Alkylthio Chains Research Articles

The effects of alkylthio chains on the properties of symmetric liquid crystal dimers

The properties of four series of dimers are discussed to investigate the effect of thioether links on their mesogenic behaviour.

Use of the head-twitch response to investigate the structure–activity relationships of 4-thio-substituted 2,5-dimethoxyphenylalkylamines

Rationale4-Thio-substituted phenylalkylamines such as 2,5-dimethoxy-4-ethylthiophenethylamine (2C-T-2) and 2,5-dimethoxy-4-n-propylthiophenethylamine (2C-T-7) produce psychedelic effects in humans and have been distributed as recreational drugs.ObjectivesThe present studies were conducted to examine the structure–activity relationships (SAR) of a series of 4-thio-substituted phenylalkylamines using the head twitch response (HTR), a 5-HT2A receptor-mediated behavior induced by psychedelic drugs in mice. The HTR is commonly used as a behavioral proxy in rodents for human psychedelic effects and can be used to discriminate hallucinogenic and non-hallucinogenic 5-HT2A agonists.MethodsHTR dose–response studies with twelve different 4-thio-substituted phenylalkylamines were conducted in male C57BL/6 J mice. To detect the HTR, head movement was recorded electronically using a magnetometer coil and then head twitches were identified in the recordings using a validated method based on artificial intelligence.Results2C-T, the parent compound of this series, had relatively low potency in the HTR paradigm, but adding an α-methyl group increased potency fivefold. Potency was also increased when the 4-methylthio group was extended by one to three methylene units. Fluorination of the 4-position alkylthio chain, however, was detrimental for activity, as was the presence of a 4-allylthio substituent versus a propylthio group. 2C-T analogs containing a 4-benzylthio group showed little or no effect in the HTR paradigm, which is consistent with evidence that bulky 4-substituents can dampen agonist efficacy at the 5-HT2A receptor. Binding and functional studies confirmed that the compounds have nanomolar affinity for 5-HT2 receptor subtypes and act as partial agonists at 5-HT2A.ConclusionsIn general, there were close parallels between the HTR data and the known SAR governing activity of phenylalkylamines at the 5-HT2A receptor. These findings further support the classification of 2C-T compounds as psychedelic drugs.

Machine Learning-Assisted Polymer Design for Improving the Performance of Non-Fullerene Organic Solar Cells.

Despite the progress in machine learning (ML) in terms of prediction of power conversion efficiency (PCE) in organic photovoltaics (OPV), the effectiveness of ML in practical applications is still lacking owing to the complex structure-property relationship. Therefore, verifying the potential of ML through experiments can amplify the use of ML models. Herein, we developed a new series of π-conjugated polymers comprising benzodithiophene and thiazolothiazole with fluorination and alkylthio chains (PBDTTzBO, PFSBDTTzBO, and PFBDTTzBO) for non-fullerene (NF) acceptors based on our random-forest ML model for OPVs. Notably, the order of the ML-predicted PCEs of these polymers with IT-4F (9.93, 11.35, and 11.47%) was in good agreement with their experimental PCEs (5.24, 7.35, and 10.30%). In contrast, an inverse correlation was observed between the predicted (9.20, 12.29, and 12.20%) and experimental (11.98, 1.57, and 6.53%) PCEs with Y6. Both the findings are interpreted in terms of surface morphology, transient photoconductivity, charge carrier mobility, polymer orientation, and miscibility, quantified by the Flory-Huggins parameters. Herein, we present an ML-assisted polymer design for high-performance non-fullerene organic photovoltaics (NFOPVs) and elucidate the importance of the subtle alterations in the morphology of NFOPVs.

Non-halogenated solvent processable wide bandgap polymer based on carboxylate-substituted benzodithiophene for high-efficiency polymer solar cells

