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A series of fluorene-free bipolar star-shaped molecules, Sn-Cz-OXD (n = 1–5), with increasing conjugated length in branches were synthesized as high efficient blue emitters for OLEDs. With the extension of conjugated branches, the solid PL quantum efficiency and external quantum efficiency of Sn-Cz-OXD significantly increased with longer spacer, while the emission spectrum of these materials exhibited a blue-shift with enhanced color purity due to the unique molecular design. All materials maintained exceptionally high thermal stability after prolonged heat treatment at 150 °C in air. The photophysical, electrochemical, thermal properties of these emitters were studied in relation to the molecular structure. Nondoped device based on S4-Cz-OXD with structure ITO/PEDOT:PSS/EML/TPBI/LiF/Al emitted stable pure blue light with CIE coordinates of (0.157, 0.146). It exhibited high current efficiency and external quantum efficiency of 4.96 cd A−1 and 4.20%, respectively. These values are among the best results for solution-processed non-doped blue device based on fluorene-free materials, indicating its potential for commercial applications.

Appositely functionalized dithienobenzo-thiadiazole and dithienobenzo-oxadiazole-monomers were prepared and used in the synthesis of conjugated electron donor-acceptor (D-A) polymers. Detailed systematic investigations were carried out to study the effects of chalcogen atoms and three donor units on the optical and electrochemical properties as well as photovoltaic and field-effect transistor performance of the D-A polymers. All polymers displayed good thermal properties. Polymers containing benzooxadiazole moiety showed deeper LUMO levels as compared to their benzothiadiazole-containing analogues, whereas those derived from weak donor unit exhibited deeper HOMO levels than those with stronger donors. Photovoltaic power conversion efficiency of over 2% and hole field-effect mobility of 2.6 × 10 −2 cm 2 V −1 s −1 and on/off ratio of over 10 5 were obtained. These results demonstrate that dithienobenzo-chalcogenodiazole structures are potentially useful electron acceptor building blocks for the construction of D-A polymers for organic electronics applications.

Three low band gap thienopyridazine-based donor–acceptor conjugated polymers, PDTTPTT, PDTTPBT, and PDTTPBDT were synthesized by the Stille copolymerization of thienopyridazine with thienothiophene, benzodithiophene, and bithiophene, respectively. The optical band gaps of PDTTPTT, PDTTPBT, and PDTTPBDT polymers were determined as 1.41 eV, 1.43 eV, and 1.58 eV, respectively by UV absorption. The deep HOMO level of the three polymers was determined by cyclic voltammetry. The three polymers were fabricated to form organic field-effect transistors and their performance as p-type semiconductors were studied.

Two new fluorenone-based conjugated polymers, F1 and F2 , were synthesized via the Stille cross-coupling polymerization. Spectral measurements showed that both polymers had optical band gaps of 1.99 eV and 1.89 eV, respectively, calculated based on the film onset absorption edge. Cyclic voltammetric studies gave HOMO/LUMO energy levels of −5.18 eV/−3.19 eV and −5.40 eV/−3.51 eV, respectively, and the polymers were thermally stable at temperatures over 300 °C. Organic field-effect transistor and bulk-heterojunction solar cell performance characteristics of both polymers as p-type semiconductors were evaluated.

A novel cyclodextrin intermediate, mono-2(A)-allylcarbamido-2(A)-deoxy-permethylated β-cyclodextrin, was synthesized by reacting allylamine and newly prepared mono-2(A)-azido-2(A)-deoxy-permethylated β-cyclodextrin by the Staudinger reaction and anchored onto porous silica beads by a one-pot hydrosilylation and immobilization procedure to afford a novel chiral stationary phase. This stationary phase acts as a new member of the previous chiral stationary phase series immobilized on the cyclodextrin C2 position. This stationary phase depicted enantiomeric separation abilities toward a series of bicyclic and tricyclic racemates under reversed-phase conditions. The resolutions for hesperetin and naringenin achieved on the current phase reached 3.91 and 1.11, respectively, much higher than the previous permethylated β-cyclodextrin with the linkage at the C6 position.

TIPs-pentacene OFETs were fabricated on a plastic substrate using polymer nanocomposite dielectric. The blend polymer P(VDF-TrFE)/PMMA (30 wt%) was used as polymer matrix and BaTiO 3 nanoparticles modified by 3-glycidoxypropyltrimethoxysilane (GPTMS) were dispersed as ceramic fillers. The effects of different loadings of BaTiO 3 on the surface morphology and electrical properties of dielectric films were investigated. The formulation of screen-printable dielectric ink of P(VDF-TrFE)/PMMA/BaTiO 3 /Silica (SII) was achieved by adding fumed silica as the viscosity modifier. TIPs-pentacene OFETs using SII as the gate dielectric features a mobility of 0.01 cm 2 /V s, and having a threshold voltage of −6 V. This screen-printable dielectric ink is promising for low operating-voltage fully-printed OFETs.

Multi-walled carbon nanotubes are functionalized with triazole moieties using ‘click’ chemistry and successfully incorporated into a polyurethane nano-composite by in situ polymerization. It is found that the functionalized multi-walled carbon nanotubes provide enhanced interactions with the polyurethane matrix. In addition, incorporation of the triazole moieties into the polyurethane nano-composites significantly increases their heat of decomposition.

