Molecular structures, charge distributions, and vibrational analyses of the tetracoordinate Cu(II), Zn(II), Cd(II), and Hg(II) bromide complexes of p-toluidine investigated by density functional theory in comparison with experiments

Imidazopyridine Based Fluorescent Turn-Off Sensor for Selective Recognition of Fe3+ Ions and its Application in Test Strips

A series of 2-ethoxycarbonyl imidazopyridines have been synthesised and characterised by various spectroscopic techniques (1H NMR, 13C NMR, FTIR and HRMS). Among these compounds, 3e was selected for metal sensing applications due to its favourable photophysical properties. 3e demonstrated high selectivity and sensitivity for detecting Fe3+ ions, even in the presence of other competing ions in a mixture of acetonitrile/water (1:9, v/v). It showed a turn-off fluorescence response with a fluorescence detection limit of 3.9 µM. The decrease in the fluorescence intensity of 3e is due to paramagnetic quenching resulting from its interaction with Fe3+ ions. Job's plot analysis indicated a 1:1 binding ratio between 3e and Fe3+. Density Functional Theory (DFT) calculations revealed a reduced HOMO-LUMO energy gap for the 3e-Fe3+ complex, suggesting successful complexation. The binding constant, calculated using the Benesi-Hildebrand equation, was determined to be 2.845 × 103 M-1, further confirming the strong interaction between 3e and Fe3+. Time-based studies revealed excellent photostability of 3e and its rapid response time for detecting Fe3+. Real-time detection of Fe3+ was successfully achieved using sensor-coated filter paper, demonstrating the practical utility of 3e for rapid assays in real samples.

Effects of Temperature on Enantiomerization Energy and Distribution of Isomers in the Chiral Cu13 Cluster

In this study, we report the lowest energy structure of bare Cu₁₃ nanoclusters as a pair of enantiomers at room temperature. Moreover, we compute the enantiomerization energy for the interconversion from minus to plus structures in the chiral putative global minimum for temperatures ranging from 20 to 1300 K. Additionally, employing nanothermodynamics, we compute the probabilities of occurrence for each particular isomer as a function of temperature. To achieve that, we explore the free energy surface of the Cu₁₃ cluster, employing a genetic algorithm coupled with density functional theory. Moreover, we discuss the energetic ordering of isomers computed with various density functionals. Based on the computed thermal population, our results show that the chiral putative global minimum strongly dominates at room temperature.