Showing papers on "Alkoxy group published in 2022"

High‐Performance All‐Small‐Molecule Organic Solar Cells Enabled by Regio‐Isomerization of Noncovalently Conformational Locks

Abstract: The power conversion efficiencies (PCEs) of organic solar cells (OSCs) have surpassed 19% thanks to the innovation of polymer donors and molecular acceptors. However, the batch‐to‐batch variations in polymer materials are detrimental to the reproducibility of the device performance. In comparison, small‐molecule donors (SMDs) possess some unique advantages, such as well‐defined molecular weights, easy purification, and excellent batch‐to‐batch repeatability. Herein, a pair of regioisomeric SMDs (BT‐O1 and BT‐O2) has been synthesized with alkoxy groups as S···O noncovalently conformational locks (NoCLs) at the inner and outer position, respectively. Theoretical and experimental results reveal that the regioisomeric effect has a significant influence on the light‐harvest ability, energy levels, molecular geometries, internal reorganization energy, and packing behaviors for the two SMDs. As a result, BT‐O2‐based binary device shows an impressive PCE of 13.99%, much higher than that of BT‐O1 based one (4.07%), due to the better‐aligned energy level, more balanced charge transport, less charge recombination, lower energy loss, and more favorable phase separation. Furthermore, the fullerene derivative PC71BM is introduced into BT‐O2:H3 as the third component to achieve a notable PCE of 15.34% (certified 14.6%). Overall, this work reveals that NoCLs is a promising strategy to achieve high‐performance SMDs for all‐small‐molecule OSCs.

Regioselective Ring-Opening of Spiro-Epoxyoxindoles by a Dual-Ligand Zinc-Based Metal–Organic Framework as an Efficient Heterogeneous Catalyst

Abstract: Developing a heterogeneous catalyst for alcoholysis/hydrolysis of spiro-epoxyoxindoles to form β-alkoxy/β-hydroxy alcohols is an emerging and promising research area in the academia and industry due to its importance in the pharmaceutical industry. In this work, a chiral-phase pure Zn-based metal–organic framework (MOF), {[Zn2(D-CAM)2(L)]·MeOH·2H2O}n (ADES-6), has been constructed from mixed organic ligands involving D(+)-camphoric acid (D-H2CAM) and an amide-functionalized N-donor ligand ((E)-N′-(pyridin-4-ylmethylene)isonicotinohydrazide (L)) through versatile synthetic modes and characterized by different analytical techniques along with single-crystal X-ray diffraction (SXRD) analysis. The catalytic activity reveals that the prepared ADES-6 MOF could be exploited as a heterogeneous catalyst for regioselective ring-opening of different spiro-epoxyoxindoles to form β-alkoxy/β-hydroxy/β-chloro alcohols efficiently in the presence of appropriate nucleophiles. Furthermore, ADES-6 displays excellent activity for diverse substrates and can be reused in at least five successive cycles without significant reduction in activity. Mechanistic explorations indicate that the high efficiency of ADES-6 is attributed to the presence of a vacant Lewis acidic metal center, and an amide group of the ligand L in the framework as a Lewis basic site can synergistically activate the catalytic reaction. Importantly, ADES-6 behaved as one of the rare first main-group MOF-based catalysts reported in the ring-opening of spiro-epoxyoxindoles efficiently and few catalytic products are validated unambiguously by SXRD analysis.

Branched Alkoxy Side Chain Enables High-Performance Non-Fullerene Acceptors with High Open-Circuit Voltage and Highly Ordered Molecular Packing

Abstract: The linear alkyl chains on the β-position of the thieno[3,2-b]thiophene units of Y6 play a critical role in determining the molecular properties of non-fullerene acceptors (NFAs) and device performance of the corresponding organic solar cells (OSCs). This linear chain can be substituted with either alkoxy or branched alkyl side chains, which are two common strategies to modify the property of Y6-type molecules. In this paper, we use a combination of these two strategies by using branched alkoxy side chains to modify Y6 and develop a new NFA named Y6-O2BO. Interestingly, this branched alkoxy substitution introduces different effects from previously used branched alkyl or linear alkoxy modifications. More ordered molecular packing and enhanced crystallinity are observed for Y6-O2BO-based blend films, which should be beneficial for charge carrier transportation. The Y6-O2BO-based device exhibits a much enhanced open-circuit voltage (VOC) compared to those based on linear alkoxy or branched alkyl chain substituted molecules. By using a mixture of Y6 and Y6-O2BO, the VOC of ternary devices can be linearly tuned between 0.84 and 0.96 V based on the ratio of these two acceptors. As a result, the optimal OSC yields an improved VOC of 0.88 V and a high FF of 0.79, leading to a maximum efficiency of 17.5%. This reveals the effectiveness of branched alkoxy chains in elevating VOC and further optimizing the performance of OSCs.