New π-conjugated alternating donor–acceptor polymers, BPD–DTT and PPD–DTT, based respectively on benzo[c]pyrrole-4,6-dione (BPD) and pyrrolo[3,4-c]pyrrole-4,6-dione (PPD) acceptor structures with the 2,5-dithienylthieno[3,2-b]thiophene (DTT) donor structure were synthesized via Stille cross-coupling polymerization to study their physical and optoelectronic properties. For comparison, an analogous polymer, TPD–DTT, derived from thieno[3,4-c]pyrrole-4,6-dione (TPD) was also prepared by the same approach. These polymers displayed reasonably good solubility in common organic solvents (e.g., THF, toluene, etc.), and were thermally stable to about 350 °C in nitrogen or air. Both BPD–DTT and PPD–DTT showed blue shifts in their UV-vis absorptions and photoluminescence compared with those of TPD–DTT, suggesting that both possess lower degrees of π-delocalization than TPD–DTT, and thus shorter effective π-conjugation lengths and higher air stability as evidenced from their lower HOMO energy levels. Optical band gaps of 1.61 eV, 1.82 eV, and 1.73 eV and HOMO levels of −5.06 eV, −5.32 eV, and −5.20 eV were estimated for TPD–DTT, BPD–DTT and PPD–DTT respectively from spectral and electrochemical measurements. Electrical characterization showed that all three polymers behaved predominantly as p-type semiconductors in organic field-effect transistor and bulk-heterojunction organic solar cell devices.

A star-shaped blue small-molecule 1,3,5-tris(5-(4-(3,6-di-tert-butylcarbazol-9-yl)phenyl)-1,3,4-oxadiazol-2-yl)benzene (S-Cz-OXD) with donor–π–acceptor (D–π–A) structure was designed and synthesized by incorporating three (3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl arms into an tris(1,3,4-oxadiazole)phenylene core. It gives pure blue photoluminescence emission at 424 nm with high quantum efficiency (Φf) (93%) in dilute toluene and has good solubility in common solvents. This star-shaped molecule also demonstrates enhanced Φf (72%) in the film state. Moreover, the spectral stability of S-Cz-OXD is also excellent due to its low lying HOMO level and absence of fluorene moiety. The PL spectrum of S-Cz-OXD remains virtually unchanged even after annealing at 150 °C for 220 hours in air. The solution-processed non-doped electroluminescent device shows a low turn-on voltage of 3.7 V although there exists a big energy barrier due to the bipolar design. The device emits stable pure blue light, CIE (Commission Internationale de L'Eclairage) coordinates of (0.16, 0.16) with high current efficiency (CE) and external quantum efficiency (EQE) of 4.22 cd A−1 and 3.37% respectively. Mechanistic discussion is also carried out in relation to the molecular structure.

In this study, perphenylcarbamated cyclodextrin clicked chiral stationary phase (CSP) was developed with high column efficiency. The characteristics of the column were evaluated in terms of linearity, limit of detection and limit of quantification. The enantioselectivity of the as-prepared clicked CSP was explored with 26 recemates including aryl alcohols, flavanoids and adrenergic drugs in reversed phase high-performance liquid chromatography. The effect of separation parameters including flow rate, column temperature, organic modifier and buffer on the enantioselectivity of the clicked CSP was investigated in detail. The correlation study of the analytes structure and their chiral resolution revealed the great influence of analytes' structure on the enantioseparations with cyclodextrin CSP. Methanol with 1% of triethylammonium acetate buffer (pH 4) was proved to be the best choice for the chiral separation of basic enantiomers.

Polymer nanocomposite dielectric inks based on P(VDF-TrFE)/PMMA/BaTiO3/silica were formulated for screen printing. GPTMS-modified BaTiO3 was incorporated to improve their dielectric properties and fumed silica to achieve good printability of the dielectric inks. Fully-printed TIPs-pentacene OFETs were successfully fabricated using the optimized dielectric ink with 52% BaTiO3 loading. ASTAR (Agency for Sci., Tech. and Research, S’pore)

5,6-Difluorobenzo[c][1,2,5]thiadiazole (FBT)-based conjugated donor–acceptor (D-A) polymers with straight and branched side chains were synthesized via Stille-coupling copolymerization to study their physical, optoelectronic and photovoltaic properties. The results show that both the nature of pendant side chains and the electron acceptor strength of the acceptor moiety of D–A polymers have critical impacts on material and photovoltaic properties. Better π–π stacking of polymer backbones enabled by appropriate substituents such as fluorine atoms and branched alkyl chains leads to a reasonably high power conversion efficiency of over 6% when the polymer is utilized as a donor material with PC71BM as an active layer in bulk heterojunction solar cells.

A novel cationic cyclodextrin, mono-6(A)-(2-hydroxyethyl-1-ammonium)-6(A)-β-cyclodextrin chloride (HEtAMCD) has been successfully synthesized and applied as chiral selector in capillary electrophoresis. The NMR study revealed this chiral selector has three recognition sites: β-CD, ammonium cation and hydroxy group in the sidearm to contribute three corresponding driving forces including inclusion complexation, electrostatic interaction and hydrogen bonding. The effect of buffer pH and HEtAMCD concentration (2.5-10 mM) on enantioselectivity, chiral resolution as well as effective mobility of analytes was investigated. This elegantly designed CD exhibits outstanding enantioselectivities toward the studied hydroxyl acids and ampholytic racemates in CE with the aid of extra hydrogen bonding. Under optimum pH 6.0, chiral resolutions over 5 can be readily obtained for hydroxy acids with CD concentration below 5mM. The comparison study between HEtAMCD and our earlier reported ammonium CDs indicates the hydroxyethylammonium group of HEtAMCD significantly increased the enantioselective capability.

