Rational Design of ICT-Based Fluorescent Probe with AIE and NIR Properties for Hypochlorite Determination

In recent years, the easily synthesized fluorescent probes with good photophysical and sensing properties have attracted widespread attention. Herein, by utilizing the fluorescence regulation effect of electron push-pull effect and the oxidation property of hypochlorite (ClO-) to C=N double bonds, we proposed two intramolecular charge transfer (ICT)-based fluorescent probes with typical aggregation-induced emission (AIE) properties for ClO- detection. The synthesis process of the two probes is very convenient, and both of them can exhibit significant colorimetric and fluorescence changes within 3 min in the presence of ClO-. Moreover, compared with Probe A, the Probe B with near-infrared (NIR) fluorescence centered at 677 nm was successfully applied to ClO- determination in tap water and food samples as well as live cell imaging.

Substituent Effect on AIE Mechanism of Two Coumarin Derivatives: Uncommon TICT Fluorescence in Aggregation State

Two coumarin derivatives, 7-diethylamino-3-(4-nitrophenyl)coumarin (DNC) and 7-hydroxy-3-(4-nitrophenyl)coumarin (HNC), were synthesized via Knoevenagel condensation of salicylaldehyde derivatives with 4-nitrophenylacetonitrile and then cyclization reaction. Both of them were characterized by single-crystal X-ray diffraction. The molecules of DNC are stacked via π-π interaction, while the hydrogen bond interactions instead of π-π interaction were observed in the crystal packing of HNC. Both of DNC and HNC showed solvatochromic properties and aggregation-induced emission (AIE) activities, but the AIE characteristics of them were entirely different. HNC exhibited an AIE phenomenon as the result of the restriction of twisted intramolecular charge transfer (TICT), while DNC emited peculiar dual fluorescence which was assigned to the emission based on the inhibition of TICT state formation and the emission from the TICT state respectively.

An Urchin-Shaped Copper-Based Metalloporphyrin Nanosystem as a Sonosensitizer for Sonodynamic Therapy

Sonodynamic therapy (SDT), as a novel cancer therapy strategy, might be a promising approach due to the depth-penetration property in tissue. Sonosensitizers are the key element for efficient SDT. However, the development of sonosensitizers with strong sonosensitization efficacy is still a significant challenge. Herein, an urchin-shaped copper-based metalloporphyrin liposome nanosystem (FA–L–CuPP) is constructed and identified as an excellent sonosensitizer. Under ultrasound (US) irradiation, FA–L–CuPP can be highly excited to generate several reactive oxygen species (ROS), such as singlet oxygen (1O2) and free radicals (⋅OH). The molecular orbital distribution calculations reveal that a strong intramolecular charge transfer might occur in the CuPP complex under US irradiation, which could afford enough energy to the surrounding O2 and H2O to concert 1O2, O2− and ⋅OH. Working as “ammunitions”, the largely produced ROS can kill 4T1 tumor cells, effectively inhibiting tumor growth. This work provides an urchin-shaped nanosonosensitizer based on a copper complex, which might provide an idea to design a novel sonosensitizer for noninvasive and precise SDT antitumor applications.

Effects of molecular geometry on the efficiency of intramolecular charge transfer–based luminescence in o-carboranyl-substituted 1H-phenanthro[9,10-d]imidazoles

Herein, we compared the optical properties of four compounds with an o-carborane cage linked to 1H-phenanthro[9,10-d]imidazole at the ortho- (oPC), meta- (mPC), or para-position (pPC) of the 2-phenyl ring or...

Rapid Colorimetric Discrimination of Cyanide Ions – Mechanistic Insights and Applications

In this work, we have employed an intramolecular charge transfer-based DMN colorimetric probe for the rapid naked-eye detection of cyanide ions in solution as well as real water samples. The...

Carboxylato-Pillar[6]arene-Based Fluorescent Indicator Displacement Assays for Caffeine Sensing

In the present work, we have developed a new indicator displacement system based on pillararene for anionic water-soluble carboxylato pillar [6] arene (WP6) and aromatic fluorescent dye safranine T (ST). A large fluorescence enhancement and colour change of ST were observed after complexation with electron-rich cavity in WP6 because of host-guest twisted intramolecular charge-transfer interactions. The constructed pillararene-indicator displacement system can be applied for caffeine selective detection in water.

Intramolecular charge transfer-based linear and nonlinear optical properties of a D–π–A–π–D type organic chromophore: Experimental and computational approach

In the sight of the present demand of scientific exploration in nonlinear optics (NLO), we synthesized a symmetric donor–[Formula: see text]–acceptor–[Formula: see text]–donor (D–[Formula: see text]–A–[Formula: see text]–D) type organic chromophore [2-[2,6-di((E)-styryl)]-4H-pyran-4-ylidene]malononitrile (M1) for linear and nonlinear optical studies. The structural character of the compound M1 was confirmed using 1H NMR, [Formula: see text]C NMR, and IR spectroscopy. The intramolecular charge transfer (ICT) in molecule M1 has been analyzed using absorption and fluorescence spectrometry in different nonpolar and polar solvents. The optical bandgap, optical conductivity, and linear refractive index of M1 were also calculated using UV–Vis absorption spectrum in CHCl3. The thermogravimetric analysis (TGA) was also carried out to check the thermal stability of the compound M1 and it was found to be thermally stable up to 200∘C. Furthermore, the third-order optical nonlinearity in M1 has been investigated elaborately using the [Formula: see text]-scan technique with a continuous wave (CW) diode laser at 520[Formula: see text]nm. The nonlinear absorption ([Formula: see text]), nonlinear refraction ([Formula: see text]), and nonlinear optical susceptibility ([Formula: see text]) were computed for various solution concentrations as well as several laser powers and the magnitude of all the parameters were found to vary linearly with concentration and power. The magnitude of two-photon absorption cross-section ([Formula: see text]) was also calculated and found to be of the order of 10[Formula: see text] GM. The optical limiting performance of the compound was also studied in different solution concentrations using the same laser. Furthermore, DFT and TD-DFT theoretical calculations were performed for the support of experimental results.

Controlling the Twisted Intramolecular Charge-Transfer Character of Pyrene Derivatives Through Solvent Polarity

Intramolecular charge transfer (ICT) plays a critical role in determining the photophysical properties of organic molecules, including their luminescence efficiencies. Twisted intramolecular charge transfer (TICT) is a process in which structural change accompanies ICT. Despite significant research, the relationship between TICT and solvent polarity, and its effects on photophysical properties, have been rarely investigated. Herein, we used time-resolved spectroscopy to study TICT in pyrene derivatives that are promising blue organic light emitting diode (OLED) emitter candidates; these derivatives show strong solvent-dependent charge-transfer (CT) behavior. Slight structural changes that do not affect excited state dynamics were observed in nonpolar solvents, while polar solvents were found to affect excited state dynamics and CT characteristics. The TICT behavior of these pyrene derivatives could be modulated through structural modification. Our study provides valuable guidelines for the control of optical properties, including the luminescence efficiencies of OLED emitters that show TICT characteristics.