Theoretical and experimental studies on the fluorescence properties of aluminum(III), cadmium(II), zinc(II), and copper(II) complexes of substituted 8-hydroxyquinoline

Fifty-five 8-hydroxyquinoline (8-HQ) derivatives are synthesized and the corresponding aluminum(III), cadmium(II), copper(II), and zinc(II) metal complexes are prepared and their fluorescent activities are evaluated. The results indicate that the aluminum complexes have the best fluorescence properties, followed by zinc and cadmium complexes, while almost no fluorescence is observed with the copper complexes. The relationship between the fluorescence properties and complex structure is summarized and a predictive three-dimensional quantitative structure–property relationship model is established using the multifit molecular alignment rule of Sybyl program. With the introduction of groups at the C-2 position or electron-withdrawing groups to the 8-hydroxyquinoline framework, fluorescence wavelength blue shifts are observed with the zinc, aluminum, and cadmium complexes. At the same time, a red shift of the fluorescence emission wavelength is detected for the aluminum and zinc complexes when C-5 of 8-hydroxyquinoline was substituted with halogens or a methyl group. Moreover, the zinc, cadmium, and aluminum complexes with 2,4-dimethyl substituents on the 8-hydroxyquinoline all show good fluorescence properties. The highest occupied molecular orbital and lowest unoccupied molecular orbital energies of the complexes are also calculated and the fluorescence properties of the metal complexes are analyzed from the viewpoint of molecular orbitals.

EXTRACTION OF ANIONIC CADMIUM COMPLEXES WITH ORGANIC SOLUTIONS OF QUATERNARY AMMONIUM SALTS

The anion-exchange extraction of thiocyanate, chloride and iodide cadmium complexes by solutions of quaternary ammonium salts chlorides in organic solvents (toluene, carbon tetrachloride, ethyl acetate, isobutyl alcohol, nitrobenzene) was studied. Extraction involves solutions of alkyl dimethylbenzylammonium chlorides (R-N+(CH3)2-CH2C6H5-Cl-) and alkyl dimethylethyl-benzylammonium (R-N+(CH3)2-CH2-CH2C6H5-Cl-), where R is a straight alkyl chain, mainly C12 - C14. The composition of the cadmium anionic complexes was established by the analysis of the calibration curves E = f (pCCd (II)) constructed from cadmium sulfate solutions against the background of various contents of thiocyanate, chloride and iodide ions (ndicator electrode - ion-selective electrode with a membrane, which based on a nitrobenzene solution of tetradecylammonium bromide). The extraction process is estimated quantitatively using a distribution coefficient (D). The value of D is calculated taking into account the cadmium concentration in the aqueous phase before and after extraction. The dependence of the distribution coefficient on the organic solvent dielectric constant, the concentration and stability of the anionic complexes of cadmium is shown. So, for the indicated cadmium acidocomplexes, the minimum D values were obtained using low-polar toluene and carbon tetrachloride, and the maximum values were obtained using highly polar isobutyl alcohol and nitrobenzene. If the concentration of cadmium (II) is reduced by a factor of 100 for the cadmium rhodanide and iodide complexes, the value of D decreases by 1.6-1.9 times, for the chloride complex, by 1.2 times in the case of polar isobutyl alcohol and nitrobenzene, and 2.9-3.5 times in the case of low-polar solvents. It was experimentally established that in the series [Cd(SCN)4]2- - [CdI4]2-- [CdCl4]2- the value of D decreases for all the studied systems. The observed regularity is related both to the stability of the corresponding cadmium (II) complexes in aqueous solutions and to their hydrophobicity.

On the supramolecular properties of neutral, anionic and cationic cadmium complexes harvested from dithiolate–polyamine binary ligand systems

Three Cd(ii) complexes [Cd(i-mnt)(DMSO)2]n (1), {[Cd(i-mnt)pn]·2H2O} (2), and [Cd(i-mnt)3][Cd(tren)2]2 (3) harvested from 1,1-dicyanoethylene-2,2-dithiolate (i-mnt2−) and polyamine ligand systems have been designed, synthesized and structurally characterized.

In vitro nephrotoxicity and anticancer potency of newly synthesized cadmium complexes

Complexes based on heavy metals have great potential for the treatment of a wide variety of cancers but their use is often limited due to toxic side effects. Here we describe the synthesis of two new cadmium complexes using N(4)-phenyl-2-formylpyridine thiosemicarbazone (L1) and 5-aminotetrazole (L2) as organic ligands and the evaluation of their anti-cancer and nephrotoxic potential in vitro. The complexes were characterized by Single-crystal X-ray data diffraction, 1HNMR, FT-IR, LC/MS spectrometry and CHN elemental analysis. Next, cytotoxicity of these cadmium complexes was evaluated in several cancer cell lines, including MCF-7 (breast), Caco-2 (colorectal) and cisplatin-resistant A549 (lung) cancer cell lines, as well as in conditionally-immortalized renal proximal tubule epithelial cell lines for evaluating nephrotoxicity compared to cisplatin. We found that both compounds were toxic to the cancer cell lines in a cell-cycle dependent manner and induced caspase-mediated apoptosis and caspase-independent cell death. Nephrotoxicity of these compounds was compared to cisplatin, a known nephrotoxic drug, in vitro. Our results demonstrate that compound {2}, but not compound {1}, exerts increased cytotoxicity in MCF-7 and A549 cell lines, combined with reduced nephrotoxic potential compared to cisplatin. Together these data make compound {2} a likely candidate for further development in cancer treatment.