2-phenylpyridine Research Articles

Supramolecular assembly activated single-molecule phosphorescence resonance energy transfer for near-infrared targeted cell imaging

Pure organic phosphorescence resonance energy transfer is a research hotspot. Herein, a single-molecule phosphorescence resonance energy transfer system with a large Stokes shift of 367 nm and near-infrared emission is constructed by guest molecule alkyl-bridged methoxy-tetraphenylethylene-phenylpyridines derivative, cucurbit[n]uril (n = 7, 8) and β-cyclodextrin modified hyaluronic acid. The high binding affinity of cucurbituril to guest molecules in various stoichiometric ratios not only regulates the topological morphology of supramolecular assembly but also induces different phosphorescence emissions. Varying from the spherical nanoparticles and nanorods for binary assemblies, three-dimensional nanoplate is obtained by the ternary co-assembly of guest with cucurbit[7]uril/cucurbit[8]uril, accompanying enhanced phosphorescence at 540 nm. Uncommonly, the secondary assembly of β-cyclodextrin modified hyaluronic acid and ternary assembly activates a single intramolecular phosphorescence resonance energy transfer process derived from phenyl pyridines unit to methoxy-tetraphenylethylene function group, enabling a near-infrared delayed fluorescence at 700 nm, which ultimately applied to mitochondrial targeted imaging for cancer cells.

Optoelectronic properties and charge transfer dynamics in graphene quantum dot/Ir(III) nanocomposites: Enhancing photocatalytic performance through strategic BTF conjugate binding and end-capping variations

The aim of this study is to analyze the optoelectronic properties and charge transfer kinetics in nanocomposites comprising graphene quantum dots (GQDs) and Ir(III) complexes, with a specific focus on their relevance in photocatalytic applications. The investigation explores how the extent of π-conjugation, variations in end-capping substituents, and the binding position of benzothiazole fluorene (BTF) conjugates influence the electronic structures. The results indicate that attaching GQDs alters the band gaps and results in different energy alignments. By adjusting the position of BTF conjugate binding and the end-capping substituent, optimal photocatalytic performance can be achieved. Binding the BTF conjugate at the para-position enhances electron injection into TiO2, thereby improving photocatalysis. Conversely, binding the BTF at the meta-position contributes to the regeneration of the ground state, leading to increased light absorption and photoelectric conversion. Furthermore, incorporating a BTF conjugate at the meta-position of the 2-phenyl pyridine ligand enhances light absorption and photoelectric conversion in the nanocomposites. These findings pave the way for further exploration of the effects of different conjugate binding positions and substituents on the overall properties and potential applications of these nanocomposites.

An Ir (III) complex with multiphoton absorption in the near-infrared region as a probe for mtDNA-specific recognition and mitochondrial imaging

The multiphoton absorbing (MPA) materials have been extensively investigated due to their crucial merits of long wavelength excitation and short wavelength emission, of which the organometallic complexes are the most promising but still challenging candidates for developing efficient MPA materials. Herein, a novel cyclometallated iridium complex (abbreviated as SQ) is reported as a multiphoton absorption phosphorescent probe, which is constructed by coordinating the central metal Ir with diethoxyphenyl terpyridine, phenyl pyridine and SCN ligands. The single crystal of SQ exhibits a twisted octahedral structure that can avoid phosphorescence quenching caused by π-π stacking, and the push-pull electron effect of the ligand endows SQ with excellent nonlinear optical (NLO) properties under near-infrared excitation. As a result, two-photon imaging with deep tissue penetration depths is realized at the excitation wavelength of 750 nm. Meanwhile, the planar conjugated structure of diethoxyphenyl terpyridine facilitates the insertion of SQ into base pairs of mitochondrial DNA (mtDNA), thus limiting the intramolecular rotation. Consequently, the emission intensity of the SQ solution enhanced approximately 10-fold after mtDNA was introduced, which led to mtDNA-specific recognition. Our work proves a new way of designing a phosphorescence probe that can specifically identify mtDNA, thus realizing dynamic monitoring of mitochondria.

