Linear Alkyl Side Chains Research Articles

Phenanthrodithiophene (PDT)–Difluorobenzothiadiazole (DFBT) Copolymers: Effect on Molecular Orientation and Solar Cell Performance of Alkyl Substitution onto a PDT Core

Synthesis, characterization, and solar cell application of three 4,7-dialkylated phenanthro[1,2-b:8,7-b′]dithiophene (PDT)–difluorobenzothiadiazole (DFBT copolymers (P1–P3) with different linear alkyl side chains to improve solubility, molecular weight, and molecular orientation are described. The utilization of Ir-catalyzed direct borylation and sequential functionalization can selectively afford the target 4,7-dialkylated PDT as the monomers. Migita–Kosugi–Stille coupling in the presence of CuI can accelerate polymerization to afford high-molecular-weight polymers along with their improved solubility. The effect of alkyl substitution at the 4,7-positions on the electronic structure of PDT–DFBT copolymers is negligible. By installation of additional alkyl chains at the 4,7-positions of PDT, the synthesized polymers P1–P3 have lower intermolecular interaction than that of nonalkylated P0, but they still maintained aggregation behavior in solution. In addition, they formed a favorable face-on orientation w...

Electronic properties of isoindigo-based conjugated polymers bearing urea-containing and linear alkyl side chains

A side-chain engineering study has been performed with isoindigo-based conjugated polymers to modulate their physical and electronic properties through the incorporation of urea-containing and saturated linear side chains.

Effects of alkyl side chains positioning and presence of fused aromatic units in the backbone of low‐bandgap diketopyrrolopyrrole copolymers on the optoelectronic properties of organic solar cells

ABSTRACTThe systematic optimization of the chemical structure of low‐bandgap (LBG) donor‐acceptor polymeric semiconductors is a challenging task for which accurate guidelines are yet to be determined. Several different structural and molecular parameters are crucial ingredients for obtaining LBG polymers that simultaneously possess high power conversion efficiencies, good processability in common organic solvents, and enhanced stability in organic photovoltaic devices. In this work, we present an extensive structure–optoelectronic properties–solar cell performance study on the emerging class of diketopyrrolopyrrole‐based LBG polymers. In particular, we investigate alkyl side chain positioning by introducing linear alkyl side chains into two different positions (α‐ and β‐), and the distance of the electron rich and electron deficient monomers within the repeat units of the polymer chain. We demonstrate that anchoring linear alkyl side chains to the α‐positions and introducing fused moieties into the polymer backbone, can be beneficial toward maintaining photocurrents similar to the unsubstituted derivative, and concurrently exhibit better processabiliy in common organic solvents. These results can provide a design rationale towards further optimization of semiconducting polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 138–146

Spotlight on Excitonic Coupling in Polymorphic and Textured Anilino Squaraine Thin Films

Structural diffraction analysis of an anilino squaraine with branched isobutyl side chains shows crystallization into two polymorphic structures in the bulk and in spin-casted thin films. We observe multipeaked and pleochroic absorption spectra being blue-(red)-shifted for the monoclinic (orthorhombic) polymorph. We understand the packing as Coulombic molecular H-(J)-aggregates supporting Davydov splitting. Pictures of projected Davydov components in oriented thin films fit well to polarization resolved spectro-microscopy and crossed-polarized light microscopy investigations. By comparison with literature on anilino squaraines with linear alkyl side chains, we point out a general trend for steering the thin film excitonic properties by simple side chain and/or processing condition variation. Combined with the ability to locally probe the direction of transition dipole moments, this adds value to the rational design of functional thin films for optoelectronic applications, especially envisioning ultrastron...

Non-fullerene small molecular acceptors with a carbazole core for organic solar cells with high open-circuit voltage

Two novel carbazole-cored small molecules CzC6C8 and CzC8 bearing different side chains and two 3-ethylrhodanine end-capping groups were synthesized and used as electron acceptors in organic solar cells (OSCs). Devices based on these two acceptors showed a high open circuit voltage (Voc) about 1 V. Due to more closely molecular stacking and improved film morphology, CzC8 bearing a linear alkyl side chain showed a better photovoltaic performance than CzC6C8 bearing a branched one. CzC8 based OSCs can still exhibit a good performance even though the ΔELUMO and ΔEHOMO between donor and acceptor are both small. Three polymer donors (PBT, PTB7-Th, and PTFBDT) with a similar LUMO level but various HOMO levels were tested and they all showed good PCE values larger than 4.6%. Among them, PTB7-Th:CzC8 based devices afforded the highest PCE of 4.91% and PTFBDT:CzC8 based ones gave the highest Voc of 1.16 V.

