Structural, Optical Properties, and Biological Activity of Complexes Based on Derivatives of Quinoline, Quinoxaline, and Quinazoline with Metal Centers from Across the Periodic Table

Synergy of experimental and computational chemistry: structure and biological activity of Zn(II) hydrazone complexes

In this paper, three different Zn(II) complexes with (E)-2-(2-(1-(6-bromopyridin-2-yl)ethylidene)hydrazinyl)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride (HLCl) have been synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR and NMR spectroscopy. All complexes are mononuclear, with the ligand (L) coordinated in a deprotonated formally neutral zwitterionic form via NNO donor set atoms. Complex 1 forms an octahedral geometry with the composition [ZnL2](BF4)2, while complexes 2 [ZnL(NCO)2] and 3 [ZnL(N3)2] form penta-coordinated geometry. Density functional theory (DFT) calculations were performed to enhance our understanding of the structures of the synthesized complexes and the cytotoxic activity of the complexes was tested against five human cancer cell lines (HeLa, A549, MDA-MB-231, K562, LS 174T) and normal human fibroblasts MRC-5. Additionally, antibacterial and antifungal activity of these complexes was tested against a panel of Gram-negative and Gram-positive bacteria, two fungal strains, and a yeast strain. It is noteworthy that all three complexes show selective antifungal activity comparable to that of amphotericin B. Molecular docking analysis predicted that geranylgeranyl pyrophosphate synthase, an enzyme essential for sterol biosynthesis, is the most likely target for inhibition by the tested complexes.

Mechanistic Insights into Tf2O-Promoted Electrophilic Activation of 2-Propynamides and a New Synthesis of 2,4-Disubstituted Quinolines

Direct evidence explaining why 2-propynamides have never been used as substrates in Tf₂O-promoted electrophilic activations was obtained. Furthermore, a new method for the synthesis of structurally special 2,4-disubstituted quinolines was developed, by which the substituent at position 2 of quinolines can be diversified easily.

A Novel Family of Cage-like (CuLi, CuNa, CuK)-phenylsilsesquioxane Complexes with 8-hydroxyquinoline Ligands: Synthesis, Structure, and Catalytic Activity

The first examples of metallasilsesquioxane complexes, including ligands of the 8-hydroxyquinoline family 1–9, were synthesized, and their structures were established by single crystal X-ray diffraction using synchrotron radiation. Compounds 1–9 tend to form a type of sandwich-like cage of Cu₄M₂ nuclearity (M = Li, Na, K). Each complex includes two cisoid pentameric silsesquioxane ligands and two 8-hydroxyquinoline ligands. The latter coordinates the copper ions and corresponding alkaline metal ions (via the deprotonated oxygen site). A characteristic (size) of the alkaline metal ion and a variation of characteristics of nitrogen ligands (8-hydroxyquinoline vs. 5-chloro-8-hydroxyquinoline vs. 5,7-dibromo-8-hydroxyquinoline vs. 5,7-diiodo-8-hydroxyquinoline) are highly influential for the formation of the supramolecular structure of the complexes 3a, 5, and 7–9. The Cu₆Na₂-based compound 2 exhibits high catalytic activity towards the oxidation of (i) hydrocarbons by H₂O₂ activated with HNO₃, and (ii) alcohols by tert-butyl hydroperoxide. Studies of kinetics and their selectivity has led us to conclude that it is the hydroxyl radicals that play a crucial role in this process.

Substituted 2-(2-hydroxyphenyl)-3H-quinazolin-4-ones and their difluoroboron complexes: Synthesis and photophysical properties

2-(2-Hydroxyphenyl)-3H-quinazolin-4-ones with diverse substituents at phenol ring and their six-membered difluoroboron complexes have been synthesized via few-stage approach. The photophysical properties of target compounds have been investigated in two solvents as well as in the solid state. The nature of substituents and substitution point in the phenol moiety of ligands and resulting BF₂-complexes on the photophysical properties of dyes have been explored. The complex bearing two t-Bu groups proved to be the most emissive in solid state, whereas its 5-methoxy and 4-diethylamino counterparts possess strong emission in toluene solution. The dyes exhibited large Stokes shifts which was attributed to excited state intramolecular proton transfer (ESIPT). Additionally, fluorescence of quinazolinones in the mixture of THF/water was studied. All ligands demonstrated emission enhancement with increase of water fraction which was due to aggregation induced emission.

