Conjugation Of Chromophore Research Articles

Stepwise Stiffening Chromophore Strategy Realizes a Series of Ultralong Blue Room-Temperature Phosphorescent Materials.

Ultralong room-temperature phosphorescent (URTP) materials have attracted wide attention in anti-counterfeiting, optoelectronic display, and bio-imaging due to their special optical properties. However, room-temperature blue phosphorescent materials are very scarce during applications because of the need to simultaneously populate and stabilize high-energy excited states. In this work, a stepwise stiffening chromophore strategy is proposed to suppress non-radiative jump by continuously reducing the internal spin of the chromophore, and successfully developing a series of blue phosphorescent materials. Phosphorescence lifetimes of more than 3 s are achieved, with the longest lifetime reaching 5.44 s and lasting more than 70 s in the naked eye. As far as is know, this is the best result that has been reported. By adjusting the chromophore conjugation, multicolor phosphorescences from cyan to green have been realized. In addition, these chromophores exhibit the same excellent optical properties in urea and polyvinyl alcohmance (PVA). Finally, these materials are successfully applied to luminescent displays.

Intramolecular charge transfer and the function of vibronic excitons in photosynthetic light harvesting.

A widely discussed explanation for the prevalence of pairs or clusters of closely spaced electronic chromophores in photosynthetic light-harvesting proteins is the presence of ultrafast and highly directional excitation energy transfer pathways mediated by vibronic excitons, the delocalized optical excitations derived from mixing of the electronic and vibrational states of the chromophores. We discuss herein the hypothesis that internal conversion processes between exciton states on the <100fs timescale are possible when the excitonic potential energy surfaces are controlled by the vibrational modes that induce charge transfer character in a strongly coupled system of chromophores. We discuss two examples, the peridinin-chlorophyll protein from marine dinoflagellates and the intact phycobilisome from cyanobacteria, in which the intramolecular charge-transfer (ICT) character arising from out-of-plane distortion of the conjugation of carotenoid or bilin chromophores also results in localization of the initially delocalized optical excitation on the vibrational timescale. Tuning of the ground state conformations of the chromophores to manipulate their ICT character provides a natural photoregulatory mechanism, which would control the overall quantum yield of excitation energy transfer by turning on and off the delocalized character of the optical excitations.

Effects of nonaromatic through‐bond conjugation and through‐space conjugation on the photoluminescence of nontraditional luminogens

AbstractPhotoluminescence (PL) mechanisms of nontraditional luminogens (NTLs) have attracted great interest, and they are generally explained with intra/intermolecular through‐space conjugation (TSC) of nonconventional chromophores. Here a new concept of nonaromatic through‐bond conjugation (TBC) is proposed and it is proved that it plays an important role in the PL of NTLs. The PL behaviors of the three respective isomers of cyclohexanedione and gemdimethyl‐1,3‐cyclohexanedione were studied and correlated with their chemical and aggregate structures. These compounds show different fluorescence emissions as well as different concentration, excitation and solvent‐dependent emissions. The compounds which undergo keto‐enol tautomerism and hence with a conjugated ketone‐enol structure (i.e., nonaromatic TBC) show more red‐shifted emissions. TBC effect reduces the energy gaps and facilitates the formation of stronger TSC in the aggregate state. The compounds in the ketone‐enol form are also prone to occur excited state intra/intermolecular proton transfer (ESIPT). The cooperative effect of nonaromatic TBC and TSC determines the PL behaviors of NTLs. This work provides a novel understanding of the PL mechanisms of NTLs and is of great importance for directing the design and synthesis of novel NTLs.

Large-Scale Preparation for Multicolor Stimulus-Responsive Room-Temperature Phosphorescence Paper via Cellulose Heterogeneous Reaction.

The large-scale preparation of sustainable room-temperature phosphorescence (RTP) materials, particularly those with stimulus-response properties, is attractive but remains challenging. This study develops a facile heterogeneous B─O covalent bonding strategy to anchor arylboronic acid chromophores to cellulose chains using pure water as a solvent, resulting in multicolor RTP cellulose. The rigid environment provided by the B─O covalent bonds and hydrogen bonds promotes the triplet population and suppresses quenching, leading to an excellent lifetime of 1.42 s for the target RTP cellulose. By increasing the degree of chromophore conjugation, the afterglow colors can be tuned from blue to green and then to red. Motivated by this finding, a papermaking production line is built to convert paper pulp reacted with an arylboronic acid additive into multicolor RTP paper on a large scale. Furthermore, the RTP paper is sensitive to water because of the destruction of hydrogen bonds, and the stimuli-response can be repeated in response to water/heat stimuli. The RTP paper can be folded into 3D afterglow origami handicrafts and anti-counterfeiting packing boxes or used for stimulus-responsive information encryption. This success paves the way for the development of large-scale, eco-friendly, and practical stimuli-responsive RTP materials.

