Truxene Units Research Articles

Truxene-Based Porous Triazole-Linked Polymers for Dye Removal through Synergetic Adsorption and Photodegradation

Two high surface area porous polymers (TxTri and PhTxTri) consisting of semiconducting truxene units connected through triazole nodes have been synthesized via Cu(I)-catalyzed azide–alkyne click polymerization, and their ability to remove different organic dyes (Nile blue, Rhodamine B, and Methyl orange) from aqueous solutions has been investigated. The presence of triazole moieties in the polymer walls, capable of binding guest molecules through different intermolecular interactions (such as dipole–dipole interactions, hydrogen bonding, and π–π interactions), is expected to benefit dye capture. We have found that these materials show a high adsorption capacity toward cationic dyes (reaching values as high as 1562 mg g–1 for Nile blue). This preference is probably due to the high electron density of the polymeric networks, which will favor electrostatic interactions with electron-deficient dyes. Interestingly, owing to the semiconducting nature of the truxene units, these polymers also act as photocatalysts in the oxidative degradation of the dyes, allowing for easy recovery and reuse of the polymers without the need for additional cleaning steps to remove trapped dyes. This interesting adsorption/photodegradation synergy represents a huge advantage compared to common dye adsorbents and makes them promising candidates for water remediation.

Truxene-BODIPY dyads and triads: Synthesis, spectroscopic characterization, one and two-photon absorption properties and electrochemistry

Eight green and blue BODIPY dyes, substituted by diverse truxene units, have been synthesized and fully characterized by HRMS and NMR spectroscopy as well as electrochemistry to determine their redox properties. Different substituents such as bromine, thiophene and ethynylthiophene were introduced at the 7,12-positions of the truxene units to further extend the conjugation pathway and increase their TPA properties. Their linear (one photon) and non-linear (two-photon) photophysical properties were also carefully investigated.

Chiral Self-Sorting in Truxene-Based Metallacages

Two chiral face-rotating metalla-assembled polyhedra were constructed upon self-assembling achiral components, i.e., a tritopic ligand based on a truxene core (10,15-dihydro-5H-diindeno[1,2-a;1′,2′-c]fluorene) and two different hydroxyquinonato–bridged diruthenium complexes. Both polyhedra were characterized in solution as well as in the solid state by X-ray crystallography. In both cases, the self-sorting process leading to only two homo-chiral enantiomers was governed by non-covalent interactions between both truxene units that faced each other.

Insight into the positional effect of bulky rigid substituents in organic sensitizers on the performance of dye-sensitized solar cells

Bulky rigid substituents, featuring distinctive steric configuration and interesting electronic properties, play an important role in advancing performance of metal-free sensitizers toward dye-sensitized solar cells (DSSCs). However, the question about how to choose the relative position of bulky substituent for optimum device performance remains unclear, which necessitates understanding the structure-property relationship of organic sensitizers. In this work, two new isomeric dyes, W09 and W10, are designed to study the role of bulky rigid truxene unit which locates at the π-bridge and electron-donor, respectively. The comparative effects of truxene position on the optical properties, interfacial kinetic parameters and their synergistic contribution to the photovoltaic performance have been systematically investigated. A significantly improved molar absorption coefficient accompanied with a larger driving force for dye regeneration is obtained for W10 relative to those of W09, manifesting the effect of changing the truxene location. Combined with the slower charge recombination kinetics at the TiO2/dye/electrolyte interface, W10 sensitized solar cells exhibit the highest conversion efficiency of 7.62%, which is around 20% higher than that of W09. This work has demonstrated the feasibility of judiciously locating bulky rigid substituents into the right position to construct highly-efficiency metal-free sensitizers.

Efficient energy transfer in a tri-chromophoric dyad containing BODIPYs and corrole based on a truxene platform

A star-shaped molecule was designed and synthesized based on a known central truxene platform. Two BODIPY derivatives and one corrole macrocycle were introduced and connected to the 2, 7 and 12-positions of the truxene unit by Suzuki coupling. The dyad was fully characterized by UV-vis absorption, proton nuclear magnetic resonance, mass spectrometry. The direction of energy transfer upon electronic excitation was explored, and the star-shaped molecule system exhibits a highly efficient photoinduced energy transfer process from the excited BODIPY part to the corrole unit.