Double-tailed long chain BODIPYs - Synthesis, characterization and preliminary studies on their use as lipid fluorescence probes

In this paper we report the synthesis of a series of double-tailed BODIPYs bearing twin alkoxy groups with long linear alkyl side chains (C10, C12, C14, C16) attached to the meso positioned phenyl unit. The compounds were fully characterized and exhibited the typical BODIPY strong absorbance in the visible region and emission maxima around 530 nm, with high fluorescence quantum yields (ca. 0.8) and small Stokes shifts. The goal was to improve the lipophilicity of the BODIPYs without disturbing their excellent fluorescent properties. All synthetized BODIPYs were tested in vivo as fluorescent sensors for lipids and one of them (BD-C12) showed great potential to act as a lipid fluorescent probe.

Synthesis and Cytotoxic Evaluation of N‐Aroylureas through Rhodium(III)‐Catalyzed C−H Functionalization of Indolines with Isocyanates

AbstractThe rhodium(III)‐catalyzed C−H amidation and subsequent C−N bond formation reaction of indolines with aryl and alkyl isocyanates at room temperature are reported. These transformations allow the generation of N‐aroylurea functionality at the C7‐position of indolines, which is known as a crucial scaffold found in biologically active molecules. In addition, the synthesis of pyrroloindolidione derivatives is also described through sequential C6‐amidation reaction and intramolecular cyclization of C7‐amidated indolines. All synthesized products were evaluated for in vitro cytotoxic effect against human prostate adenocarcinoma cells (DU145), human breast cancer cells (MCF‐7), and triple negative human breast cancer cells (MDA‐MB‐231), respectively. Notably, compounds 4 d and 4 e with linear alkyl side chains were found to be highly cytotoxic, which is comparable to that of anticancer doxorubicin and cisplatin as positive controls.magnified image

5. Inhibitory Potency of Tamiflu Oseltamivir and DANA and their Modified Derivatives on Lipopolysaccharide-Induced Neu1 Sialidase Activity in Live BMA Macrophage Cells

Toll-like receptors (TLRs) are a group of ancient receptors found on the surface of cells in our innate immune system. They are responsible for detecting conserved molecules found on pathogenic microbes, called Pathogen Associated Molecular Patterns (PAMP), such as lipopolysaccharide (LPS) molecules on the cell surfaces of Gram-negative bacteria. The activation of TLRs leads to immune responses against the pathogen infection. Although the cell signalling follow the activation of TLRs is well characterized, the initial mechanisms for TLR activation upon detecting PAMPs are not well understood. For the TLR-2,-3 and-4 receptors, we reported that an enzyme called Neu1 sialidase forms a complex with the TLR receptors on the cell surface of naïve and activated macrophages (Amith et al, 2009). Activation of this Neu1 is induced by the binding of TLR ligands, such as LPS, to their respective receptors; a specific sialyl -2,3-linked β-galactosyl residue on the TLR is hydrolyzed by the activated Neu1 enzyme. Neuraminidase inhibitors such as BCX1827, DANA, zanamivir and oseltamivir carboxylate have a limited inhibition of this LPS-induced Neu1 activity in live macrophage cells. In contrast, Tamiflu (oseltamivir phosphate) completely blocked this Neu1 activity. Here, we tested the inhibitory potency of a series of DANA and modified Tamiflu derivatives against the activity of the Neu1 enzyme. The results suggest that the linear alkyl side chains of DANA derivatives may contribute to their increased inhibitory potency on LPS-induced Neu1 activity compared to the derivatives with methyl side chain branches and to the parent DANA compound.

New insights into the self-assembling of some hydrophobically modified polyacrylates in aqueous solution

A series of hydrophobically modified sodium polyacrylates (NaPACn) grafted with linear alkyl side chains with 10 to 18 atoms of carbon (n) has been synthesized. FT-IR and 1H-NMR characterization proved that the alkyl grafts were attached to the polymer backbone via the amide link and the grafted amount was around 3 % (mol). The aqueous solutions of NaPACn were investigated by a score of methods including viscosity, fluorescence (steady-state and time-resolved), refractive index, and dynamic rheology. The results revealed that each NaPACn has a characteristic overlapping concentration (c*), which lowers as the grafted chain is more hydrophobic. Above c*, the viscosity deviates from that of sodium polyacrylate (NaPA) and solutions of high viscosity are obtained. The phenomenon is more evident as the alkyl chain increases in length and was attributed to the cross-association of the grafts. The NaPAC16 and NaPAC18 are viscoelastic solids, whereas the C10–C14 derivatives are viscoelastic liquids. The comportment of NaPAC16 and NaPAC18 is sustained by the positive yield stress and the high relaxation time values. Steady-state fluorescence unveiled intracoil hydrophobic microdomains (HMD), whereas dynamic fluorescence and refractive index showed the existence of both intra- and intercoil aggregates.

