Tiron (sodium 4,5-dihydroxybenzene-1,3-disulfonate) is often used as a probe for detection of superoxide radicals. In this work, we have studied the interaction of Tiron with superoxide radicals dissolved in water solutions. The density functional theory (DFT) method was used for scrutinizing electron and energy characteristics of Tiron radicals in the systems modeling freshwater and salt water. In water solution at neutral pH, deprotonated form of superoxide radical, O₂^•-, dominates over the protonated form HO₂^•. Fully reduced (TH₂) and fully oxidized (T) species of Tiron react with superoxide radicals, leading to the formation of the Tiron semiquinone radicals. DFT calculations show that the reactions of O₂^•- with TH₂ and T in water solution will advance if these reactions are catalyzed by hydronium ions: TH₂ + O₂^•- + H₃O⁺ → TH^• + H₂O₂ + H₂O and T + O₂^•- + H₃O⁺ → TH^• + O₂ + H₂O. Electron paramagnetic resonance (EPR) and DFT data show that Tiron radicals dissolved in water solution with neutral pH exist predominantly in deprotonated state T^•-. The constants of the hyperfine coupling between an unpaired electron and the hydrogen atoms of deprotonated radicals T^•-, computed for freshwater and seawater solutions, are in a fairly good agreement with experimental constants derived from the EPR spectra of Tiron radicals.

钛（4,5-二羟基苯-1,3-二磺酸钠）通常用作检测超氧自由基的探针。在这项工作中，我们研究了Tiron与溶解在水溶液中的超氧自由基的相互作用。在模拟淡水和盐水的系统中，使用密度泛函理论（DFT）方法研究了Tiron自由基的电子和能量特征。在中性pH的水溶液中，超质子自由基O ₂ ^•的去质子化形式优于HO ₂ ^•的质子化形式。Tiron的完全还原（TH ₂）和完全氧化（T）物种与超氧自由基反应，导致形成Tiron半醌自由基。DFT计算表明，O ₂的反应^•-如果水合氢离子催化以下反应，则TH ₂和T在水溶液中会前进：TH ₂  + O ₂ ^•-  + H ₃ O ⁺  →TH ^•  + H ₂ O ₂  + H ₂ O和T + O ₂ ^{• -}  + H ₃ ö ⁺  →TH ^•  + O ₂  + H ₂ O.电子顺磁共振（EPR）和DFT的数据显示，溶解钛试剂基团在水中的溶液与中性pH存在主要是在脱质子态T ^{• -}。针对淡水和海水溶液计算出的未配对电子与去质子化自由基T ^•-的氢原子之间的超精细偶合常数与从Tiron自由基的EPR光谱得出的实验常数非常吻合。