Methine-Quinoidal Fragment Induces Significant Bathochromic Shifts in Organic Dyes

Abstract

Bathochromical shifts in the UV–vis absorption (and emission) spectra and reduced molecular sizes are two desirable features of organic dyes in many applications, i.e., live-cell fluorescence imaging and solar cells. Yet, these two features are often viewed as contradictory requirements as expanding the π-conjugation is one of the most widely used methods for prompting this redshift. Interestingly, it has been reported that linking a methine-quinoidal unit can result in a significant redshift in the UV–vis absorption spectra in comparison with the methine-benzenoidal constitutional isomers (by 61 nm in dioxane). Herein, using comprehensive quantum chemical calculations with various functionals and solvent formalisms in 10 solvents with different polarities, we demonstrated that the formation of the quinoidal moiety plays a decisive role in this redshift. We further showed that the inclusion of a quinoidal unit without increasing the molecular size represents a general design strategy for the bathochromic shifts of many organic dyes.

The fluorescence quenching mechanism of tetrazine-functionalized fluorogenic labels with integrated π-conjugations: internal conversion to a dark state

“…S18–S21, ESI†). 57 Indeed, our calculations show that 4b-Q / 4b-Q-BCN displays much improved bathochromic shifts than 4b / 4b-BCN (Fig. 7(b)).…”

“…Two frequently employed strategies to bathochromically shift the λ abs / λ em of organic dyes were explored including expanding the π-conjugation and incorporating quinoidal structures. 54–60…”

“…Two frequently employed strategies to bathochromically shift the l abs /l em of organic dyes were explored including expanding the p-conjugation and incorporating quinoidal structures. [54][55][56][57][58][59][60] Strategy 1: expanding the p-conjugation. Based on 3a, we introduced another coumarin fragment to form 3e (Fig.…”

Photoinduced electron transfer endows fluorogenicity in tetrazine-based near-infrared labels

“…The NIR fluorophores with bathochromically shifted peak absorption/emission wavelengths ( λ abs / λ em ) often correlate with the reduced electronic gaps between the highest occupied molecular orbital (HOMO) and LUMO (Δ E H–L ). 30 For enhancing PET efficiency in a tetrazine-based NIR label, it is crucial that the LUMO energy of the main fluorophore remains relatively close to that of the tetrazine. Therefore, an ideal decrease in Δ E H–L should predominantly result from an elevation of the HOMO energy level (Fig.…”

Follow Your Heart

“…The strength I feel from their support reminds me of the fluorescent dyes I study every day, which can emit colorful fluorescence under the irradiation of excitation light. I remember the moment all the members of my research group cheered for me when my first manuscript was accepted in the Journal of Physical Chemistry B , 1 which was a significant milestone in my academic career. I remember on the day I turned 25, my second article was published in Analyst , 2 which was the best birthday present for me.…”