Anthracene‐Bridged Sensitizers for Dye‐Sensitized Solar Cells with 37% Efficiency under Dim Light

Abstract: New anthracene‐bridged organic dyes CXC12 and CXC22 are designed and synthesized for high‐efficiency dye‐sensitized solar cells (DSSCs) under dim light. Compared to their parent dye TY6, CXC dyes have additional anthracene‐acetylene group to extend the π‐conjugation of the molecules, resulting in red‐shifted absorption and an enhanced molar extinction coefficient. The absorption spectra of CXC12 and CXC22 with a maximum located at 561 and 487 nm, respectively, match to those of AM 1.5G sunlight and T5 fluorescent light better than that of TY6 (419 nm). It was initially anticipated that long alkoxyl chains introduced to the 2,6‐position of the bridged anthracenyl in CXC12 will retard charge recombination and dye molecular aggregation, and achieve a higher device open‐circuit voltage. However, adsorption of CXC12 molecules on the photoanode dramatically decrease to less than half as compared to that of CXC22 and TY6, resulting in lower short‐circuit current and thus power conversion efficiency. Among these three anthracene‐based dyes, CXC22 has the most appropriate molecular structure for light harvesting and striking the balance between dye loading and molecular aggregation, to exhibit a remarkable power conversion efficiency as high as 37.07% under dim‐light. Therefore, this work shows the potential of anthracene‐bridged organic dyes for indoor photovoltaic applications.

Tacticity Control of Cyclic Poly(3-Thiobutyrate) Prepared by Ring-Opening Polymerization of Racemic β-Thiobutyrolactone.

Abstract: We report here on the ring-opening polymerization (ROP) of racemic β-thiobutyrolactone (rac-TBL), as the first chemical synthesis of poly(3-thiobutyrolactone) (P3TB), the thioester analogue of the ubiquitous poly(3-hydroxybutyrate) (P3HB). The ROP reactions proceed very fast (TOF > 12,000 h-1 at r.t.) in the presence of various metal-based catalysts. Remarkably, catalyst systems based on non-chiral yttrium complexes stabilized by tetradentate amino alkoxy- or diamino-bis(phenolate) ligands {ONXOR1,R2}2- (X = O, N) provide access to cyclic P3TB with either high isoselectivity (Pm up to 0.90) or high syndiotactic bias (Pr up to 0.70). The stereoselectivity can be controlled by manipulation of the substituents on the ligand platform and adequate choice of the reaction solvent and temperature as well. The cyclic polymer topology is evidenced by MALDI-ToF MS, NMR and TGA. Highly isotactic cyclic P3TB is a semi-crystalline material as revealed by DSC.

PTB7-Th-Based Organic Photovoltaic Cells with a High VOC of over 1.0 V via Fluorination and Side Chain Engineering of Benzotriazole-Containing Nonfullerene Acceptors.

Abstract: PTB7-Th is considered one of the most classic donor polymers for organic photovoltaic (OPV) cells. However, the power conversion efficiency (PCE) of PTB7-Th-based OPV is lagging behind that of other promising polymers mainly because of the relatively low open-circuit voltage (VOC). To increase the VOC and PCE of PTB7-Th-based OPV, the development of nonfullerene acceptors (NFAs) and studies of structure-property-performance relationship are vital. Here, three A2-A1-D-A1-A2-type acceptors, namely BTA45, F-BTA45, and F-BTA5, were developed by fluorination on the benzotriazole (BTA) unit and regulating alkoxy or alkyl phenyl side chains. Compared with BTA45, light absorption and π-π packing can be simultaneously improved for the two fluorinated BTA acceptors, resulting in an increased JSC and FF. Moreover, the F-BTA5-based blend film exhibits better phase separation morphology and electron transport than those of BTA45 and F-BTA45, which contribute to a device efficiency of 10.36% with a VOC of 1.03 V. In addition, the ΔE2 values of the three blends are less than 0.15 eV, together with their moderate ΔE3, efficiently decreasing their energy loss. These results highlight the importance of fluorination and side chain engineering for NFAs to boost the VOC and PCE for low-band gap photovoltaic polymers.

