Imidazoanthraquinone derivatives for the chromofluorogenic sensing of basic anions and trivalent metal cations.

Four imidazoanthraquinone derivatives (2a-d) were synthesized and characterized and their coordination behavior against selected anions and cations tested. Acetonitrile solutions of probes showed charge-transfer absorptions in the 407-465 nm range. The four probes emitted in the 533-571 nm interval.

Triphenylamine-benzimidazole derivatives: synthesis, excited-state characterization, and DFT studies.

The synthesis and comprehensive characterization of the excited states of four novel triphenylamine-benzimidazole derivatives has been undertaken in solution (ethanol and methylcyclohexane) at room temperature. This includes the determination of the absorption, fluorescence, and triplet-triplet absorption spectra, together with quantum yields of fluorescence, internal conversion, intersystem crossing, and singlet oxygen. From the overall data the radiative and radiationless rate constants could be obtained, and it is shown that the compounds are highly emissive with the radiative decay dominating, with more than 70% of the quanta loss through this deactivation channel.

Synthesis and evaluation of thiosemicarbazones functionalized with furyl moieties as new chemosensors for anion recognition.

A family of heterocyclic thiosemicarbazone dyes (3a-f and 4) containing furyl groups was synthesized in good yields, characterized and their response in acetonitrile in the presence of selected anions was studied. Acetonitrile solutions of 3a-f and 4 showed absorption bands in the 335-396 nm range which are modulated by the electron donor or acceptor strength of the heterocyclic systems appended to the thiosemicarbazone moiety. Fluoride, chloride, bromide, iodide, dihydrogen phosphate, hydrogen sulphate, nitrate, acetate and cyanide anions were used in recognition studies.

(Oligo)thienyl-imidazo-benzocrown ether derivatives: synthesis, photophysical studies and evaluation of their chemosensory properties.

A series of novel (oligo)thienyl-imidazo-benzocrown ethers were synthesised through a simple method and evaluated as fluorimetric chemosensors for transition metal cations. Interaction with Ni(2+), Pd(2+), and Hg(2+) in ACN/DMSO solution (99:1) was studied by absorption and emission spectroscopy. Chemoselectivity studies in the presence of Na(+) were also carried out and a fluorescence enhancement upon chelation (CHEF) effect was observed following Hg(2+) complexation.

The influence of the relative position of the thiophene and pyrrole rings in donor-acceptor thienylpyrrolyl-benzothiazole derivatives. A photophysical and theoretical investigation.

A detailed spectroscopic and photophysical study has been carried out on a series of heterocyclic compounds-known to display nonlinear optical properties-consisting on a electron donating thienylpyrrolyl pi-conjugated system functionalized with an electron acceptor benzothiazole moiety. The absorption, emission and triplet-triplet absorption together with all relevant quantum yields (fluorescence, intersystem crossing and internal conversion), excited state lifetimes and the overall set of deactivation rate constants (k(F), k(IC) and k(ISC)) were obtained in solution at room (293 K) and low (77 K) temperature. The optimized ground-state molecular geometries for the compounds together with the prediction of the lowest vertical one-electron excitation energy and the relevant molecular orbital contours for the compounds were also determined using density functional theory (DFT) at the B3LYP/3-21G* level.

Synthesis and characterization of the ground and excited states of tripodal-like oligothienyl-imidazoles.

Six new thiophene oligomers, here designated as tripodal-like oligothienyl-imidazoles, were synthesized and have been investigated in ethanol solution at room and low temperature. The oligomers bear a common core where two or more thiophenes are linked to one or more imidazole units that further links through its alpha-position to a different number of incremental thiophene units. The study involves a comprehensive spectral and photophysical investigation where the properties of the singlet and triplet states have been investigated regarding absorption, fluorescence and phosphorescence, transient triplet-triplet absorption together with all relevant quantum yields (fluorescence, phi(F), internal conversion, phi(IC), intersystem crossing, phi(T,) and singlet oxygen, phi(Delta)) and lifetimes.

Spectral and photophysical characterization of donor-pi-acceptor arylthienyl- and bithienyl-benzothiazole derivatives in solution and solid state.

A comprehensive study has been made in solution at room temperature (293 K), low temperature (77 K), and in thin films (Zeonex matrixes) of the spectral and photophysical properties of six arylthienyl- and bithienyl-benzothiazole derivatives functionalized with different donor groups. Similar experiments have been carried out with two related precursors (containing the arylthienyl and aryl-bithienyl conjugated systems), and results are compared. Singlet-singlet and triplet-triplet absorption spectra, emission spectra together with lifetimes and quantum yields have been obtained, and from these data the rates for all the radiative and nonradiative processes determined, providing information on the dominant decay processes.

Synthesis and ion sensing properties of new colorimetric and fluorimetric chemosensors based on bithienyl-imidazo-anthraquinone chromophores.

Novel colorimetric receptors for fluoride ion sensing containing anthraquinone as a chromogenic signaling unit and imidazo-2,2'-bithiophene binding sites are reported. Well-defined color change was observed upon addition of fluoride ions to acetonitrile solutions of receptors 2. Compounds 2a-c, deprotonated after fluoride ion addition, were studied as metal ion chemosensors in the presence of Zn(II), Hg(II), and Cu(II) in acetonitrile solutions, especially compound 2a which displayed a marked change from pink to yellow-gold colors upon complexation.