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.     

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. The arylthienyl-benzothiazole derivatives show high fluorescence quantum yields (phi(F)) with negligible internal conversion (phi(IC)), whereas the bithienyl-benzothiazoles display lower but still significant phi(F) values, but now radiationless processes (phi(IC) and phi(ISC)) are competitive. A comparison with the analogous oligothiophenes is made. Singlet oxygen yields were also determined and the triplet energy transfer to (3)O2 to produce (1)O2 was found to be highly efficient with values of S(Delta)(= phi(Delta)/phi(T)) varying from 0.4 to 1.     

The Expression of The Laplace Transform of (P±i0)λ as a K-transform

In this article we obtain the Laplace transform (1.1) of the distributions ( P ± i 0)^λ (2.2) as a K _ν-transform of order ν=( n -2)/2 (see Theorem 4, formula (3.17)).     

Optimization of high pressure bioactive compounds extraction from pansies (Viola × wittrockiana) by response surface methodology

Response surface methodology (RSM) was employed for the first time to optimize high pressure extraction (HPE) conditions of bioactive compounds from pansies, namely: pressure (X₁: 0–500?MPa), time (X₂: 5–15?min) and ethanol concentration (X₃: 0–100%). Consistent fittings using second-order polynomial models were obtained for flavonoids, tannins, anthocyanins, total reducing capacity (TRC) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity. The optimum extraction conditions based on combination responses for TRC, tannins and anthocyanins were: X₁?=?384?MPa, X₂?=?15?min and X₃?=?35% (v/v) ethanol, shortening the extraction time when compared to the classic method of stirring (approx. 24?h). When the optimum extraction conditions were applied, 65.1?mg of TRC, 42.8?mg of tannins and 56.15?mg of anthocyanins/g dried flower were obtained. Thus, HPE has shown to be a promising technique to extract bioactive compounds from pansies, by reducing the extraction time and by using green solvents (ethanol and water), for application in diverse industrial fields.     

Synthesis and Structural Analysis of New Palladium(II) Thiosaccharinates with Triphenylphosphane or Diphosphanes

A series of palladium(II) thiosaccharinates with triphenylphosphane (PPh₃), bis(diphenylphosphanyl)methane (dppm), and bis(diphenylphosphanyl)ethane (dppe) have been prepared and characterized. From mixtures of thiosaccharin, Htsac, and palladium(II) acetylacetonate, Pd(acac)₂, the palladium(II) thiosaccharinate, Pd(tsac)₂ (tsac: thiosaccharinate anion) ( 1 ) was prepared. The reaction of 1 with PPh₃, dppm, and dppe leads to the mononuclear species Pd(tsac)₂(PPh₃)₂ · MeCN ( 2 ), [Pd(tsac)₂(dppm)] ( 3 ), Pd(tsac)₂(dppm)₂ ( 4 ), and [Pd(tsac)₂(dppe)] · MeCN ( 5 ). Compounds 2 , 4 , and 5 have been prepared also by the reaction of Pd(acac)₂ with the corresponding phosphane and Htsac. All the new complexes have been characterized by chemical analysis, UV/Vis, IR, and Raman spectroscopy. Some of them have been also characterized by NMR spectroscopy. The crystalline structures of complexes 3 , and 5 have been studied by X‐ray diffraction techniques. Complex 3 crystallizes in the monoclinic space group P2₁/n with a = 16.3537(2), b = 13.3981(3), c = 35.2277(7) Å, β = 91.284(1)°, and Z = 8 molecules per unit cell, and complex 5 in P2₁/n with a = 10.6445(8), b = 26.412(3), c = 15.781(2) Å, β = 107.996(7)°, and Z = 4. In compounds 3 and 5 , the palladium ions are in a distorted square planar environment. They are closely related, having two sulfur atoms of two thiosaccharinate anions, and two phosphorus atoms of one molecule of dppm or dppe, respectively, bonded to the Pd^II atom. The molecular structure of complex 3 is the first reported for a mononuclear Pd^II‐dppm‐thionate system.     

Bioaerosols chemometric characterization by laser-induced fluorescence: Air sample analysis

A laser-induced fluorescence (LIF) system was optimized using a solution of Micrococcus luteus in ethanol/water 50% (v/v) to obtain spectra in the gas phase of 46 bioaerosols. Experimental designs such as Plackett-Burman and factorial design were applied. The fluorescence spectra were treated chemometrically by principal component analysis, linear discriminant analysis and hierarchical cluster analysis to classify the microorganisms according to family, morphology and gram. The best results were obtained using LDA. The method was applied to air samples and the LIF results allowed to characterize bioaerosols reliability. The robustness of the technique was demonstrated by the identification of many bacteria.     

The domino chemistry approach to molecular complexity: competing domino processes modulated by the substitution pattern

Oxidative cleavage with lead tetraacetate results in the synthesis of different oxygen heterocycles starting from the same unsaturated 1,2-diol of type I by tuning of the substitution pattern at the angular position. When this compound bears a functional substituent, such as an alkoxy, ester, alkenyl, or simply a hydrogen, more than one reaction pathway are in competition. The process allows for the selective formation of three different complex ring systems, by the appropriate choice of the angular substituent, leading to either a ring-expanded type 1, ring-retained type 2, or domino products 3.