Mesophase behavior of four ring ester/azomethine/ester liquid crystals in pure and mixed states

Abstract: ABSTRACT New four-ring ester/azomethine/ester liquid crystal series, 4-alkoxybenzoyloxy 4’-phenylazomethine phenyloxy 4”-alkoxybenzoate I n, were prepared, and their thermal stability and mesomorphic activity were investigated. The two wing carboxylic units were used aiming to achieve new mesomorphic properties for the prepared materials. The two ester linkages and the two terminal alkoxy chains were incorporated to modify the molecular structure. The chemical structures of the synthesised compounds were confirmed via FT-IR, NMR and elemental analysis. Differential scanning calorimetry (DSC) and polarising optical microscopy were applied to determine the mesomorphic features of the designed homologues. All of the studied homologous were shown to exhibit superior thermal stability and enormous mesomorphic temperature ranges. Moreover, enantiotropic smectic A and nematic phases were shown to cover all of the homologues. The influence of inclusion the di-ester moieties on the mesophase behaviour was investigated through a comparison with the previously investigated three-ring series bearing only one ester linkage. Two binary phase diagrams were constructed and addressed in terms of the smectic and nematic temperature ranges.

Identification of Alkoxy Radicals as Hydrogen Atom Transfer Agents in Ce-Catalyzed C-H Functionalization.

Abstract: The intermediacy of alkoxy radicals in cerium-catalyzed C-H functionalization via H-atom abstraction has been unambiguously confirmed. Catalytically relevant Ce(IV)-alkoxide complexes have been synthesized and characterized by X-ray diffraction. Operando electron paramagnetic resonance and transient absorption spectroscopy experiments on isolated pentachloro Ce(IV) alkoxides identified alkoxy radicals as the sole heteroatom-centered radical species generated via ligand-to-metal charge transfer (LMCT) excitation. Alkoxy-radical-mediated hydrogen atom transfer (HAT) has been verified via kinetic analysis, density functional theory (DFT) calculations, and reactions under strictly chloride-free conditions. These experimental findings unambiguously establish the critical role of alkoxy radicals in Ce-LMCT catalysis and definitively preclude the involvement of chlorine radical. This study has also reinforced the necessity of a high relative ratio of alcohol vs Ce for the selective alkoxy-radical-mediated HAT, as seemingly trivial changes in the relative ratio of alcohol vs Ce can lead to drastically different mechanistic pathways. Importantly, the previously proposed chlorine radical-alcohol complex, postulated to explain alkoxy-radical-enabled selectivities in this system, has been examined under scrutiny and ruled out by regioselectivity studies, transient absorption experiments, and high-level calculations. Moreover, the peculiar selectivity of alkoxy radical generation in the LMCT homolysis of Ce(IV) heteroleptic complexes has been analyzed and back-electron transfer (BET) may have regulated the efficiency and selectivity for the formation of ligand-centered radicals.

Wide Nematogenic Azomethine/Ester Liquid Crystals Based on New Biphenyl Derivatives: Mesomorphic and Computational Studies

Abstract: The thermal stability and mesomorphic behavior of a new biphenyl azomethine liquid crystal homologues series, (E)-4-(([1,1′-biphenyl]-4-ylmethylene)amino)phenyl 4-(alkoxy)benzoate, In, were investigated. The chemical structures of the synthesized compounds were characterized using FT-IR, NMR, and elemental analyses. Differential scanning calorimetry (DSC) and polarized optical microscopy were employed to evaluate the mesomorphic characteristics of the designed homologues. The examined homologues possessed high thermal stability and broad nematogenic temperature ranges. Furthermore, the homologues were covered by enantiotropic nematic phases. The experimental measurements of the mesomorphic behavior were substantiated by computational studies using the density functional theory (DFT) approach. The reactivity parameters, dipole moments, and polarizability of the studied molecules are discussed. The theoretical calculations demonstrated that as the chain length increased, the polarizability of the studied series increased; while it did not significantly affect the HOMO–LUMO energy gap and other reactivity descriptors, the biphenyl moiety had an essential impact on the stability of the possible geometries and their thermal as well as physical parameters.

Efficient Dye-Sensitized Solar Cells Based on a New Class of Doubly Concerted Companion Dyes.

