Oligo Ethylene Research Articles

Performance and Solution Structures of Side-Chain-Bridged Oligo (Ethylene Glycol) Polymer Photocatalysts for Enhanced Hydrogen Evolution under Natural Light Illumination.

Converting solar energy into hydrogen energy using conjugated polymers (CP) is a promising solution to the energy crisis. Improving water solubility plays one of the critical factors in enhancing the hydrogen evolution rate (HER) of CP photocatalysts. In this study, a novel concept of incorporating hydrophilic side chains to connect the backbones of CPs to improve their HER is proposed. This concept is realized through the polymerization of carbazole units bridged with octane, ethylene glycol, and penta-(ethylene glycol) to form three new side-chain-braided (SCB) CPs: PCz2S-OCt, PCz2S-EG, and PCz2S-PEG. Verified through transient absorption spectra, the enhanced capability of PCz2S-PEG for ultrafast electron transfer and reduced recombination effects has been demonstrated. Small- and wide-angle X-ray scattering (SAXS/WAXS) analyses reveal that these three SCB-CPs form cross-linking networks with different mass fractal dimensions (f) in aqueous solution. With the lowest f value of 2.64 and improved water/polymer interfaces, PCz2S-PEG demonstrates the best HER, reaching up to 126.9µmolh-1 in pure water-based photocatalytic solution. Moreover, PCz2S-PEG exhibits comparable performance in seawater-based photocatalytic solution under natural sunlight. In situ SAXS analysis further reveals nucleation-dominated generation of hydrogen nanoclusters with a size of ≈1.5nm in the HER of PCz2S-PEG under light illumination.

Controlled synthesis and solution properties of copolymers of methacrylic esters and ammonium-containing methacrylamide

Copolymers based on oligo(ethylene glycol) methacrylate, dodecyl methacrylate, and the cationic monomer N-methacryloylaminopropyl-N,N-dimethyl-N-propylammonium bromide have been obtained by reversible addition−fragmentation chain-transfer polymerization in high yields and in a controlled mode. The influence of the composition of the obtained polymers on the solubility in water and organic solvents, distribution in the water-octanol system, and interfacial tension at the water-oil interface is shown. The presence of thermoresponsive properties for polymers in water was found, and their aggregation in aqueous media was also studied.

Enhanced Optical Contrast and Switching in Near‐Infrared Electrochromic Devices by Optimizing Conjugated Polymer Oligo(Ethylene Glycol) Sidechain Content and Gel Electrolyte Composition

AbstractA detailed investigation addressing the effects of functionalizing conjugated polymers with oligo(ethylene glycol) (EGn) sidechains on the performance and polymer‐electrolyte compatibility of electrochromic devices (ECDs) is reported. The electrochemistry for a series of donor‐acceptor copolymers having near‐infrared (NIR)‐optical absorption, where the donor fragment is 3,4‐ethylenedioxythiophene (EDOT) or an EGn functionalized bithiophene (g2T) and the acceptor fragment is diketopyrrolopyrrole (DPP) functionalized with branched alkyl or EGn sidechains, is extensively probed. ECDs are next fabricated and it is found that EGn sidechain incorporation must be finely balanced to promote polymer‐electrolyte compatibility and provide efficient ion exchange. Proper electrolyte‐cation pairing and polymer structural tuning affords a 2x increase in optical contrast (from 12% to 24%) and >60x reduction in switching time (from 20 to 0.3 s). Atomic force microscopy (AFM)/grazing incidence wide‐angle X‐ray scattering (GIWAXS) characterization of the polymer film morphology/microstructure reveals that an over‐abundance of EGn sidechains generates large polymer crystallites, which can suppress ion exchange. Lastly, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) indicates sidechain/electrolyte identity does not influence the electrolyte penetration depth into the films, and EGn sidechain inclusion increases electrolyte cation uptake. The material structural design insight and guidelines regarding the polymer‐electrolyte ion insertion/expulsion dynamics reported here should be of significant utility for developing next‐generation mixed ionic‐electronic conducting materials.

Persistence Length of PEGMA Bottle Brushes Determined by Pyrene Excimer Fluorescence.