Continuous-flow directed C–H amidation reactions using immobilized Cp*Rh(iii) catalysts

A highly efficient heterogeneous Cp*Rh(iii) catalysts were developed for continuous-flow C–H amidation reactions of phenyl pyridines. The catalyst maintained the activity for 200 h continuous reaction without leaching of Rh species.

Enantioenriched Boron C,N-Chelates via Chirality Transfer.

Molecules stereogenic only at tetrahedral boron atoms show great promise for applications, for example as chiroptical materials, but are scarcely investigated due to their synthetic challenge. Hence, this study reports a two-step synthesis of enantioenriched boron C,N-chelates. First, the diastereoselective complexation of alkyl/aryl borinates with chiral aminoalcohols furnished boron stereogenic heterocycles in up to 86 % yield and d.r. >98 : 2. Treatment of these O,N-complexes with chelate nucleophiles was surmised to transfer the stereoinformation via the ate-complex into the C,N-products. This chirality transfer succeeded by substitution of the O,N-chelates with lithiated phenyl pyridine to give boron stereogenic C,N-chelates in up to 84 % yield and e.r. up to 97 : 3. The chiral aminoalcohol ligands could be recovered after isolation of the C,N-chelates. The chirality transfer tolerated alkyl, alkynyl and (hetero-)aryl moieties at boron and could be further extended by post-modification: transformations such as catalytic hydrogenations or sequential deprotonation/electrophilic trapping were feasible while maintaining the stereochemical integrity of the C,N-chelates. Structural aspects of the boron chelates were studied by variable temperature NMR and X-ray diffraction.

Controlling the sensitivity and selectivity for the detection of nitro-based explosives by modulating the electronic substituents on the ligand of AIPE-active cyclometalated iridium(III) complexes.

Nitroaromatic compounds are extremely explosive materials that pose a national security risk and raise environmental concerns. The design and development of sensitive and selective compounds for explosive materials are highly desirable. 'Aggregation-Induced Emission' (AIE) active materials are best suited for sensing purposes because of their sensitivity, fast detection time, and easy operation. By rationally incorporating substituents on the cyclometalated (C^N) ligand, four different AIE active iridium(III) based monocyclometalated complexes with the general formula [Ir(PPh3)2(H)(Cl)(C^N)] were synthesized. The phenyl ring of the phenyl pyridine cyclometalated portion of an iridium(III) complex was substituted with the right substituents to adjust the FMO levels thus, leading to appropriate alignment of the energy levels. Each of the resulting complexes displayed a significant property known as 'Aggregation-Induced Phosphorescent Emission' (AIPE). The complexes were subjected to structural characterization, electrochemical analysis, and photophysical property studies. The synthesized complexes were employed for the detection of aromatic nitro explosive compounds such as trinitrophenol (TNP) and trinitrotoluene (TNT) in the aqueous phase with a high degree of sensitivity. The sensing capabilities of each complex were assessed for these nitro explosive compounds and compared to those of the unsubstituted iridium(III) complex (M). Notably, the best limits of detection for TNP and TNT have been achieved with iridium(III) complexes [M1 (489 pM) and M3 (3.6 nM)] within the literature reported until now. For detecting picric acid with M1, FRET was found to be the potential mechanism, and for TNT, PET was found to be the cause of emission quenching by M3. Furthermore, for low-cost detection, filter paper-based sensing was also found effective for each complex. Real-field sensing of PA in soil samples was also performed.

Versatile Electroluminescence Color-Tuning Strategy of an Efficient Light-Emitting Electrochemical Cell (LEC) by an Ionic Additive.

