New syntheses for 11-(mercaptoundecyl)triethylene glycol and mercaptododecyltriethyleneoxy biotin amide

Novel syntheses for mercaptododecyltriethyleneoxy biotin amide and 11-(mercaptoundecyl)triethylene glycol are presented here. Such alkyl thiols are popular components in creating monolayers capable of specifically binding proteins. The development of a variety of functionalized alkyl thiol compounds has a great impact on biosensor substrate design. In our synthesis of mercaptododecyltriethyleneoxy biotin amide, we couple aminotriethyleneoxydodecane disulfide to the NHS-activated biotin; this technique is amenable to attaching a carboxylated molecule of interest in order to create the functionalized alkyl thiol of choice. The 11-(mercaptoundecyl)triethylene glycol synthesis presented here is an alternative method easily completed in three steps.     

Palladium-catalyzed coupling of thiol esters with aryl and primary and secondary alkyl organoindium reagents

Thiol esters and organoindium reagents undergo palladium-catalyzed cross-coupling under mild conditions to give ketones in moderate to excellent yields. Aryl and primary/secondary alkyl organoindium reagents can be used as coupling partners. This method has two advantages over the cross-coupling of thiol esters with boron and tin reagents: (1) no added copper reagent is required to mediate the reaction and (2) for the case of alkyl transfer, no added base is required to activate organoindium reagents for cross-coupling as is required for the coupling of alkyl boron reagents with thiol esters.     

Synthesis and Characterization of Self-Assembling Some Thiol Surfactants on Gold Nanoparticles

The purpose of this work is to study the self-assembling of some synthesized thiol surfactants namely (mercaptopropane-, mercaptohexane-, mercaptooctane-, and mercaptodecane sodium sulfonate) on the fabricated gold nanoparticles. The self-assembling of these surfactants on gold nanoparticles characterized using different techniques such as FTIR spectroscopy, UV spectroscopy, and transmission electron microscopy (TEM). Spectroscopic evidence suggests that the synthesized thiol surfactants have been attached to the gold nanoparticles. The effect of self-assembling of these surfactants on the size of the gold nanoparticles was studied using TEM images. The growth of the gold nanoparticles was investigated with respect to the increase of alkyl chain in the synthesized thiol surfactants. The results show that the stabilization of gold nanoparticles was affected by the increase in alkyl chain length of these surfactants. The effect of gold nanoparticles on the interfacial tension and the emulsion stability of these surfactants with crude oil was studied.     

Stability of self-assembled monolayers on titanium and gold

Methyl- and hydroxyl-terminated phosphonic acid self-assembled monolayers (SAMs) were coated on Ti from aqueous solution. Dodecyl phosphate and dodecyltrichlorosilane SAMs were also coated on Ti using solution-phase deposition. The stability of SAMs on Ti was investigated in Tris-buffered saline (TBS) at 37 degrees C using X-ray photoelectron spectroscopy, contact angle goniometry, and atomic force microscopy. For comparison purposes, a hydroxyl-terminated thiol SAM was coated on Au, and its stability was also investigated under similar conditions. In TBS, a significant proportion of phosphonic acid or phosphate molecules were desorbed from the Ti surface within 1 day, while the trichlorosilane SAM on Ti or thiol SAM on Au was stable for up to 7 days under similar conditions. The stability of hydroxyl-terminated phosphonic acid SAM coated Ti and thiol SAM coated Au was investigated in ambient air and ultraviolet (UV) light. In ambient air, the phosphonic acid SAM on Ti was stable for up to 14 days, while the thiol SAM on Au was not stable for 1 day. Under UV-radiation exposure, the alkyl chains of the phosphonic acid SAM were decomposed, leaving only the phosphonate groups on the Ti surface after 12 h. Under similar conditions, decomposition of alkyl chains of the thiol SAM was observed on the Au surface accompanied by oxidation of thiolates.     

Oxidation of Thiols to Their Disulfides with Bis Trinitratocerium (IV)l Chromate [Ce(NO3)312 CrO4 and Pyridinum Chlorochromate

Oxidation of thiophenols, benzyl thiol, and alkyl thiols with bis [trinitratocerium (IV)] chromate and pyridinum chlorochromate are investigated. Pyridinum chlorochromate is quite ineffective for the oxidative dimerization of alkyl thiols.     

