Deciphering the Interaction of a Macrocyclic Tetranuclear Zn(II) complex with Biomimicking Surfactant: A Case Study using Cetyltrimethylammonium Bromide

The detection of various biologically important cationic and anionic species has led to the synthesis of various Zinc (II) Schiff base complexes, which bear a large application in catalysis and sensors. A recently reported study has indicated a synthesis of a 48 membered macrocyclic Zn(II) Schiff base complex, which functions as a dual anion sensor (DAS) containing a protonated amine group. In the present investigation, an attempt has been made to study the interaction of the Zn tetranuclear complex (Zn-TCom), a neutral complex, with a cationic surfactant cetyltrimethylammonium bromide (CTAB), employing steady-state absorption and fluorescence studies. The change in the photophysical properties of the fluorophore is studied on binding with the surfactant. The steady-state absorption and emission studies reveal that the polarity of the surrounding of the fluorophore has been modified upon binding with CTAB. A study on the alteration of polarity during the interaction of Zn-TCom with the surfactant is studied by comparing the fluorescence behavior of the probes in a micro heterogeneous environment in a mixture of dioxane and water of varying composition. The binding constant magnitude (analyzed using the Hildebrand equation) manifests that the Schiff base binds to the micellar compartment. These results are manifested to enhance the potential application of the macrocyclic complex in the field of biochemistry. Furthermore, quantum chemical calculations are undertaken to correlate the molecular structure of Zn-TCom with the associated frontier molecular orbitals. The parameters like the energy of HOMO, LUMO and the associated Mulliken charges with respect to individual elements are computed using the single point geometry. The studied reports are correlated with the feasibility of binding with bio mimicking environment or bio proteins for selective application as drug carriers.

Elucidating the Photoluminescence Quenching in Ensulizole: An Artificial Water Soluble Sunscreen

Employing natural or artificial sunscreens is essential to protect the skin from ultraviolet radiations that cause premature aging and develop melanoma and other forms of skin cancer. The 2-Phenylbenzimidazole-5-sulfonic acid, commonly known as ensulizole is a water-soluble artificial sunscreen that absorbs mostly UV-B (280 nm − 315 nm) radiations and protects the skin against the harmful effects of these radiations. Steady-state absorption indicates a strong absorption feature at 303 nm and a weak at 316 nm that have been identified as π → π* and n → π* transitions, respectively. The photoluminescence (PL) spectra indicate that the PL of ensulizole is less Stokes-shifted in polar solvents and more Stokes-shifted in non-polar solvents. The average PL lifetime of ensulizole is longer in non-polar solvents as compared to polar solvents and it exhibits the shortest PL lifetime in aqueous medium that signifies its efficiency in water. This suggests in non-polar solvents intersystem crossing is the dominant mode of relaxation of the excited ππ* state. Furthermore, an increase of pH of ensulizole solution decreases the PL intensity and the lifetime. Stern-Volmer equation is employed to evaluate bimolecular quenching rate constant kq that suggests the diffusional dynamic mode of PL quenching is operative.

Spectroscopic Evidence for Photooxidation of Tocopherols in n-Hexane

This paper presents the results of an investigation into the photooxidation of tocopherols (Tocs) dissolved in argonated and non-argonated n-hexane. During irradiation, steady-state absorption and fluorescence spectra as well as lifetimes were measured. In all experiments, the photoreactions were of the first order type. The reaction rate was higher for all Tocs in argonated solvent. A new emission band with a maximum at 298 nm as well as new absorption and fluorescence bands beyond the 300 nm connected with charge-transfer (C-T) complexes for all Tocs appeared during the irradiation of γ- and δ-Toc. The above results indicate that the photooxidation process is very complex and that the observed phenomena strongly depend on the number and position of methyl groups in the chromanol ring.

Spectroscopic Investigations of Electron and Hole Dynamics in MAPbBr3 Perovskite Film and Carrier Extraction to PEDOT Hole Transport Layer

Organometallic halide perovskite (MAPPbBr3), Rust-based Vapor Phase Polymerization (RVPP)-PEDOT hole transporting layers and (RVPP-PEDOT)/MAPPbBr3 dual-layer, deposited on fluorine doped tin oxide glass were studied at room temperature using steady-state absorption,...