The use of non-halogenated solvents for the fabrication of polymer solar cells (PSCs) is a crucial step for commercial applications in the future. Herein, we synthesize a wide bandgap polymer PBDT-ST with alkylthio chains substituted benzodithiophene (BDT) as donor unit and carboxylate-substituted BDT as acceptor unit. The polymer PBDT-ST possesses a wide bandgap over 1.90 eV and a deep highest occupied molecular orbitals (HOMO) levels below −5.50 eV, which is beneficial to obtain a high open circuit voltage (Voc). In addition, PBDT-ST shows good solubility in halogenated and non-halogenated solvents. The o-xylene processed PBDT-ST:ITIC-2F blend film exhibits improved molecular order, film morphology and charge mobilities compared with o-dichlorobenzene (o-DCB) processed one. As the results, the o-DCB processed PBDT-ST:ITIC-2F based device can achieve a power conversion efficiency (PCE) of 10.48%. When the non-halogenated o-xylene as solvents and non-halogenated diphenyl ether (DPE) as additive, an improved PCE of 11.14% can be obtained with Voc of 0.90 V, Jsc of 17.83 mA/cm2 and FF of 69.36%. Our research indicates that carboxylate-substituted BDT based polymer PBDT-ST as a promising wide bandgap donor material can achieve excellent photovoltaic performance for PSCs processed by non-halogenated solvent.

Mirror Symmetry Breaking and Network Formation in Achiral Polycatenars with Thioether Tail.

Mirror symmetry breaking in systems composed of achiral molecules is of importance for the design of functional materials for technological applications as well as for the understanding of the mechanisms of spontaneous emergence of chirality. Herein, we report the design and molecular self‐assembly of two series of rod‐like achiral polycatenar molecules derived from a π‐conjugated 5,5’‐diphenyl‐2,2’‐bithiophene core with a fork‐like triple alkoxylated end and a variable single alkylthio chain at the other end. In both series of liquid crystalline materials, differing in the chain length at the trialkoxylated end, helical self‐assembly of the π‐conjugated rods in networks occurs, leading to wide temperature ranges (>200 K) of bicontinuous cubic network phases, in some cases being stable even around ambient temperatures. The achiral bicontinuous cubic Ia 3‾ d phase (gyroid) is replaced upon alkylthio chain elongation by a spontaneous mirror symmetry broken bicontinuous cubic phase (I23) and a chiral isotropic liquid phase (Iso1 [*]). Further chain elongation results in removing the I23 phase and the re‐appearance of the Ia 3‾ d phase with different pitch lengths. In the second series an additional tetragonal phase separates the two cubic phase types.

Reduced Nonradiative Recombination Energy Loss Enabled Efficient Polymer Solar Cells via Tuning Alkyl Chain Positions on Pendent Benzene Units of Polymers.

Nonradiative recombination energy loss (ΔE3) plays a key role in enhancing device efficiencies for polymer solar cells (PSCs). Until now, there is no clear resolution for reducing ΔE3 via molecular design. Herein, we report two conjugated polymers, PBDB-P-p and PBDB-P-m, which are integrated from benzo[1,2-b:4,5-b']dithiophene with alkylthio chain substituted at para- or meta-position on pendent benzene and benzo[1,2-c:4,5-c']dithiophene-4,8-dione. Both the polymers have different temperature-dependent aggregation properties but similar molecular energy levels. When BO-4Cl was used as an acceptor to fabricate PSCs, the device of PBDB-P-p:BO-4Cl displayed a maximal power conversion efficiency (PCE) of 13.83%, while the best device of PBDB-P-m:BO-4Cl exhibited a higher PCE of 14.12%. The close JSCs and fill factors in both PSCs are attributed to their formation of effective nanoscale phase separation as confirmed by atomic force microscopy measurements. We find that the PBDB-P-m-based device has 1 order of magnitude higher electroluminescence quantum efficiency (EQEEL) than in the PBDB-P-p-based one, which could arise from the relatively weak aggregation in the PBDB-P-m-based film. Thus, the PBDB-P-m-based device has a remarkably enhanced VOC of 0.86 V in contrast to 0.80 V in the PBDB-P-p-based device. This study offers a feasible structural optimization way on the alkylthio side chain substitute position on the conjugated polymer to enhance VOC by reducing nonradiative recombination energy loss in the resulting PSCs.

Incorporation of alkylthio side chains on benzothiadiazole-based non-fullerene acceptors enables high-performance organic solar cells with over 16% efficiency

This is the first time alkylthio chains are employed on Y6-like NFAs to achieve organic solar cells of power conversion efficiency higher than 16%.

Side-Chain-Promoted Benzodithiophene-based Conjugated Polymers toward Striking Enhancement of Photovoltaic Properties for Polymer Solar Cells.