Organo-soluble porphyrin mixed monolayer-protected gold nanorods with intercalated fullerenes

Organo-soluble porphyrin mixed monolayer-protected gold nanorods were synthesized and characterized. The resulting gold nanorods encapsulated by both porphyrin thiol and alkyl thiol on their entire surface with strong covalent Au-S linkages were very stable in organic solvents without aggregation or decomposition and exhibited unique optical properties different from their corresponding spherical ones. Alkyl thiol acts as a stabilizer not only to fill up the potential space on gold nanorod surface between bulky porphyrin molecules but also to provide space for further insertion of C(60) molecules forming a stable C(60)-porphyrin-gold nanorod hybrid nanostructure.     

Potential dependence of the kinetics of thiol self-organization on Au(111)

The self-assembly of thiol molecules from ethanolic solution on Au(111) depends significantly on the electrode potential. Especially at cathodic potentials, chemisorption of thiol molecules and the development of the highly ordered structure are slowed down significantly. At potentials near the point of zero charge, first a disordered thiol film of already high thiol density is formed, and then domains of the highly ordered phase develop and grow together. At cathodic potentials, first a disordered film of very low density of predominant flat adsorbed thiol molecules is formed; the formation of ordered domains takes time three orders of magnitude longer than at potentials near the point of zero charge. Received: 27 May 1997 / Accepted: 8 September 1997     

Electrochemical and spectroscopic characterization of surface sol-gel processes

(3-Mercaptopropyl)trimethoxysilane (MTS) forms a unique film on a platinum substrate by self-assembly and sol-gel cross-linking. The gelating and drying states of the self-assembled MTS sol-gel films were probed by use of electrochemical and spectroscopic methods. The thiol moiety was the only active group within the sol-gel network. Gold nanoparticles were employed to detect the availability of the thiol group and their interaction further indicated the physicochemical states of the sol-gel inner structure. It was found that the thiol groups in the open porous MTS aerogel matrix were accessible to the gold nanoparticles while thiol groups in the compact MTS xerogel network were not accessible to the gold nanoparticles. The characteristics of the sol-gel matrix change with time because of its own irreversible gelating and drying process. The present work provides direct evidence of gold nanoparticle binding with thiol groups within the sol-gel structures and explains the different permeability of "aerogel" and "xerogel" films of MTS on the basis of electrochemical and spectroscopic results. Two endogenous species, hydrogen peroxide and ascorbic acid, were used to test the permeability of the self-assembled sol-gel film in different states. The MTS xerogel film on the platinum electrode was extremely selective against ascorbic acid while maintaining high sensitivity to hydrogen peroxide in contrast to the relatively high permeability of ascorbic acid in the MTS aerogel film. This study showed the potential of the MTS sol-gel film as a nanoporous material in biosensor development.     

Fabrication and characterization of metal-molecule-metal junctions by conducting probe atomic force microscopy

Metal-molecule-metal junctions were fabricated by contacting Au-supported alkyl or benzyl thiol self-assembled monolayers (SAMs) with an Au-coated atomic force microscope (AFM) tip. The tip-SAM microcontact is approximately 15 nm(2), meaning the junction contains approximately 75 molecules. Current-voltage (I-V) characteristics of these junctions were probed as a function of SAM thickness and load applied to the microcontact. The measurements showed: (1) the I-V traces were linear over +/-0.3 V, (2) the junction resistance increased exponentially with alkyl chain length, (3) the junction resistance decreased with increasing load and showed two distinct power law scaling regimes, (4) resistances were a factor of 10 lower for junctions based on benzyl thiol SAMs compared to hexyl thiol SAMs having the same thickness, and (5) the junctions sustained fields up to 2 x 10(7) V/cm before breakdown. I-V characteristics determined for bilayer junctions involving alkane thiol-coated tips in contact with alkane thiol SAMs on Au also showed linear I-Vs over +/-0.3 V and the same exponential dependence on thickness. The I-V behavior and the exponential dependence of resistance on alkyl chain length are consistent with coherent, nonresonant electron tunneling across the SAM. The calculated conductance decay constant (beta) is 1.2 per methylene unit ( approximately 1.1 A(-)(1)) for both monolayer and bilayer junctions, in keeping with previous scanning tunneling microscope and electrochemical measurements of electron transfer through SAMs. These measurements show that conducting probe-AFM is a reliable method for fundamental studies of electron transfer through small numbers of molecules. The ability to vary the load on the microcontact is a unique characteristic of these junctions and opens opportunities for exploring electron transfer as a function of molecular deformation.     