The current article reviews the development and applications of novel cyclodextrin chiral stationary phases (CD-CSPs) in liquid chromatography (LC), capillary electrochromatography (CEC), gas chromatography (GC) and supercritical fluid chromatography (SFC) over the period of January 2007 to March 2012. The synthetic routes of CD-CSPs, as well as the presence of selective functional groups in effecting inclusion complexation and molecular interactions have been found to exert profound influence in the enantioseparation process. In this article, various synthetic and functional groups immobilization strategies of novel CD-CSPs, and their applications in chiral resolution using different chromatography techniques are discussed. After introducing the topic in Section 1, Section 2 describes novel CD-CSPs in LC applications, where the CSPs are classified according to its coating approaches (physical and chemical manners) for ease of readership. Section 3 discusses recent development of CD-CSPs in open tubular CEC (OT-CEC), packed-bed CEC (P-CEC), pseudostationary phase CEC (PSP-CEC) and monolithic CEC. The last part illustrates novel CD-CSPs in gas chromatography (GC) and supercritical fluid chromatography (SFC).

Vinylene-functionalized cationic β-cyclodextrins are co-polymerized with vinylized silica in the presence of AIBN and conjugated monomers. The chemically immobilized cationic β-cyclodextrins were thereafter applied as chiral stationary phases in packed column supercritical fluid chromatography and demonstrated good and reproducible enantioseparations of racemic pharmaceutical compounds.

Fully or partially sub-2 μm porous silica materials have garnered strong interests as column packing materials in separation and analytical technologies due to the promise of rapid separation, enhanced efficiency and separation resolution. Silica support materials of different morphology and sub-2 μm size have been developed to improve separation performances in liquid chromatography (LC) and capillary electrochromatography (CEC). The current review highlights the recent development of sub-2 μm fully/partially porous silica materials and the demonstrations of their enhanced performance in achiral and chiral chromatography.

We describe an effective and simple protocol that uses click chemistry to attach native β-cyclodextrin (β-CD) to silica particles, resulting in a chiral stationary phase (CCNCSP) that can be used for the enantioseparation of chiral drugs by high-performance liquid chromatography (HPLC). Starting from β-CD, the CCNCSP is prepared in several steps: (i) reaction of β-CD with 1-(p-toluenesulfonyl)-imidazole to afford mono-6-toluenesulfonyl-β-CD; (ii) azidolysis of mono-6-toluenesulfonyl-β-CD in dimethylformamide to give mono-6-azido-β-CD (N(3)-CD); (iii) reaction of cuprous iodide with triphenylphosphine to form an organic soluble catalyst CuI(PPh(3)); (iv) preparation of alkynyl-modified silica particles; and (v) click chemistry immobilization of N(3)-CD onto alkynyl-modified silica to afford the desired chiral stationary phase. Synthesis of the stationary phase and column packing takes ∼1 week.

A novel perylene bisimide derivative, N, N′-Bis(9, 9, 9′, 9′-tetraoctyl-bisfluoren-2-yl)-3, 4:9, 10-perylene bisimide (BFPBF) , has been successfully synthesized via a condensation reaction. The new compound having a donor–acceptor–donor (D–A–D) structure is soluble in common organic solvents such as chloroform and toluene and thus can be easily processed by wet techniques such as spin-coating. BFPBF is thermally stable with a decomposition temperature ( T d ) above 430 °C and exhibits a glass transition temperature ( T g ) of 160 °C under nitrogen atmosphere. Electrochemical investigation indicates that BFPBF has a LUMO level of −4.07 eV which is similar to that of [6,6]-phenyl C 61 butyric acid methyl ester ( PCBM ). Bulk heterojunction photovoltaic device was fabricated using a blend of poly(3-hexylthiophene) (P3HT) and BFPBF (1:1, w-w) as an active layer and power conversion efficiency of the device was 0.13% under simulated solar light AM 1.5 G (100 mW/cm 2 ).

Mesoporous silica particles of relatively uniform sub-1-micron size (0.6–0.9 μm) were successfully prepared by a modified synthesis strategy and applied in chiral separation in an ultra-high pressure liquid chromatography system. These particles were prepared via a ternary surfactant system (Pluronic P123, F127 and hexadecyltrimethyl-ammonium bromide) and subsequently derivatized with perphenylcarbamoylated-β-cyclodextrin moieties. The mesoporous silica particles, despite their submicron size, enabled low back-pressure operation on an ultra-high pressure liquid chromatography system at a maximum flow rate of 2 ml/min. In addition, the particles possessed high surface area (480 m2/g) and thus afforded high cyclodextrin derivative loading (32 μmol/g), demonstrating rapid enantioseparation and good resolution of 6 basic and neutral racemates.

Three new alternating conjugated polymers consisting of pyrene and 3-dodecylthiophene (PPyMT), 4,4'-didodecyl-2,2'-bithiophene (PPyBT), or 9,9-didodecylfluorene (PPyFlu) moieties have been prepared using Suzuki coupling reaction or Sugimoto approaches. The polymers were readily soluble in common organic solvents and exhibited good thermal stability in nitrogen and air atmospheres. The structures and optical properties of the polymers were characterized by NMR, FTIR, XRD, UV-vis, and fluorescence spectroscopy. PPyMT and PPYBT showed blue-light emission in solution, whereas PPyFlu performed blue-light emitting in film state. The polymers exhibited an intermolecular aggregation and structural ordering due to pyrene-pyrene π-π stacking interaction.

