Methylene Chain Length Research Articles

The tunability of the electronic structures for poly(carbosilylsilanes): a theoretical study

To tune purposefully the electronic structures of poly(carbosilylsilanes), a theory study has been investigated using the density functional theory combined with AM1 method. Attentions were paid to the dependence of molecular geometries and absorption spectra on the backbone conformation and the various substituting groups. The strong electronegative substituents can more effectively tune the geometries and spectra of the polysilanes than the alkyl ones. Their main-chain substitutions can induce the great red-shift of the absorption spectra, and the side-chain substitutions can induce the blue-shift. The length of methylene chain in the carbosilyl groups exerts the small effect on the absorption spectra, but with the lengthening of side chain, poly(carbosilylsilanes) have a preference for the all-trans conformation with the loose helix backbone. Different from the alkyl side chain in poly(alkylsilanes), the lengthening of carbosilyl chain leads to the decrease of the positive charges of silicon backbone.

Synthesis and Electropolymerization of Phosphorylcholine-Containing Pyrroles and Their Hemocompatible Properties

A series of N-substituted pyrroles having phosphorylcholine with different methylene chain lengths between pyrrole group and phosphorylcholine group were synthesized and their electropolymerizations were performed in aqueous solution. The methylene chains were trimethylene (n = 3), pentamethylene (n = 5), nonamethylene (n = 9), and undecamethylene (n = 11), for 3-(1-pyrrolyl)propyl-2-(trimethylammonium)ethyl phosphate (5a), 5-(1-pyrrolyl)pentyl-2-(trimethylammonium)ethyl phosphate (5b), 9-(1-pyrrolyl)nonyl-2-(trimethylammonium)ethyl phosphate (5c), and 11-(1-pyrrolyl)undecyl-2-(trimethylammonium)ethyl phosphate (5d), respectively. Although electropolymerized films were produced from all pyrrole derivatives, thick and black polymer films were prepared from 5a, 5b and 5c. The pyrrole derivative with long methylene-chain 5d provided only colorless or slightly blackish thin film. Hemocompatibilities of the polymers from 5a, 5b and 5c were evaluated by platelet rich plasma (PRP) contacting studies and scanning electron microscopy (SEM) observations. The results indicated that these polymers have excellent hemocompatibility.

Synthesis of Metal Complexes with 1-Substituted 3-Hydroxy-2(1H)-pyridinethiones and Their Insulin-Mimetic Activities

Eight kinds of 1-alkyl-3-hydroxy-2(1H-pyridinethiones were synthesized from a commercially available 3-methoxy-2(1H)-pyridinone via 3 steps. Zn(II) and vanadyl complexes were synthesized by treatment with Zn(OAC) 2 or ZnS0 4 , and VOS0 4 , respectively. Vanadyl complexes were found to exist in VO(S 2 O 2 ) coordination mode by means of ESR spectroscopy. From in vitro evaluation of the inhibitory effect on FFA release from rat adipocytes treated with epinephrine, it was found that IC 50 values of Zn(II) complexes with 1-alkyl-3-hydroxy-2(1H)-pyridinethiones, regardless of the methylene-chain length at N-1 position, were in micromolar levels. In other words, these Zn(II) complexes showed higher insulin-mimetic activities than those synthesized previously. On the other hand, the insulin-mimetic activity of vanadyl complexes unfortunately could not be measured owing to their insolubility in KRB buffer which is used in vitro assay.

Synthetic polyamines: an overview of their multiple biological activities

The binding of polyamines to a variety of receptors and other defined recognition sites has been widely reported. It is well-known that polyamines interact with aspartate, glutamate, and aromatic residues of a given receptor and/or enzyme mainly through the formation of ion bonds, since at physiological pH, protonation of amino groups is nearly complete. From this, the hypothesis arises that a polyamine may be a universal template able to recognize different receptor systems. This hypothesis suggests that both affinity and selectivity may be fine-tuned by inserting appropriate substituents onto the amine functions and by varying the methylene chain lengths between them on the polyamine backbone. In this paper, we detail several application of this design strategy aimed at discovering potent and selective polyamines able to bind neurotransmitter receptors and enzymes, such as muscarinic receptor subtypes, muscle-type nicotinic receptors and acethylcholinesterase.