Self-assembled monolayers (SAMs) of alkoxycyanobiphenyl thiols on gold--a study of electron transfer reaction using cyclic voltammetry and electrochemical impedance spectroscopy

Self-assembled monolayers (SAMs) of liquid crystalline thiol-terminated alkoxycyanobiphenyl molecules with different alkyl chain lengths on Au surface have been studied for the first time using electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The barrier property of the SAM-modified surfaces was evaluated using two different redox probes, namely potassium ferro/ferri cyanide and hexaammineruthenium(III) chloride. It was found that for short-length alkyl chain thiol (C5) the electron transfer reaction of hexaammineruthenium(III) chloride takes place through tunneling mechanism. In contrast, redox reaction of potassium ferro/ferri cyanide is almost completely blocked by the SAM-modified Au surface. From the impedance data, a surface coverage value of >99.9% was calculated for all the thiol molecules.     

An Experimental and Theoretical Approach to Investigate the Effect of Chain Length on Aminothiol Adsorption and Assembly on Gold

Despite the numerous studies on the self‐assembled monolayers (SAMs) of alkylthiols on gold, the mechanisms involved, especially the nature and influence of the thiol–gold interface are still under debate. In this work the adsorption of aminothiols on Au(111) surfaces has been studied by using surface IR and X‐ray photoelectron spectroscopy (XPS) as well as by density functional theory (DFT) modeling. Two aminothiols were used, cysteamine (CEA) and mercaptoundecylamine (MUAM), which contain two and eleven carbon atoms, respectively. By combining experimental and theoretical methods, it was possible to draw a molecular picture of the thiol–gold interface. The long‐chain aminothiol produced better ordered SAMs, but, interestingly, the XPS data showed different sulfur binding environments depending on the alkyl chain length; an additional peak at low binding energy was observed upon CEA adsorption, which indicates the presence of sulfur in a different environment. DFT modeling showed that the positions of the sulfur atoms in the SAMs on gold with similar unit cells [(2√3×2√3)R30°] depended on the length of the alkyl chain. Short‐chain alkylthiol SAMs were adsorbed more strongly than long‐chain thiol SAMs and were shown to induce surface reconstruction by extracting atoms from the surface, possibly forming adatom/vacancy combinations that lead to the additional XPS peak. In the case of short alkylthiols, the thiol–gold interface governs the layer, CEA adsorbs strongly, and the mechanism is closer to single‐molecule adsorption than self‐assembly, whereas for long chains, interactions between alkyl chains drive the system to self‐assembly, leading to a higher level of SAM organization and restricting the influence of the sulfur–gold interface.     

7-N-(mercaptoalkyl)mitomycins: implications of cyclization for drug function

The Kyowa Hakko Kogyo and Bristol-Myers Squibb companies reported that select mitomycin C(7) aminoethylene disulfides displayed improved pharmacological profiles compared with mitomycin C (1). Mechanisms have been advanced for these mitomycins that differ from 1. Central to many of these hypotheses is the intermediate generation of 7-N-(2-mercaptoethyl)mitomycin C (5). Thiol 5 has been neither isolated nor characterized. Two efficient methods were developed for mitomycin (porfiromycin) C(7)-substituted thiols. In the first method, the thiol was produced by a thiol-mediated disulfide exchange process using an activated mixed mitomycin disulfide. In the second route, the thiol was generated by base-mediated cleavage of a porfiromycin C(7)-substituted thiol ester. We selected four thiols, 7-N-(2-mercaptoethyl)mitomycin C (5), 7-N-(2-mercaptoethyl)porfiromycin (12), 7-N-(2-mercapto-2-methylpropyl)mitomycin C (13), and 7-N-(3-mercaptopropyl)porfiromycin (14), for study. Thiols 5 and 12-14 differed in the composition of the alkyl linker that bridged the thiol with the mitomycin (porfiromycin) C(7) amino substituent. Thiol generation was documented by HPLC and spectroscopic studies and by thiol-trapping experiments. The linker affected the structure of the thiol species and the stability of the thiol. We observed that thiols 5 and 12 existed largely as their cyclic isomers. Evidence is presented that cyclization predominantly occurred at the mitomycin C(7) position. Correspondingly, alkyl linker substitution (13) or extension of the linker to three carbons (14) led to enhanced thiol stability and the predominant formation of the free thiol species. The dominant reaction of thiols 5 and 12-14 or their isomers was dimerization, and we found no evidence that thiol formation led to mitosene production and aziridine ring-opening. These findings indicated that thiol generation was not sufficient for mitomycin ring activation. The potential pharmacological advantages of mitomycin C(7) aminoethylene disulfides compared with 1 is discussed in light of the observed thiol cyclization pathway.     

One-Pot Convenient and High Yielding Synthesis of Dithiocarbamates

Summary. A convenient and high yielding method for the synthesis of diverse dithiocarbamates having various substituents including alkyl, aryl, heteroaryl, and alkylaryl at the thiol chain or at the amine chain or at both thiol and amine chains were developed by the one-pot reaction of mercaptans, amines, and bis(benzotriazolyl)methanethione in presence of amidine base under mild reaction conditions.     

