary fluorescence and time-resolved fluorescence. Therefore, a global mechanism is finally provided based on the complementary characterization data. Oxime ester derivatives were also tested under air for the generation of 3D patterns (by Direct Laser Write DLW) using a diode laser at 405 nm.

PH-Sensitive Fluorescence Switching of Pyridylanthracenes: The Effect of the Isomeric Pattern.

9,10-substituted anthracenes are known for their useful optical properties like fluorescence, which makes them frequently used probes in sensing applications. In this article, we investigate the fundamental photophysical properties of three pyridyl-substituted variants. The nitrogen atoms in the pyridinium six-membered rings are located in the ortho-, meta-, and para-positions in relation to the anthracene core. Absorption, fluorescence, and transient absorption measurements were carried out and were complemented by theoretical calculations. We monitored the photophysics of the anthracene derivatives in chloroform and water investigating the protonated as well as their nonprotonated forms. We found that the optical properties of the nonprotonated forms are strongly determined by the anthracene chromophore, with only small differences to other 9,10-substituted anthracenes, for example diphenyl anthracene. In contrast, protonation leads to a strong decrease in fluorescence intensity and lifetime. Transient absorption measurements and theoretical calculations revealed the formation of a charge-transfer state in the protonated chromophores, where electron density is shifted from the anthracene moiety toward the protonated pyridyl substituents. While the para- and ortho-derivatives' charge transfer is still moderately fluorescent, the meta-derivative is affected much stronger and shows nearly no fluorescence. This nitrogen-atom-position-dependent sensitivity to hydronium activity makes a combination of these fluorophores very attractive for pH-sensing applications covering a broadened pH range.

The enduring legacy of Koji Nakanishi's research on natural products and bioorganic chemistry. Part 2. Inception and establishment of the ECD exciton chirality method in 1960s to 1970s: A marvel of Nakanishi's Japanese team.

The electronic circular dichroism (ECD) exciton chirality method is very useful for determining the absolute configuration (AC) of chiral compounds. In the ECD spectroscopy, the chromophore-chromophore interaction, ie, exciton coupling, is very important. For example, Harada and Nakanishi first discovered in 1969 that chiral dibenzoates exhibit exciton split bisignate Cotton effects, from the sign of which the screw sense between two long axes of benzoate chromophores, ie, the AC of dibenzoate, can be determined. This method was named the dibenzoate chirality rule and has been successfully applied to various natural products to determine their ACs. During these studies, it was also found that this CD method was expanded to encompass other aromatic and olefin chromophores like naphthalene, diene, enone, etc. Therefore, the name of the dibenzaote chirality rule was changed to the CD exciton chirality method. In 1970s, there were heated controversies about the inconsistency between X-ray Bijvoet and CD exciton chirality methods, which was a shocking and serious problem in the community of molecular chirality research. Harada and coworkers synthesized the most ideal cage compound with two anthracene chromophores to connect X-ray Bijvoet and CD exciton chitality methods and proved that these two methods are consistent with each other.

Influence of Polymer Charge on the Localization and Dark- and Photo-Induced Toxicity of a Potential Type I Photosensitizer in Cancer Cell Models.

A current trend within photo-dynamic therapy (PDT) is the development of molecular systems targeting hypoxic tumors. Thus, type I PDT sensitizers could here overcome traditional type II molecular systems that rely on the photo-initiated production of toxic singlet oxygen. Here, we investigate the cell localization properties and toxicity of two polymeric anthracene-based fluorescent probes (neutral Ant-PHEA and cationic Ant-PIm). The cell death and DNA damage of Chinese hamster ovary cancer cells (CHO-K1) were characterized as combining PDT, cell survival studies (MTT-assay), and comet assay. Confocal microscopy was utilized on samples incubated together with either DRAQ5, Lyso Tracker Red, or Mito Tracker Deep Red in order to map the localization of the sensitizer into the nucleus and other cell compartments. While Ant-PHEA did not cause significant damage to the cell, Ant-PIm showed increased cell death upon illumination, at the cost of a significant dark toxicity. Both anthracene chromophores localized in cell compartments of the cytosol. Ant-PIm showed a markedly improved selectivity toward lysosomes and mitochondria, two important biological compartments for the cell’s survival. None of the two anthracene chromophores showed singlet oxygen formation upon excitation in solvents such as deuterium oxide or methanol. Conclusively, the significant photo-induced cell death that could be observed with Ant-PIm suggests a possible type I PDT mechanism rather than the usual type II mechanism.