Curcumin-Loaded Nanocapsules: Formulation and Influence of the Nanoencapsulation Processes Variables on the Physico-Chemical Characteristics of the Particles

The aim of this work was to assess the influence of various formulation parameters on the incorporation of Curcumin into nanoparticles. For this purpose, the influence of the aqueous monomer (ethylene diamine, hexamethylene diamine, and 1,4-diaminobutane), as well as the effect of the stirring rate and the influence of the nanoencapsulation method on the encapsulation efficiency were investigated. It was found that variation in the amount of ingredients had profound effects on the curcuminoid loading capacity, the mean particle size, and size distribution. Furthermore, from the thermal results, it is concluded that the reactivity of diamine and the length of flexible methylene chain in diamine determine the thermal properties of resultant polymer wall membrane. The encapsulation yield depends not only on the encapsulation process but also on the chemical structure of the diamine. Whereas, the size and its distribution vary according to the process choice and the emulsification stirring rate.

A ‘magic bridge’: effect of methylene chain length on the photochemistry of radical cations produced from bifunctional X–(CH 2) n–Y molecules

The radical cations of aminoamides Me 2 N(CH 2 ) n C(O)NMe 2 and aminoethers Me 2 N(CH 2 ) n OMe reveal selective photoinduced intramolecular H transfer from methylene bridge at a specific chain length ( n = 3).

Cytotoxicity of methoctramine and methoctramine-related polyamines

Methoctramine and its analogues are polymethylene tetramines that selectively bind to a variety of receptor sites. Although these compounds are widely used as pharmacological tools for receptor characterization, the toxicological properties of these polyamine-based structures are largely unknown. We have evaluated the cytotoxic effects of methoctramine and related symmetrical analogues differing in polymethylene chain length between the inner nitrogens against a panel of cell lines. Methoctramine caused cell death only at high micromolar concentrations, whereas its pharmacological action is exerted at nanomolar level. Increasing the spacing between the inner nitrogen atoms resulted in a significative increase in cytotoxicity. In particular, an elevated cytotoxicity is associated to a methylene chain length of 12 units dividing the inner amine functions (compound 5). H9c2 cardiomyoblasts were the most sensitive cells, followed by SH-SY5Y neuroblastoma, whereas HL60 leukaemia cells were much more resistant. Methoctramine and related compounds down-regulated ornithine decarboxylase, the first enzyme of polyamine biosynthesis even at non-toxic concentration. Further, methoctramine and compound 5 caused a limited up-regulation of spermine/spermidine N-acetyltransferase, suggesting that interference in polyamine metabolism is not a primary mechanism of toxicity. Methoctramine and its analogues bound to DNA with a higher affinity than spermine, but the correlation with their toxic effect was poor. The highly toxic compound 5 killed the cells in the absence of caspase activation and caused an increase in p53 expression and ERK1/2 phosphorylation. Compound 5 was directly oxidized by cell homogenates producing hydrogen peroxide and its toxic effect was partially subdued by the inhibition of its uptake, by the NMDA ligand MK-801, and by the antioxidant N-acetylcysteine, suggesting that compound 5 can act at different cellular levels and lead to oxidative stress.

Self-Assembled Carbon Nanotube Electrode Arrays: Effect of Length of the Linker between Nanotubes and Electrode

The influence of the length of the carbon chain of a self-assembled monolayer (SAM) on gold electrodes on the electrochemical performance of carbon nanotube arrays attached to the SAM was explored. Four electrode constructs were assessed, all of which were modified with four different lengths (C2−C11) of amine-terminated alkanethiols. The four constructs were gold electrodes modified (1) with SAMs alone, (2) with carbon nanotubes randomly dispersed onto the SAM-modified electrodes by drop coating, (3) with vertically aligned carbon nanotubes formed by self-assembly onto the SAMs, and (4) with vertically aligned nanotubes with ferrocene attached to the nanotubes. By use of ruthenium hexaammine as a redox probe, the attachment of the carbon nanotubes to the SAM, either randomly dispersed or aligned, enabled electrochemistry to be observed at SAMs that were passivating prior to attachment of the nanotubes. The electrochemistry decayed exponentially with methylene chain length as expected but with a surprisingly low attenuation factor (β value) for the nanotube-modified surfaces. For randomly dispersed nanotubes, the β value was 0.27 per -CH2- (s = 0.04, n = 4), and for the vertically aligned nanotubes, 0.66 per -CH2- (s = 0.04, n = 4). A similar β value of 0.62 per -CH2- for vertically aligned nanotubes with ferrocene attached provided good evidence that the results with ruthenium hexaammine were due to tunneling through the SAM rather than electrochemistry proceeding via defects in the SAM or the nanotubes penetrating the SAM to the underlying electrode.

