Michael T. Blanda

Syntheses and characterizations of three vinyl copolymers containing pendant calix[4]arenes

Three new copolymers containing pendant calix[4]arene units have been synthesized via radical initiated reactions involving a vinylic calix[4]arene monomer with methylacrylate, acrylonitrile, and styrene. The calix[4]arene monomer was locked into tie cone conformation by appending four ethoxyethyl groups to its lower rim. The upper rim of the calix[4]arene monomer, which was the site of polymerization, was monofunctionalized with a modified acrylate ester moiety. A seven atom spacer group was incorporated between the bulky calixarene core and the acrylate moiety in order to minimize steric interactions which proved to impede the polymerization. The copolymers were designed to take advantage of the well-established binding interactions of calixarenes with neutral molecules and ions. The ultimate goal of this project is to develop materials that are suitable for incorporation into chemical sensor devices such as ion-specific electrodes, semipermeable membranes and quartz microbalances.

Determination of alkali metal ion binding selectivities of calixarenes by matrix-assisted laser desorption ionization and electrospray ionization in a quadrupole ion trap

Abstract Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and electrospray ionization mass spectrometry (ESI-MS) are used to evaluate the alkali metal ion binding selectivities of a series of calixarenes. Each calixarene of interest is mixed with one or more alkali metal salts (1:100 ratio of calixarene to metal), either in the ESI solution or on the MALDI probe surface, and the relative binding selectivities are directly determined from the intensities of the calixarene/metal complexes in the mass spectra. For t -butylcalix[4]arene-tetraacetic acid tetraethyl ester (calixarene 1 ), complexation of Na + is favored over complexation of K + , in agreement with prior solution results obtained by conventional methods. For the three calixarenes that do not have t -butyl groups on the upper rims, the calixarenes preferentially bind K + over Na + , thus demonstrating that size selective complexation can be probed with both the ESI and MALDI methods. Collision-activated dissociation results indicate that the phenyl oxygens, but not necessarily the ethoxy ethyl oxygens of the lower rims, are the primary binding sites for the alkali metal ions.

Syntheses and characterizations of two copolymers containing cone conformations of calix[4]arenes in the polymer backbone

Two new polymers containing calix[4]arenes in the cone conformation were synthesized via condensation reactions.

Efficient syntheses of calix[4]arenes in the 1,2-alternate conformation via intramolecular benzoate ester migrations

Abstract A previously known imidazole-initiated intramolecular ester migration was modified by replacing the imidazole with Cs2CO3 to effect the efficient conversion of 25, 27-bis-p-methoxy-, 25,27-bis-p-fluoro and 25, 27-bisbenzoyloxycalix[4]arene in the flattened cone conformation to the corresponding 25,26-benzoyloxy compounds in the 1,2-alt. The rearrangement was highly efficient for the unsubstituted and methoxy-substituted esters; the 1,2-alternate isomers were isolated in 80–88% yield, but less efficient for the fluoro-substituted ester (isolated yield 58%). The p-methoxy- and p-fluoroesters were further functionalized in subsequent alkylation reactions with methyl p-toluenesulfonate and pentaethyleneglycol-di-p-tosylate to produce dimethoxy- and calixcrown-ester derivatives in the 1,2-alt. in moderate to good yields. The high yields of the 1,2-alt. are attributed to a π-metal template effect involving the soft cesium ion from the base, two aryl rings and the two phenolate oxygens of the deprotonated calixarene.

Syntheses of Ditopic Calix[4]arene Receptor Molecules Containing Silicon on the Upper Rim

Abstract Calix[4]arene molecules containing two and four silicon atoms appended to the upper rim of the cone conformation were synthesized via hydrosilation of the corresponding di- and tetra-p-allyl calixarene ethers. The p-allyl calixarene ethers were prepared via the well known Claisen rearrangement which transferred the allyl groups originally on the lower rim of the cone to the upper rim. The silated calix[4]arenes were designed to function as ditopic receptor molecules that will bind cations through the oxygen atoms at the lower rim and anions through the silicon atoms on the upper rim. The hydrosilation reaction provided an easy method for introducing different functionality on the silicon atoms in order to attenuate their relative stability and Lewis acidity.

Synthesis and chloride binding properties of a Lewis acidic tetratin(IV) calixarene

The Lewis acidic calix[4]arene with four covalently attached diphenylmonochlorotin(IV) centers was synthesized and its stannate complex with chloride was studied by 119Sn NMR.

Functionalization dependence of the electron beam sensitivity for a conformationally immobile calix[6]arene resist

Calixarenes form a group of compounds that have been studied as high resolution negative electron beam resists. In this work, resists based on a conformationally immobile calix[6]arene molecule were synthesized and their sensitivities measured while the number of attached functional groups was systematically varied. This provided a direct test of the effect of the degree of functionalization on the electron beam resist sensitivity. The synthesis produced two basic molecular conformations: a cone conformer and a 1,2,3-alternate conformer. The number of attached allyl groups was deliberately varied from 0 to 8 allyls in steps of 2 allyls per synthesis. The resulting nine different resists were exposed and contrast curves were measured by atomic force microscopy. The least sensitive were the unfunctionalized calix[6]arenes with threshold doses of about 2 mC/cm2. The fully functionalized conformers had threshold doses around 0.1 mC/cm2. The sensitivities of both conformers were found to scale directly with th...

Synthesis, characterization, and investigation of a conformationally immobile calix[6]arene as a negative electron beam resist

Calixarenes of a variety of molecular weights and with several different functional attachments have been studied as high resolution, high contrast negative electron beam resists. In this article, results are presented for a new type of calixarene molecule to be used as an electron beam resist. The molecule differs from previous calixarene resists through the use of bridging groups to limit its conformational mobility and by having only a partial functionalization of the available phenol units with allyl groups to enhance the resist sensitivity. Both the sensitivity and contrast of the calixarene were measured. The measured contrast was found to be 4, while the sensitivity was 3.6mC∕cm2 which is comparable to other fully functionalized calix[6]arene resists. A closer comparison of this calixarene with similar calixarenes indicates that the measured sensitivity is better than would be expected for this partially functionalized molecule and that full functionalization might not be necessary to obtain a sign...