Comparison of a dimeric and a monomeric indium-quinolinato complex: synthesis, structure and photoluminescence

Two indium(iii) complexes, mer-[In(Ox)₃]·2H₂O (1) and [In₂(Ox)₂Cl₂-μ-[κ²-O,O′-(Ox)₂]]·C₇H₈ (2) (Ox = 8-hydroxyquinolinate), were synthesized and characterised for comparison by NMR, X-ray diffraction and photoluminescence.

Synthesis, Crystal Structures, Fluorescence and Quantum Chemical Investigations of some Multi-Substituted Quinoline Derivatives

Starting from eugenol (4-allyl-2-methoxyphenol) three new quinoline derivatives, namely 5-bromo-7-(carboxymethoxy)-6-hydroxy-1-methylquinolin-1-ium-3-sulfonate (Q2, C₁₂H₁₀BrNO₇S), 5-amino-7-(carboxymethoxy)-6-hydroxyquinolin-1-ium-3-sulfonate (Q4, C₁₁H₁₀N₂O₇S) and 7-(carboxymethoxy)-5,6-dihydroxylquinolin-1-ium-3-sulfonate (Q6, C₁₁H₉NO₈), have been synthesized and crystallised as dihydrate. The best planes through the quinoline ring and the carboxymethoxy substituent is 6.60 (14), 7.28 (6) and 4.73 (7)° for Q2, Q4 and Q6, respectively. The crystal packing of Q2 is characterised by O-H…O, π …π and Br …pyridine interactions. The two water molecules bridge three sulphate groups. Infinite chains of Q4 running in the direction [021] are formed by O/N-H …O hydrogen bonds at both ends of the molecule. Parallel chains interact by O/N-H…O hydrogen bonds and π…π and C=O…phenyl stacking. The -NH₂ substituent bridges two sulphate groups, while the two water molecules bridge the other functional groups. The packing of Q6 consists of sheets of molecules interaction through O/N-H…O hydrogen bonds while the two water molecules bridge all function groups present. Parallel sheets interact through π…π and C=O…pyridine stacking. An aqueous solution of Q2 and its precursor 7-(carboxymethoxy)-6-hydroxyquinolin-1-ium-3-sulfonate (Q) exhibits fluorescence which is pH dependent. The fluorescence intensity of a 10 μM solution of Q containing Zn²⁺ reaches its maximum for a [Zn²⁺]:[Q] ratio of 1:1. The fluorescence properties of Q, Q2, Q4 and Q6 were further investigated by DFT calculation methods.

Statistical Paradigm for Organic Optoelectronic Devices: Normal Force Testing for Adhesion of Organic Photovoltaics and Organic Light-Emitting Diodes

In this study, we assess the utility of a normal force (pull-test) approach to measuring adhesion in organic solar cells and organic light-emitting diodes. This approach is a simple and practical method of monitoring the impact of systematic changes in materials, processing conditions, or environmental exposure on interfacial strength and electrode delamination. The ease of measurement enables a statistical description with numerous samples, variant geometry, and minimal preparation. After examining over 70 samples, using the Weibull modulus and the characteristic breaking strength as metrics, we were able to successfully differentiate the adhesion values between 8-tris(hydroxyquinoline aluminum) (Alq₃) and poly(3-hexyl-thiophene) and [6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) interfaces with Al and between two annealing times for the bulk heterojunction polymer blends. Additionally, the Weibull modulus, a relative measure of the range of flaw sizes at the fracture plane, can be correlated with the roughness of the organic surface. Finite element modeling of the delamination process suggests that the out-of-plane elastic modulus for Alq₃ is lower than the reported in-plane elastic values. We suggest a statistical treatment of a large volume of tests be part of the standard protocol for investigating adhesion to accommodate the unavoidable variability in morphology and interfacial structure found in most organic devices.