8.0% Efficient all-polymer solar cells based on novel starburst polymer acceptors

The polymer N2200, with its π-conjugated backbone composed of alternating naphthalene diimide (NDI) and bithiophene (DT) units, has been widely used as an acceptor for all-polymer solar cells (all-PSCs) owing to its high electron mobility and suitable ionization potential and electron affinity. Here, we developed two naphthalene diimide derivatives by modifying the molecular geometry of N2200 through the incorporation of a truxene unit as the core and NDI-DT as the branches. These starburst polymers exhibited absorption spectra and molecular orbital energy levels that were comparable to N2200. These copolymers were paired with the wide-bandgap polymer donor PTzBI-O to fabricate all-polymer solar cells (all-PSCs), which displayed impressive power conversion efficiencies up to 8.00%. The improved photovoltaic performances of all-PSCs based on these newly developed starburst acceptors can be ascribed to the combination of increased charge carrier mobilities, reduced bimolecular recombination, and formation of more favorable film morphology. These findings demonstrate that the construction of starburst polymer acceptors is a feasible strategy for the fabrication of high-performance all-PSCs.

Truxene-Based Hyperbranched Conjugated Polymers: Fluorescent Micelles Detect Explosives in Water.

We report two hyperbranched conjugated polymers (HCP) with truxene units as core and 1,4-didodecyl-2,5-diethynylbenzene as well as 1,4-bis(dodecyloxy)-2,5-diethynylbenzene as comonomers. Two analogous poly(para-phenyleneethynylene)s (PPE) are also prepared as comparison to demonstrate the difference between the truxene and the phenyl moieties in their optical properties and their sensing performance. The four polymers are tested for nitroaromatic analytes and display different fluorescence quenching responses. The quenching efficiencies are dependent upon the spectral overlap between the absorbance of the analyte and the emission of the fluorescent polymer. Optical fingerprints are obtained, based on the unique response patterns of the analytes toward the polymers. With this small sensor array, one can distinguish nine nitroaromatic analytes with 100% accuracy. The amphiphilic polymer F127 (a polyethylene glycol-polypropylene glycol block copolymer) carries the hydrophobic HCPs and self-assembles into micelles in water, forming highly fluorescent HCP micelles. The micelle-bound conjugated polymers detect nitroaromatic analytes effectively in water and show an increased sensitivity compared to the sensing of nitroaromatics in organic solvents. The nitroarenes are also discriminated in water using this four-element chemical tongue.

Yellow emitting materials: Truxene-based conjugated hyperbranched polymer containing difluoroboron-diketonate complexes

A series of novel hyperbranched polymers BF2-HP(1–4) containing difluoroboron-diketonate complexes and truxene units have been synthesized. To achieve the target polymers, the precursors Boc-HP(1–4) were obtained through the Pd (0)-catalyzed Suzuki polymerization with an “A2 + B3” or “A2 + B2 + B3” approach in different molar ratios. After the deprotection of Boc-groups, the reaction with BF3 gave the polymers BF2-HP(1–4). The new BF2 containing polymers exhibited red-shifts in their UV–vis absorption and emission compared with their uncomplexed counterparts. The tunable hyperbranched architectures of BF2-HP(1–4) resulted in diverse optical properties. With the decrease of linear units in BF2-HP(1–4), the emission peaks in chloroform solution presented a significant blue-shift, whereas a red-shift was noted in films. Notably, the hyperbranched architectures could suppress the aggregation more effectively than the linear architectures not only in poor solvents such as DMF but also in the film states. In addition, these polymers showed high thermal stability, and good solubility in common organic solvents.

Assembled molecular face-rotating polyhedra to transfer chirality from two to three dimensions.

