Dual fluorescence of (E)-N-(4-(dimethylamino)benzylidene)-2H-1,2,4-triazol-3-amine (DMABA-Amtr): A ground state perspective

Research Progress on the Application of Multifunctional Amino Derivative Fluorescent Probes in Food, the Environment, and the Microenvironment

The amino group is regarded as a multifunctional recognition group in fluorescent probes. It is nucleophilic, a strong electron-donating group and is a polar group with active hydrogen. Based on these characteristics, amino-based fluorescent probes combined with various fluorescent precursors have been constructed, with excellent sensing performance and low cytotoxicity. These probes have significant application value in the detection of food, living cells and organisms. Here, the relevant studies on amino fluorescent probes from 2016 to 2024 are systematically reviewed and their molecular design principles, recognition mechanisms and applications are described. These studies included 14 on exogenous and endogenous formaldehyde detection, five that detected polarity changes in the external environment and organelles in vivo, four intracellular mitochondrial and lysosomal viscosity detections, seven physiological environment and intracellular pH detections, seven metal ion detections in biological and environmental systems and four rapid detections of the hypochlorite anion (ClO-) in a variety of physiological processes and cells. The application scope of amino fluorescent probes is constantly expanding at present but, research progress in multiple application fields has not been summarized. This article mainly reviews the latest progress in amino fluorescent probes in the fields of food, the environment and the microenvironment, as well as looking forward to the development prospects of these fluorescent probes. Improving the reactivity of amino recognition groups and visual detection may become hot issues in future research.

Unique structural effect on the fluorosolvatochromism and dual fluorescence emission of D-π-A+ cationic chromophores with furyl bridge. An approach to white light emitters

Photophysical behavior of two D - π - A+ cationic compounds with the same furyl bridge and nicotinamidine group as an electron acceptor moiety and two electron donating groups, namely methoxy (I) and N,N-dimethylamino (II) groups was examined using steady-state and time-resolved techniques in variety of solvents. Time-dependent density functional theory (TDDFT) calculations were performed in some representative solvents and compared with the experimental results. Steady state and time-resolved studies in different solvents reveal that fluorescence emission of (I) is ascribed to an emission from an excited state (ICT) with higher dipole moment than the ground state while the emission of (II) is a dual emission from a state with high charge transfer nature (ICT) in addition to the locally excited state (LE). The fluorescence emission spectra of (II) were found to depend on the excitation wavelength and an increase in the excitation wavelength led to the formation of a longer wavelength emission band with lower quantum yield. It has also been found that the fluorescence excitation spectra were dependent on the emission wavelength. The effect of solvent on the nature of dual emission was examined. Correlation of the photophysical properties of the excited states of (I) and (II) with the solvent polarity, ε, reveals the charge transfer nature of (I) and the long wavelength emission band of (II), while their correlation with the solvent polarity parameter (ETN) shows two different trends when the solvents are divided to aprotic and protic solvents. For precise investigation of the impact of each solvent parameter on each photophysical property, Catalán's and Laurence's four parametric linear solvation energy relationships were studied. We have found that the non-specific interactions of the solvent are primarily responsible for controlling the photophysical properties, as demonstrated by Catalán's and Laurence's treatments. DFT and TDDFT calculations were used to anticipate the dipole moments in the ground and excited states and geometry of both states.

Spectral Properties of Highly Emissive Derivative of Coumarin with N,N-Diethylamino, Nitrile and Tiophenecarbonyl Moieties in Water-Methanol Mixture

The new derivative of coumarin (E)-3-[7-(diethyloamino)-2-oxo-chromen-3yl]-2-(tiophene-2-carbonyl)prop-2-enenitrile (NOSQ) was easy synthesized with commercial substrates as a result of the search of new Michael type addition sensors based on coumarins. Spectral properties of highly emissive NOSQ were investigated by steady state analysis (absorption and fluorescence measurements) and time-resolved analysis (fluorescence lifetime measurements). The effect of water-methanol mixture on the photophysical properties of the NOSQ molecule was analyzed. With increasing of volumetric fraction of water the intensity of absorbance and fluorescence was strongly reduced. The NOSQ quantum yield in methanol was quite high and the first portions of water caused a significant increase in this value. Water, which is usually a quencher, in this case caused the increase in the quantum yield. The fluorescence lifetimes had second-order decay and the values of fluorescence lifetime increased with increasing alcohol content. Density functional theory (DFT) calculations and experimental data remained in agreement and showed that the interaction between the NOSQ molecule and the solvent affects the appearance of the new conformer.