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Öğe Application of L-prolinamides as highly efficient organocatalysts for the asymmetric Michael addition of unmodified aldehydes to nitroalkenes(Pergamon-Elsevier Science Ltd, 2012) Naziroglu, Hayriye Nevin; Durmaz, Mustafa; Bozkurt, Selahattin; Demir, Ayhan Sitki; Sirit, AbdulkadirThe asymmetric Michael addition of aldehydes to nitroolefins was investigated using a combination of L-prolinamide derivatives and various acidic additives. (S)-1,1'-Bi-2-naphthol was found to be the most effective co-catalyst and afforded the nitroaldehyde products with excellent yields (up to 95%), enantiomeric excesses (up to 99%) and diastereoselectivity ratios (up to 99:1). (C) 2012 Elsevier Ltd. All rights reserved.Öğe Calixarene based chiral solvating agents for ?-hydroxy carboxylic acids(Elsevier, 2013) Bozkurt, SelahattinNovel chiral calix[4]arene derivatives functionalized at the lower rim have been prepared from the reactionof p-tert-butylcalix[4]arene diamine derivative with N-Phthaloyl-L-phenylalanine or (2S)-2-((benzyloxy)carbonyl)amino)-3-hydroxypropanoic acid or (2S,3R)-2-((benzyloxy)carbonyl)amino-3-hydroxybutanoic acid in 63-81% yield. The structures of these receptors were characterized by FTIR, H-1, C-13 and 2D COSY NMR spectroscopy. The enantioselective recognition of these receptors towards the enantiomers of racemic carboxylic acids was studied by H-1 NMR spectroscopy. The molar ratios of the chiral compounds with each of the enantiomers of guests were determined by using Job plots. The Job plots indicate that the hosts form 1:2 instantaneous complexes with all guests. The receptors exhibited different chiral recognition abilities toward the enantiomers of racemic guests. NMR studies demonstrated that the receptors function as highly effective chiral shift reagents for determining the enantiomeric purity of a series of carboxylic acids. (c) 2013 Elsevier B.V. All rights reserved.Öğe Fabrication and characterization of calix[4]arene Langmuir-Blodgett thin film for gas sensing applications(Springer, 2017) Acikbas, Yaser; Bozkurt, Selahattin; Halay, Erkan; Capan, Rifat; Guloglu, Mehmet Levent; Sirit, Abdulkadir; Erdogan, MatemIn this work, the Langmuir-Blodgett (LB) technique was applied onto the different substrates such as quartz, quartz crystals and gold coated glass for fabricating LB thin films with 25,27-(Dipropylmorpholinoacetamido)-26,28-dihydroxycalix[4]arene. The characteristics of the calix[4]arene LB films were evaluated by UV-Vis, atomic force microscopy (AFM), quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) measurements. The mass deposited on the quartz crystal per bilayer was predicted as 2028.80 ng (7.65 ng mm(-2)) for the calix[4]arene LB film. The sensing abilities of this LB film towards the development of room temperature organic vapor sensing devices were also examined. QCM and SPR systems were fixed to investigate vapor sensing performance of macrocyclic LB films during exposure to volatile organic compounds (VOCs). The macrocyclic LB thin films were more sensitive to dichloromethane than other vapors. The sensitivity and detection limit values of the calix[4]arene QCM sensor to dichloromethane vapor were calculated as 2.023 Hz ppm(-1) and 1.482 ppm, respectively. The sensitivities of the calix[4]arene LB films against organic vapors can be explained with the host-guest interaction between the cavity of molecule and the organic vapor molecules. It is determined that the calix[4]arene LB film is more sensitive to dichloromethane than other vapors at room temperature and the calix[4]arene is a promising material serving as a vapor sensing device.Öğe A Novel Calix[4]arene Thiourea Decorated with 2-(2-Aminophenyl)benzothiazole Moiety as Highly Selective Chemical Gas Sensor for Dichloromethane Vapor(Wiley-V C H Verlag Gmbh, 2021) Durmaz, Mustafa; Acikbas, Yaser; Bozkurt, Selahattin; Capan, Rifat; Erdogan, Matem; Ozkaya, CansuA newly synthesized calix[4]arene thiourea derivative decorated with 2-(2-aminophenyl)benzothiazole unit is selected to take part important role in host-guest interactions of the macrocyclic molecules. p-tert-butylcalix[4]arene dithiourea (C[4]-DT) Langmuir-Blodgett (LB) thin films are prepared and characterized to develop a new sensing element for the detection of seven different organic vapors (dichloromethane, chloroform, acetone, benzene, carbon tetrachloride, toluene and