In this paper, the morphology and bulk physical properties of 1,3-dialkylimidazolium bis{(trifluoromethane)sulfonyl}amide ([(C(N/2))(2)im][NTf(2)]) are compared to that of 1-alkyl-3-methylimidazolium bis{(trifluoromethane)sulfonyl}amide ([C(N-1)C(1)im][NTf(2)]) for N = 4, 6, 8, and 10. For a given pair of ionic liquids (ILs) with the same N, the ILs differ only in the symmetry of the alkyl substitution on the imidazolium ring of the cation. Small-wide-angle X-ray scattering measurements indicate that, for a given symmetric/asymmetric IL pair, the structural heterogeneities are larger in the asymmetric IL than in the symmetric IL. The correlation length of structural heterogeneities for the symmetric and asymmetric salts, however, is described by the same linear equation when plotted versus the single alkyl chain length. Symmetric ILs with N = 4 and 6 easily crystallize, whereas longer alkyl chains and asymmetry hinder crystallization. Interestingly, the glass transition temperature is found to vary inversely with the correlation length of structural heterogeneities and with the length of the longest alkyl chain. Whereas the densities for a symmetric/asymmetric IL pair with a given N are nearly the same, the viscosity of the asymmetric IL is greater than that of the symmetric IL. Also, an even-odd effect previously observed in molecular dynamics simulations is confirmed by viscosity measurements. We discuss in this paper how the structural heterogeneities and physical properties of these ILs are consistent with alkyl tail segregation.

The stepwise synthesis of two new selenium coronands containing an odd number of selenium atoms, starting from the fragments HO-(CH,),-C1, HO-(CH,),-Br, HO-(CH,),-SeCN, and NCSe-(CH,),-SeCN, is described. The key diol containing one selenium atom, 4-selenaheptan-l,7-diol4, was obtained in 97% yield from the reaction of 3-bromo-1 -propano1 3 and the selonolate anion derived from 3-selenocyanato-1 -propano1 2 by sodium metal reduction in liquid ammonia. The ditosylate 5, obtained from 4, was then treated with the bisselenolate anion derived from 1,3-bisselenocyanatopropane 6 to give the target selenium coronand, 1,5,9-triselenacyclododecane [12Se3] 7, in 96% yield. The ditosylate 5 was treated with two equivalents of the selenolate anion derived from 2 to give a second key acyclic diol8 now containing three selenium atoms. The ditosylate 9, obtained from 8, was then treated with the bisselenolate anion derived from 6 to afford the second target coronand, 1,5,9,13,17-pentaselenacycloeicosane [20Se5] 11 in 44% yield.Key words: selenium coronands, stepwise synthesis, macrocycles, heterocycles.RCsumC : Utilisant des fragments OH-(CH,),-C1, HO-(CH,),-Br, HO-(CH,),-SeCN et NCSe-(CH,),-SeCN, on a rCalisC la synthkse par Ctapes de deux nouveaux coronands du stlCnium contenant un nombre impair d'atomes de stlCnium. On a obtenu le diol clC contenant un atome de sClCnium, le 4-~Cltnahepta-l,7-diol(4), avec un rendement de 97% par la reaction du 3-bromopropan-1-ol(3) avec l'anion sClCnolate dCrivC du 3-sC1Cnocyanato-propan-1-01 (2) par riduction avec du sodium mCtallique dans l'ammoniac liquide. On traite alors le ditosylate 5, obtenu i partir du composC 4, avec l'anion bissClCnolate dCrivC du 1,3-bissC1Cnocyanatopropane 6 pour obtenir le coronand sClCniC dtsirk, le 1,5,9-trisC1CnacyclododCcane [12Se3] (7), avec un rendement de 96%. On traite le ditosylate 5 avec deux Cquivalents de l'anion sClCnolate obtenu i partir du composC 2, pour obtenir le deuxikme diol acyclique clC (8) qui contient maintenent trois atomes de sC1Cnium. Le ditosylate 9, obtenu i partir du produit 8, est alors trait6 par l'anion bissClCnolate dCrivC du composC 6 pour fournir le deuxieme coronand dCsirt, le 1,5,9,13,17-pentasCltnacycloeicosane [20Se5] (ll), avec un rendement de 44%.