Click Polyester: Synthesis of Polyesters Containing Triazole Units in the Main Chain by Click Chemistry and Improved Thermal Property

A "click" polymerization of dialkynes that contain an ester linkages and diazides to has been performed to synthesize various polyesters, termed "click polyesters" with a high $\overline M _{\rm n}$ of 1.0 × 10(4) to 7.0 × 10(4) in an excellent yield. This polymerization accompanied a formation of 1,4-disubstituted triazoles in the polyester main chain by a Cu(I) catalyst. The triazole ring formation in the polyester main chain leads to improved thermal properties and enhancement of the even-odd effect of methylene chain length of the produced click polyesters. This report is the first report of the application of click chemistry to synthesize a series of polyesters under mild conditions.

Synthesis and Characterization of New Heterocyclic Liquid Crystals

This investigation enumerates the synthesis and mesomorphic properties of 1,2,3‐triazole containing azobenzene liquid crystals. In these liquid crystals the methylene chain length at non polar end was varied from six to ten carbons to investigate the association properties of non polar chain on the melt. The compound was designed to have a polar ether chain at the other side of the molecule adjacent to the triazole ring and synthesized to enhance the dipolar interactions. These alterations in chemical structure produce two series of new liquid crystalline compounds with each series containing five variations in the methylene chain. The structure of the target compounds and the intermediates were confirmed by the 1H NMR, 13C NMR and IR spectral techniques. Polarized microscopic studies revealed that all the compounds in the series exhibited enantiotropic liquid crystalline properties. This was further confirmed using differential scanning calorimetric experiments. The energy minimized structure supports the mesogenic behavior of the structure.

Dual-mode recognition of transition metal ions by bis-triazoles chained pyrenes

Fluorescent chemosensors 7−10, with variable methylene chain length as spacers between the two triazole methyl ether units, have been synthesized under ‘Click’ condition, where the bistriazoles are used as the metal ion binding sites and the pyrenes as the fluorophores. Compound 10, having the longest methylene chain among 7−10, shows monomer and excimer fluorescence quenching in acetonitrile toward Ni 2+, Pb 2+, Cu 2+, Hg 2+, and Cr 3+ ions, however, it shows an enhanced monomer but a decreased excimer emission when complexed with Cd 2+ and Zn 2+ ions.

Synthesis of 5-fluoroalkylated pyrimidine nucleosides via Negishi cross-coupling.

5-Fluoroalkylated pyrimidine nucleosides (1) have potential as therapeutic agents and molecular imaging agents targeting HSV1-tk suicide gene therapy. Thus, straightforward preparation of 5-fluoroalkylated nucleoside derivatives has been developed. Reported herein are the first examples of Pd-catalyzed Negishi cross-coupling of 3-N-benzoyl-3',5'-di-O-benzoyl-5-iodo-2'-deoxyuridine (2a) and 3-N-benzoyl-3',5'-di-O-benzoyl-5-iodo-2'-deoxy-2'-fluoroarabinouridine (2b) with unactivated Csp(3) fluoroalkylzinc bromides. This paper demonstrates the first synthesis of six 5-fluoroalkyl-2'-deoxypyrimidine nucleoside derivatives with three to five methylene chain lengths (5). Furthermore, this methodology has been extended to create a series of 13 5-alkyl-substituted nucleosides, including the target nucleosides 5 and 5-silyloxypropyl and 5-cyanobutyl derivatives.