The color-tuning strategies of solid-state light-emitting devices (ss-LEDs) are mainly focused on engineering molecular structures. In this paper, for the first time, we developed a facile strategy for tuning the electroluminescence (EL) color from orange to green through the addition of the ionic additive TBAP (tetrabutylammonium perchlorate). To achieve the active ionic emissive compound for use in a light-emitting electrochemical cell (LEC), the neutral biscyclometalated bromo tetrazole iridium(III) [Ir(ppy)2(BrTz)] was exchanged to its cationic complex, [Ir(ppy)2(BrTz-Me)]ClO4 (ppy = 2-phenyl pyridine, BrTz = 4-bromo-2-pyridine tetrazole, BrTz-Me = 4-bromo-2-pyridine methyl tetrazole) with a new synthetic strategy. This method allows employing neutral Ir-cyclometalated complexes, which are ruled out for use in LECs because of their non-ionic behaviors. In the following, an LEC based on the new cationic [Ir(ppy)2(BrTz-Me)]ClO4 as the emissive layer was fabricated between the FTO (fluorine-doped tin oxide) anode and Ga:In alloy cathode without using any additive or polymers, which makes this configuration the simplest ss-LED so far. By adding the ionic additives, the electroluminescence characteristics of [Ir(ppy)2(BrTz-Me)]ClO4 were dramatically increased, including luminance (L) from 162.8 cd/m2 for the device with an additive to 212.9 and 355.9 cd/m2 for devices containing LiTFSI (bis(trifluoromethane)sulfonamide lithium salt) and TBAP, respectively. In particular, when TBAP was added to the [Ir(ppy)2(BrTz-Me)]ClO4 complex, the irradiance was significantly increased from 166.4 to 220.8 μW/cm2 with an efficacy of 1.78 cd/A and external quantum efficiency (EQE) value of 2.14%. The obtained EL results clearly showed that adding TBAP and LiTFSI significantly improved the electroluminescence characteristics and tuned the electroluminescence color.

Structure‐activity relationships for several series of fragment‐based inhibitors that target Trichomonas vaginalis nucleoside ribohydrolase enzymes

Trichomoniasis, the most common sexually transmitted infection in the world, is caused by the parasitic protozoan Trichomonas vaginalis. Upon infection, T. vaginalis has been known to cause a variety of adverse effects as well as predisposition to other illnesses. Trichomoniasis is commonly treated with 5‐nitroimidazole drugs; however, some strains have developed resistance to these drugs and novel treatments are needed. Since T. vaginalis cannot synthesize nucleobases de novo, it relies on nucleoside ribohydrolases within its pyrimidine and purine salvage pathways in order to acquire nucleobases from its host. Nucleoside ribohydrolases, such as adenosine/guanosine preferring nucleoside ribohydrolase (AGNH) and uridine nucleoside ribohydrolase (UNH), cleave the N‐glycosidic bond of purine and pyrimidine nucleosides resulting in the formation of a nucleobase and a ribose sugar. Inhibiting the AGNH or UNH enzymes would block the salvage pathway resulting in parasite cell death. Fragment screening of AGNH and UNH identified ligand‐efficient scaffolds to serve as medicinal chemistry starting points for drug design. A variety of phenyl pyridine, phenyl pyrimidine, and phenyl pyrazine compounds were then synthesized and screened for inhibitory properties. 1H and 19F NMR‐based activity assays were employed, using adenosine and 5‐fluorouridine as substrates for AGNH and UNH, respectively. It was found that compounds containing a hydroxyl group at the 2‐position resulted in lower IC50 values for AGNH, and that the UNH IC50 was lower for compounds with hydroxy or methoxy functional groups at the 2’ and 3’ positions. With the enzyme inhibition data at hand structure‐activity relationships are being derived and will be used in combination with molecular modeling to design the next generation of compounds to be synthesized. Structural data is also being pursued for both enzymes to guide compound design. Highly purified AGNH and UNH, including selenomethionine‐AGNH, have been prepared for crystallography collaborations.

