Given the unique spectral properties of exhibiting dual-band fluorescence, excited-state intramolecular proton transfer (ESIPT) materials have attracted wide attention. In light of a promising, highly efficient fluorescent probe with potential ratiometric emission detection, in this work, 3-Hydroxy-2-(1-ethyl-1H-pyrazol-3-yl)-4H-chromen-4-one (3ePz3HC) has been explored its photo-induced excited-state behaviours. In analyses of structural variations and infrared (IR) vibrational spectra between S₀ and S₁ states, the enhanced hydrogen-bonding interactions could reveale that promote the ESIPT tendency. Particularly, 3ePz3HC in aprotic nonpolar solvents with stronger hydrogen bonds shows an easier proton-transfer tendency. Paying attention to the changes of primarily related frontier molecular orbitals, we find that the charge transfer process occurs in excited-state molecules, and the reorganisation of charge densities should be conducive to promoting the ESIPT process. Simulated potential energy curves indicate that the ultrafast ESIPT reaction occurs for 3ePz3HC with low barriers, which could be further regulated and controlled by solvent polarity.

HIGHLIGHTS

• Photo-induced, enhanced hydrogen bonding provides the tendency for ESIPT reaction of the 3ePz3HC fluorophore.

• Increased electronic densities around the O3 moiety of 3ePz3HC play vital roles in facilitating the ESIPT process.

• Aprotic nonpolar solvents are more favourable for accelerating the ESIPT behaviour for the 3ePz3HC compound.

鉴于表现出双波段荧光的独特光谱特性，激发态分子内质子转移（ESIPT）材料引起了广泛关注。鉴于具有潜在比率发射检测的有前途的高效荧光探针，在这项工作中，3-Hydroxy-2-(1-ethyl-1H-pyrazol-3-yl)-4H-chromen-4-one (3ePz3HC)已经探索了它的光诱导激发态行为。在分析 S ₀和 S _{1之间的结构变化和红外 (IR) 振动光谱}状态，增强的氢键相互作用可以揭示促进 ESIPT 趋势。特别是，3ePz3HC 在具有更强氢键的非质子非极性溶剂中表现出更容易的质子转移趋势。关注主要相关前沿分子轨道的变化，我们发现电荷转移过程发生在激发态分子中，电荷密度的重组应该有利于促进 ESIPT 过程。模拟的势能曲线表明，低势垒的 3ePz3HC 发生了超快 ESIPT 反应，这可以通过溶剂极性进一步调节和控制。

强调

• 光诱导、增强的氢键为 3ePz3HC 荧光团的 ESIPT 反应提供了趋势。

• 3ePz3HC 的 O3 部分周围增加的电子密度在促进 ESIPT 过程中起着至关重要的作用。

• 质子非极性溶剂更有利于加速 3ePz3HC 化合物的 ESIPT 行为。