Seven pyrene-labeled poly(oligo(ethylene glycol) methyl ether methacrylate)s (PyEG5-PEGnMAs) were prepared with n = 0, 3, 4, 5, 7, 9, and 19 ethylene glycol units by copolymerizing a small amount of penta(ethylene glycol) 1-pyrenemethyl ether methacrylate with an EGnMA monomer. The conformation of the PyEG5-PEGnMA polymers evolved from a random coil for PyEG5-PEG0MA or poly(methyl methacrylate) to a polymeric bottle brush (PBB) architecture with increasing side chain length. The fluorescence decays of the PyEG5-PEGnMA samples were fitted according to the fluorescence blob model (FBM) whose parameters were used, in combination with the Kratky-Porod equation, to calculate the persistence length of these polymers. The persistence lengths obtained from the PEF experiments were found to increase with the square of the number (NS) of non-hydrogen atoms in the side chain as expected theoretically. The persistence lengths found with the PyEG5-PEGnMA samples in DMF also matched those found earlier for another series of PEGnMA samples labeled with 1-pyrenebutanol. The good agreement found between the persistence lengths obtained with the PEGnMA samples labeled with two different pyrene derivatives illustrates the robustness of the method and its applicability for measuring the unknown persistence length of polydisperse polymer samples.

Hydrogen-Bonded Polymer Nanomedicine with AIE Characteristic for Intelligent Cancer Therapy.

One of the major goals of biomedical science is to pioneer advanced strategies toward precise and smart medicine. Hydrogen-bonding (H-bonding) assembly incorporated with an aggregation-induced emission (AIE) capability can serve as a powerful tool for developing supramolecular nanomedicine with clear tumor imaging and smart therapeutic performance. We here report a H-bonded polymeric nanoformulation with an AIE characteristic toward smart antitumor therapy. To do so, we first design a structurally novel tetraphenylethylene (TPE)-based H-bonding theranostic prodrug, TPE-(FUA)4, characterized by four chemotherapeutic fluorouracil-1-acetic acid (FUA) moieties arched to the TPE core. A six-arm star-shaped amphiphilic polymer vehicle, P(DAP-co-OEGEA)6, is prepared, bearing hydrophilic and biocompatible POEGEA (poly(oligo (ethylene glycol) ethyl acrylate) segments, along with a hydrophobic and H-bonding PDAP (poly(diaminopyridine acrylamide)) segment. Thanks to the establishment of the DAP/FUA H-bonding association, incorporating the TPE-(FUA)4 prodrug to the P(DAP-co-OEGEA)6 vehicle can yield H-bond cross-linked nanoparticles with interpenetrating networks. For the first time, AIE luminogens are interwoven into a six-arm star-shaped polymer via an intrinsic H-bonding array of the chemotherapeutic agent FUA, thus imposing an effective restriction of TPE molecular rotations. Concomitantly, encapsulated photothermal agent (IR780) via a hydrophobic interaction facilitates the formation of nanoassemblies, TPE-(FUA)4/IR780@P(DAP-co-OEGEA)6, featuring synergistic cancer chemo/photothermal therapy (CT/PTT). Our study can contribute a practical solution to fulfill biomedical requirements with a conductive advance in precision nanomedicine.

Entropic Penalty Switches Li+ Solvation Site Formation and Transport Mechanisms in Mixed Polarity Copolymer Electrolytes.

Emerging solid polymer electrolyte (SPE) designs for efficient Li-ion (Li+) conduction have relied on polarity and mobility contrast to improve conductivity. To further develop this concept, we employ simulations to examine Li+ solvation and transport in poly(oligo ethylene methacrylate) (POEM) and its copolymers with poly(glycerol carbonate methacrylate) (PGCMA). We find that Li+ is solvated by ether oxygens instead of the highly polar PGCMA, due to lower entropic penalties. The presence of PGCMA promotes single-chain solvation, thereby suppressing interchain Li+ hopping. The conductivity difference between random copolymer PGCMA-r-POEM and block copolymer PGCMA-b-POEM is explained in terms of a hybrid solvation site mechanism. With diffuse microscopic interfaces between domains, PGCMA near the POEM contributes to Li+ transport by forming hybrid solvation sites. The formation of such sites is hindered when PGCMA is locally concentrated. These findings help explain how thermodynamic driving forces govern Li+ solvation and transport in mixed SPEs.