Rhodium-Catalyzed C-H Methylation and Alkylation Reactions by Carbene-Transfer Reactions.

In this combined computational and experimental study, the C−H functionalization of 2‐phenyl pyridine with diazoalkanes was investigated. Initial evaluation by computational methods allowed the evaluation of different metal catalysts and diazoalkanes and their compatibility in this C−H functionalization reaction. With these findings, suitable reaction conditions for the C−H methylation reactions were quickly identified by using highly reactive TMS diazomethane and C−H alkylation reactions with donor/acceptor diazoalkanes, which is applied to a broad scope on alkylation reactions of 2‐aryl pyridines with TMS diazomethane and donor/acceptor diazoalkane (51 examples, up to 98 % yield).

Iridium complexes having phosphrous ligands of large steric hindrance: Photophysical comparison between solution state, solid state and electrospun fibers

In this work, two luminescent iridium complexes were synthesized with 2-phenyl pyridine (ppy) and two phosphine-based ligands. There was large steric hindrance in these phosphine-based ligands, so that there would be enough time for the excited state based on highly luminescent 3MLLCT (metal-to-ligand-ligand-charge-transfer) electronic transformation It was found that there was limited aggregation-induced phosphorescence emission (AIPE) effect in these two iridium complexes since their ligands with large steric hindrance minimized the intermolecular (π-π) interactions between molecules. A distorted octahedral coordination field was found in the single crystals of these two iridium complexes. A systematical comparison on the photophysical parameters of these two iridium complexes in solution state, in solid state and in electrospun fiber was carried out, so that the limited aggregation-caused quenching (ACQ) could be confirmed. The potential surface crossing and energy transfer in the excited state of these two iridium complexes were analyzed by means of density functional theory calculation and temperature-dependent emission spectra. The limited ACQ effect in these two iridium complexes was finally confirmed due to the large ligand steric hindrance, which allowed phosphorescent decay of excited state. High emission quantum yield (0.27) and long emissive lifetime (0.43 µs) in solid state were observed.

Polar Alkoxy Group and Pyridyl Effects on the Mesomorphic Behavior of New Non-Symmetrical Schiff Base Liquid Crystals

A series of non-symmetrical Schiff base liquid crystals were prepared and investigated. Schiff bases of p-alkyloxy aniline derivatives and 4-phenyl pyridine-4′-carbaldehyde were synthesized. The terminal alkoxy groups substituting aniline are of varied chain length, namely C6, C8, and C16. The structures of the compounds were confirmed via 1H NMR and 13C NMR spectroscopy. Different mesophases of the samples were thermally and optically characterized by differential thermal analysis (DSC) and polarized optical microscopy (POM). All samples revealed enantiotropic smectic B (SmB) and smectic A (SmA) mesophases. The results obtained were further correlated with the density functional theory (DFT) theoretical calculations. The results are compared to a series of compounds bearing biphenyl moiety in their mesogens. The thermal stabilities of the different mesophase reduced upon the increment of the alkoxy chain length. The temperature ranges of both the smectic mesophases of new compounds bearing the 4-phenyl pyridine moiety are generally expanded higher than the other series. In addition, the total mesophase range is greater in the new compounds when compared to their biphenyl analogues. The DFT results were investigated in terms of the molecular geometries and the frontier molecular orbitals as well as the charge distribution mapping to show and illustrate the difference in the mesomorphic properties.