In nature, protein subunits on the capsids of many icosahedral viruses form rotational patterns, and mathematicians also incorporate asymmetric patterns into faces of polyhedra. Chemists have constructed molecular polyhedra with vacant or highly symmetric faces, but very little is known about constructing polyhedra with asymmetric faces. Here we report a strategy to embellish a C3h truxene unit with rotational patterns into the faces of an octahedron, forming chiral octahedra that exhibit the largest molar ellipticity ever reported, to the best of our knowledge. The directionalities of the facial rotations can be controlled by vertices to achieve identical rotational directionality on each face, resembling the homo-directionality of virus capsids. Investigations of the kinetics and mechanism reveal that non-covalent interaction among the faces is essential to the facial homo-directionality.

Synthesis of Conjugated Hyperbranched Polytriazoles Containing Truxene Units by Click Polymerization

AbstractIt has been a challenge to synthesize high molecular weight and soluble conjugated hyperbranched poly(1,2,3‐triazole)s (hb‐PTAs). In this paper a series of soluble hyperbranched polytriazoles, whose number‐average molecular weight (Mn) and polydispersity index ranged in (1.2–3.3)×104 and 1.7–3.0, respectively, were synthesized with A2+B3 approach. In the polymerization process, diazides A1–A4 and triyne B1 were used as A2 and B3 monomers; Cu(I)‐catalyst, THF and water were used as their reaction system. At room temperature the final molecular weight could be controlled through reaction time, so finally we obtained soluble conjugated hyperbranched poly(1,2,3‐triazole)s hb‐PTAs (1–4). The polymers were soluble in common organic solvents, and all emitted blue light; the films of polymers emitted yellow and blue light, due to the difference in the aggregation of their chromophoric units in the solid state. The thermal properties of the final copolymers were analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Efficient dye-sensitized solar cells with triarylamine organic dyes featuring functionalized-truxene unit

Four triarylamine organic dyes featuring functionalized-truxene unit ( MXD1– 4) have been designed, synthesized, and characterized. It was found that these dyes favored light harvesting, prevented dye aggregation and suppressed the dark current significantly in dye-sensitized solar cells (DSSCs), leading to enhanced performance compared to the corresponding triphenylamine dye. As a result of retarding charge recombination benefiting from the steric hindrance of truxene units, high open circuit voltages (740–772 mV) were achieved based on the as-synthesized dyes. For a typical device a maximum power conversion efficiency of 6.04% was obtained under simulated AM 1.5 irradiation (100 mW cm −2) with J sc = 11.5 mA cm −2, V oc = 772 mV, and ff = 0.68.

Energy Transfer Dynamics in Multichromophoric Arrays Engineered from Phosphorescent PtII/RuII/OsII Centers Linked to a Central Truxene Platform

A rigid star-shaped tetrachromophoric trimetallic complex engineered from a 5,5',10,10',15,15'-hexabutyltruxene platform functionalized in the 2,7,12 positions with three different metal centers, namely, a terpyridine-Pt(II) ethynylene unit and Ru(II) and Os(II) bipyridine centers, was synthesized in a controlled fashion and characterized by (1)H NMR and mass spectrometry. The protocol was devised in such a way that key mono and dinuclear model complexes and two reference truxene ligands could also be prepared. Room temperature (RT) optical absorption and RT and 77 K luminescence studies were performed on the truxene ligands, the trimetallic species, the various mono- and binuclear complexes and precursors lacking the truxene fragment; RT nanosecond transient absorption measurements were also carried out in particular cases. The electronic properties of the Ru and Os subunits in the arrays were found to be unaffected by the presence of the truxene core whereas direct linking of the Pt subunit to the truxene via the σ-alkyne bond markedly influences the spectroscopic behavior of the Pt center. Remarkably the truxene phosphorescence was clearly established in the two ligands (lifetime of 4.3 s for the mono ethynyl-bipy substituted truxene and 17.5 ms for the bis ethynyl-bipy substituted truxene) and also detected in the Pt-containing complexes PtL' (model Pt-truxene) and Pt-Os (Pt-truxene-Os dyad) at low temperature. This is attributed to the closeness in energy of the Pt (3)CT level and the truxene triplet at low temperature and to the spin-orbit coupling induced by the Pt heavy atom. Transient absorbance measurements evidenced the population of the Pt-based triplet in the Pt-truxene mononuclear complex PtL' at room-temperature. For the trimetallic complex, where the various centers exhibit an energy gradient for the local excited levels, and following an approach based on the use of selected excitation of the components, an initial energy transfer was found to occur from the central truxene unit toward the peripheral Pt, Ru, and Os metal-based centers. Subsequent Pt-based and Ru-based excited state depletion contributes to the final sensitization of the low-lying Os triplet excited state; the excited state dynamics for these multicascade processes are examined in detail.