Abstract: To develop efficient dye-sensitized solar cells (DSSCs), concerted companion (CC) dyes XW60-XW63 constructed from the covalent linkage of a strapped porphyrin dye unit and an organic dye unit have been reported to exhibit panchromatic absorption and excellent photovoltaic performance. However, these CC dyes only afforded moderate VOC values of ca. 763 mV, demonstrating relatively weak antiaggregation ability, which remains an obstacle for further enhancing the photovoltaic behavior. To address this problem, we herein develop porphyrin dyes XW77-XW80 with the macrocycles wrapped with alkoxy chains of various lengths (OC6H13-OC22H45) and the corresponding CC dyes XW81-XW84 containing these porphyrin dye units. Interestingly, the new CC dyes XW81-XW83 exhibit increasing VOC from 745 to 784 mV with the chain lengths extended from C6 to C18, and a lowered VOC of 762 mV was obtained for XW84 when the chain length was further extended to C22. As a result, XW83 afforded the highest PCE of 12.2%, which is, to the best of our knowledge, the record efficiency for the iodine electrolyte-based solar cells sensitized with a single dye. These results can be rationalized by the so-called doubly concerted companion (DCC) effects, that is, the two subdye units exhibit not only complementary absorption but also concerted antiaggregation with the long wrapping chains on the porphyrins unit simultaneously protecting the porphyrin macrocycle and the neighboring organic subdye unit, thus affording panchromatic absorption and strong antiaggregation and anticharge-recombination ability. These results provide a new approach for constructing a class of DCC dyes to achieve high-performance DSSCs without using any antiaggregating coadsorbent or absorption-enhancing cosensitizer.

Radical Activation of N–H and O–H Bonds at Bismuth(II)

Abstract: The development of unconventional strategies for the activation of ammonia (NH3) and water (H2O) is of capital importance for the advancement of sustainable chemical strategies. Herein we provide the synthesis and characterization of a radical equilibrium complex based on bismuth featuring an extremely weak Bi–O bond, which permits the in situ generation of reactive Bi(II) species. The ensuing organobismuth(II) engages with various amines and alcohols and exerts an unprecedented effect onto the X–H bond, leading to low BDFEX–H. As a result, radical activation of various N–H and O–H bonds—including ammonia and water—occurs in seconds at room temperature, delivering well-defined Bi(III)-amido and -alkoxy complexes. Moreover, we demonstrate that the resulting Bi(III)–N complexes engage in a unique reactivity pattern with the triad of H+, H–, and H• sources, thus providing alternative pathways for main group chemistry.

Alkoxy Substitution on Asymmetric Conjugated Molecule Enabling over 18% Efficiency in Ternary Organic Solar Cells by Reducing Nonradiative Voltage Loss

Abstract: A ternary strategy is considered to be an efficient and simple way to further enhance the performance of organic photovoltaics (OPVs). However, the “structure–performance” correlation of the third component in the ternary device has rarely been clearly understood from the aspect of the material’s eigenproperties. Herein, this relationship is investigated in depth by employing three asymmetric skeleton nonfullerene acceptors as the third component in the host system of PM6:BTP-eC9, respectively. Compared with TB-S and TB-S1, the alkoxy-substituted TB-S1-O possesses a more stable planar conformation, a higher surface energy, and a larger ordered stacking domain due to the existence of noncovalent conformational locking (O···H). Consequently, the PM6:BTP-eC9:TB-S1-O device exhibits the highest efficiency of 18.14% as compared with the devices based on PM6:BTP-eC9:TB-S (16.16%) and PM6:BTP-eC9:TB-S1 (16.18%). Most interestingly, only the PM6:BTP-eC9:TB-S1-O device can maintain the positive effect of VOC improvement, because a significant reduction in nonradiative voltage loss can be observed in this device. Our systematic study reveals that alkoxy substitution on an asymmetric backbone is an efficient method to construct the third component for high-performance ternary organic solar cells.

Effects of Oxygen Position in the Alkoxy Substituents on the Photovoltaic Performance of A-DA′D-A Type Pentacyclic Small Molecule Acceptors

Abstract: In this work, we explore the reason that the alkoxy substituent on the terminal thiophene in a fused DA′D unit results in an abnormal blue-shifted absorption of A-DA′D-A type small molecule acceptors (SMAs), and we further propose a simple molecular strategy of altering the oxygen position along the alkoxy side chains to fine-tune the optoelectronic properties. By replacing the n-hexyl side chains of our previously reported pentacyclic acceptor Y26 (BZ4F) with hexyoxyl groups and moving the oxygen atom to the second and third positions along the alkoxy chains, we synthesize BZ4F-O-1, BZ4F-O-2, and BZ4F-O-3. BZ4F-O-1 shows blue-shifted absorption, while BZ4F-O-2 and BZ4F-O-3 exhibit red-shifted absorption. Using PM6 as the polymer donor, the BZ4F-O-3 based device achieves a favorable efficiency of 14.69%. This is the first work to study the effects of the oxygen position along the alkoxy side chains on the photovoltaic performance of the A-DA′′D-A type SMAs, which can provide important guidance toward future molecular design.

