AIE Based Coumarin Chromophore - Evaluation and Correlation Between Solvatochromism and Solvent Polarity Parameters

Strategies to convert organic fluorophores into red/near-infrared emitting analogues and their utilization in bioimaging probes

Organic fluorophores aided by current microscopy imaging modalities are essential for studying biological systems. Recently, red/near-infrared emitting fluorophores have attracted great research efforts, as they enable bioimaging applications with reduced autofluorescence interference and light scattering, two significant obstacles for deep-tissue imaging, as well as reduced photodamage and photobleaching. Herein, we analyzed the current strategies to convert key organic fluorophores bearing xanthene, coumarin, and naphthalene cores into longer wavelength-emitting derivatives by focussing on their effectiveness and limitations. Together, we introduced typical examples of how such fluorophores can be used to develop molecular probes for biological analytes, along with key sensing features. Finally, we listed several critical issues to be considered in developing new fluorophores.

A visible-light-induced “on–off” one-pot synthesis of 3-arylacetylene coumarins with AIE properties

A mild one-pot approach to 3-arylacetylene coumarins with potential AIE activities was developed via photosensitizer-free photocatalysis and thermocatalysis.

Fluorescent 7-Substituted Coumarin Dyes: Solvatochromism and NLO Studies

The effect of three substituents N,N-diethylamine, carbazole and diphenylamine at the 7 position of coumarin on linear and nonlinear optical properties are studied using absorption and emission solvatochromism, and DFT. By varying the substituent 53 nm red shift is achieved in emission. The polarity plots with regression close to unity revealed good charge transfer in the system. Solvent polarizability and dipolarity are mainly responsible for solvatochromic shift as proved by multilinear regression analysis. General Mulliken Hush analysis shows diphenylamine substituent leads to more charge separation in compound 6c. The hyperpolarizabilities are evaluated by quantum mechanical calculations. Structure of the compounds are optimized at B3LYP/6-31G(d) level and NLO computations are done using range separated hybrid functionals with large basis sets. Second order hyperpolarizability (γ) found 589.27 × 10^-36, 841.29 × 10^-36 and 1043.00 × 10^-36 e.s.u for the compounds 6a, 6b and 6c respectively.

Nonlinear Optical Properties of Pyrene Based Fluorescent Hemicurcuminoid and their BF2 Complexes -Spectroscopic and DFT Studies

The acetyl acetone and benzoyl acetone pyrene based difluoroboron scaffolds and their respective decomplexed congeners were investigated for their nonlinear optical properties in various microenvironment. The geometries of the chromophore were optimized and electronic excitation properties were estimated using time dependant density functional theory. The vertical excitation properties were found to be complimentary to the experimental results. Nolinear optical properties were evaluated using solvatochromism and Density Functional Theory. The experimental nonlinear optical properties well correlated using Mulliken Hush parameters and also compared with calculated values. CAM-B3LYP results were found to be superior over the B3LYP and BHandHLYP methods. The positive solvatochromism in emission were well explained by multilinear regression and bond length alteration.

Aggregation-induced emission enhancement and cell imaging of a novel (carbazol-N-yl)triphenylamine–BODIPY

The AIEE fluorogen BCPA–BODIPY emits strong red fluorescence and shows a good uptake by MCF-7 cells.