Two Luminescent Iridium Complexes with Phosphorous Ligands and Their Photophysical Comparison in Solution, Solid and Electrospun Fibers: Decreased Aggregation-Caused Emission Quenching by Steric Hindrance

In this paper, we prepared two phosphorescent Ir complexes with ligands of 2-phenyl pyridine (ppy), and two phosphorous ligands with large steric hindrance, hoping to allow enough time for the transformation of the highly phosphorescent 3MLLCT (metal-to-ligand-ligand-charge-transfer) excited state. Their large steric hindrance minimized the π-π interaction between complex molecules, so that the aggregation-induced phosphorescence emission (AIPE) influence could be minimized. Their single crystals indicated that they took a distorted octahedral coordination mode. Photophysical comparison between these Ir complexes in solution, in the solid state and in electrospun fibers was performed to confirm the realization of limited aggregation-caused quenching (ACQ). The potential surface crossing and energy transfer from 3MLBPECT/3MLBPELppyCT to 3MLppyCT in these Ir complexes were revealed by density functional theory calculation and temperature-dependent emission. It was confirmed that these two phosphorous ligands offered large steric hindrance, which decreased the ACQ effect, allowing the efficient emissive decay of the 3MLppyCT excited state. This is one of the several luminescent Ir complexes with a high emission yield (Φ = 0.27) and long emission lifetime (0.43 μs) in the solid state.

Catalytic activity of 2-phenyl pyridine palladacycle and its structural studies using DFT calculations

2-phenyl pyridine palladacycle [Pd (κ2 -N, C-C11H8N) (O3SC7H7)-{P (C6H5)3}] (1) was tested for the catalytic activity in the vinylation of 3-Bromo-benzophenone to give 3-Vinyl benzophenone, a precursor for the synthesis of Ketoprofen an anti-inflammatory drug. The effect of various reaction parameters such as temperature, palladacycle loading, ethylene pressure and material balance for the vinylation reaction was studied. The palladacyle (1) exhibited excellent catalytic activity with a TOF of 4842 h-1 in the vinylation reaction. The structural properties of palladacycle (1) were studied by employing the B3LYP density functional theory with SDD and 6-311++G (d, p) basis sets at the Gaussian 09 package of programs. The computed density functional theory (DFT) structural parameters (bond lengths and bond angles) of the optimized geometry using the B3LYP/6-311G basis set were found to compare favourably with those of the X-ray crystal structure.

Mesomorphic Behaviour and DFT Insight of Arylidene Schiff Base Liquid Crystals and Their Pyridine Impact Investigation

A new series of Schiff base liquid crystal have been prepared and studied. Schiff bases of p-alkyl aniline derivatives and 4-phenyl pyridine-4′-carbaldehyde were prepared. The terminal alkyl groups substituting aniline are of varied chain length, namely C8, C12 and C14. The structures of the compounds were elucidated by 1H NMR and 13C NMR. The mesomorphic thermal and optical characteristics of the samples were determined via differential thermal analysis (DSC) and polarization optical microscopy (POM). All compounds exhibit enantiotropic dimorphic mesophase behaviour, referred to as smectic X1 (SmX1) and smectic X2 (Sm A). Experimental results obtained for the mesophases were correlated with density functional theory (DFT) theoretical calculations. The results of the new series are further compared to two series of compounds bearing pyridine (two ring Schiff bases) and biphenyl, respectively, in their mesogens. The series of compounds of one pyridine ring are generally not mesomorphic. The results indicate that the alkyl chain length has a strong impact on the mesomorphic characteristics and thermal stabilities of the different mesophases. As a trend, the temperature ranges of both of smectic mesophases of all compounds are higher in new compounds bearing the 4-phenyl pyridine moiety. In addition, the total mesophase range is generally higher in the new compounds when compared to their biphenyl analogues. Finally, theoretical DFT calculations were performed to illustrate the experimental finding of the mesomorphic behaviour in terms of the molecular geometry and aromaticity, π–π stacking and LOL-π.