Osmium Complex-Chromophore Conjugates with Both Singlet-to-Triplet Absorption and Long Triplet Lifetime through Tuning of the Heavy-Atom Effect.

Os(II) complexes showing singlet-to-triplet absorption are of growing interest as a new class of triplet sensitizers that circumvent energy loss during intersystem crossing, and they enable effective utilization of input photon energy in various applications, such as photoredox catalysis, photodynamic therapy, and photon upconversion. However, triplet excited-state lifetimes of Os(II) complexes are often too short (τ < 1 μs) to transfer their energy to neighboring molecules. While the covalent conjugation of chromophores has been known to extend the net excited-state lifetimes through an intramolecular triplet energy transfer (IMET), heavy-atom effects of the central metals on the attached chromophore units have rarely been discussed. Here, we investigate the relationship between the spin-density contribution of the heavy metals and the net triplet excited-state lifetimes for a series of Os(II) and Ru(II) bis(terpyridine) complexes modified with perylene units. Phosphorescence lifetimes of these compounds strongly depend on the lifetimes of the perylenyl group-localized excited states that are shortened by the heavy-atom effect. The degree of heavy-atom effect can be largely circumvented by introducing meta-phenylene bridges, where the perylene unit retains its intrinsic long excited-state lifetime. The thermal activation to the short-lived excited states is suppressed, thanks to sufficient but still small energy losses during the IMET process. Involvement of the metal center was also confirmed by the prolonged lifetime by replacing Os(II) with Ru(II) that possesses a smaller spin-orbit coupling constant. These results indicate the importance of ligand structures that give a minimum heavy-atom effect as well as the sufficient energy gap among the excited states and fast IMET for elongating the triplet excited-state lifetime without sacrificing the excitation energy.

Di[12]aneN3-Functionalized Green Fluorescent Protein Chromophore for GFP Luminescence Simulation and Efficient Gene Transfection In Vitro and In Vivo.

Although a plethora of gene carriers have been developed for potential gene therapy, imageable stimuli-responsive gene vectors with fast access to the nucleus, high biocompatibility, and transfection efficiency are still scarce. Herein, we report the design and synthesis of four dendrite-shaped cationic liposomes, MPA-HBI-R/DOPE (R: n-butyl, 1; n-octyl, 2; n-dodecyl, 3; palmyl, 4), prepared via esterification of 4-alkoxybenzylideneimidazolinone containing aliphatic chains of different lengths (HBI-R), the green fluorescent protein (GFP) chromophore, with a di[12]aneN3 unit. Liposomes were fabricated via the self-assembly of MPA-HBI-R, assisted with 1,2-dioleoyl-sn-glycerol-3-phosphorylethanolamine (DOPE). These liposomes (MPA-HBI-R/DOPE) exhibited efficient DNA condensation, pH-responsive degradation, excellent cellular biocompatibility (up to 150 μM), and high transfection efficiency. Molecular docking experiments were also used to verify the optimal interaction between MPA-HBI-R and DNA, as well as the fluorescence enhancements. In particular, MPA-HBI-2/DOPE delivered DNA into the nucleus in less than an hour, and its luciferase transfection activity was more than 10 times that by Lipo2000, across multiple cell lines. The GFP chromophore conjugation allowed trackable intracellular delivery and release of DNA in real time via fluorescence imaging. Furthermore, efficient red fluorescent protein (RFP) transfection in zebrafish, with an efficiency of more than 6 times that by Lipo2000, was also achieved. The results not only realized, for the first time, the combination of gene delivery and GFP-simulated light emission, allowing fluorescent tracking and highly efficient gene transfection, but also offered valuable insights into the use of biomimetic chromophore for the development of the next-generation nonviral vectors.

Engineering couplings for exciton transport using synthetic DNA scaffolds

Summary Control over excitons enables electronic energy to be harnessed and transported for light harvesting and molecular electronics. Such control requires nanoscale precision over the molecular components. Natural light-harvesting systems achieve this precision through sophisticated protein machinery, which is challenging to replicate synthetically. Here, we introduce a DNA-based platform that spatially organizes cyanine chromophores to construct tunable excitonic systems. We synthesized DNA-chromophore nanostructures and characterized them with ensemble ultrafast and single-molecule spectroscopy and structure-based modeling. This synthetic approach facilitated independent control over the coupling among the chromophores and between the chromophores and the environment. We demonstrated that the coupling between the chromophores and the environment could enhance exciton transport efficiency, highlighting the key role of the environment in driving exciton dynamics. Control over excitons, as reported here, offers a path toward the development of designer nanophotonic devices.