Fluorophore position of headgroup-labeled Gb3 glycosphingolipids in lipid bilayers

Fluorescent lipid probes are an invaluable tool for investigating lipid membranes. In particular, localizing certain receptor lipids such as glycosphingolipids within phase-separated membranes is of pivotal interest to understanding the influence of protein-receptor lipid binding on membrane organization. However, fluorescent labeling can readily alter the phase behavior of a lipid membrane because of the interaction of the fluorescent moiety with the membrane interface. Here, we investigated Gb3 glycosphingolipids, serving as receptor lipids for the protein Shiga toxin, with a headgroup attached BODIPY fluorophore separated by a polyethylene glycol (PEG) spacer of different lengths. We found that the diffusion coefficients of the fluorescently labeled Gb3 species in 1,2-dioleoyl-sn-glycero-3-phosphocholine/Gb3 (98:2, n/n) supported lipid bilayers are unaltered by the PEG spacer length. However, quenching as well as graphene-induced energy transfer experiments indicated that the length of the PEG spacer (n = 3 and n = 13) alters the position of the BODIPY fluorophore. In particular, the graphene-induced energy transfer technique provided accurate end-to-end distances between the fluorophores in the two leaflets of the bilayer thus enabling us to quantify the distance between the membrane interface and the fluorophore with sub-nanometer resolution. The spacer with three oligo ethylene glycol groups positioned the BODIPY fluorophore directly at the membrane interface favoring its interaction with the bilayer and thus may disturb lipid packing. However, the longer PEG spacer (n = 13) separated the BODIPY moiety from the membrane surface by 1.5 nm.

Efficient formation of poly(ethylene glycol) polymer brushes on gold electrodes via surface-initiated electrochemically mediated ATRP (SI-eATRP)

Electrochemically mediated surface-initiated atom transfer radical polymerization (SI-eATRP) is an interesting grafting from technique used to grow, in a controlled way, polymeric films from a wide range of surfaces, including metal substrates. Aqueous SI-eATRP offers an appealing strategy for the preparation of polymers by using water-soluble monomers, employing an oxidatively stable catalyst complex. The goal of this work is to tailor compact poly-(oligo(ethylene glycol)methacrylate) (p-OEGMA) brushes on gold electrodes by combining the formation of self-assembled monolayers (SAMs) containing a suitable ATRP initiator molecule, and the SI-eATRP polymerization approach. We have investigated the effects of the SAM-initiator nature, the applied potential, and the duration of the polymerization process on the properties of the grafted p-OEGMA-brushes. In addition, we employed electrochemical quartz crystal microbalance measurements to evidence the living character of the polymerization. The final properties of the tailored p-OEGMA-brush were studied by cyclic voltammetry and electrochemical impedance spectroscopy, obtaining information on the electronic and ionic blocking behaviour of these films, under different experimental conditions. Further information on structural conformation, composition, and organization was obtained from different characterization techniques: IRRAS and XPS spectroscopies, contact angle measurements, and SEM and AFM microscopies. These techniques confirmed that an efficient formation of p-OEGMA-brushes via SI-eATRP was achieved. Thus, the designed SI-eATRP system offers an interesting option to functionalize a wide variety of substrates with water-soluble and biocompatible monomers. Such coatings present potential applications in various fields, including biomedical applications.

Molecular Dynamics Calculations for the Temperature Response of Poly(alkylated tri(ethylene oxide)isocyanate) Aqueous Solution

Aqueous solutions of conventional temperature-responsive amphiphilic polymers undergo a coil–globule conformational transition around the lower critical solution temperature (LCST) that causes the polymer surfaces to become hydrophobic and the polymers to aggregate together. Isocyanate polymers with alkylated oligo(ethylene oxide) side chains are expected to have rigid main chains and, thus, do not undergo the coil–globule structural transition, but they have recently been reported to exhibit temperature-responsive properties. In this study, molecular dynamics was used to calculate the agglomeration tendencies of two chains of poly(alkylated tri(ethylene oxide)isocyanate) (PRTEOIC, where R = methyl (Me) or ethyl (Et)) in aqueous solution to elucidate the LCST phenomenon in the absence of coil–globule conformational transition. Our MD simulations showed that aggregation also occurs in rod polymers. Furthermore, we found that both (PMeTEOIC)2 and (PEtTEOIC)2 showed parallel agglomeration of the two molecular chains with increasing temperature, but only (PMeTEOIC)2 showed a metastable T-shaped agglomeration in the middle temperature range. The crossing-point temperature (TCRP) at which the density of the first hydrophobic hydration shell around the sidechain alkyl group equals the bulk water density is a useful indicator for predicting the LCST of rod polymers with dense side chains terminated by alkyl groups.