硫醇化合物在银盐CTP版材上的疏水作用

本文采用线形CCD(ChargeCoupledDevice)技术、接触角等方法研究了一种长链硫醇化合物对计算机直接制版材料物理显影动力学及疏水性能的影响。结果表明,该化合物是物理显影过程的抑制剂,在显定合一的加工液中添加该化合物可以显著提高版材物理显影银区的疏水性能。同时,通过表面显微拉曼光谱进一步证明了硫醇化合物在物理显影银表面的吸附增加了版材的亲油性。     

Phenyl trifluorovinyl sulfide: a radical acceptor for preparation of gem-difluoromethylene compounds

Phenyl trifluorovinyl sulfide was prepared from the reaction of trifluorovinyllithium and S-phenyl benzenethiosulfonate. The fluorinated olefin showed reactivity with alkyl radicals generated from halogen-abstraction from alkyl halides. Reactions with alkyl halides required tris(trimethylsilyl)silane as a chain transfer reagent to improve selectivity of the products. Initiation of radical reaction was effected by thermal decomposition of AIBN. Oxidation of the thioether products gave the corresponding sulfoxides, which were successively converted into α,α-difluoroalkanecarboxylic acid thiol esters by Pummerer reaction.     

A novel vertical alignment technology for nematic liquid crystals based on electrostatic self-assembled method

A novel vertical alignment film for nematic liquid crystals is reported based on electrostatic self-assembly of alkyl sulfonic salts in aqueous solution. A series of self-assembled films with different alkyl chain lengths were prepared and used as alignment films. It was revealed that only when the number of carbon atoms in the alkyl chain approaches 11 or larger, could the self-assembled film induce vertical alignment of liquid crystals. We also found that the homeotropic alignment of liquid crystals was related to the surface roughness of self-assembled films. In addition, this vertical alignment film showed good electro-optical characteristics and excellent thermal stability.     

Cu-catalyzed one-pot synthesis of unsymmetrical diaryl thioethers by coupling of aryl halides using a thiol precursor

An efficient Cu-catalyzed one-pot approach for the synthesis of unsymmetrical diaryl thioethers using potassium ethyl xanthogenate as a thiol surrogate is developed. This new protocol avoids usage of intricate thiols and makes use of its easily available xanthate as a precursor, and thiol will be generated in situ to prepare the diaryl thioethers through a Cu-catalyzed double arylation. This strategy was further successfully utilized for the synthesis of symmetrical diaryl thioethers, aryl alkyl thioethers, and benzothiazoles.     

NOVEL SYNTHESIS OF THIOL ESTERS VIA A SULFUR TRANSFER AGENT-POTASSIUM ALKYL OR BENZYL DITHIOCARBONATES

Abstract

The reaction of certain acid chlorides with potassium alkyl or benzyl dithiocarbonates afforded a novel synthesis of thiol esters.     

Controlling the reactivity of adsorbed DNA on template surfaces

The ability to place DNA on surfaces with increased and controllable reactivity is of fundamental importance in the development of next-generation DNA and protein biochips. The present work demonstrates the ability to control both the localization of the DNA on a surface and its reactivity by a self-assembly approach that is dependent on two variables: DNA structure and surface environment. Here we utilize a two-step adsorption scheme to control the adsorption and reactivity of DNA embedded within two types of alkyl thiol monolayers (either methyl-terminated or hydroxyl-terminated). In addition, by changing the structure of the chemisorbed DNA from fully single stranded to a 50% double stranded at its side adjacent to the surface, we were able to observe a clear dependence of DNA reactivity on both the DNA structure and the type of alkyl thiol monolayer covering the surface. The adsorption and the reactivity yield of the DNA were monitored either by its ability to hybridize to a complementary target molecule or by an enzymatic reaction involving DNA phosphorylation catalyzed by the enzyme T4 polynucleotide kinase.     

A novel vertical alignment technology for nematic liquid crystals based on electrostatic self‐assembled method

A novel vertical alignment film for nematic liquid crystals is reported based on electrostatic self‐assembly of alkyl sulfonic salts in aqueous solution. A series of self‐assembled films with different alkyl chain lengths were prepared and used as alignment films. It was revealed that only when the number of carbon atoms in the alkyl chain approaches 11 or larger, could the self‐assembled film induce vertical alignment of liquid crystals. We also found that the homeotropic alignment of liquid crystals was related to the surface roughness of self‐assembled films. In addition, this vertical alignment film showed good electro‐optical characteristics and excellent thermal stability.