Development of a selective fluorimetric technique for rapid trace determination of zinc using 3-hydroxyflavone

Synthesis, spectroscopic characterization and biological activities of complexes of light lanthanide ions with 3-hydroxyflavone

New solid compounds of light lanthanide ions with 3-hydroxyflavone were synthesized in good yields (up to 85 %). The resulting complexes have been thoroughly characterized using various analytical and spectral techniques, including elemental analysis, complexometry, thermogravimetry, UV-VIS, FT-IR, 1H NMR, 109AgNPET LDI MS and fluorescence spectroscopy. The molecular formulas of the complexes were determined as follows: Ln(3HF)3, where 3HF-3-hydroxyflavone, Ln = La(III), Pr(III), Nd(III) and Ln(3HF)3·nH2O, where n = 1 for Ln = Ce(III), Sm(III), Eu(III), and n = 2 for Gd(III). Thermogravimetric studies revealed that the water molecules in the hydrated compounds are located in the outer coordination sphere. Based on the spectral data, it was noted that lanthanide ions interacted with the 3OH and 4CO groups of 3-hydroxyflavone. The effect of lanthanide ion chelation on the excited-state intramolecular proton transfer (ESIPT) process and fluorescence emission of 3HF was investigated. It was found that coordination with metal ions can suppress the ESIPT process and enhance the fluorescence emission of 3HF. The synthesized compounds were also screened for their antibacterial activity, free radical scavenging capacity, and interaction with BSA. The results showed that the complexes exhibit higher biological activity compared to the ligand.

Ligand-Tuned Multi-Color Luminescence of Single Aluminum (III) Ion Atomic Centers and Their Selective Sensitivity to Different Metal Ions

Achieving multi-color luminescence with a single atomic center in transition metal complexes is a challenge. In this work, luminescent materials with tunable emission properties were realized by complexation between aluminum (III) ions with the ligands 3-hydroxyflavone (3-HF) and 5,7-dichloro-8-hydroxyquinoline (DCHQ). Aluminum (III) complexes with a single ligand emitted blue from 3-HF and green from DCHQ. High quantum yields (QYs) of 29.42% and 37.00% were also obtained, respectively. DFT calculations revealed details of the photophysical properties of the complexes. Correspondingly, cyan light emission was obtained if these two complexes were mixed together, from which the emission wavelength was located at 470 nm and the QY was 20.52%, under 290 nm excitation. More importantly, the cyan light emitted by the mixtures had selective sensitivity to different metal ions, resulting in either quenching the fluorescence (in the case of Fe3+) or enhancing the fluorescence (in the case of In3+). The fluorescence enhancement effect of In3+ on metal complexes has not been previously reported, neither for transition metal nor lanthanide ions. The linear quenching behavior of Fe3+ functions in the 50–700 μM concentration range, and the linear enhancement behavior of In3+ is demonstrated in the 300–800 mM concentration range.

Spectroscopic study of molecular structure, antioxidant activity and biological effects of metal hydroxyflavonol complexes

Flavonols with varied hydroxyl substitution can act as strong antioxidants. Thanks to their ability to chelate metals as well as to donate hydrogen atoms they have capacity to scavenge free radicals. Their metal complexes are often more active in comparison with free ligands. They exhibit interesting biological properties, e.g. anticancer, antiphlogistic and antibacterial. The relationship between molecular structure and their biological properties was intensively studied using spectroscopic methods (UV-Vis, IR, Raman, NMR, ESI-MS). The aim of this paper is review on spectroscopic analyses of molecular structure and biological activity of hydroxyflavonol metal complexes.

A Simple Spectrofluorimetric Method for Iron Determination with a Chalcone-Based Schiff Base

A chalcone-based Schiff base (5), capable of detecting iron (III) in partially aqueous media, has been designed, then synthesized by the condensation of 3-formyl-2-hydroxyquinoline and acetophenone. To determine iron (III) ion, a simple spectrofluorimetric method was developed by using the synthesized Schiff base. The developed method was validated by analyzing the certified reference material (CRM-SA-C Sandy Soil C). During the process of the determination of iron in food samples, satisfactory accuracy was obtained for spinach and rocket. Nitric acid and hydrogen fluoride were used for the digestion of the certified reference material whereas only nitric acid was used for food samples, in a closed microwave system. Measurements were carried out by using the modified standard addition method. The standard addition graph was linear until 5.0 mg/L. in determination of iron (III). Detection and quantification limits were 0.06 and 0.20 mg/L., respectively. The presented method is simple, time-saving, cost-effective and suitable for determination of iron content of soil and foods.