A Novel Quinoline Derivative for Selective and Sensitive Visual Detection of PPB Level Cu2+ in Aqueous Solution.

Aim: Selective and sensitive visual detection of Cu2+in aqueous solution at PPB level using easily synthesized compound. Background: The search for a chemosensor that can detect Cu2+ is very long owing to the fact that an optimum level of Cu2+ is required for human health and the recommended amount of Cu2+ in drinking water is set to be 1-2 mgL-1 . Thus, it is very important to detect Cu2+ even at a very low concentration to assess the associated health risks. Objective: We are still seeking for the easiest, cheapest, fastest and greenest sensor that can selectively, sensitively and accurately detect Cu2+ with lowest detection limit. Our objective of this work is to find one such Cu2+ sensor. Methods: We have synthesized a quinoline derivative following very easy synthetic procedures and characterize the compound by standard methods. For sensing study, we used steady state absorption and emission spectroscopy. Results: Our sensor can detect Cu2+ selectively and sensitively in aqueous solution instantaneously even in the presence of excess amount of other salts. The pale-yellow color of the sensor turns red on the addition of Cu2+ . There is no interference from other cations and anions. A 2:1 binding mechanism of the ligand with Cu2+ is proposed using Jobs plot with binding constant in the order of 109 M-2 . We calculated the LOD to be 18 ppb, which is quite low than what is permissible in drinking water. Conclusion: We developed a new quinoline based chemo-sensor following straightforward synthetic procedure from very cheap starting materials that can detect Cu2+ visually and instantaneously in aqueous solution with ppb level sensitivity and zero interference from other ions.

Спектральные свойства индотрикарбоцианинового красителя в процессе самоорганизации его H-=SUP=-*-=/SUP=-- и J-агрегатов

Self-assembly of H*- and J-aggregates of an indotricarbocyanine dye in phosphate buffered saline was investigated. At pH value of 7.0 the dye studied was shown to form non-luminescent H*-aggregates with the absorption band peaked at 516 nm, its FWHM being 35 nm (1303 cm-1), whereas, J-aggregates are absent. At pH value of 7.4 the H*-aggregates are not formed, whereas, the J-aggregates are observed. The absorption band of the J-aggregates is peaked at 777 nm, its FWHM being 30 nm (497 cm-1). Photoluminescence quantum yield of the J-aggregates does not exceed 10-6. An increase in the solution temperature from 20 to 31oC results in a 25-fold decrease in the self-assembly time of the H*-aggregates. An increase in the solution temperature from 20 to 80oC is followed by a reversible decay of both the H*- and J-aggregates. The H*-aggregate (J-aggregate) absorption band is reduced two-fold at the solution temperature of 37oC (32oC). Thansitions of the dye aggregates to high-lying electronic excited states were evidenced in the steady-state absorption in the spectral range between 400 and 480 nm.

Electron photoejection from dianion of an expanded phthalocyanine

Photoelectron ejection from the dianion of pentabenzotriazasmaragdyrin (PBTAS) which is an expanded phthalocyanine, is observed using femtosecond transient absorption spectroscopy. The PBTAS dianion was produced by chemical reduction using excess cobaltocene as a reductant, which was confirmed by their steady-state absorption spectrum as compared to the absorption spectrum obtained by electrochemical reduction, and characterized by magnetic circular dichroism (MCD). Upon photoexcitation of the PBTASdianion, the generation of a radical anion was confirmed by the characteristic absorption peaks that are observed at 950 and 1000 nm. The radical anion was relaxed to form a dianion with a time constant of 0.7 ps.

Syntheses and studies of electron/energy transfer of new dyads based on an unsymmetrical perylene diimide incorporating chelating 1,10-phenanthroline and its corresponding square-planar complexes with dichloroplatinum(ii) and dichloropalladium(ii )

Photophysical properties of new dyads have been studied with steady-state absorption and TDDFT.