Recently, a series of chiral mesoporous silicas with various pore sizes and nanostructures (including chiral MCM-41, chiral SBA-15, and chiral SBA-16) have been successfully synthesized in our group by using achiral templates and a chiral cobalt complex as cotemplate. Enantioselective discrimination ability of these chiral materials was observed when they were applied on the controlled release of a chiral drug. The enantioselectivity of these silica materials was attributed to the local chirality at a molecular level on the pore wall surfaces. Nevertheless, the formation mechanism of local chirality, i.e., the chirality transferring from chiral cobalt complex to inorganic mesoporous silica matrix, remains indeterminate at this juncture. In this report, by tuning the synthesis parameters based on the previously reported method, chiral MCM-41 with left-handed enantiomeric excess in twisted hexagonal particle morphology was obtained. Enantioselective adsorption of racemic valine corroborated the general chir...

Poly{[N-dodecyl-dithieno(3,2-b:2′,3′-d)pyrrole-2,6-diyl]-alt-[2,1,3-benzothiadiazole-4,7-diyl]} ( PBTDTP ) was successfully prepared via Stille coupling. The new polymer is soluble in common organic solvents such as chloroform (CHCl 3 ), tetrahydrofuran (THF) and o-dichlorobenzene. Compared with N-alkyl dithieno[3,2-b:2′,3′-d]pyrrole (DTP) homopolymer, the maximum absorption of PBTDTP was red-shifted approximately 40 nm. The optical band gap of the polymer in film state is 1.55 eV calculated from the onset of absorption spectrum. The cyclic voltammetry measurements of the polymer depicted a HOMO energy level of −5.0 eV and a LUMO energy level of −3.3 eV of PBTDTP . This work demonstrates that this newly synthesized polymer is a promising p-type material for application in bulk hetero-junction organic solar cells.

Two cyclodextrin-based chiral stationary phases have been prepared by immobilization of functionalized mono-6-azido-β-CD derivatives to alkynyl modified silica via “click” chemistry and applied to the HPLC enantioseparation of various chiral compounds. The perphenylcarbamated CD CSP (CCP-CSP) exhibited excellent chiral recognition of a wide range of analytes including racemic aryl alcohols, flavonoids, bendroflumethiazide, atropine and some β-blockers. Methanol proved to be a better organic modifier than acetonitrile for most of the analytes with the exception of bendroflumethiazide. The “click” chemistry immobilized permethylated CD CSP (CCM-CSP) afforded poor chiral recognition for most analytes, but could resolve non-aromatic ionone derivatives which were not separated on CCP-CSP. These results suggest that resolution with cyclodextrin derived CSPs depend on a complex interplay of ‘host’–‘guest’ inclusion, hydrogen bonding, π–π and hydrophobic interactions.

New single-isomer, cationic β-cyclodextrins, including mono-6-deoxy-6-pyrrolidine-β-cyclodextrin chloride (pyCDCl), mono-6-deoxy-6-(N-methyl-pyrrolidine)-β-cyclodextrin chloride (N-CH 3 -pyCDCl), mono-6-deoxy-6-(N-(2-hydroxyethyl)-pyrrolidine)-β- cyclodextrin chloride (NEtOH-pyCDCl), mono-6-deoxy-6-(2-hydroxymethyl- pyrrolidine)-β-cyclodextrin chloride (2-MeOH-pyCDCl) were synthesized and used as chiral selectors in capillary electrophoresis for the enantioseparation of carboxylic and hydroxycarboxylic acids and dansyl amino acids. The unsubstituted pyCDCl exhibited the greatest resolving ability. Most analytes were resolved over a wide range of pH from 6.0 to 9.0 with this chiral selector. In general, increasing pH led to a decrease in resolution. The effective mobilities of all the analytes were found to decrease with increasing CD concentration. The optimal concentration for most carboxylic acids and dansyl amino acid was in the range 5-7.5mM and >15mM for hydroxycarboxylic acids. 1H NMR experiments provided direct evidence of inclusion in the CD cavity. ©2010 Wiley-VCH Verlag GmbH & Co. KGaA.

A novel and effective method has been developed for chiral discrimination using a quartz crystal microbalance (QCM) biosensor with self-assembled bovine serum albumin (BSA) or human serum albumin (HSA). The successfully constructed QCM chiral biosensors exhibited rapid and real-time enantioselective recognition. The QCM chiral discrimination factor (alpha(QCM)) can be calculated through resonance frequency shifts in response to five pairs of enantiomers. Moreover, the interactions between these ten enantiomers and two serum albumins (SA) were investigated in detail by means of ultraviolet-visible (UV-vis) and fluorescence (FL) spectra. The results indicated that the discrimination ability were quite different between BSA and HSA. R,S-1-(3-Methoxyphenyl)ethylamine (R,S-3-MPEA) and R,S-1-(4-methoxyphenyl)ethylamine (R,S-4-MPEA) can be easily differentiated by the BSA sensor, while the selectivity of the HSA sensor for R,S-tetrahydronaphthylamine (R,S-TNA), R,S-2-octanol (R,S-2-OT) and R,S-methyl lactate (R,S-MEL) was higher than that of the BSA sensor. The UV and FL spectra indicated the formation of a complex between SA and enantiomers and strong fluorescence quenching through static quenching mechanism. The in-depth study demonstrated that the calculated UV/FL discrimination factors (alpha(UV) and alpha(FL)) were consistent with the QCM experimental results (alpha(QCM)).