In this work, we have reported a highly efficient photovoltaic material, PBDTTz-SBP, by fine-tuning the side chains of the benzodithiophene (BDT) unit. With the replacement of alkoxy chains with alkylthio chains, a large increase in power conversion efficiency (PCE) was realized. Non-fullerene polymer solar cells (PSCs) without any post-treatment generate an optimal PCE of up to 12.09%, with a high VOC of 0.914 V, JSC of 18.52 mA cm-2, and fill factor of 71.43%. Notably, the efficiency of a PBDTTz-SBP-based solar cell was about 1.31-fold of the PCE (9.20%) of its counterpart based on the polymer, PBDTTz-BP, with alkoxy chains, indicating the striking modulation effect of side-chain engineering. Although VOC and JSC were lower than those of non-fullerene devices, the PSCs with PC71BM as the acceptor exhibited a fairly high fill factor of up to 76.69%, affording a moderate PCE. Our work reported a highly efficient polymer solar cell with a PCE of 12.09% and clearly demonstrated the great tuning effect of alkylthio chains on photovoltaic performance.

Conjugated polymer donor with alkylthio-thiophene π-bridge for efficient polymer solar cells

Abstract A new conjugated polymer donor with alkylthio-substituted thiophene as π-bridge (namely PBZ-TS) is developed to further exploit the capability of alkylthio chains in designing high-performance donor materials. PBZ-TS possesses a broad absorption feature, a low-lying HOMO level, and high crystallinity. The polymer solar cell devices based on PBZ-TS:m-ITIC demonstrate high open-circuit voltage (Voc) of 0.93 V. Especially, relative to the PBZ-TS:m-ITIC (1:1, w/w) based binary device, an enhanced power conversion efficiency (PCE) of 8.66% is achieved from the PBZ-TS:m-ITIC:PC71BM (1:0.6:0.4, w/w) based ternary device resulting from the suppressed carrier recombination of binary blends. The results demonstrate that using alkylthio-substituted thiophene as π-bridge is an effective strategy to down-shift HOMO level and increase Voc of the polymer donor materials for PSCs.

Fine-tuning blend morphology via alkylthio side chain engineering towards high performance non-fullerene polymer solar cells

Two medium bandgap polymers (ffQx-TS1, ffQx-TS2) were designed and synthesized to investigate the influence of different alkylthio side chain on the morphology and photovoltaic performance of non-fullerene polymer solar cells (PSCs). Both polymers exhibit similar molecular weights and comparable the highest occupied molecular orbital (HOMO) energy level. However, the polymer with straight alkylthio chain delivers a root-mean-square (RMS) of 0.86 nm, which is slightly lower than that with branched chain (1.40 nm). The lower RMS benefits the ohmic contact between the active lay and interface layer, thus enhancedshortcircuitcurrent (Jsc) (from 13.54 mA cm−1 to 15.25 mA cm−1) could be obtained. Due to the enhancement of Jsc, better power conversion efficiency (PCE) of 7.69% for ffQx-TS2 could be realized. These results indicated that alkylthio side chain engineering is a promising method to improve photovoltaic performance.

Manipulating the photovoltaic properties of small-molecule donor materials by tailoring end-capped alkylthio substitution

The capability of alkylthio chain as end groups in tuning the photovoltaic properties of small-molecule donor materials is investigated.

Alkylthio substituted thiophene modified benzodithiophene-based highly efficient photovoltaic small molecules

Two new small molecules, namely DRSBDTT-EH and DRSBDTT-BO, with alkylthio thienyl substituted benzodithiophene as the central unit and 3-ethylrhodanine as end groups, were designed and studied as the donors for solution processed organic solar cells. The optimized device based on DRSBDTT-EH bearing shorter alkylthio chain gave a power conversion efficiency (PCE) of 8.78%, which is slightly higher than that of device (8.53%) based on DRSBDTT-BO with longer alkylthio chain.

Aromatic Heterocycle 1,3,4-Oxadiazole-Substituted Thieno[3,4-b]thiophene to Build Low-Bandgap Polymer for Photovoltaic Application.

