Copper complexes with new oxaaza-pendant-armed macrocyclic ligands: X-ray crystal structure of a macrocyclic copper(II) complex

A Five-Coordinate Copper(II) Complex Constructed from Sterically Hindered 4-Chlorobenzoate and Benzimidazole: Synthesis, Crystal Structure, Hirshfeld Surface Analysis, DFT, Docking Studies and Antibacterial Activity

A new CuII complex (1) was synthesized by reacting 4-chlorobenzoic acid, benzimidazole and metal salt using ethanol–water (1:1 v/v) as a solvent at room temperature. The complex was characterized by single-crystal X-ray analysis, FTIR and UV—vis spectroscopy. A distorted square pyramidal geometry of the CuII center was observed from the single-crystal X-ray study, which also revealed that the uncoordinated oxygen atom of the carboxylate anions forms intermolecular hydrogen bonds with the N–H groups of the benzimidazole ligands. The Hirshfeld analysis results revealed that the molecular packing of 1 is mainly controlled by O...H (12.7%), Cl...H (16.4%), C...H (24.4%) and H...H (31.1%) contacts. Density functional theory (DFT) calculations were performed to compute the HOMO–LUMO energy gap and electrostatic potential map for the charge transfer regions within the molecule and identify the possible electrophilic and nucleophilic regions of the molecule. A number of reactivity parameters calculated on the basis of EHOMO and ELUMO show its significant polarizability and reactive nature. Complex 1 was also examined and screened for its potential antibacterial effect using the agar well diffusion method. The newly synthesized complex showed an effective and higher killing rate of the microbes in antibacterial testing compared to the parent ligand. The CuII complex (1) showed an enhanced inhibitory activity against P. aeruginosa and equally demonstrated greater binding affinity with DNA gyrase (1KIJ) compared to its ligands according to the molecular docking studies.

Fluorene-based metal-ion sensing probe with high sensitivity to Zn2+ and efficient two-photon absorption

The photophysical, photochemical, two-photon absorption (2PA) and metal ion sensing properties of a new fluorene derivative (E)-1-(7-(4-(benzo[d]thiazol-2-yl)styryl)-9,9-bis(2-(2-ethoxyethoxy)ethyl)-9H-fluoren-2-yl)-3-(2-(9,10,16,17,18,19,21,22,23,24-decahydro-6H dibenzo[h,s][1,4,7,11,14,17]trioxatriazacycloicosin-20(7H)-yl)ethyl)thiourea (1) were investigated in organic and aqueous media. High sensitivity and selectivity of 1 to Zn(2+) in tetrahydrofuran and a water/acetonitrile mixture were shown by both absorption and fluorescence titration. The observed complexation processes corresponded to 1:1 stoichiometry with the range of binding constants approximately (2-3) x 10(5) M(-1). The degenerate 2PA spectra of 1 and 1/Zn(2+) complex were obtained in the 640-900 nm spectral range with the maximum values of two-photon action cross section for ligand/metal complex approximately (90-130) GM, using a standard two-photon induced fluorescence methodology under femtosecond excitation. The nature of the 2PA bands was analyzed by quantum chemical methods and a specific dependence on metal ion binding processes was shown. Ratiometric fluorescence detection (420/650 nm) provided a good dynamic range (10(-4) to 10(-6) M) for detecting Zn(2+), which along with the good photostability and 2PA properties of probe 1 makes it a good candidate in two-photon fluorescence microscopy imaging and sensing of Zn ions.

Characterisation of novel macroacyclic hexadentate (N4O2 and N2O4) Schiff base ligands and their zinc(II), copper(II) and cobalt(II) complexes, with ligands derived from reduction

The macrocyclic, hexadentate (N4O2 and N2O4) Schiff base ligands, 1,2-bis(2′-nitrophenoxy)benzene, 1,2-bis (2′-nitrophenoxy)-4- t-butylbenzene), 1,2-bis(2′-aminophenoxy)benzene and 1,2-bis(2′-aminophenoxy)-4- t-butyl-benzene have been synthesised, together with macroacyclic hexadentate ligands formed from their reduction. Zinc(II), copper(II) and cobalt(II) complexes of the Schiff base ligands have also been prepared and all compounds have been characterised by spectroscopy and elemental analysis.