A highly selective acridine-based fluorescent probe for detection of Al3+ in alcoholic beverage samples.

4,5-Bis(phtalimidomethyl)acridine (L) was studied as a chemosensor for metal ions in alcoholic matrices and showed to be selective for Al3+, through a linear fluorescence enhancement of 230% in the concentration range of 10-70 µmol L-1. Benesi-Hildebrand and Job's formalisms indicated the formation of a 1:1 (Al3+:L) complex with a binding constant of 6.30 × 103 L mol-1. DFT/TDDFT calculations allowed access to the energies of frontier orbitals and could explain the fluorescence augmentation upon complex formation, due to the restraining of PET process. Limit of detection and limit of quantification (R2 = 0.998, least squares method) are 1.130 and 3.768 µmol L-1, respectively, and validation was verified based on the variation of several analytical conditions. Practical application in spiked Brazilian sugarcane spirit showed recovery of (84 ± 0.42)% with no effect of interfering ions.

A Facile Preparation of a New Water-Soluble Acridine Derivative and Application as a Turn-off Fluorescence Chemosensor for Selective Detection of Hg2.

A new acridine-based chemosensor was prepared, characterized and investigated for quantitative detection of Hg2+ ions in aqueous solutions. DFT and TD-DFT calculations showed that formation of a coordination bond between Hg2+ and the thiolate-sensor accounts for the fluorescence quenching, forming [HgLSCl2]2- as the most stable species. Limit of detection and limit of quantification were as low as 4.40 and 14.7 µmol L-1, respectively (R2 = 0.9892, least squares method), and a linear concentration range of 14.7-100 µmol L-1. Benesi-Hildebrand and Job formalisms are in accordance with the formation of a stable complex with a 1:1 (metal ion/sensor) ratio, and a determined binding constant of 5.14 × 103 L mol-1. Robustness was verified based on the variation of several analytical conditions. In addition, the method presented maximum relative standard deviation of 4.6%, and recovery results was (90.3 ± 4,6)% from distilled water, with no effect of interfering ions. Analytical figures of merit showed that the sensor can be an attractive low cost alternative for detection of Hg2+.

DFT analysis of the linkage isomerism in penta(ammine)ruthenium(II/III) complexes of benzotriazole: Natural bond orbital method approach and a comprehensive energy decomposition analysis.

Penta(ammine)ruthenium benzotriazole complexes [RuII/III (NH3 )5 bta]+/2+ and [RuII/III (NH3 )5 btaH]2+/3+ (bta and btaH are the deprotonated and neutral form of the triazole ligand, respectively) can exhibit two linkage isomers κN1 and κN2. This system was investigated by density functional theory natural bond orbitals analysis and Su-Li energy decomposition analysis. Steric, electrostatic, exchange, repulsion, polarization, and dispersion energy components of the total metal-ligand interaction were quantitatively evaluated, and revealed that the overall metal-triazole ligand is comprised of donor-acceptor interactions like σ-donation and π-back-donation, which favors a specific isomer depending on the oxidation state of the ruthenium and the charge of the ligand. Further, activation energies (ΔG‡ ) for linkage isomerization reactions were calculated. Results were correlated with experimental chemical-electrochemical data and two plausible mechanisms are discussed. © 2019 Wiley Periodicals, Inc.

Metal complexes of a pentadentate N2O3bis(semicarbazone) Schiff-base. A case study of structure-spectroscopy correlation.

Schiff condensation of 2,6-diformyl 4-methylphenol with semicarbazide hydrochloride in 1:2 molar ratio produces the bis(semicarbazone) ligand, herein called H3L. A comprehensive spectroscopic analysis of the compound was performed by (1)H and (13)C NMR, FTIR and electronic spectroscopies. Assignments to the UV-vis spectrum of H3L were supported by semi-empirical quantum mechanics ZINDO/S calculations. The ligand H3L forms monoclinic crystals in the space group P21/c and its structure is stabilized by classic hydrogen bonds with propanone molecules. It promptly reacts with first row metal ions to produce the following coordination compounds: [Co2(L)(µ-NO3)]·DMF, [Ni2(H2L)(µ-CH3COO)(CH3COO)2]·2H2O, [Cu2(L)(µ-NO3)(H2O)2]·H2O, [Cu2(L)(µ-CH3COO)(H2O)2]·H2O and [Cu2(H2L)(µ-Cl)Cl2]·3H2O, that have different compositions, depending on the degree of deprotonation of the ligand upon coordination. Electronic and EPR spectroscopies as well as effective magnetic moment measurements of the complexes were used in an attempt to better understand their mode of coordination, the microsymmetry around the metal ions and magnetic properties.