Diketopyrrolopyrrole (DPP)-Based Donor-Acceptor Polymers for Selective Dispersion of Large-Diameter Semiconducting Carbon Nanotubes.

Low-bandgap diketopyrrolopyrrole (DPP)-based polymers are used for the selective dispersion of semiconducting single-walled carbon nanotubes (s-SWCNTs). Through rational molecular design to tune the polymer-SWCNT interactions, highly selective dispersions of s-SWCNTs with diameters mainly around 1.5 nm are achieved. The influences of the polymer alkyl side-chain substitution (i.e., branched vs linear side chains) on the dispersing yield and selectivity of s-SWCNTs are investigated. Introducing linear alkyl side chains allows increased polymer-SWCNT interactions through close π-π stacking and improved C-H-π interactions. This work demonstrates that polymer side-chain engineering is an effective method to modulate the polymer-SWCNT interactions and thereby affecting both critical parameters in dispersing yield and selectivity. Using these sorted s-SWCNTs, high-performance SWCNT network thin-film transistors are fabricated. The solution-deposited s-SWCNT transistors yield simultaneously high mobilities of 41.2 cm(2) V(-1) s(-1) and high on/off ratios of greater than 10(4) . In summary, low-bandgap DPP donor-acceptor polymers are a promising class of polymers for selective dispersion of large-diameter s-SWCNTs.

Oligo(ethylene glycol)-incorporated hybrid linear alkyl side chains for n-channel polymer semiconductors and their effect on the thin-film crystalline structure.

Oligo(ethylene glycol)-incorporated hybrid linear alkyl side chains, serving as solubilizing groups, are designed and introduced into naphthalene-diimide-based n-channel copolymers. The synthesized polymers exhibit unipolar n-type operation with an electron mobility of up to 1.64 cm(2) V(-1) s(-1), which demonstrates the usefulness of the hybrid side chains in polymer electronics applications.

The effect of branched versus linear alkyl side chains on the bulk heterojunction photovoltaic performance of small molecules containing both benzodithiophene and thienopyrroledione

To evaluate the effect of side chain characteristics on the photovoltaic performance of small molecules containing both benzodithiophene (BDT) and thienopyrroledione (TPD), we designed and synthesized two such molecules, one containing a branched 2-ethylhexyl (2EH) side chain on the BDT unit (BDTEH-TTPD) and the other containing a linear n-octyl (C8) side chain on the BDT unit (BDTO-TTP). The optical and electrochemical properties and crystalline structures of these molecules were examined. Compared to BDTO-TTPD, BDTEH-TTPD, showed stronger light absorption, longer-range ordering and shorter π-π stacking distances between backbones. As a result, the power conversion efficiency of a bulk heterojunction solar cell based on BDTEH-TTPD (2.40%) was substantially higher than that of the BDTO-TTPD device (1.12%).

Activity Coefficients at Infinite Dilution for Organic Solutes Dissolved in Three 1-Alkyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquids Bearing Short Linear Alkyl Side Chains of Three to Five Carbons

In this work, we report the infinite dilution activity coefficients (γ1,2∞) of 39 to 43 diverse organic solutes dissolved in three 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids (IL) homologues bearing propyl, butyl, and pentyl n-alkyl side chains, respectively, as determined by inverse gas chromatography at temperatures from 323 K to 343 K. The organic solutes include various (cyclo)alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, thiophene, ethers, nitroalkanes, and ketones. The measured retention data were further transformed to gas-to-IL and water-to-IL partition coefficients using established thermodynamic approaches based upon the corresponding gas-to-water partition coefficients of the test solutes. Both sets of partition coefficients were interpreted with a modified form of the basic Abraham general solvation parameter model. The mathematical correlations obtained by regression analysis back-calculated the observed gas-to-IL and water-to-IL partition coeff...