Pure Blue-Light-Emitting Materials: Hyperbranched Ladder-Type Poly(p-phenylene)s Containing Truxene Units

A series of novel hyperbranched ladder-type poly(p-phenylene)s containing truxene units have been prepared through the Pd(0)-catalyzed Suzuki polymerization with an “A2 + B3” or “A2 + B2+ B3” approach. The polymers with different linear length show pure blue light emission from 417 to 465 nm. All the ladder-type polymers exhibit well-resolved absorption and emission spectra and small Stokes shifts in both solutions and thin films, which are the characteristics of full ladder-type poly(p-phenylene)s. The three-dimensional structures make the materials soluble in common organic solvents and able to form quality amorphous films, leading to polymer light-emitting diodes (PLEDs) with improved stability and efficiency.

A Mechanically Interlocked [3]Rotaxane as a Light‐Harvesting Antenna: Synthesis, Characterization, and Intramolecular Energy Transfer

A mechanically interlocked light-harvesting system [3]rotaxane A has been synthesized in high yield through Cu(I)-catalyzed azide-alkyne cycloaddition; the hexyl-substituted truxene units are introduced into the wheels as donors and an oligo(para-phenylenevinylene) (OPV) unit into the axis as the acceptor. The structure and the purity of [3]rotaxane A were confirmed by (1)H and (13)C NMR spectroscopy and ESI HRMS. The azide-alkyne cycloaddition is demonstrated to be an efficient stoppering method in the synthesis of the rotaxane containing dibenzo[24]crown-8 and dibenzyl ammonium units. Detailed steady-state UV/Vis absorption, photoluminescent, and time-resolved fluorescence spectroscopy were performed to investigate the photophysical properties of [3]rotaxane A and its reference compounds in solution and as thin films. Even in dilute solution, efficient energy transfer from the truxene-functionalized wheels to the OPV-based axis, through the dibenzo[24]crown-8 and dibenzyl ammonium interaction, is observed in [3]rotaxane A. The unique topology of [3]rotaxane A not only efficiently promotes the intramolecular energy-transfer process, but also prevents intermolecular aggregation in the solid state. The new antenna system opens up the possibility of controllable light-harvesting molecular machines or other optoelectronic devices on the nanometer scale.

Molecular Wires Based on Thienylethynylene: Synthesis, Photophysical Properties, and Excited-State Lifetime

A series of pi-conjugated molecular wires based on thienylethynylene units have been developed to understand the effect of the molecular structures on their photophysical properties. The investigation of their photophysical properties indicates that the formation of aggregates at the ground state is effectively suppressed by the incorporation of truxene units. The excited-state lifetimes are observed to be biexponential for these molecular wires.

Star-shaped oligo( p-phenylene)-functionalized truxenes as blue-light-emitting materials: synthesis and the structure–property relationship

In this contribution, we described a strategy to prepare a series of well-defined, blue-light-emitting materials with truxene unit as the core and oligo( p-phenylene) (from one to four phenyl units) as the branches. The Suzuki coupling reactions between truxene bromide derivatives and phenylboronic acid or 1,1′-biphenyl-4-boronic acid catalyzed by Pd(0) afforded the desired compounds Tr-1-Ph, Tr-2-Ph, Tr-3-Ph and Tr- 4-Ph. With stepwise increases of the benzene rings, the desired molecules exhibited exceptional photophysical properties as well as increasing thermal stability. T gs increased from 39 °C for Tr-1-Ph to 192 °C for Tr-4-Ph. The absorption and the emission maximum peaks of these four compounds were red-shifted from the ultraviolet to the blue region with the increase of effective conjugation length. All results demonstrated that the physical properties were facilely tuned by connecting different types and different conjugated lengths to C-2, C-7, and C-12 positions of the truxene core.