Fine-tuning morphology via oligo(ethylene oxide) side chain engineering for squaraine-based organic solar cells

Two squaraine dyes (SQs), USQ-O bearing oligo(ethylene oxide) (OE) chain, and USQ-C bearing alkyl chain, were synthesized. The influence of OE side chain on photovoltaic performances was systematically investigated. USQ-C and USQ-O show similar absorption spectra in dilute solutions, energy levels, charge mobility and the molecular electrostatic potential (ESP) on the conjugated skeleton. However, USQ-O exhibits hypsochromic absorption band compared to that of USQ-C in the film, and the distribution of positive and negative alternating ESP on the OE side chain. Significantly different electrostatic interactions and multiple hydrogen bonds among OE side chains could greatly affect the behaviors of intermolecular interactions, and, in turn, influence the photophysical properties of pristine/blend films and the miscibility with PC71BM acceptor. USQ-O-based devices exhibit higher short circuit current than that of USQ-C-based (13.94 vs 12.36 mA cm−2), which could be principally put down to the effective improvement of the blending morphology. These results indicate that simply substituted alkyl chain by OE chain for SQ is an effective strategy for optimizing morphology.

Size‐Selective Ionic Crosslinking Provides Stretchable Mixed Ionic–Electronic Conductors

AbstractMechanically compliant conductors are of utmost importance for the emerging fields of soft electronics and robotics. However, the development of intrinsically deformable organic conductors remains a challenge due to the trade‐off between mechanical performance and charge mobility. In this study, we report a solution to this issue based on size‐selective ionic crosslinking. This rationally designed crosslinking mediated by length‐regulated oligo(ethylene glycol) pendant groups and metal ions simultaneously improved the softness and toughness and ensured excellent mixed ionic–electronic conductivity in poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate composite materials. Moreover, the added ions remarkably promoted accumulation of charge carriers in response to temperature gradient, thus offering a viable approach to stretchable thermoelectric generators with enhanced stability against humidity.

Size-Selective Ionic Crosslinking Provides Stretchable Mixed Ionic-Electronic Conductors.

Mechanically compliant conductors are of utmost importance for the emerging fields of soft electronics and robotics. However, the development of intrinsically deformable organic conductors remains a challenge due to the trade-off between mechanical performance and charge mobility. In this study, we report a solution to this issue based on size-selective ionic crosslinking. This rationally designed crosslinking mediated by length-regulated oligo(ethylene glycol) pendant groups and metal ions simultaneously improved the softness and toughness and ensured excellent mixed ionic-electronic conductivity in poly(3,4-ethylenedioxythiophene):polystyrene sulfonate composite materials. Moreover, the added ions remarkably promoted accumulation of charge carriers in response to temperature gradient, thus offering a viable approach to stretchable thermoelectric generators with enhanced stability against humidity.

Aggregation of Thermoresponsive Polymethacrylates in a Dulbecco's Modified Eagle Medium and Its Salts.

The thermal behavior and aggregation process of the poly(N-isopropyl acrylamide), poly[oligo(ethylene glycol) methyl ether methacrylate], and poly[(2-hydroxyethyl methacrylate)-co-oligo(ethylene glycol) methyl ether methacrylate] thermoresponsive polymers were studied in a commonly used Dulbecco's Modified Eagle Medium (DMEM) cell culture medium and solutions of its individual components in the same concentration as found in DMEM. All studied copolymers exhibited an unexpected transmittance profile in the DMEM. During heating above the cloud point temperature (TCP), the polymers additionally aggregated, which led to the formation of their precipitates. The behavior of the polymers was further studied to evaluate how individual salts affected the transition temperature, size (Dh), and stability of the polymer particles. Organic additives, such as amino acids and glucose, had a significantly lesser impact on the thermoresponsive aggregation of the polymers than inorganic ones. Changes to the TCP were small and the formation of precipitates was not observed. The presence of small amounts of amino acids caused a decrease in the polymer aggregate sizes. Obtained results are of utmost importance in thermoresponsive drug nanocarrier studies.

Preparing cyclic polymers at high concentrations via self-folding cyclization technique by adjusting the contents of hydrophilic units in linear precursors