Synthesis, Photophysics, Live Cell Imaging, and Aggregation Behavior of Some Structurally Similar Alkyl Chain Containing Bromonaphthalimide Systems: Influence of Alkyl Chain Length on the Aggregation Behavior

A series of 4-bromonaphthalimide systems (BNI-Cn ; n = 4, 6, 10, 12, and 16) comprising different alkyl side chains have been synthesized and used as the building blocks to fabricate organic fluorescent micro materials. The systems have been developed basically to investigate the effect of alkyl side chains on the aggregation behavior of the systems. The aggregation behavior of these systems has been studied by spectroscopic and microscopic techniques. Microscopic investigation reveals that there is a decrease in the size of the aggregates with an increase in the linear alkyl side chain length. A change in the shape from rod-like to spherical with an increase in the length of alkyl group has also been observed during microscopic investigation. The photophysical properties of these well-characterized aggregates have been studied and compared with those in molecular form. A bathochromic shift both in absorption and in emission spectrum of the aggregates has indicated the formation of J aggregates. A confocal fluorescence microscopic investigation also reveals that the long chain systems (12 and 16 member) are cell permeable and can be used as the imaging probe in live cells.

Time-Resolved Observation of Chiral-Index-Selective Wrapping on Single-Walled Carbon Nanotube with Non-Aromatic Polysilane

In the present paper, we ascertain two novel findings on chiral-index-selective binding/separating of single-walled carbon nanotubes (SWNTs) with a nonaromatic polymer, poly(dialkylsilane) (PSi). PSi is a typical σ-conjugated polymer, composed of alkyl side chains attached to the silicon (Si)-catenated main chain. First, PSi's with linear alkyl side chains showed significant diameter-selective wrapping for SWNTs with ca. 0.9 nm in diameter, resulting in the selective separation of (7,6) and (9,4) SWNTs. Its driving force was demonstrated to be cooperative CH-π interactions among the alkyl side chains of PSi's and the curved graphene of SWNTs. Second, the dynamic wrapping behavior of PSi's onto SWNTs was elucidated with time-resolved UV spectroscopy. Highly anisotropic UV absorption of PSi along the Si main chain was utilized as a "chromophoric indicator" to monitor the global/local conformations, which enabled us to track kinetic structural changes of PSi's on SWNTs. Consequently, we concluded that upon wrapping, flexible/helical PSi with an average dihedral angle (φ) of 145° and Kuhn's segment length (λ(-1)) of 2.6 nm interconverted to the more stiffer/planar conformation with 170° and λ(-1) of 7.4 nm. Furthermore, through kinetic analyses of the time-course UV spectra, we discovered the fact that PSi's involve three distinct structural changes during wrapping. That is, (i) the very fast adsorption of several segments within dead time of mixing (<30 ms), following (ii) the gradual adsorption of loosely wrapped segments with the half-maximum values (τ(1)) of 31.4 ms, and (iii) the slow rearrangement of the entire chains with τ(2) of 123.1 ms, coupling with elongation of the segment lengths. The present results may be useful for rational design of polymers toward chiral-index-selective binding/separating of desired (n,m) SWNTs.

Side-Chain Tunability of Furan-Containing Low-Band-Gap Polymers Provides Control of Structural Order in Efficient Solar Cells

The solution-processability of conjugated polymers in organic solvents has classically been achieved by modulating the size and branching of alkyl substituents appended to the backbone. However, these substituents impact structural order and charge transport properties in thin-film devices. As a result, a trade-off must be found between material solubility and insulating alkyl content. It was recently shown that the substitution of furan for thiophene in the backbone of the polymer PDPP2FT significantly improves polymer solubility, allowing for the use of shorter branched side chains while maintaining high device efficiency. In this report, we use PDPP2FT to demonstrate that linear alkyl side chains can be used to promote thin-film nanostructural order. In particular, linear side chains are shown to shorten π-π stacking distances between backbones and increase the correlation lengths of both π-π stacking and lamellar spacing, leading to a substantial increase in the efficiency of bulk heterojunction solar cells.

