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在有过量邻菲罗啉(phen)存在的铁(Ⅲ)—phen溶液体系中,当溶液pH>1.0～1.5时(与Fe(Ⅲ)浓度有关),能够发生光化还原反应,形成配离子[Fe(phen)3]~+。导致光化还原反应的光的有效波长与溶液体系组成有关:当溶液中不含其他有机配体时,有效波长为<300nm;含有柠檬酸等有机配体时,为420～450nm;而含有乙酸时,在上述两波长范围内均可缓慢地发生光化还原反应。反应速率随照射光强度的增大而增大。太阳光、荧光高压汞灯、高压铟灯等是光化反应的有效光源。OH~-、X~-、PO_4~(3-)等能与Fe(Ⅲ)配位的无机离子初始阶段严重抑制光化反应。除大量Co~(2+)、Cr~(3+)外,一般金属离子对光化反应无干扰。Fe(Ⅲ)浓度(<10μg-Fe/ml)较低时,量子产率近似与Fe(Ⅲ)浓度成正比;Fe(Ⅲ)浓度(>50μg-Fe/ml)较高时,还原反应难以完全。
In the iron (Ⅲ) -phen solution system with excess phenanthroline (phen), when the pH value of the solution is between 1.0 and 1.5 (related to the concentration of Fe (Ⅲ)), photochemical reduction can occur to form a complex ion [Fe (phen) 3] ~ +. The effective wavelength of the light leading to the photoreduction reaction depends on the composition of the solution system: when the solution contains no other organic ligands, the effective wavelength is <300 nm; when the organic ligands such as citric acid are contained, the effective wavelength is 420 to 450 nm; , The photochemical reduction reaction can occur slowly in both of the above two wavelength ranges. The reaction rate increases with the increase of irradiation light intensity. Sunlight, fluorescent high-pressure mercury lamp, high-pressure indium lamp is an effective photochemical reaction light source. The initial stage of inorganic ions which can coordinate with Fe (Ⅲ) such as OH ~ -, X ~ -, PO_4 ~ (3-) can seriously inhibit the photochemical reaction. In addition to a large number of Co ~ (2 +), Cr ~ (3 +), the general metal ions on the photochemical reaction without interference. When the concentration of Fe (Ⅲ) is lower than 10μg-Fe / ml, the quantum yield is approximately proportional to the concentration of Fe (Ⅲ) and the reduction reaction is difficult when the concentration of Fe (Ⅲ) complete.