Substitution of thiophene oligomers with macrocyclic end caps and the colorimetric detection of Hg(II).

Alkyl substitution at the α position(s) of mono-, bi-, and terthiophenes via electrophilic addition of macrocyclic end caps combines linear, π-conjugated aromatic compounds and annular macrocycles. Addition of the Hg(II) ion to terthiophene adducts produces intense color changes, allowing for the selective, colorimetric detection of mercury(II). Chemical oxidation of the asymmetric terthiophene adduct produces the sexithiophene oligomer.

Large amplitude, proton- and cation-activated latch-type mechanical switches: O-protonated amides stabilized by intramolecular, low-barrier hydrogen bonds within macrocycles.

Large amplitude molecular switches have been developed using oxonium ions as the novel switching mechanism. Macrocycles that contain a polyether ring that are preorganized and of optimum geometry such that strong, linear Low-Barrier Hydrogen Bonds (LBHB, 2.4 to 2.6 A in length) are formed between a protonated amide oxygen and a cyclic ether, that lend significant iminol character to the amide. Deprotonation yields a large conformational change between closed and open forms, mindful of a new hinged, latch-type mechanical proton switch. Numerous open and closed forms have been characterized by X-ray crystallography, and the intramolecular hydrogen bond that forms between the protonated amide oxygen and the cyclic polyether oxygen accounts for the stability of these new acids. The open form of the deprotonated adducts persist in solution as indicated by the magnitude of coupling constants and other Nuclear Overhauser Effect experiments. Different saturated and unsaturated solid acids have been characterized including products derived from acetonitrile, propionitrile, caprylonitrile, acrylonitrile and adiponitrile, and also by reaction with primary amides in the case of phenyl and norbornene derivatives. We have also demonstrated that metal cations can replace the proton in the switching mechanism, characteristic of nascent synthetic pores.

Luminescence detection of transition and heavy metals by inversion of excited states: synthesis, spectroscopy, and X-ray crystallography of Ca, Mn, Pb, and Zn complexes of 1,8-anthraquinone-18-crown-5.

A lumophore composed of anthraquinone attached to a macrocyclic polyether ring containing an intraannular carbonyl is capable of selectively detecting Pb(2+)() ion in solution using an alternative photophysical detection mechanism. Of the various methods available for detection of ions in solution, a mechanism involving inversion of excited states has not been previously employed for the detection of transition and heavy metals. In this mechanism, nonradiative n-pi transitions are replaced by radiative pi-pi transitions upon complexation by a suitable guest cation. Optimum fluorescence enhancement is achieved using cations of high charge, large cations that form long bonds within the host, and cations which do not coordinate solvent or the counteranion, all of which are necessary for inversion of excited states to occur. Photophysical properties and binding constants of this new class of luminescence sensors are provided, as well as the X-ray crystallographic results for Pb(2+), Mn(2+), and Zn(2+) complexes of 1,8-oxybis(ethylene-oxyethyleneoxy)anthracene-9,10-dione (1), referred to as 1,8-anthraquinone-18-crown-5. ([1.Pb](ClO(4))(2) (2) (monoclinic, P21/n, a = 8.0303(6) A, b = 25.976(2) A, c = 12.1616(9) A, beta = 94.956(1) degrees , Z = 4, 4980 reflections [I > or = 2sigma(I)], R1 = 0.0266, wR2, 0.0500, 173(2) K). [1.Mn(H(2)O)(NCCH(3))](ClO(4))(2) (5) (monoclinic, P21/c, a = 10.132(2) A, b = 11.8030(4) A, c = 23.999(7) A, beta = 95.75(2) degrees , Z = 4, 3000 reflections [I > or = 2sigma(I)], R1 = 0.0488, wR2, 0.0938, 203(2) K). [1.Zn(H(2)O)(NCCH(3))](ClO(4))(2) (6) (monoclinic, P21/c, a = 10.177(10) A, b = 11.977(6) A, c = 24.166(4) A, beta = 95.83(4) degrees , Z = 4, 3061 reflections [I > or = 2sigma(I)], R1 = 0.0673, wR2, 0.1729, 295(2) K).).