Novel donor-acceptor type polymers consisting of alternating quaterthiophene and an electron withdrawing moiety, pyrazinyl or pyridinyl, have been prepared using Stille coupling approach with moderate yields. The polymers were highly soluble in common organic solvents such as tetrahydrofuran and chloroform. The structure and optical properties of the polymers were characterized by NMR, UV-vis and fluorescence spectroscopy, and cyclic voltammetry, respectively. The polymer having pyrazine unit exhibited a red-shift in both absorption and emission in comparison with those analogs containing pyridine because of strong electron withdrawing character of the pyrazinyl group. The polymer containing pyrazinyl as acceptor units also depicted decrease in its optical and electrochemical bandgap relative to those polymers containing 2,5- or 2,6-pyridine moieties. The electrochemical behavior showed facile n-doping and p-doping properties of those polymers consisting of alternating quaterthiophene and the acceptor moiety.

A novel positively charged single-isomer of β-cyclodextrin, mono-6-deoxy-6-(3R,4R-dihydroxypyrrolidine)-β-CD chloride (dhypy-CDCl), was synthesized and employed as a chiral selector for the first time in capillary electrophoresis (CE) for the enantioseparation of anionic and ampholytic acids. The effects of the running buffer pH, chiral selector concentration, analyte structure and organic modifier on the enantioseparation were studied in detail. The chiral selectivity and resolution for most of the studied analytes decreased as the buffer pH increased in the range of 6.0–9.0. Increasing selector concentration led to decreased effective mobility, increased chiral selectivity and resolution for most of the studied analytes. Moreover, the hydroxyl groups located on the dihydroxypyrrolidine substituent of the dhypy-CDCl could have influence on the chiral separation.

Several series of novel structurally well-defined positively charged CDs, applicable to alpha-, beta- and gamma-CDs for chiral separation using CE and chromatographic techniques have been developed. The chiral resolution capabilities of different series CDs towards amino acids and anionic analytes in CE are systematically investigated by considering all separation parameters including CD type, alkyl chain length of the cations attached to the CD rim, CD concentration, buffer pH, separation temperature and organic solvent. Typical results are demonstrated in the context. Examples of chiral separation with HPLC and supercritical fluid chromatography are first demonstrated by using coated chiral stationary phases (CSPs). Optimum CD loading content on the coated CSPs was explored in the chiral separation of neutral analytes.

Enantiomer separations were performed on three beta-cyclodextrin-based chiral stationary phases (CSP) containing the pernaphthylcarbamoylated beta-cyclodextrin (CSP 1), peracetylated beta-cyclodextrin (CSP 2) and permethylated beta-cyclodextrin (CSP 3) as chiral selectors by capillary liquid chromatography and pressure-assisted capillary electrochromatography in this study. Triethylammonium acetate/MeOH or phosphate buffer/MeOH was used as the mobile phase. The experimental factors affecting chiral separations have been examined for each CSP, including pH of the buffers, methanol content and applied voltage. Under optimal separation conditions, a number of racemic compounds were resolved into their enantiomers on three cyclodextrin-based CSP. A comparative study on the performance of three CSP revealed the presence of carbonyl functional groups as well as aromatic rings in the cyclodextrin derivatives, enhanced the interaction between the analytes and CSP, and thus improved enantioselectivity of the CSP.

Four cationic beta-cyclodextrin derivatives, namely mono-6-(3-methylimidazolium)-6-deoxy-perphenylcarbamoyl-beta-cyclodextrin chloride (MPCCD), mono-6-(3-methylimidazolium)-6-deoxyper(3,5-dimethylphenylcarbamoyl)-beta-cyclodextrin chloride (MDPCCD), mono-6-(3-octylimidazolium)-6-deoxyperphenylcarbamoyl-beta-cyclodextrin chloride (OPCCD) and mono-6-(3-octylimidazolium)-6-deoxyper(3,5-dimethylphenylcarbamoyl)-beta-cyclodextrin chloride (ODPCCD), have been synthesized and physically coated onto porous spherical silica gel to obtain novel chiral stationary phases (CSPs). The performances of these CSPs are studied on high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) using 18 racemic aryl alcohols as test analytes. Among these four CSPs, OPCCD shows the best separation results for all analytes on both HPLC and SFC analyses. Chromatographic studies reveal that the CSPs consisting of an n-octyl group on the imidazolium moiety and phenylcarbamoyl groups on the cyclodextrin ring provide enhancement of analyte-chiral substrate interactions over CSPs bearing the methyl group on the imidazolium moiety and 3,5-dimethylphenylcarbamoyl groups on the cyclodextrin ring.