9,10-Di(hydroxymethylphenyl)anthracenes: Highly efficient triplet annihilators with small singlet-triplet energy gap (ΔEST) and planar configuration

A series of 9,10-di(hydroxymethylphenyl)anthracene chromophores (named as E-o-DHMPA, Z-o-DHMPA, m-DHMPA and p-DHMPA) are designed to tailor triplet-triplet annihilation upconversion through isomer engineering. It was found that improving molecular planarity makes for molecular π-π interaction, meanwhile, molecular excited singlet energy level (ES1) shows decreasing; however, the triple energy level (ET1) exhibits almost equal. Thus, small singlet-triplet energy gap (ΔEST) of chromophores could be designed.Selective excitation of sensitizer (palladiumIItetrabromophenylporphyrin, PdBrTPP) in solution containing annihilator results in the upconversion (UC) efficiency (ΦUC) increasing from E-o-DHMPA (15.9%), Z-o-DHMPA (18.7%), m-DHMPA (26.0%) to p-DHMPA (26.8%), accompanied by the excitation threshold intensity (Ith, mW⋅cm−2) decreasing from E-o-DHMPA (292.74), Z-o-DHMPA (174.41), m-DHMPA (36.58) to p-DHMPA (29.78), which are in agreement with the ΔEST decreasing and planarity improving of these isomers.Annihilator with small energy gap (ΔEST) and planar configurtion has contribution to triplet-triplet annihilation (TTA), supported by the fact of the Ith value reducing, and thereby increasing UC efficiency (ΦUC), which provides a new strategy for molecule design to develop new triplet annihilator. Finally, the TTA-UC powered photolysis of bilirubin was conducted for the first time, suggesting that TTA-UC can act as an effective light source used in the light therapy for neonatal hyperbilirubinemia.

Two anthracene chromophore based metal–organic frameworks for gas adsorption and promising nitro aromatic sensing

Two novel metal–organic frameworks (MOFs) have been synthesized under solvothermal conditions. Studies on luminescence sensing show 1 and 2 are highly selective and recyclable in the detection of nitroaromatic explosives, especially for TNP.

Synthesis and Luminescence Properties of Diamine Monomers and Polyamides with Highly Twisted N,N‐Bis(dialkylamino)arene AIE Luminogens

AbstractA synthesis of aggregation‐induced emission (AIE)‐active polyamides through the polycondensation of diamine monomers 1,4‐bis(N,N‐dialkylamino)‐2,3‐dimethylnaphthalene or 9,10‐bis(N,N‐dialkylamino)anthracene chromophores with α,ω‐bis(chlorocarbonyl)alkane is reported. The obtained anthracene polyamide was soluble in common organic solvents, such as dichloromethane and methanol, and demonstrated good film‐forming properties. The quantum yields in the solid state of the naphthalene and anthracene polyamides were both 0.26, and the quantum yields in solution of the naphthalene and anthracene polyamides were 0.23 and 0.04, respectively. The results of this study will provide valuable information regarding the application of AIE‐active polymers in organic light‐emitting diodes (OLED) and in polymer research.

Photochemical CO2 reduction with mononuclear and dinuclear rhenium catalysts bearing a pendant anthracene chromophore.

A series of anthracene-substituted mononuclear and dinuclear rhenium complexes have been studied for photocatalytic CO2 reduction. The effects on catalytic activity of one versus two covalently-linked active sites, their relative proximity to one another, and the pendant organic chromophore are discussed.

Dual Fluorophore Containing Efficient Photoinduced Electron Transfer Based Molecular Probe for Selective Detection of Cr3+ and PO43- Ions through Fluorescence " Turn-On-Off" Response in Partial Aqueous and Biological Medium: Live Cell Imaging and Logic Application.

The present work describes a new photoinduced electron transfer (PET) based molecular probe in which naphthalimide (NPI) and anthracene (AN) chromophores are linked through a molecular bridge of piperazine and triazole units by the Click reaction. A typical meaningful structural variation has made the present probe highly selective for Cr3+ ion (limit of detection (LOD), 5.567 × 10-8 M) that displayed enhanced, " turn-On" emission (due to the PET- Off photophysical mechanism) and naked-eye sensitive bright green color fluorescence in the environment of interfering and competitive ions, in Tris-HCl buffer. The minimum energy structure obtained through theoretical calculations (density functional theory (DFT) and time-dependent (TD)-DFT) revealed a "tub" shape structure for probe 10. Upon complexation, the conformation of piperazine fragment changes from chair to boat in which the triazole and piperazine units create a cavity to tether Cr3+. Moreover, the probe showed excellent biocompatibility and cell permeability to sense Cr3+ sensitively in live cells and, thus, holds great promise for application in biological and environmental sciences. Additionally, the sensitive " Off-On-Off" sensing behavior of probe 10 providing two chemical inputs (Cr3+ and PO43-) helps to construct an INHIBIT logic gate. Also the probe has been utilized as printing material to decode secret information through the Cr3+ ion containing "marker ink" under UV light.