Clustering-Triggered Emission and Luminescence Regulation by Molecular Arrangement of Nonaromatic Polyamide-6.

Photoluminescent polymers with merely nonaromatic chromophores have attracted rapidly growing attention owing to their importance in the significant fundamental, encryption, and anticounterfeiting fields. Based on the clustering-triggered emission mechanism, through-space conjugation and conformational rigidification of nonaromatic chromophores are crucial to photoluminescence, which are also dependent on molecular arrangement. Herein, polyamide-6 (PA-6) with well-defined molecular arrangements was thus studied. The luminescence from the PA-6 solution is enhanced upon aggregation from solution to amorphous solid and further boosted with the formation of highly regular molecular arrangement. More importantly, both blue and green fluorescence from PA-6/formic acid (FA) solutions were observed because of the variable clusters formed among PA-6 and FA. To make clear of this, PA-6 cast film (PCF) and PA-6 electrospun film (PEF) were prepared and belonged to α- (antiparallel molecular arrangement) and γ (parallel molecular arrangement)-form crystals, as confirmed by Fourier transform infrared, X-ray diffraction, and Raman measurements. The relationship between molecular arrangement and luminescence of PA-6 molecules was clarified by their photophysical properties in solids and solutions. Notably, color-tunable cryogenic phosphorescence of PA-6 solids was also detected. Such aggregation-enhanced emission and tunable phosphorescence of PA-6 solids are ascribed to the formation of diversified amide clusters together with remarkably rigidified molecular conformations owing to the highly regular molecular arrangement in the aggregated states.

Achieving red room temperature afterglow carbon dots in composite matrices through chromophore conjugation degree controlling

Carbon dots (CDs), as new purely organic afterglow materials, show great potential applications in many fields, but efficient red room temperature afterglow (RTA) CDs are very scarce due to lack of effective synthetic method and blur RTA mechanism. Herein, an easy, high-output synthesis strategy for in-situ preparation of red RTA CD-based composites is developed through one-step microwave radiating large conjugated structure precursor. The systematic research shows that N, O-doped large conjugated structures on CD surfaces are responsible for the red RTA emission in view of their effectively reducing the band gap between the excited and ground state as well as creating afterglow center. Meanwhile the in-situ synthetic method makes CDs to be tightly embedded into the matrices by robust chemical covalent and multiple hydrogen bonding interactions, thus, greatly suppressing non-radiative transitions. Based on the above theoretical guidance, multi-color (green, yellow-green and red) RTA CDs-based materials were successfully prepared by controlled the conjugation degree of chromophore. In addition, the CD-based composites have potential applications in light-emitting diode and anti-counterfeiting. This work could provide an effective strategy to prepare red RTP materials.

Control of Energy Transfer Between Pyrene- and Perylene-Nucleosides by the Sequence of DNA-Templated Supramolecular Assemblies.

DNA was used as supramolecular scaffold to order chromophores and control their optical properties. Ethynylpyrene as energy donor was attached to 2′‐desoxy‐2‐aminoadenosine that binds selectively to thymidines (T) in the template. Ethynylperylene as acceptor was attached to 2′‐desoxyuridine that is complementary to 2′‐desoxyadenosine (A). This donor‐acceptor pair was assembled along single‐stranded DNA templates of different A−T sequences to investigate the sequence control of the energy transfer between the chromophores. The fluorescence intensities increase in the mixed assemblies along the DNA templates from A10T10 over (AATT)5 to (AT)10, although these templates provide equal numbers of potential binding sites for the two different nucleoside chromophore conjugates and exhibit similar absorbances. This shows that the sequence selective assembly of the two building blocks along DNA templates is programmable and alters the fluorescence readout. Such sequence‐controlled supramolecular chemistry represents the key element for future functional π‐systems in materials for light harvesting of solar energy.