Allyl phenyl thiophene ether as novel potential dielectric materials for organic thin film transistors have been synthesized by coupling 2-bromothiophene with 4-bromo allyl phenyl ether and was systematically characterized by elemental analysis and NMR. 4-bromo allyl phenyl ether was synthesized by the reaction between 4-bromophenol and allyl bromide. Self assembled mono-layers of these materials have been covalently grafted onto (111) hydrogenated silicon surfaces through thermal hydrosilation with the alkene end by Si–C bonding mechanism. Monolayer formation was carried out using solutions of the alkene in the high boiling point solvent 1,3,5-triethylbenzene and was characterized by X-ray photoelectron spectroscopy (XPS), contact angle, Atomic Force Microscopy(AFM) and Scanning Tunneling Microscopy (STM). We anticipate these monolayers as potential dielectric materials for organic electronics

We describe a protocol for the synthesis of mono-6-amino-6-deoxy-cyclodextrin hydrochloride (CD-NH3Cl), applicable to alpha-, beta- and gamma-cyclodextrin. These structurally simplest, highly water-soluble cationic cyclodextrins can be widely used in molecular recognition, chiral separation and drug delivery studies. Starting from commercially available chemicals, CD-NH3Cl is synthesized in four steps: (i) selective tosylation of cyclodextrin by the use of p-toluenesulfonyl chloride to afford mono-6-(p-toluenesulfonyl)-6-deoxy-cyclodextrin (Ts-CD); (ii) azide substitution of Ts-CD with sodium azide to afford mono-6-azido-6-deoxy-cyclodextrin (CD-N3); (iii) reduction of CD-N3 with triphenylphospine followed by hydrolysis to prepare mono-6-amino-6-deoxy-cyclodextrin (CD-NH2); and (iv) treatment of CD-NH2 with hydrochloric acid to afford the titled CD-NH3Cl with good yield. The overall protocol requires approximately 2 weeks.

The synthesis of mono-6-(3-methylimidazolium)-6-deoxyperphenylcarbamoyl-β-cyclodextrin chloride (MPCCD) and its application in chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) are being reported. This chiral selector is coated onto silica gel in different weight percentages (15, 20 and 35%, w/w) to obtain CSPs having different loading content. These new chiral stationary phases are tested using normal-phase HPLC for enantioseparation of racemic aromatic alcohols. Indeed, the enantiodiscrimination abilities of these CSPs are found to be influenced by the loading content of the chiral selector. Among the three columns (MPCCD-C15, MPCCD-C20 and MPCCD-C35), the best enantioseparation results are obtained using a column containing 20% (w/w) of MPCCD (MPCCD-C20). The resolution ( R s ) obtained for p -fluorophenylethanol, p -chlorophenylethanol, p -bromophenylethanol, p -iodophenylethanol and p -fluorophenyl-3-buten-1-ol using MPCCD-C20 ranges from 3.83 to 5.65. Good enantioseparation results are obtained for these analytes under SFC separation conditions using the MPCCD-C20 column.

We describe a protocol for the synthesis of mono-6(A)-(1-butyl-3-imidazolium)-6(A)-deoxy-beta-cyclodextrin chloride (BIMCD), a cationic, water-soluble cyclodextrin used in the chiral separation of amino acids and anionic pharmaceuticals by capillary electrophoresis. Starting from commercially available chemicals, BIMCD is synthesized in five steps. The first step involves a nucleophilic substitution between p-toluenesulfonyl chloride and imidazole to afford 1-(p-toluenesulfonyl)imidazole (A). In the second step, a nucleophilic substitution between beta-cyclodextrin and A affords mono-6(A)-(p-toluenesulfonyl)-6(A)-deoxy-beta-cyclodextrin (B). In the third step, a nucleophilic substitution between 1-bromobutane and imidazole affords 1-butylimidazole (C). In the fourth step, a nucleophilic addition between A and C affords BIMCD tosylate. In the final step, anion exchange using an ion-exchange resin yields BIMCD as a highly water-soluble solid. Each step takes up to 2 d, including the time required for product purification. The overall protocol requires approximately 6 d.

Ionic hydrogels are attractive for the protection, delivery and controlled release of charged biomacromolecules such as proteins, growth factors or DNA. We have preparted and characterized a series of photocrosslinked anionic hydrogels based on water soluble methacrylated (MA) O-carboxymethylchitosan (OCMCS) and polyethylene glycol (PEG) diacrylate. OCMCS samples with varying degree of substitution of carboxymethyl group ranging from 0.69 to 1.86 were prepared by reacting native chitosan with different amounts of monochloroacetic acid. The OCMCS products demonstrated differences in solubility, zeta potential (-52.7 to -12.8 mV) and thermal decomposition temperature (260 to 283 degrees C). The OCMCS products were then reacted with glycidyl methacrylate to make ultra-violet (UV) crosslinkable OCMCS-MAs which were blended with PEG diacrylate, a photoinitiator and water and successfully photocrosslinked to create OCMCS-MA/PEG hydrogels. Water uptake of the hydrogels varied between 226 % to 358 % and the porous structures of the prepared OCMCS-MA/PEG hydrogels could be modulated by the degree of methacrylation. All the OCMCS-MA/PEG hydrogel substrates similarly supported attachment and proliferation of Smooth Muscle Cells (SMCs). The in vitro biodegradation of these hydrogels, in the presence of SMCs, could be controlled by the degree of methacrylation; weight loss after 9-week was (15+/-1) % and (19+/-2) % using OCMCS 4-MA (12.7 % MA) and OCMCS 1-MA (4.6 % MA), respectively. In addition, the hydrogel based on the most anionic OCMCS 1 showed higher adsorption of basic TGF-beta(1) than similarly modified -agarose, -dextran, and -chondroitin sulfate hydrogels.