Crystal structure of 4-formyl-pyridine semicarbazone hemihydrate.

The mol-ecule of the title compound C7H8N4O·0.5H2O, alternatively called (E)-1-(pyridin-4-yl-methyl-ene)semi-carb-azide hemihydrate, is in the E conformation and is almost planar; the r.m.s. deviation of the positions of the atoms of the pyridine ring from the best-fit plane is 0.0039 Å. The C, N and O atoms of the rest of the mol-ecule sits close on this plane with a largest deviation of 0.115 (4) Šfor the O atom of the semicarbazone moiety. There is an intra-molecular N-H⋯N hydrogen bond. In the crystal, mol-ecules are linked into an infinite three-dimensional network by classical N-H⋯Os (s = semicarbazone) and Ow-H⋯N (w = water) hydrogen bonds.

A comprehensive electronic structure description of a biscyanotetraazacobalt(III) macrocyclic complex.

Molecular modeling and a detailed spectroscopic characterization of the macrocyclic complex [Co(meso)(CN)(2)](+) (meso = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) is herein presented. Structural, electronic and vibrational features are discussed and assignments were proposed on the basis of semi-empirical (molecular mechanics (MM+), ZINDO/S and PM3) quantum-mechanics calculations. The energy and the composition of the molecular orbitals of the complex were calculated and a quantitative diagram was constructed. The simulated UV-vis spectrum exhibited a reasonably good accordance with the experimental one and fully assignments of seven bands were made. An optimized configuration of the complex showed a strong cobalt-cyanide axial bond in agreement with the major contribution of the cyanide to the composition of the molecular orbitals in contrast to a discrete participation of the macrocyclic meso to the ground state of the complex.

Synthesis and spectroscopic characterization of copper(II) tetraazaiminooxime macrocyclic complexes--a tetragonal distortion analysis.

Herein we describe the synthesis and spectroscopic (infrared and UV-vis) analysis of [Cu(II)(dohpn)(L)](n+) (dohpn=imineoximic tetraazamacrocyclic ligand 2,3,9,10-tetramethyl-1,4,8,11-tetraazaundecane-1,3,8,10-tetraen-11-ol-1-olate) and L=SCN(-), I(-), Cl(-) (n=0) and 4-aminopyridine (ampy), 4,4'-bipyridine (bipy), imidazole (im), 2-aminopyrazine (ampz) and water (n=1+). The following order of the Jahn-Teller stabilization energy (cm(-1)) was observed: I(-)(6452)

Interaction of 2- and 4-mercaptopyridine with pentacyanoferrates and gold nanoparticles.

2-Mercapto- and 4-mercaptopyridine (2- and 4MPy) react with the [Fe(CN)(5)(H(2)O)](3-) complex, forming the S-coordinated [Fe(CN)(5)(2MPy)](3-) and the N-coordinated [Fe(CN)(5)(4MPy)](3-) complexes. The rates of formation and dissociation of the [Fe(II)(CN)(5)(2MPy)](3-) complex were determined as k(f) = 294 dm(3) mol(-1) s(-1) and k(d) = 0.019 s(-1) by means of stopped-flow technique. The equilibrium constants for the iron(II) and -(III) species were calculated as K(f)(II) = 1.5 x 10(4) mol(-1) dm(3) and K(f)(III) = 1.3 x 10(6) mol(-1) dm(3), in comparison with 2.6 x 10(5) and 3.4 x 10(4) mol(-1) dm(3), respectively, for the 4MPy isomer. In the presence of gold nanoparticles, both 2- and 4MPy can displace the stabilizing citrate species, leading to substantial aggregation in aqueous solution, as deduced from the surface-enhanced Raman spectroscopy effect and from the decay of the 520-nm plasmon band accompanied by the rise of the characteristic exciton band at 650 nm. The [Fe(CN)(5)(4MPy)](3-) complex promotes strong stabilization of the gold nanoparticles by interacting through the S atom. On the other hand, the labile [Fe(CN)(5)(2MPy)](3-) complex induces aggregation, delivering the 2MPy ligand to the gold nanoparticles.