Achieving non-doped deep-blue OLEDs by applying bipolar imidazole derivatives

Abstract In this work, we designed and synthesized two novel bipolar deep-blue emitting materials, 2-(4'-(9H-carbazol-9-yl)-[1,1′-biphenyl]-4-yl)-1 (4(tri-fluoromethyl) phenyl)-1H-phenanthro[9,10-d] imidazole (CzB-FMPPI) and 9-(4'-(4,5-diphenyl-1 (4-(trifluoromethyl) phenyl)-1H-imidazole-2-yl)-[1,1′-biphenyl]-4-yl)-9H-carbazole (CzB-FMPIM). Among them, carbazole and phenanthroimidazole are bridged linkage by the biphenyl ring and act as electron-donating part. The CF3-substituted phenyl ring applies as strong electron-withdrawing moiety. The exhibit highly twisted molecular configuration of two compounds efficiently shorten π-conjugation and inhibit intermolecular interaction, resulting in superior thermal stability and deep blue emission. High decomposition temperature of 431 °C and 414 °C, glass transition temperature of 150 °C and 135 °C for CzB-FMPPI and CzB-FMPIM, respectively, had been achieved. As a consequence of breaking the conjugation of phenanthroimidazole chromophore, CzB-FMPIM achieves an 8 nm blue-shifted emission compared with CzB-FMPPI. CzB-FMPPI exhibits a higher relative fluorescence quantum yield of 92.5% than 83.3% of CzB-FMPIM. Moreover, bipolar property was observed in both compound and homogeneous amorphous films were deposited and applied in the non-doped deep-blue OLEDs. The devices based on two emitters showed maximum luminance of 6667 cd/m2 and 3084 cd/m2, maximum EQE of 4.10% and 3.17%, respectively. Commission International de l'Eclairage (CIE) coordinates of CzB-FMPIM based device achieved (0.15, 0.07) which is extremely close to the NTSC standard blue CIE (0.14, 0.08).

Effect of initial precursor concentration on the spectral-luminescent characteristics and cytotoxicity of carbon nanoparticles

Colloidal carbon nanoparticles (CNPs) were obtained by hydrothermal method from fructose solutions with different initial concentrations. The morphology and size of CNPs were studied using methods of dynamic light scattering and transmission electron microscopy. Spectral-luminescent characteristics of CNPs were investigated by UV–vis absorption and fluorescence spectroscopy. It was revealed that the average particle size rises with the increase of the initial fructose concentration. A visible ‘tunable’ luminescence was recorded for the obtained CNPs colloids. It was found that the minimum value of the excitation wavelength which is necessary for obtaining luminescence rises with an increase of CNPs’ average size. This fact is probably associated with the conjugation of unsaturated chromophores on the particle surface, which will lead to a bathochromic shift of the absorption and luminescence bands. CNPs were extracted and investigated with IR and Raman spectroscopy to identify unsaturated chromophores. Possible cytotoxic effects of CNPs with different average particle size were investigated.

One Scaffold, Many Possibilities – Copper(I)‐Catalyzed Azide–Alkyne Cycloadditions, Strain‐Promoted Azide–Alkyne Cycloadditions, and Maleimide–Thiol Coupling of Ruthenium(II) Polypyridyl Complexes

The applicability of RuII polypyridyl complexes with appropriate functionalities as substrates for biorthogonal coupling reactions is investigated. In detail, copper(I)‐catalyzed azide–alkyne cycloadditions (CuAAC), strain‐promoted azide–alkyne cycloadditions (SPAAC), and maleimide–thiol coupling reactions of ruthenium complexes are examined. The first examples of SPAAC in which the organic azide is provided by the metal complex are presented. All of the chromophores belong to one easy‐to‐synthesize scaffold, which has proven to be convenient for the application of metal chromophores. The fundamental photophysical properties of the examined compounds do not change with substitution, which is important for the design of chromophore conjugates. Furthermore, the limitations of CuAAC reactions will be discussed with regard to copper impurities in the products formed.

Synthesis and Evaluation of Self-Assembled Nanostructures of Peptide-π Chromophore Conjugates.

Peptides provide a biomolecular scaffold for solubilizing and assembling π-conjugated molecules in aqueous media. The properties of such peptide-π chromophore conjugates can be manipulated by varying the constituent amino acid residues in the peptide backbone as well as the chromophore moieties. Such a precise handle on molecular structure leads to molecules with diverse macromolecular and material properties. We developed a versatile synthetic protocol that leads to a wide range of peptide-π chromophore conjugates in which the chromophores are covalently attached to the peptide backbone such that the chromophore is flanked by two peptide chains. This "trimer" structure lends interesting self-assembly properties to these materials which may be useful for a plethora of biological applications.