New positively charged monosubstituted α- and γ-cyclodextrins at the primary face were synthesized in good yields by displacement of the monotosylates of α- and γ-cyclodextrin with amine, alkylamines or alkylimidazoles. The influence of CD’s cavity size on the resolution abilities of CD derivatives towards model analytes, that is, dansyl amino and carboxylic acids, were investigated. Results show that the formation of the inclusion complex might play an important role in chiral recognition, in that cationic γ-CD derivatives gave better resolution abilities than their α- and γ-CD analogues, presumably due to tight fit between CD hosts and the anionic guest racemates.

Azido cellulose phenylcarbamate (AzCPC) was synthesized regioselectively and chemically immobilized onto aminized silica gel to afford urea-bonded chiral stationary phases (CSPs). The obtained CSPs showed good enantioselectivity in HPLC towards various racemates using normal phase eluants (hexane/2-propanol, hexane/chloroform or hexane/2-propanol/chloroform).

Enantioseparations of fourteen dansyl amino acids were achieved by using a positively-charged single-isomer beta-cyclodextrin, mono-(3-methyl-imidazolium)-beta-cyclodextrin chloride, as a chiral selector. Separation parameters such as buffer pH, selector concentration, separation temperature, and organic modifier were investigated for the enantioseparation in order to achieve the maximum possible resolution. Chiral separation of dansyl amino acids was found to be highly dependent on pH since the degree of protonation of these amino acids can alter the strength of electrostatic interaction and/or inclusion complexation between each enantiomer and chiral selector. In general, the chiral resolution of dansyl amino acids was enhanced at higher pH, which indicates that the carboxylate group on the analytes may interact with the imidazolium group of cationic cyclodextrin. For most analytes, a distinct maximum in enantioresolution was obtained at pH 8.0. Moreover, the chiral separation can be further improved by careful tuning of the separation parameters such as higher selector concentration (e.g. 10 mM), lower temperature, and addition of methanol. Enantioseparation of a standard mixture of these dansyl amino acids was further achieved in a single run within 30 min.

A family of 6-mono(3-alkylimidazolium)-β-cyclodextrins with one primary hydroxyl group replaced by an alkylimidazolium cation has been developed. The effect of alkyl substitutents on the enantioresolution ability of these single-isomer cyclodextrins towards dansyl amino acids has been studied by capillary electrophoresis. Systematical investigations on the effect of buffer pH and selector concentration on the enatioseparation show that chiral selectors with a shorter alkyl chain (R = C n H 2 n +1 , n ≤ 4) presented more powerful chiral recognition ability. These newly introduced single-isomer β-cyclodextrin derivatives proved to be effective chiral selectors for most selected dansyl amino acids at low buffer pH (e.g. pH 5.0) with selector concentration no less than 3 mM. The apparent complex stability constants between alkylimidazolium β-CDs and dansyl amino acids were also theoretically determined by using the mobility difference model proposed by Wren and Rowe. The side alkyl chains from both dansyl amino acids and alkylimidazolium β-CDs displayed significant effect on the apparent complex stability constants. Both the optimum selector concentrations calculated according to the model, however, were much lower than the experimental values giving the maximum chiral resolution of enantiomers.

A novel cyclodextrin intermediate, mono-2(A)-allylcarbamido-2(A)-deoxy-permethylated β-cyclodextrin, was synthesized by reacting allylamine and newly prepared mono-2(A)-azido-2(A)-deoxy-permethylated β-cyclodextrin by the Staudinger reaction and anchored onto porous silica beads by a one-pot hydrosilylation and immobilization procedure to afford a novel chiral stationary phase. This stationary phase acts as a new member of the previous chiral stationary phase series immobilized on the cyclodextrin C2 position. This stationary phase depicted enantiomeric separation abilities toward a series of bicyclic and tricyclic racemates under reversed-phase conditions. The resolutions for hesperetin and naringenin achieved on the current phase reached 3.91 and 1.11, respectively, much higher than the previous permethylated β-cyclodextrin with the linkage at the C6 position.

The chiral resolving ability of a novel single-isomer cationic β-cyclodextrin (CD), mono-6A-propylammonium-6A-deoxy-β-cyclodextrin chloride (PrAMCD), as a chiral selector in capillary electrophoresis (CE) is reported in this work for the enantioseparation of hydroxy, carboxylic acids and amphoteric analytes. The effect of chiral selector concentration on the resolution was studied. Good resolutions were achieved for hydroxy acids. Optimum resolutions were obtained even at 3.5 mM CD concentration for carboxylic acids. The electrophoretic method showed good linearity and reproducibility in terms of migration times and peak areas, which should make it suitable for routine analysis. In addition, baseline chiral separation of a six-acid mixture was achieved within 20 min. PrAMCD proved to be an effective chiral selector for acidic analytes.