Synthesis of Dihydroisoquinoline and Dihydropyridine Derivatives via Asymmetric Dearomative Three-Component Reaction

Synthesis of Dihydroisoquinoline and Dihydropyridine Derivatives via Asymmetric Dearomative Three-Component Reaction

On bio-MOF materials doped with phosphorescent iridium complexes for molecular oxygen determination: Synthesis, characterization and performance

In this paper, two phosphorescent Ir(III) complexes, Ir(ppy)2(Ln), were synthesized using 2-phenyl pyridine (ppy) as the first (major) ligand and two phosphorous compounds (L1 and L2) as the auxiliary ligand. Their single crystal structure and electronic structure were discussed. Ir(ppy)2(Ln) complexes were doped into a supporting matrix of bio-MOF-1 via cationic exchange to ensure their uniform distribution. Their successful doping was confirmed by SEM, fluorescence microscopy image, XRD, N2 adsorption/desorption and ICP measurement. Their photophysical parameters, including absorption spectra, excitation spectra, emission spectra, emission lifetime and quantum yield, were discussed in detail. Their phosphorescent emission was confirmed by density functional theory and emission lifetime, making them applicable for oxygen sensing. Linear working curves were observed for both composite samples, showing sensitivity as high as 23.65 with response/recovery time of 9/22 s. Humidity effect on sensing performance was limited. These parameters were found superior to literature ones based on phosphorescent Cu(I), RE(III), Ru(II) and Re(I) complexes. The sensing mechanism was revealed as a dynamic collision between Ir(ppy)2(Ln) and O2 molecules. The novelty of this work was the combination of phosphorescent Ir(III) complexes with porous bio-MOF-1, resulting in greatly improved sensitivity and linear sensing with short response time.

Febuxostat Inhibits MPP+-Induced Inflammatory Response Through Inhibiting the JNK/NF-κB Pathway in Astrocytes.

Parkinson's disease (PD) is a severe neurodegenerative disease lacking effective clinical therapies. It is reported that astrocyte-associated neuroinflammation and oxidative stress are involved in the pathological mechanism of PD. In the present study, we aimed to investigate the protective effect of febuxostat against 1 methyl 4 phenyl pyridine (MPP+)-induced injury on primary astrocytes to highlight the potential therapeutic property of febuxostat in PD.MPP+ was used to induce an in vitro PD model in primary rat astrocytes. The levels of ROS and intracellularly reduced GSH were determined using DCFH-DA assay and a commercial GSH kit, respectively. MTT and LDH release assays were utilized to evaluate the cell viability of astrocytes. The expressions of IL-8, IL-1β, TNF-α, MMP-2, and MMP-9 in the astrocytes were detected using qRT-PCR and ELISA assays. QRT-PCR and Western blot analysis were used to determine the expression levels of GFAP in astrocytes. The expression of p-JNK and nuclear levels of NF-κB p65 were evaluated using Western blot analysis. The transcriptional activity of NF-κB was measured using the luciferase activity assay.Firstly, the elevated levels of ROS and decreased levels of intracellularly reduced GSH in primary astrocytes induced by MPP+ were significantly ameliorated by febuxostat. Secondly, treatment with febuxostat rescued MPP+-induced reduction in cell viability and increased LDH release. Thirdly, febuxostat alleviated MPP+-induced inflammatory responses in astrocytes by reducing the expressions of IL-8, IL-1β, TNF-α, GFAP, MMP-2, and MMP-9. Importantly, we found that febuxostat mitigated activation of the JNK/NF-κB signaling pathway by inhibiting the phosphorylation of JNK and nuclear translocation of NF-κB p65.Febuxostat attenuated MPP+-induced inflammatory response by suppressing the JNK/NF-κB signaling pathway in astrocytes.