Abstract:The stepwise synthesis of 1,5,9,13-tetraselenacyclohexadecan-3-017 from the reaction of sodium propane-1,3-bisselenolate-2-01 with 4.8-diselenaundecan-1,ll -di-p-toluenesulfonate 5 in THF and ethanol in 62% yield is described. Compound 5 is obtained from the corresponding diol3, which is obtained, in turn, from the reaction of sodium propane-1,3-bisselenolate with two equivalents of 3-chloropropanol. 1,5-Diselenacyclooctan-3-019 and 1,5,9,13-tetraselenacyclohexadecan-3,l I-diol 10 are obtained in yields of 43% and 1 I%, respectively, from the one-step reaction of sodium propane-1,3-bisselenolate-2-01 with 1,3-dibromopropane. Polymers with pendant selenium coronands, 1,5-diselenacyclooctane (8Se2) and 1,5,9,13-tetraselenacyclohexadecane ( 16Se4), have been prepared by free radical polymerization of the corresponding selenium coronands 9 and 7, derivatized as their acryloyl esters 11 and 12. Copolymers of methyl acrylate and 3,7-diselenacyclooctyl acrylate 11 have also been prepared in analogous fashion. The polymers have been characterized by 'H and I3C NMR, IR, and UV-visible spectroscopy. The redox chemistry of polymer-bound selenium coronands in solution, and in the form of thin films coated on electrodes, has been determined by electrochemical methods. Selenium coronands attached to the polymer chain exhibit enhanced oxidative stability compared to monomeric analogues, presumably because restrictive motion of polymerbound moieties inhibits inter-and intra-molecular degradation reactions. Electroactivity of polymer-modified electrodes is restricted to a few monolayers close to the electrode surface. Spatial separation of coronands along the chain, achieved by copolymerization with electro-inert methyl acrylate, gave copolymer-modified electrodes that possessed even greater redox stability than their corresponding homopolymers. Furthermore, by blending electro-inert poly(methy1 acrylate) with electroactive selenium coronand copolymers, polymer-modified electrodes that possessed superior electrochemical stability were obtained.Key words: selenium coronands, polymers, electrochemistry, dications.Resume : On dCcrit la synthkse par Ctape (rendement de 62%) du 1,5,9,13-tCtrasC1CnacyclohexadCcan-3-ol,7, rCalisie par rtactions par Ctapes du propane-l,3-bissC1Cnolate-2-01 de sodium avec le di-I>-toluknesulfonate de 4,s-disC1CnundCcan-1,11-diyle, 5, dans le THF et I'Cthanol. On obtient le composC 5 a partir du diol3 correspondant qui est obtenu, j . son tour, par la rCaction du propane-1.3-bissC1Cnolate de sodium avec deux Cquivalents de 3-chloropropanol. Les I ,5-disClCnacyclooctan-3-0l,9, et 1,5,9,13-tCtrasClCnacyclohexadCcan-3,l I -diol, 10, ont Ct C obtenus avec des rendements respectifs de 43% et de I 1 % par des rCactions en une Ctape du propane-1.3-bissC1Cnolate-2-01 de sodium avec le 1,3-dibromopropane. On a prCparC des polymbres portant des pendants de coronands de sClCnium, 1,5-disC1Cnacyclooctane (8Se2) et 1,5,9,13-tCtrasClCnacyclohexadCcane (16Se4). en procCdant j. la polymCrisation des coronands st...

imum intercondylar distance, maximum bicondylar distance and maximum medial intercondylar distance were measured. All data were subjected to discriminant functions analysis.All nine measurements were significantly higher in males than females. Among these measurements, the right condyle length, minimum intercondylar distance and foramen magnum width were able to deter-

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