Electron-deficient heterocycle 1,3,4-oxadiazole is first introduced to the 2-position of thieno[3,4-b]thiophene (TT) to construct a new building block 2-(thieno[3,4-b]thiophen-2-yl)-5-(alkylthio)-1,3,4-oxadiazole (TTSO) with alkylthio chain. The polymer PBDT-TTSO based on TTSO and benzodithiophene (BDT) exhibits a deep lying highest occupied molecular orbital (HOMO) energy level of -5.32 eV and low-bandgap of 1.62 eV. The power conversion efficiency (PCE) of 5.86% is obtained with a relatively high V OC of 0.74 V, a J SC of 13.1 mA cm(-2), and FF of 60.5%. Furthermore, as S atom in thioether can be oxidized easily, the optoelectronic properties of PBDT-TTSO treated with different oxidants are preliminary investigated. Interestingly, the oxidation products still maintain high PCE with reduction less than 30%. This work demonstrates a new method to regulate HOMO energy levels by introducing electron-deficient aromatic heterocyclic moiety.

Liquid Crystals of Phthalocyanine-Fullerene Dyads Exhibiting Homeotropic Alignment and Spiranthes-like Supramolecular Structure Useful for Solar Cells

If liquid crystals of phthalocyanine-fullerene (Pc-C60) dyads would exhibit homeotropic alignment at r.t., they would be very useful for the application to solar cells. Hence, we have synthesized nine novel Pc-C60 dyads, (CnS)6PcCu-Cm-C60 (n = 14, 16, 18; m = 8, 10, 12), to investigate whether they would exhibit perfect homeotropic alignment at r.t. by changing lengths of the peripheral alkylthio chains (Cn) and the spacer chain (Cm) between Pc and C60. As a result, each of them exhibited a hexagonal ordered columnar (Colho) mesophase and the Colho mesophase for n = 14 and m = 8, 10, 12, showed perfect homeotropic alignment in a wide temperature region from r.t. to clearing point. Moreover, the Colho mesophases exhibited spiranthes-like supramolecular structure, which is compatible with one-dimensional nano-array expecting the high conversion efficiency of solar cells.

STM Studies of Self-Assembled Tetrathiafulvalene (TTF) Derivatives on Graphene: Influence of the Mode of Deposition

The conformations and the self-assembly process of tetrathiafulvalene (TTF) derivatives functionalized by lateral alkylthio chains deposited on graphene/SiC(0001) in ultrahigh vacuum (UHV) and at the solid–liquid interface are studied by scanning tunneling microscopy (STM). The study in UHV evidences a “molecular fastener” effect induced by the increase of van der Waals interactions between the alkylthio side chains which forces the major part of the molecules to self-organize in π–π stacked edge-on conformation. The study at the solid–liquid interface reveals a drastically different behavior with molecules lying flat on the surface as the solvent is involved in the stabilization of the molecular layer. This work raises a burning issue concerning the choice of the deposition method for graphene functionalization with such molecules.

High-performance polymer solar cells with >10% efficiency

Polymer solar cells (PSCs) with bulky heterojunction structure have attracted considerable attention due to their advantages in making flexible, light weight and large area solar cell panels through the low cost roll-to-roll printing technologies. In the past decades, tremendous efforts have been devoted to developing new materials and device fabrication methods to improve the power conversion efficiencies (PCEs) of PSCs. In 2014, the PCEs have been boosted to ~10% for the PSCs with single junction and ~11% for the PCS with double/triple junctions. According to the reported results, the new materials and processing methods of the photovoltaic active layer in PSCs are of equal importance. In 2004, Yongfang Li and Jianhui Hou et al. at the Institute of Chemistry, Chinese Academy of Sciences (ICCAS) pioneered the concept of two dimensional -conjugation in the design and synthesis of photovoltaic polymers. The conjugated side chains could broaden the absorption spectrum and enhance the hole mobility of 2D-conjugated photovoltaic polymers. After that, they focused on the design of highly efficient photovoltaic polymers based on 2Dconjugated benzodithiophene (2D-BDT). In early 2014, Li et al. [1] first used alkylthio groups to improve photovoltaic properties of 2D-BDT-based polymers. More recently, Hou et al. [2] further modified the 2D-BDT using linear alkylthio groups. In this work, a novel photovoltaic polymer PBDT-TS1 (Figure 1) was designed and synthesized with a linear alkylthio chain staying in the state-of-the-art polymer PTB7-Th for the well balance of absorption range, molecular order and energy level. Owing to the broad spectral coverage, ordered packing and high mobility of 1×10 2

Self-assembly and nanostructure formation of amphiphilic 4,5-bis(2-pyridylethynyl)tetrathiafulvalenes

Amphiphilic tetrathiafulvalene (TTF) having both long alkylthio chains and pyridylethynyl groups was synthesised, and its nanostructure and redox properties were investigated. The bis(pyridylethynyl)TTF formed 1D flat and helical tapes. Since these tapes were of micrometre size, the conductivities of neutral and I2-doped tapes could be measured by directly attaching gold wires to the tape. After doping with I2, the colour of the tape changed from purple to black, and the tape behaved as a semiconductor up to 2.6 × 10− 4 S cm− 1.

