Hydrogen bond configuration and protonation of ground and lowest excited triplet states of 4‑amino‑4′‑nitrobiphenyl based on nanosecond transient absorption spectroscopy

Leveraging Coupled Solvatofluorochromism and Fluorescence Quenching in Nitrophenyl‐Containing Thiazolothiazoles for Efficient Organic Vapor Sensing

“…To confirm the presence of the ICT state, strong acid (TFA) was used to protonate the aTTz derivative, limiting the shift of electron density and increasing polarity in the excited state (Figure S19, Supporting Information). [ 18,39 ] Due to the dual solvatofluorochromic effect in Bu 2 N‐TTz‐NO 2 and Ph 2 N‐TTz‐NO 2, the excited‐state dipole moments ( Table 1 ) were calculated separately for the SWB and LWB bands using the Lippert‐Mataga (LM) equation (Equation ): $$$$\begin{eqnarray} {\nu }_a - {\nu }_f = \frac{{2{{\left( {{\mu }^{\rm{*}} - \mu } \right)}}^2}}{{4{{\pi}}{\epsilon }_0hc{a}^3}}\Delta f + const. ;\Delta f = \left( {\frac{{\varepsilon - 1}}{{2\varepsilon + 1}} - \frac{{{\eta }^2 - 1}}{{2{\eta }^2 + 1}}} \right)\nonumber\\ \end{eqnarray}$$$$where ν a and ν f are the absorption and emission peaks in cm −1 , µ * and µ are the excited state and ground state dipoles, ε 0 is the vacuum permittivity, h is Planck's constant, c is the speed of light, a is the Onsager cavity radius, Δ f is the orientation polarizability, ε is the relative permittivity, and η is the refractive index.…”

“…To confirm the presence of the ICT state, strong acid (TFA) was used to protonate the aTTz derivative, limiting the shift of electron density and increasing polarity in the excited state (Figure S19, Supporting Information). [18,39] Due to the dual solvatofluorochromic effect in Bu 2 N-TTz-NO 2 and Ph 2 N-TTz-NO 2, the excited-state dipole moments (Table 1) were calculated separately for the SWB and LWB bands using the Lippert-Mataga (LM) equation (Equation 1):…”

Fluorescent Chromophores Containing the Nitro Group: Relatively Unexplored Emissive Properties

“…As a result, nπ* is involved in the lowest excited singlet state, which facilitates both ISC and nonradiative decay rate. On the other hand, the non-fluorescence behavior of 3 e in ethanol can be explained by the non-radiative decay routes aroused form the hydrogen bond interactions between the protic solvent molecules and nitro groups as illustrated by Jin et al [40] The results manifest the importance of relative energy alignment between nπ* and ππ* state and its interplay with the strong À NO 2 electron withdrawing property. These unique properties make À NO 2 substituents versatile in applications, among which the fluorescence probe and fluorescence sensing have received particular attention and will be reviewed in the following section.…”

Excited state proton transfer in the triplet state of 8-hydroxy-5-nitroquinoline: a transient absorption and time-resolved resonance Raman spectroscopic study

“…2B. Unlike most NPAHs, which have a microsecond lifetime in their T 1 states in solution, 8,49–51 the T 1 state NO 2 -QN-OH decays within ∼10 ns (Fig. 2B), resulting in transient absorption with an additional band in the 450 to 500 nm range compared to the T 1 state NO 2 -QN-OH.…”

“…The nanosecond TA measurements were performed using a laser flash photolysis system (LP-920, Edinburgh Instruments) as previously described. [49][50][51] The excitation laser pulse was generated using the third harmonic output of an Nd:YAG Q-switched laser. The laser pulse has a 355 nm wavelength, a 10 ns pulse width, and an 80 mJ pulse energy.…”