Importance of DOTA derivatives in bimodal imaging

AbstractThe clinical applications of multimodal probes are numerous since a few decades. 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) has played an important role in diagnostic and therapeutic areas. The vast applications of DOTA as chelator have been explored in magnetic resonance imaging (MRI) and in radioisotope chemistry. Moreover, the possibility to functionalize the macrocycle with pendant arms has allowed to explore new functionalities as bimodal imaging agents. Different combinations are possible between the different possible imaging techniques like Magnetic Resonance Imaging, Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), and Optical imaging (OI). The main use of DOTA and its derivatives was for MRI as gadolinium complexes. It was then further extended to the complexation with europium or terbium for optical imaging. Although other chelates are available such as DTPA or NOTA, derivatives of DOTA were often the primary choice due to their versatility. DOTA derivatives can indeed also be complexed with radioisotopes and conjugated to peptides which leads to targeted contrast agents for PET or SPECT. Depending on the chosen imaging modality, a variety of radiometals can be complexed with DOTA, e.i. 64Cu and 68Ga for PET, or 111In and 90Y for SPECT. Conjugation of chromophores to gadolinium complexes of DOTA derivatives can also lead to bimodal agents for MRI and OI. In this review, we will provide the applications of DOTA and its derivatives in different imaging modalities and their clinical applications.

人工色素の付加による光合成アンテナ色素タンパク質複合体（LH2）の光捕集機能の拡張

人工色素の付加による光合成アンテナ色素タンパク質複合体（LH2）の光捕集機能の拡張

Fast, Ratiometric FRET from Quantum Dot Conjugated Stabilized Single Chain Variable Fragments for Quantitative Botulinum Neurotoxin Sensing.

Botulinum neurotoxin (BoNT) presents a significant hazard under numerous realistic scenarios. The standard detection scheme for this fast-acting toxin is a lab-based mouse lethality assay that is sensitive and specific, but slow (∼2 days) and requires expert administration. As such, numerous efforts have aimed to decrease analysis time and reduce complexity. Here, we describe a sensitive ratiometric fluorescence resonance energy transfer scheme that utilizes highly photostable semiconductor quantum dot (QD) energy donors and chromophore conjugation to compact, single chain variable antibody fragments (scFvs) to yield a fast, fieldable sensor for BoNT with a 20-40 pM detection limit, toxin quantification, adjustable dynamic range, sensitivity in the presence of interferents, and sensing times as fast as 5 min. Through a combination of mutations, we achieve stabilized scFv denaturation temperatures of more than 60 °C, which bolsters fieldability. We also describe adaptation of the assay into a microarray format that offers persistent monitoring, reuse, and multiplexing.

Effects of Chromophore Conjugation Length and Concentration on the Photostability of Indoline-Based Nonlinear Optical Chromophore/Polymer Films

Photostability measurements were made on host–guest thin films containing nonlinear optical chromophores with an indoline donor and amorphous polycarbonate. We find that the indoline-based chromoph...

Correction to: Photoconversion changes bilin chromophore conjugation and protein secondary structure in the violet/orange cyanobacteriochrome NpF2163g3

Correction to: Photoconversion changes bilin chromophore conjugation and protein secondary structure in the violet/orange cyanobacteriochrome NpF2163g3

Synthesis of covalently linked boron–dipyrromethene–chromophore conjugates using 3-bromo boron–dipyrromethene as a key precursor

3-Bromo boron dipyrromethene (3-bromo BODIPY) has been used as key synthon to prepare one ethynyl bridged and six ethynylphenyl bridged BODIPY–chromophore conjugates using mild Pd(0) coupling conditions. The chromophores possessing very distinct features, such as anthracene, BODIPY, terpyridine, porphyrin, Zn(II)porphyrin, 21,23-dithiaporphyrin and thiasapphyrin were connected at 3-position of boronboron–dipyrromethene dye by coupling of 3-bromo BODIPY with ethynyl or ethynylphenyl chromophore in toluene/triethylamine in the presence of catalytic amount of AsPh 3/Pd 2(dba) 3 at 40 °C followed by column chromatographic purification. The spectral studies indicated that the interaction is stronger in ethynyl bridged BODIPY–chromophore conjugate compared to ethynylphenyl bridged BODIPY–chromophore conjugates. The steady-state fluorescence indicated that in ethynyl bridged BODIPY–anthracene conjugate, the BODIPY unit act as energy acceptor and showed a possibility of energy transfer from donor anthracene unit to acceptor BODIPY unit on selective excitation of anthracene unit. However, in ethynylphenyl bridged BODIPY–porphyrin conjugates, the BODIPY unit act as energy donor and exhibited a possibility of singlet-singlet energy transfer from BODIPY unit to porphyrin unit.