Cyclic polymers are a class of polymers that feature endless topology, and the synthesis of cyclic polymers has attracted the attention of many researchers. Herein, cyclic polymers were efficiently constructed by self-folding cyclization technique at high concentrations. Linear poly((oligo(ethylene glycol)acrylate)-co-(dodecyl acrylate)) (P(OEGA-co-DDA)) precursors with different ratios of hydrophilic and hydrophobic moieties were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using a bifunctional chain transfer agent with two anthryl end groups. The amphiphilic linear precursors underwent the self-folding process to generate polymeric nanoparticles in water. By irradiating the aqueous solution of the nanoparticles with 365 nm UV light, cyclic polymers were synthesized successfully via coupling of anthryl groups. The effects of the ratios of hydrophilic and hydrophobic moieties in linear P(OEGA-co-DDA) copolymers and polymer concentration on the purity of the obtained cyclic polymers were explored in detail via1H nuclear magnetic resonance (1H NMR), dynamic light scattering (DLS), UV‒visible (vis) analysis, three-detection size exclusion chromatography (TD-SEC) and transmission electron microscopy (TEM). It was found that by adjusting the content of the hydrophilic segments in linear precursors, single chain polymeric nanoparticles (SCPNs) can be generated at high polymer concentrations. Therefore, cyclic polymers with high purity can be constructed efficiently. This method overcomes the limitation of traditional ring-closure method, which is typically conducted in highly dilute conditions, providing an efficient method for the scalable preparation of cyclic polymers.

Electronic and Structural Properties of Core-Shell Amino-Silica Nanoparticles: DFT And SCC-DFTB Calculation

Introduction: Silica nanoparticles (SNP) are extremely promising tools in nanotechnology and nano medicine. In most of applications such as capture and release of bacteriophage viruses the nano-structures of silica are coated by bio-compatible groups such as amine compounds. The presence of amino groups on the surface of the biosensors enables the installation of analyte receptors and antifouling agents such as oligo (ethylene oxide). Therefore, in this study, the electronic and structural properties of Core-Shell amino- Silica Nanoparticles are investigated.Material and Methods: In this investigation, we aim at obtaining the optimized structures and evaluate the geometries of the ground state for (SiO2) n (n=16, 20) nanoclusters. The electronic properties computed by density functional theory with GGA approximation and SCC-DFTB with hybrid Slater-Koster files are investigated and the effect of functionalization on such properties is discussed.Results: Solvolysis of studied structures is examined and it is shown that the highest occupied and lowest unoccupied molecular orbital states shift to obviously higher energy levels, which lead to more stable hydrogenated nanoclusters. The stability of nanoclusters rises by functionalization with amino and methylamine groups. Charge analysis of functionalized systems indicates the reactivity of nanoclusters. The results obtained in this paper are useful for chemical and biochemical applications of silica nanostructures.Conclusion: Results show that the length of amine hydrocarbon chain can control the electronic and magnetic properties of studied silica nanocluster (SNP) with different number of SiO2 unit. Pure ultra-small nanocluster shows the impressive spin splitting around the Fermi level, which is due to the spin splitting of outer silicon atoms. This feature of silica nanoclusters may be notable for applications in electronics.

High-Performance n-Type Organic Thermoelectrics Enabled by Synergistically Achieving High Electron Mobility and Doping Efficiency.

n-Doped polymers with high electrical conductivity (σ) are still very scarce in organic thermoelectrics (OTEs), which limits the development of efficient organic thermoelectric generators. A series of fused bithiophene imide dimer-based polymers, PO8, PO12, and PO16, incorporating distinct oligo(ethylene glycol) side-chain to optimize σ is reported here. Three polymers show a monotonic electron mobility decrease as side-chain size increasing due to the gradually lowered film crystallinity and change of backbone orientation. Interestingly, polymer PO12 with a moderate side-chain size delivers a champion σ up to 92.0 S cm-1 and a power factor (PF) as high as 94.3 µW m-1 K-2 in the series when applied in OTE devices. The PF value is among the highest ones for the solution-processing n-doped polymers. In-depth morphology studies unravel that the moderate crystallinity and the formation of 3D conduction channel derived from bimodal orientation synergistically contribute to high doping efficiency and large charge carrier mobility, thus resulting in high performance for the PO12-based OTEs. The results demonstrate the great power of simple tuning of side chain in developing n-type polymers with substantial σ for improving organic thermoelectric performance.

Efficient N-Type Organic Electrochemical Transistors and Field-Effect Transistors Based on PNDI-Copolymers Bearing Fluorinated Selenophene-Vinylene-Selenophenes.

