Four 1,5-diphenyl-3-aromatic heterocyclyl-2-pyrazoline-based sulfonium salt photoacid generators (PAGs) with different aromatic heterocycles substituted on C3 atom and dimethyl sulfonium group on C5 atom were synthesized. These PAGs were highly photosensitive in the 365–425 nm light-emitting diode region, and the intramolecular charge transfer from the pyrazoline ring to sulfonium salts induced efficient photolysis and high Φ_H⁺. The heterocycles as well as their substituted positions significantly influenced the energy of the S₂ orbital, which was determined by the electrochemical and absorption properties of the PAGs. The raising of the S₂ orbital energy enlarged the energy gap of S₀–S₂ and S₁–S₂, resulting in blue shift of the absorption spectra and increase in the quantum yield of photoacid generation (Φ_H⁺), respectively. When the energy of excited electrons was higher than that of the S₂ orbital, the transition from S₀ to S₂ (π–π*) occurred before the C-S cleavage on S₁ and the PAGs showed high Φ_H⁺ values (0.52–0.72). The transition from S₀ to S₁ (π–σ*) occurred when the energy of electrons is lower than that of the S₂ orbital, and the PAGs showed low Φ_H⁺ value. The photopolymerization kinetics demonstrated that these PAGs were highly efficient cationic photoinitiators.

中文翻译：

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C3-芳香杂环对作为发光二极管敏感阳离子光引发剂的1,3,5-三芳基-2-吡唑啉锍盐光酸产生剂的影响

四1,5-二苯基-3-芳族杂环基- 2-吡唑啉基锍盐光产酸剂（PAG的）与C3原子和C5原子二甲基锍基取代的不同的芳族杂环合成。这些 PAG 在 365-425 nm 发光二极管区域具有高度光敏性，并且从吡唑啉环到锍盐的分子内电荷转移诱导了有效的光解和高 Φ _H ⁺。杂环及其取代位置显着影响 S ₂轨道的能量，这是由 PAG 的电化学和吸收特性决定的。S ₂轨道能量的提高扩大了S ₀ -S的能隙₂和 S ₁ –S ₂，分别导致吸收光谱蓝移和光酸生成量子产率 (Φ _H ⁺ ) 的增加。当激发电子的能量高于 S ₂轨道的能量时，S ₀到 S ₂的跃迁（π-π*）发生在 S ₁上的 CS 裂解之前，PAG 显示出高 Φ _H ⁺值（0.52- 0.72）。当电子的能量低于 S ₂轨道的能量时，发生从 S ₀到 S ₁ (π–σ*) 的跃迁，PAGs 表现出低 Φ _H ⁺价值。光聚合动力学表明这些 PAG 是高效的阳离子光引发剂。