Synthesis and photophysical properties of 1,4-bis(4,5-diarylimidazol) benzene dyes

Light-Induced Antiferromagnetic to Ferromagnetic Transition in Halogen Substituted 1,4-Bis(imidazolyl)benzene Systems: An Effect of Spin-Orbit Coupling and π-Stacking in Enhanced Photomagnetism

Employing the spin-orbit coupling effect by introducing halogen substituents is an excellent strategy to tune the magnetic behavior of organic or metal-organic materials. Light is an alternative tool to modulate the magnetic behavior of a material through a photoinduced electron transfer process, without changing its chemical identity. In this work, three halogen containing 1,4-bis(4,5-diphenyl-1H-imidazol-2-yl)benzene (F-BDPI, Cl-BDPI and Br-BDPI) systems have been chosen to exploit the role of halogen substituents on solid-state photoinduced phenomena. Through a comprehensive analysis involving various characterization techniques, including UV/vis diffuse reflectance, solid-state photoluminescence, and EPR measurements, it was found that the as-synthesized forms Cl-BDPI-IA and Br-BDPI-IA (IA denotes the hexahydrate form of Cl/Br-BDPI) exhibited fast photochromic response through the generation of photoinduced free radicals in the solid state. Moreover, the SQUID analysis revealed an antiferromagnetic to ferromagnetic transition in Cl-BDPI-IA through photoirradiation, which led to an increase in the magnetic moment value up to 38% at room temperature. This signifies the first occurrence of such a significant level of magnetization amplitude compared with previously reported metal-organic photomagnets. This investigation underscores the significance of halogen substitution in tailoring the magnetic properties of organic photomagnets, where strong halogen-π and π-π interactions facilitate the spin-orbit coupling effect in the solid state.

Multifunctional Hypercrosslinked Porous Organic Polymers Based on Tetraphenylethene and Triphenylamine Derivatives for High-Performance Dye Adsorption and Supercapacitor

We successfully prepared two different classes of hypercrosslinked porous organic polymers (HPPs)-the tetraphenylethene (TPE) and (4-(5,6-Diphenyl-1H-Benzimidazol-2-yl)-triphenylamine (DPT) HPPs-through the Friedel-Crafts polymerization of tetraphenylethene and 4-(5,6-diphenyl-1H-benzimidazol-2-yl)-triphenylamine, respectively, with 1,4-bis(chloromethyl)benzene (Ph-2Cl) in the presence of anhydrous FeCl₃ as a catalyst. Our porous materials exhibited high BET surface areas (up to 1000 m² g^-1) and good thermal stabilities. According to electrochemical and dyes adsorption applications, the as-prepared DPT-HPP exhibited a high specific capacitance of 110 F g^-1 at a current density of 0.5 A g^-1, with an excellent cycling stability of over 2000 times at 10 A g^-1. In addition, DPT-HPP showed a high adsorption capacity up to 256.40 mg g^-1 for the removal of RhB dye from water.

Synthesis of Bisimidazole Derivatives for Selective Sensing of Fluoride Ion

Rapid and efficient analysis of fluoride ion is crucial to providing key information for fluoride ion hazard assessment and pollution management. In this study, we synthesized one symmetrical structure called 1,4-bis(4,5-diphenyl-1H-imidazol-2-yl)benzene (1a) and two asymmetrical structures, namely 2-(4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl)-1H-phenanthro(9,10-d)imidazole (1b) and 2-(4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl)-1H-imidazo(4,5-f)(1,10)phenanthroline (1c), which served as an efficient anion sensor for fluoride ion over a wide range of other anions (Cl-, Br-, I-, NO₃-, ClO₄-, HSO₄-, BF₄-, and PF₆-) owing to imidazole group in the main backbone. The absorption intensity of compound 1a at λmax 358 nm slightly decreased; however, a new band at λmax 414 nm appeared upon the addition of fluoride ion, while no evident change occurred upon the addition of eight other anions. The photoluminescence intensity of compound 1a at λmax 426 nm was nearly quenched and fluorescence emission spectra were broadened when fluoride ion was added into dimethyl sulfoxide (DMSO) solution of compound 1a. Compared with the optical behaviors of the DMSO solution of compound 1a in the presence of Bu₄N⁺F-, compounds 1b and 1c exhibited considerable sensitivity to fluoride ion due to the increase in coplanarity. Furthermore, compared with the fluorescence emission behaviors of the DMSO solutions of compounds 1a and 1b in the presence of Bu₄N⁺F-, compound 1c exhibited the most significant sensitivity to fluoride ion due to the charge transfer enhancement. Consequently, the detection limits of compounds 1a-1c increased from 5.47 × 10-6 M to 4.21 × 10-6 M to 9.12 × 10-7 M. Furthermore, the largest red shift (75 nm) of the DMSO solution compound 1c in the presence of fluoride ion can be observed. Our results suggest that the increase in coplanarity and the introduction of electron-withdrawing groups to the imidazole backbone can improve the performance in detecting fluoride ion.

Novel A–(π–D–π–A)1–3 branched fluorophores displaying high two-photon absorption

Novel A–(π–D–π–A)₃ compounds bearing pyridine end groups are apparently effective in achieving large two-photon responses owing to strong charge transfer.

Synthesis and physicochemical properties of novel lophine derivatives as chemiluminescent in vitro activators for detection of free radicals

The overproduction of free radicals and reactive oxygen species (ROS) has been proved as a basic damage mechanism and cause for oxidative stress. Their measurement is often hindered by the low signal. This could be resolved with the application of luminescent probes (lophines, luminol, lucigenin, etc.). The focus of this study is to synthesize and describe the spectral properties and physicochemical characteristics of lophine and its derivatives as new chemiluminescent in vitro activators. The prepared luminophores are analogues of lophine. Their absorption maxima are in the range 329-340 nm, with good-to-high extinction coefficients. Their spectral properties are measured in methanol and buffer solutions with pH 3.5, 7.4 and 8.5. Same conditions were applied in the systems for chemiluminescent assay in vitro: (1) Fenton's (Fe(2+)+H2O2) for the generation of ·OH and -OH species, (2) Hydrogen peroxide (H2O2), (3) Iron (II) sulfate (FeSO4), (4) Glutathione-peroxidase, monitoring the deactivation of H2O2, (5) Ascorbic acid-Fenton's reagent: Vit.C appears a strong oxidant, generating free-radical products when applied in higher than physiological concentrations, (6) Reduced α-nicotinamide adenine dinucleotide (NADH)-phenazine methosulfate-for the generation of superoxide radicals (O2 (·-)). Lophine and all novel compounds do not alter the kinetics, except of the dimethyl amino substituted derivative (4-(3a,11b-dihydro-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-N,N-dimethylaniline) in the glutathione-peroxidase system, at pH 8.5. Same derivative showed a comparable or higher activity than Lucigenin and Rhodamine 6G. In neutral and acidic medium, in the Fenton's system, Rhodamine 6G was the most appropriate probe. In alkaline pH and oxidant H2O2, Lucigenin induced a signal twice as strong as the signal compared to all other activators.