Spectroscopic Sensing Characteristics of Novel Osmium Carbonyl Complexes to DNA and Other Polyanions

In this research, the absorbance and luminescence response of two osmium(II) phenathrane (phen) carbonyl complexes to various DNA, heparin and i-carrageenan polyanions were studied. The [Os(phen)2CO(L)]2+ complexes with L either a 4-phenyl pyridine (4-phpy) or phenyl imidazole (phimd) group exhibit moderate luminescent intensity in the visible region, their intensities are highly altered by the addition of DNA and other polyanion samples. These luminescent responses to polyanions were also compared with the [Ru(phen)3]2+ complex. In ethanol solution, the presence of polyanions significantly enhanced the luminescent emission intensity of [Os(phen)2CO(L)]2+ complexes with a blue shift. While the polyanions all showed emission enhancement on the highly lumi-nescent [Ru(phen)3]2+ complex in ethanol solution with a red spectra shift. The [Os(phen)2CO(L)] 2+ with (phimd) ligand has the lowest emission in ethanol solution, its intensity can be enhanced up to 11 times in the presence of DNA polyanions. This enhancement for all the complexes in ethanol is mainly due to their electrostatic interaction with the anion sites and with some degree of ligand intercalation into the polyanion hydrophobic structure which reduced the solvent quenching of the complexes. The blue shift of the (4-phpy) and particularly (phimd) Os(II)CO complexes indicate an insertion of the (4-phpy) or (phimd) group into the polymer chains. The two new Os(II)CO complexes has great potential to be used as luminescence sensors for DNA and polyanion detection in the low micro molar range with high sensitivity.

Bis-Tridendate Ir(III) Polymer-Metallocomplexes: Hybrid, Main-Chain Polymer Phosphors for Orange-Red Light Emission.

In this work, hybrid polymeric bis-tridentate iridium(III) complexes bearing derivatives of terpyridine (tpy) and 2,6-di(phenyl) pyridine as ligands were successfully synthesized and evaluated as red-light emitters. At first, the synthesis of small molecular bis-tridendate Ir(III) complexes bearing alkoxy-, methyl-, or hydroxy-functionalized terpyridines and a dihydroxyphenyl-pyridine moiety was accomplished. Molecular complexes bearing two polymerizable end-hydroxyl groups and methyl- or alkoxy-decorated terpyridines were copolymerized with difluorodiphenyl-sulphone under high temperature polyetherification conditions. Alternatively, the post-polymerization complexation of the terpyridine-iridium(III) monocomplexes onto the biphenyl-pyridine main chain homopolymer was explored. Both cases afforded solution-processable metallocomplex-polymers possessing the advantages of phosphorescent emitters in addition to high molecular weights and excellent film-forming ability via solution casting. The structural, optical, and electrochemical properties of the monomeric and polymeric heteroleptic iridium complexes were thoroughly investigated. The polymeric metallocomplexes were found to emit in the orange–red region (550–600 nm) with appropriate HOMO and LUMO levels to be used in conjunction with blue-emitting hosts. By varying the metal loading on the polymeric backbone, the emitter’s specific emission maxima could be successfully tuned.

Photopatterning of Azobenzene-Containing Liquid Crystalline Triblock Copolymers: Light-Induced Anisotropy and Photostabilization.

Photochromic liquid crystalline block copolymers (PLCBCs) are currently playing a significant role as light-responsive materials because of their light controllable features over multiple length scales. Herein, a study of the photoinduced optical anisotropy derived by the combination of orientation phenomena at molecular and supramolecular levels in a novel kind of side-chain PLCBCs with mesogenic phenyl benzoate groups and pyridine units that is hydrogen bonded with azobenzene-containing phenol is reported. Based on the polymeric architectures and composition, the supramolecular configuration self-organizes in different microphases that affect the material response to the external stimuli. Simple, 1D, polarization holograms are recorded to evaluate the photoinduced birefringence. The first step, light patterning, involves the orientation of the azobenzene units and precedes a thermal treatment that amplifies the induced anisotropy through the cooperative orientation of the mesogenic units. By selective extraction, the azobenzene units can be removed, making the material transparent to the visible light. Excellent photostability of the material birefringence is obtained, whose final value is strongly affected by the block copolymer's architecture. The versatility in the molecular design, the fine control of the photoinduced features by external parameters, and, finally, the possibility to achieve photostability make these materials of great potential for developing optical and photonic devices.