Rotational Dynamics of Coumarin-153 and 4-Aminophthalimide in 1-Ethyl-3-methylimidazolium Alkylsulfate Ionic Liquids: Effect of Alkyl Chain Length on the Rotational Dynamics

Rotational dynamics of two neutral organic solutes, coumarin-153 (C-153) and 4-aminophthalimide (AP), with only the latter having hydrogen-bond-donating ability, has been investigated in a series of 1-ethyl-3-methylimidazolium alkyl sulfate ionic liquids as a function of temperature. The ionic liquids differ only in the length of the linear alkyl side chain (alkyl = ethyl, butyl, hexyl, and octyl) on the anionic moiety. The present study has been undertaken to examine the role of alkyl side chains on the rotational dynamics of the two solutes in these ionic liquids. Analysis of the results using Stokes-Einstein-Debye hydrodynamic theory indicates that the rotational dynamics of C-153 lies between the stick and slip boundary condition in the ethyl analogue and finally reaches subslip condition as in case of the octyl substituent. The observed rotational behavior of C-153 has been explained on the basis of an increase in the size of the solvent, which offers lower friction for solute rotation. On the other hand, AP shows superstick behavior in the ethyl system and exceeds the stick limit in the octyl derivative. Superstick behavior of AP has been attributed to the specific hydrogen-bonding interaction between AP and the sulfate moiety. Proton NMR investigation confirms the hydrogen-bonding interaction between the N-H hydrogen of AP and the ionic liquid. The decrease in rotational coupling constant values for AP with increasing length of alkyl side chains has been attributed to the decrease in the solute-solvent-specific interaction with an increase in the alkyl side chain length on the sulfate moiety.

Aliphatic dipeptide tags for multi-2-plex protein quantification

Mass-balanced (1)H/(2)H-isotope dipeptide tag (MBIT) is diversified as aliphatic tags for multiplexed protein quantification. Aliphatic MBITs are based on the N-acetyl-Xxx-Ala dipeptide, where Xxx is an artificial amino acid with a linear alkyl side chain from C(2)H(5) to C(8)H(17) (C(2)-C(8) tags). (1)H/(2)H isotopes are encoded in the methyl groups of N-acetyl and Ala to yield a pair of isobaric tags with 2-plex quantitation signals separated by 3 Da. C(2)-C(5) tags are prepared by solid-phase synthesis, while C(6)-C(8) tags are synthesized by olefin metathesis in solution. These aliphatic tags are made reactive toward the primary amines of peptides, and the relative abundances of quantitation signals are characterized using both matrix-assisted laser desorption ionization and electrospray ionization tandem mass spectrometry. MBIT-linked peptides co-migrate in reverse-phase liquid chromatography (LC), and their tandem mass spectra exhibit 2-plex quantitation signals as well as sequence ions in similar abundances. As the length of alkyl side chain increases, C(2)-C(8) tags show a stepwise increase in both the LC retention time and the relative abundance of quantitation signals. In addition, the quantitation linearity is well-maintained in a 15-250 fmol range. The multiplexing capability of aliphatic MBITs is demonstrated by applying three different tags (C(6)-C(8) tags) to the quantification of yeast heat shock proteins expressed under four different physiological conditions.

Mapping Interactions between Germinants and Clostridium difficile Spores

Germination of Clostridium difficile spores is the first required step in establishing C. difficile-associated disease (CDAD). Taurocholate (a bile salt) and glycine (an amino acid) have been shown to be important germinants of C. difficile spores. In the present study, we tested a series of glycine and taurocholate analogs for the ability to induce or inhibit C. difficile spore germination. Testing of glycine analogs revealed that both the carboxy and amino groups are important epitopes for recognition and that the glycine binding site can accommodate compounds with more widely separated termini. The C. difficile germination machinery also recognizes other hydrophobic amino acids. In general, linear alkyl side chains are better activators of spore germination than their branched analogs. However, L-phenylalanine and L-arginine are also good germinants and are probably recognized by distinct binding sites. Testing of taurocholate analogs revealed that the 12-hydroxyl group of taurocholate is necessary, but not sufficient, to activate spore germination. In contrast, the 6- and 7-hydroxyl groups are required for inhibition of C. difficile spore germination. Similarly, C. difficile spores are able to detect taurocholate analogs with shorter, but not longer, alkyl amino sulfonic acid side chains. Furthermore, the sulfonic acid group can be partially substituted with other acidic groups. Finally, a taurocholate analog with an m-aminobenzenesulfonic acid side chain is a strong inhibitor of C. difficile spore germination. In conclusion, C. difficile spores recognize both amino acids and taurocholate through multiple interactions that are required to bind the germinants and/or activate the germination machinery.

Monovalent Anion Indicator Based on Fluorescence Quenching of Helical Fluorinated Poly(dialkylsilanes)

This paper reports that fluorinated PSis with 3,3,3-trifluoropropyl and linear alkyl side chains (F-PSi)s demonstrated monovalent anion size dependent fluorescence quenching, which has potential as...