n-Type organic electrochemical transistors (OECTs) and organic field-effect transistors (OFETs) are less developed than their p-type counterparts. Herein, polynaphthalenediimide (PNDI)-based copolymers bearing novel fluorinated selenophene-vinylene-selenophene (FSVS) units as efficient materials for both n-type OECTs and n-type OFETs are reported. The PNDI polymers with oligo(ethylene glycol) (EG7) side chains P(NDIEG7-FSVS), affords a high µC* of > 0.2Fcm-1 V-1 s-1 , outperforming the benchmark n-type Pg4NDI-T2 and Pg4NDI-gT2 by two orders of magnitude. The deep-lying LUMO of -4.63eV endows P(NDIEG7-FSVS) with an ultra-low threshold voltage of 0.16V. Moreover, the conjugated polymer with octyldodecyl (OD) side chains P(NDIOD-FSVS) exhibits a surprisingly low energetic disorder with an Urbach energy of 36meV and an ultra-low activation energy of 39meV, resulting in high electron mobility of up to 0.32cm2 V-1 s-1 in n-type OFETs. These results demonstrate the great potential for simultaneously achieving a lower LUMO and a tighter intermolecular packing for the next-generation efficient n-type organic electronics.

An easy route for preparation of carboxylic acid and urea functional block copolymer as corrosion inhibitor

A novel POEGMA-b-(PMEEU-co-PMAA) (poly(oligo(ethylene glycol) methacrylate)-b-poly((methacrylamidoethyl) ethylene urea)-co-poly(methacrylic acid) block copolymer has been synthesized by RAFT polymerization as a corrosion inhibitor. Structural characterization of the block copolymer was done by FTIR, 13C NMR and 1H NMR spectroscopic techniques. The carboxylic acid and cyclic urea units on the block copolymer exert a synergistic effect on corrosion inhibition through chelating of the metal ions or adsorption to the metal surface. Corrosion inhibition of SAE 1012 carbon steel in a 1 M HCl medium has been investigated in the presence of 5 mM polymer using both experimental (electrochemical impedance spectroscopy, Tafel polarization (TP), weight loss) and theoretical approaches. Also, SAE 1012 carbon steel surface morphology changes were followed by energy dispersive X-ray spectroscopy and scanning electron microscopy. Electrochemical techniques indicated that the presence of PMEEU-co-PMAA segments of the polymer in the acid solution inhibits corrosion of SAE 1012 carbon steel. The inhibition efficiency of the polymer was found to be about 85%. According to TP studies, PMEEU-co-PMAA segment acts as a mixed type corrosion inhibitor. The adsorption of PMEEU-co-PMAA molecules onto the metal surface follows Langmuir adsorption isotherm. The K ads value calculated from the equilibrium constant of the adsorption process reflects a strong interaction. SEM and EDAX studies provide evidence of PMEEU-co-PMAA adsorption on the metal surface.

Effect of amphiphilic copolymers of oligo(ethylene glycol)methacrylates on the synthesis of N-(dibutylaminomethyl)methacrylamide in an aqueous-organic emulsion

The accelerating effect of adding a low molecular weight sulfonic acid surfactant (alkylbenzenesulfonic acid) and nonionic or containing sulfonic acid units amphiphilic copolymers of methoxy- and higher alkoxyoligo(ethylene glycol)methacrylates on the synthesis of a promising cationic monomer, N-(dibutylaminomethyl)methacrylamide, proceeding in an aqueous-amine emulsion, by the Mannich reaction, was revealed. The infl uence of the concentration of additives and the structure of copolymers on the catalytic effect is shown.

An amphiphilic near-infrared Mn,O-chelated metallo-azadipyrromethene dye: Synthesis, acid-responsive properties, and aggregation pathway control

A new amphiphilic Mn,O-chelated azadipyrromethene dye 1 bearing dodecyl chains at the 1,7-phenyls and oligo(ethylene glycol) chains at the 3,5-phenyls was synthesized and characterized. The dye 1 exhibited an absorption maximum in NIR at 823 nm, which is largely bathochromically shifted as compared with the known aza-BODIPY as well as the B,O-chelated aza-BODIPY dyes. Meanwhile, the electrochemical studies of this dye indicated a lower HOMO-LUMO gap in comparison with the boron-chelated analogues. This dye also displayed the acid-responsive properties, as indicated by the hypsochromical shift of ca. 94 nm of the absorption band as well as the occurrence of fluorescence emission at 751 nm upon adding trifluoroacetic acid (TFA) into the dye 1 solution. Moreover, in highly polar solvent MeOH the amphiphilic dye 1 self-assembled into H-type aggregates, which exhibited a fibrous morphology in AFM studies. Further temperature-dependent UV/Vis absorption spectroscopic studies revealed a cooperative aggregation mechanism of dye 1 in MeOH. Based on the acid-responsive properties of 1, a method of control of the aggregation pathway of dye 1 by using acid and base was proposed and demonstrated by UV/Vis spectroscopic studies.