m-xylene). The preparation of C[4]-DT-based thin films onto the different substrates was successfully and uniformly achieved with linear regressions of 0.9971 and 0.9954 for coating onto quartz glass and quartz crystal, respectively. The frequency shift (61.01 Hz) and the mass deposited onto quartz crystal (969.80 ng) were calculated for each layer. The swelling dynamics of C[4]-DT QCM chemical sensor was also illuminated by developing the early time Fick's diffusion equation. The sensing measurements can be concluded that owing to its high sensitivity (6.63 Hz/ppm), fast response and low detection limit (0.45 ppm), this proposed C[4]-DT LB coated sensor is expected to be promising alternative chemical sensor for detection of DCM vapor.Öğe A novel turn-on fluorometric reporter-spacer-receptor chemosensor based on calix[4]arene scaffold for detection of cyanate anion(Wiley, 2021) Bozkurt, Selahattin; Halay, Erkan; Durmaz, Mustafa; Topkafa, Mustafa; Ceylan, OzgurHerein, a novel calix[4]arene compound, which was modified by the 2-(2-aminophenyl)benzothiazole fragment with cyanate recognition function was designed based on the reporter-spacer-receptor sensing system. The construction was done via two-step reaction, and the desired sensor 4 was characterized by FT-IR, H-1-, C-13-NMR, and fluorescence spectroscopy along with HRMS data. The sensor candidate showed distinct fluorometric cyanate detection by means of reporter feature of selected benzothiazole constituent. In the presence of cyanate, the sensor gave a turn-on-type fluorescence at 482 nm with a large stokes' shift. Furthermore, it was observed that our fluoroionophore 4 is highly selective toward cyanate over remaining anions such as sulfate, phosphate, fluoride, chloride, bromide, iodide, chlorate, and nitrate in 10% aqueous solution of DMSO. The 1:2 stoichiometric ratio of the 4-cyanate complex was given the best fit with Job's plot based on the titration data. The association constant (K-a) of sensor 4 with cyanate is determined to be 1.64 x 10(5) M-2. The obtained limit of detection (LOD) value for cyanate anion, 312 nM, clearly revealed the remarkable sensitivity of the chemosensor 4. This supramolecular method provides a highly adaptive technique for the detection of cyanate and so cyanide ions by current international standard methods.Öğe Optical and Vapor Sensing Properties of Calix[4]arene Langmuir-Blodgett Thin Films with Host-Guest Principles(Taylor & Francis Inc, 2018) Acikbas, Yaser; Bozkurt, Selahattin; Erdogan, Matem; Halay, Erkan; Sirit, Abdulkadir; Capan, Rifat25,27-(Dipropylmorpholinoacetamido)-26,28-dihydroxycalix[4]arene was used as a chemical sensor material in this work. The calix[4]arene LB thin films were prepared onto a gold-coated glass and quartz glass substrates to fabricate a thin film chemical sensor element. Atomic Force Microscopy (AFM) and Surface Plasmon Resonance (SPR) techniques were used to characterize all the calix[4]arene LB thin films. The film thickness and the refractive index of thin films can be evaluated with the fitted experimental SPR datas. The refractive index and the thickness per monolayer of LB films were determined as a 1.58 +/- 0.04 and 1.27 +/- 0.09nm, respectively. The calix[4]arene LB thin film chemical sensor element was exposed to dichloromethane, chloroform, benzene and toluene vapors. The SPR kinetic measurements displayed that, the photodetector response change, I-rf for saturated dichloromethane vapor is much larger than the other vapors with the I-rf value of 48 au and the diffusion coefficient value of 5.1 x 10(-16) cm(2)s(-1). Swelling process was analyzed by well known Fick's Equations. In this approach diffusion coefficients for swelling were conformed to the square root of time and were correlated with the volatile organic compounds. Our results showed that calix[4]arene thin film has a highly selective with a large response to dichloromethane vapor.Öğe Recent applications of chiral calixarenes in asymmetric catalysis(Beilstein-Institut, 2018) Durmaz, Mustafa; Halay, Erkan; Bozkurt, SelahattinThe use of calixarenes in asymmetric catalysis is receiving increasing attention due to their tunable three-dimensional molecular platforms along with their easy syntheses and versatile modification at the upper and lower rims. This review summarizes the recent progress of synthesis and use of chiral calixarenes in asymmetric syntheses which emerged later than 2010.