Two novel chiral stationary phases (CSPs) were prepared based upon the regioselective immobilizations of beta-cyclodextrin (beta-CD) at its C2 position to the silica support. The mono-2A-azido-2A-deoxyperphenylcarbamoylated beta-cyclodextrin and mono-2A-azido-2A-deoxyperacetylated beta-cyclodextrin were synthesized by selective tosylation and azidolysis followed by perfunctionalisation. The derivatised cyclodextrins were then immobilized onto the aminised silica gel via the Staudinger reaction to provide new chiral stationary phases. Their application to high-performance liquid chromatography (HPLC) enantioseparation of racemic compounds was demonstrated using beta-adrenergic blockers, flavonone compounds, benzodiazepinones, antihistamines and weakly protolytic compounds, of which good separations were achieved for some racemic compounds, for instance, bendroflumethiazide (Rs 6.26), oxazepam (Rs 5.99), temazepam (Rs 2.85) and althiazide (Rs 1.13) when compared with the corresponding CSPs where the beta-CD molecule was regioselectively immobilized at the C6 position. The enantiodiscriminatory properties of these CSPs were found to be affected by the orientation of the CD cavity under reversed-phase conditions, and also by the derivitising groups of the CD. The HPLC results inferred that the mono-6A-azido-6A-deoxyperphenylcarbamoylated CD CSP (CD bonded at C6 position to silica) exhibited slightly better chiral recognition ability than mono-2A-azido-2A-deoxyperphenylcarbamoylated CD CSP under the normal-phase and reversed-phase modes on the separation of 31 different racemic compounds and drugs. On the contrary, higher chiral recognition abilities were observed on the mono-2(A)-azido-2A-deoxyperacetylated CD CSP compared to mono-6A-azido-6A-deoxyperacetylated CD CSP.

A new quartz crystal microbalance (QCM) sensor that provides enantioselectivity to tryptophan enantiomers, with a high selectivity and sensitivity, was fabricated by the use of the molecularly imprinted polymers (MIPs) as the artificial biomimetic recognition material. Non-covalent molecular imprinting polymers were synthesized using acrylamide (AM) and trimethylolpropane trimethacrylate (TRIM) as a functional monomer and a cross-linking agent, respectively. The preparation of the thin permeable film coatings on QCM surface is described as well as the results and discussion on the sensitivity and selectivity of the coatings to tryptophan enatiomers under different conditions. The sensor was able to discriminate between the l - and d -tryptophan enantiomers in citric acid buffer solutions owing to the enantioselectivity of the imprinted sites. The detection limit is 8.8 μM. The influence of the cross-linking agent concentration on the sensitivity and selectivity of the fabricated polymer films was investigated and optimized. The enantionmeric composition of l - and d -tryptophan enantiomer mixtures can be determined by measuring the frequency shifts of the sample. The characteristics of the thiol monolayer and MIP film on the surface of the QCM were studied by atomic force microscopy (AFM).

The enantioseparation of a wide spectrum of anionic analytes was successfully performed by using mono(6-amino-6-deoxy)-β-cyclodextrin (β-CD-NH2). The effects of buffer pH and selector concentration on migration time and resolution of analytes were studied in detail. Good results were obtained for the chiral separations of hydroxy and carboxylic acids. A clear maximum in selectivity was found for most analytes. The introduced positive charge can greatly improve the chiral recognition ability of β-CD-NH2 towards anionic analytes. The binding constants of eight analytes with β-CD-NH2 were determined and suited well with the mobility difference model (by Wren). Moreover, a standard mixture of five acids was baseline separated within 23 min.

A facile synthetic approach for mono-6-amino-6-deoxy-beta-cyclodextrin (beta-CD-NH2) was proposed. Its hydroxy chloride salt, mono-6-ammonium-6-deoxy-beta-cyclodextrin chloride (beta-CD-NH3Cl) was further prepared and used for the enantioseparation of various anionic and ampholytic analytes by capillary electrophoresis (CE). The effect of background electrolyte (BGE) pH and selector concentration on the enantioseparation was studied. Results showed that beta-CD-NH3Cl displayed powerful chiral resolution ability towards anionic analytes. In addition, baseline separation of a standard mixture consisting of eight acids was achieved within 35 min.

A novel series of AB-type polymers comprised of alternating carbazolyl and pyridinyl units were synthesized using palladium(0)-catalyzed Suzuki cross-coupling reaction in good to high yields. In this series of alternating copolymers, the electron-rich 2,7-(N-(2-ethylhexyl)carbazolyl) unit was used as a light-emitting unit, and the electron-deficient unit of pyridinyl was introduced to tune the wavelength of the emitting light and improve their electron transportation. These polymers were characterized by 1H NMR and 13C NMR, gel permeation chromatography (GPC), thermal analysis, UV−vis, fluorescence spectroscopy, and cyclic voltammetry (CV). The glass transition temperature of these polymers ranged from 120 to 150 °C, and the polymers showed high thermal stability with decomposition temperatures in the range 370−400 °C in nitrogen. The different linkage pattern of pyridinyl units in the copolymer backbone has a significant effect on the electronic and optical properties in solution and in film phases. For ...

A novel single-isomer positively charged beta-cyclodextrin (beta-CD), mono-6(A)-butylammonium-6(A)-deoxy-beta-cyclodextrin tosylate (BuAM-beta-CD), has been synthesized, characterized, and used for the enantioseparations of alpha-hydroxy acids, carboxylic acids, and ampholytic analytes by capillary electrophoresis in acidic aqueous background electrolytes. The effective mobilities of all studied analytes decreased with increasing concentration of CD. Satisfactory resolutions were obtained for alpha-hydroxy acids over a wide range of chiral selector concentration. The optimum CD concentration was lower than 5 mM for the carboxylic acids, while higher than 20 mM for alpha-hydroxy acids. Inclusion complexation in combination with ion pair interaction seemed to account for the chiral discrimination process. The hydrogen bonding may provide secondary contribution for the chiral resolution of alpha-hydroxy acids. In addition, BuAM-beta-CD was further proved to be an effective chiral selector for anionic analytes by the baseline enantioseparation of a six-acid mixture within 20 min.