Liquid crystalline and photoactive poly[4,4′-stilbeneoxy]alkylbiphenylphosphates

A series of liquid crystalline and photoactive polymers were synthesized from biphenylphosphorodichloridate with various 4,4′-bis( m-hydroxyalkyloxy)stilbenes ( m = 2, 4, 6, 8, 10) in chloroform by solution polycondensation method using an acid scavenger. The resultant polymers were characterized by inherent viscosity, FT-IR, 1H, 13C and 31P NMR spectroscopies. The liquid crystalline (LC) properties were studied using HOPM and DSC and it was inferred that out of the five polymers synthesized, higher methylene chain containing polymers ( m = 6, 8, 10) exhibited LC properties. Thermogravimetric analysis revealed that all the polymers were stable in between 290 and 367 °C and underwent degradation thereafter. The thermal stability and char yield of the polymers decreased with increase in flexible methylene chain. The photochemical properties of these polymers were investigated by UV and fluorescence spectroscopy. Crosslinking proceeds via 2π–2π cycloaddition reaction of the –CH CH– of the stilbene moieties. The rate of crosslinking increases with increase in methylene chain length in the polymer backbone. The fluorescence spectra showed that the longer methylene spacer containing polymers exhibited larger red-shifts than the shorter spacer containing polymers.

Preparation of Amylose/Polycarbonate Inclusion Complexes by Means of Vine‐Twining Polymerization

AbstractIn this paper, we describe the preparation of inclusion complexes composed of amylose and hydrophobic polycarbonates by “vine‐twining polymerization”, which was achieved by means of the phosphorylase‐catalyzed enzymatic polymerization of an α‐D‐glucose 1‐phosphate from a maltoheptaose in the presence of the polycarbonates with appropriate methylene chain lengths. We found that the polycarbonate with the shorter methylene chain length such as poly(tetramethylene carbonate) was more favorable as the guest polymer to form the inclusion complex with amylose on vine‐twining polymerization than that with the longer one.magnified image

The Dipole Moment and Molecular Mobility of Cholesteryl-Containing Monomers in Solution: Association and Gel Formation

The permittivity, molecular dipole moment, and dielectric relaxation parameters (relaxation time and activation energy) of cholesteryl esters of alkyl-, methacryloyl-ω-oxy-, and aminocarboxylic acids were studied in dilute solutions in toluene. The influence of the chemical structure of molecules on these characteristics was considered. The presence of NH groups and cholesteryl radicals (responsible for H-bonding and specific dispersion interactions) and an increase in the length of methylene chains in molecules substantially influenced dipole moments and dipole polarization relaxation times and contributed to the development of structuring processes (association and gel formation) in solutions of these compounds.

Synthesis and Characterization of Cobalt(III) Octahedral Complexes with Flexible Salpn Schiff Base in Solution. Structural Dependence of the Complexes on the Nature of Schiff Base and Axial Ligands

of tetradentate Schiff bases derivedfrom salicylaldehyde and a variety of diamines (1:2 ratio)have been carried out previously. They have been shown thatan increase in the methylene chain length allows adequateflexibility for the complexes to change their structure from aplanar towards a distorted or pseudo-tetrahedral motif. Inaddition, the longer chains cause the ligand field strength todecrease.

Self-Assembled Monolayer of Light-Harvesting Core Complexes from Photosynthetic Bacteria on a Gold Electrode Modified with Alkanethiols

Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodoseudomonas palustris were self-assembled on a gold electrode modified with self-assembled monolayers (SAMs) of the alkanethiols NH2(CH2)nSH, n = 2, 6, 8, 11; HOOC(CH2)7SH; and CH3(CH2)7SH, respectively. Adsorption of the LH1-RC complexes on the SAMs depended on the terminating group of the alkanethiols, where the adsoption increased in the following order for the terminating groups: amino groups > carboxylic acid groups > methyl groups. Further, the adsorption on a gold electrode modified with SAMs of NH2(CH2)nSH, n = 2, 6, 8, 11, depended on the methylene chain length, where the adsorption increased with increasing the methylene chain length. The presence of the well-known light-harvesting and reaction center peaks of the near infrared (NIR) absorption spectra of the LH1-RC complexes indicated that these complexes were only fully stable on the SAM gold electrodes modified with the amino group. In the case of modification with the carboxyl group, the complexes were partially stable, while in the presence of the terminal methyl group the complexes were extensively denatured. An efficient photocurrent response of these complexes on the SAMs of NH2(CH2)nSH, n = 2, 6, 8, 11, was observed upon illumination at 880 nm. The photocurrent depended on the methylene chain length (n), where the maximum photocurrent response was observed at n = 6, which corresponds to a distance between the amino terminal group in NH2(CH2)6SH and the gold surface of 1.0 nm.