Phthalocyaninato complexes with peripheral alkylthio chains: Disk-like adsorbate species for the vertical anchoring of ligands onto gold surfaces

Thin metalorganic films were prepared on gold by self-assembly of thioether-functionalised phthalocyaninato complexes from solution. The phthalocyaninato ligands used contain eight peripheral, β-positioned, alkylthio substituents SR (1a: R=n-C8H17, 1b: R=n-C12H25), which serve as headgroups for surface binding and promote lateral assembly, while the disk-like phthalocyaninato core offers the scope for the attachment of axial ligands to the adsorbed molecules. This process was mimicked by coordination of pyridine (Py) to [Zn(1a)] and [Zn(1b)], respectively. The crystal structures of the products [Zn(1a)(Py)] and [Zn(1b)(Py)] were determined. The crystal structures of 4,5-bis(octylthio)phthalodinitrile and 4,5-bis(dodecylthio)phthalodinitrile were also determined. The films fabricated from [Mn(1a)Cl] and [Mn(1b)Cl] on gold were characterised by XPS, ToF-SIMS and NEXAFS spectroscopy, which revealed the presence of well-defined and homogeneous self-assembled monolayers (SAMs), whose constituents are bound to the substrate by thioether–gold linkages. The orientation of the macrocycles is predominantly parallel to the surface. Strong electronic interaction of the manganese(III) centre with the substrate leads to Cl loss upon adsorption and its reduction to MnII.

Lipid-Soluble Hydroquinone Modifications Induced on Membranes

We synthesized new alkylthiohydroquinones (ATHs); in order to investigate different aspects of lipid-soluble hydroquinones interactions with phospholipids normally found in cell membranes. They have the same long hydrophobic alky chains found in many lipids forming the cell membranes. In these compounds the tails should share the inner of the membrane, while the hydroquinone, as polar head group should remain on the surface. One or more alkylthio chains attached to the aromatic ring, modifies its hydrophobicity and should alter the electron distribution. Moreover, the two OH groups become chemically distinguishable, e.g. NMR spectroscopy and also show different pKa values. We investigate the interaction of ATHs with lipid membranes, POPE and POPC and observe the formation of structures with different morphologies, or curvature, of the lipid membrane, depending on temperature and pH. We attributed their formation to changes in the balance charge/polarity induced by the ATHs. Mixtures with POPE at pH=4 forms two cubic phases P4332 and Im3m that reach a maximum lattice size while in basic conditions they only expand upon heating from room temperature. They coexist with lamellar or hexagonal and have been associated with inhomogeneous distribution of the ATHs molecules over the lipid matrix. The zwitterionic POPC does not form cubic phases, but instead shows two lamellar structures up to a high temperature. In all mixtures of lipid/ATHs we observed the formation of lamellar and hexagonal phases, similar to the behaviour of pure hydrated lipid e.g. POPC, while for POPE additional cubic structures, depending on the environment conditions.

Synthesis of bitetrathiafulvalenes with FeCl 3-mediated homo-coupling of tetrathiafulvalenylmagnesium bromide and formation of nanostructures from bitetrathiafulvalenes having long alkylthio chains

The FeCl 3 -mediated homo-coupling of 4,5-bis(alkylthio)-4′-tetrathiafulvalenylmagnesium bromide 5 produced the corresponding bitetrathiafulvalene derivatives 2a– d in moderate yields (25–51%). Bitetrathiafulvalenes 2c and 2d having long alkylthio chains formed nanostructures and showed bulk electric conductivities ( σ rt = 2.6 − 8.0 × 10 −5 S cm −1) in the neutral state owing to the fastener effect. Interestingly, the nanofiber of tetrakis(dodecylthio)bitetrathiafulvalene 2d exhibited a p-type semiconductivity as detected by AFM.