Regioselective C–H Alkylation of Aromatic Ethers with Alkenes by a Half-Sandwich Calcium Catalyst

Abstract: The catalytic ortho-regioselective C–H alkylation of a variety of alkoxy-substituted benzene derivatives with alkenes can be achieved by the use of a half-sandwich calcium alkyl complex [(CpAr5)Ca{CH(SiMe3)2}(THF)] (2) (CpAr5 = C5Ar5, Ar = 3,5-iPr-C6H3) as the precatalyst. The potential catalytic reaction intermediates, half-sandwich calcium anisyl complexes [(CpAr5)Ca(o-MeO-m-Ph-C6H3) (THF)2] (8) and [(CpAr5)Ca(o-MeO-2-Np) (THF)2] (9) (Np = naphthyl), were isolated and X-ray structurally characterized. DFT calculations were carried out to elucidate the different reaction profiles of sp2 and sp3 C–H activations.

Alternating Current Electrolysis Enabled Formal C-O/O-H Cross-Metathesis of 4-Alkoxy Anilines with Alcohols.

Abstract: While multiple bond metathesis reactions, for example olefin metathesis, have seen considerable recent progress, direct metathesis of traditionally inert C-O single bonds is extremely rare and particularly challenging. Undoubtedly, metathesis reaction of C-O bonds is one of the most ideal routes for the value-added upgrading of molecules involving C-O bonds. Reported here is a new protocol to achieve the formal C-O/O-H cross-metathesis via alternating current electrolysis. Featuring mild reaction conditions, the protocol allows readily available 4-alkoxy anilines and alcohols to be converted into a wide range of valuable products in highly regioselective and chemoselective manner. Moreover, the present strategy can be used in the late-stage modification of pharmaceuticals as well as biologically active compounds, which demonstrated the potential application.

Thermally Stable D2h Symmetric Donor-π-Donor Porphyrins as Hole-Transporting Materials for Perovskite Solar Cells.

Abstract: A series of new D 2h symmetric porphyrins ( MDA4 , MTA4 , and MDA8 ) with donor-π-donor structures have been synthesized as the hole-transporting materials for perovskite solar cells (PSCs). The novel porphyrin molecules feature a D 2h symmetrically substituted Zn(II) porphyrin core and two kinds of donor systems (diarylamine (DAA) and triarylamine (TAA)), which can regulate energy level, increase thermal stability, solubility, and hydrophobicity via long alkoxyl chains. PSC devices based on MDA4 as the HTM showed impressive power-conversion efficiency (PCE) of 22.67% under AM1.5G solar illumination. Notably, the device was sent for certification, and a PCE of 22.19% was reported, representing the highest PCE from porphyrin-based HTMs. Furthermore, the MDA4 -based PSCs showed excellent thermal stability under 60 °C and RH 60% and preserved 88% of initial performance after 360 hours. The strategy opens a new avenue for developing efficient and stable porphyrin HTMs for PSCs.

Room temperature ppb level detection of chlorine using peripherally alkoxy substituted phthalocyanine/SWCNTs based chemiresistive sensors

Abstract: Carbon nanotubes (CNTs) have created their niche in the area of gas sensing applications because of their unique mechanical and electronic properties. Their long recovery time and inadequate or temperature-based recovery result in substandard sensing properties. In this account, to overcome these issues and to highlight the application of CNTs in trace level identification and sensitive detection of chlorine (Cl2), operating at room temperature; a hybrid of single-walled carbon nanotubes anchored with peripheral alkoxy substituted phthalocyanine has been prepared. The as-prepared samples have been characterized for their morphological properties via transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and structural properties via Raman, UV–vis, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) techniques. Moreover, N2-adsorption analysis reveals that Brunauer-Emmett-Teller (BET) surface area for hybrid increases more than three-fold in comparison to SWCNTs-COOH. At room temperature, gas sensing properties of fabricated hybrid sensors exhibit remarkable Cl2 sensing characteristics with a limit of detection up to 1.33 ppb. Moreover, the nature of the interaction between hybrid sensors and gas analytes has been explored based on spectroscopic studies.

Photoredox/Persistent Radical Cation Dual Catalysis for Alkoxy Radical Generation from Alcohols

Abstract: In this report, we present a mild and general strategy for the direct generation of alkoxy radical from simple aliphatic alcohols enabled by visible-light-induced photoredox/persistent radical cation dual catalysis. The...