Investigation of liquid crystalline and photocrosslinkable poly[4‐x‐phenyl‐4′‐(m‐methacryloyloxyalkyloxy)cinnamate

AbstractThree series of liquid‐crystalline‐cum‐photocrosslinkable polymers were synthesized from 4‐x‐phenyl‐4′‐(m‐methacryloyloxyalkyloxy)cinnamates (x = − H, OCH3 and CN; m = 6, 8 and 10) by free radical solution polymerization using azobisisobutyronitrile as an initiator in tetrahydrofuran at 60 °C. All the monomers and polymers were characterized using intrinsic viscosity, and FTIR, 1H NMR and 13C NMR spectroscopy. The liquid crystalline behavior of these polymers was examined using a hot stage optical polarizing microscope. All the polymers exhibited liquid crystalline behavior. The hexamethylene spacer‐containing polymers exhibited grainy textures; in contrast, the octamethylene and decamethylene spacer‐containing polymers showed nematic textures. Differential scanning calorimetry data confirmed the liquid crystalline property of the polymers. Thermogravimetric analysis revealed that all the polymers were stable between 236 and 344 °C in nitrogen atmosphere and underwent degradation thereafter. As the methylene chain length increases in the polymer side‐chain, the thermal stability and char yield of the polymers decrease. The photocrosslinking property of the polymers was investigated using the technique of exposing the polymer solution to UV light and using UV spectroscopy. The crosslinking reaction proceeds via 2π–2π cycloaddition reactions of the CHCHof the pendant cinnamate ester. The polymers containing electron‐releasing substituents (OCH3) showed faster crosslinking than the unsubstituted polymers and those containing electron‐withdrawing substituents (CN). Copyright © 2007 Society of Chemical Industry

Magnetic field and methylene chain length effects on photochemistry of bichromophoric chain species containing 7-nitro-2-fluorenyloxy and anilino chromophores

The magnetic field effects (MFEs) and methylene chain length effects on photochemistry of [(7-nitro-2-fluorenyloxy)alkyl]aniline have been investigated by means of electronic absorption spectroscopy and high performance liquid chromatography (HPLC). When the number of methylene groups was 12, appreciable MFEs were detected on photoredox reaction yields, while when the chain length was short (three or six methylenes) almost no MFEs on photoproduct yield were observed. Photoinduced absorbance changes suggest that the photochemical reaction mechanism for the long-chain species is totally different from that for the short-chain compounds. MFEs on photoproduct yields observed for the long-chain species can be explained in terms of competition between cage and escape processes, spin-lattice relaxations and methylene chain dynamics which governs the interconversion between folded and extended conformers.

Magnetic field effects and time-resolved EPR studies on the photogenerated biradicals in phenothiazine–C 60 linked systems: Clarification of the mechanism of novel magnetic field effects by dependences of methylene chain length and temperature

Magnetic field effects (MFEs) on photogenerated biradical in phenothiazine (Ph)–C 60 linked compound with four methylene group (Ph(4)C 60 ) have been investigated. Transient absorption spectra showed photoinduced intramolecular electron-transfer reactions from the Ph to triplet excited state of C 60 ( 3 C 60 ∗ ) . With increasing magnetic field, the decay rate constant of the photogenerated biradical decreased steeply at lower magnetic fields (<0.2 T), and then recovered in the 0.2 T < H < 1.0 T region. Temperature dependence on the reverse phenomenon of the MFEs in Ph(4)C 60 was clearly different from those in other linked compounds ( Ph( n)C 60 ( n = 6, 8, 10, 12)). The present MFEs can be explained by the contribution of not only spin–lattice relaxation mechanism but also spin–spin relaxation mechanism related to ∣2 J∣. In time-resolved EPR measurements, the spectra in Ph( n)C 60 ( n = 4–12) are assigned to spin-correlated radical pairs. The methylene chain dependence of the time-resolved EPR spectra also supports the mechanism suggested in MFEs.