溶剂化电子

溶剂化电子（英語：solvated electron）也称溶剂合电子，指的是溶液中存在的自由电子，也可被视为最小的阴离子。溶剂化电子可以在很多体系中产生，但由于其寿命很短，难以被直接观察到^[1]。碱金属溶于液氨之后所得溶液的深色即源于溶剂化电子，随溶剂化电子浓度升高，颜色由蓝色逐渐转变为铜色（碱金属浓度大于3mol/L时）^[2]。一般对溶剂化电子的讨论限于金属-液氨体系，因为它们在其中的寿命可达数天，但水和其它溶剂中也存在着溶剂化电子。

历史

1807-1809年间汉弗莱·戴维在氨气中加入钾的晶粒，第一次观察到了溶剂化电子所造成的颜色。1879-1880年间詹姆斯·巴兰坦·汉内（英语：James Ballantyne Hannay）和J. Hogarth使用钠重复了戴维的实验。1907年查尔斯·A·克劳斯（英语：Charles A. Kraus）测量了金属-液氨溶液的电导率，首先将电导率的变化归结为金属电离出的自由电子^[3]^[4]。1918年G. E. Gibson和W·L·阿尔戈提出了溶剂化电子的概念^[5]。他们注意到，根据吸收光谱，不同的金属在不同的溶剂如甲胺和乙胺中可以产生相同的蓝色，表明是由同一种物质，溶剂化电子导致的。1970年，科学家表征了包含电子化合物的固体盐。^[6]

性质

碱金属以及钙、锶、钡、钇等的液氨溶液，均因为溶剂化电子的存在显蓝色^[7]。

锂在零下60度的液氨中的溶解度是16 mol% metal (MPM)。当锂的浓度升高时，溶液的电导率从 10⁻²升高到了10⁴ 欧姆⁻¹厘米⁻¹ (比水银的电导率还要高)。在8 MPM附近时，会发生金属态转变。在 4 MPM 时，发生液相分离，浅金色的致密相从蓝色的基相中分离出来。当浓度大于8 MPM，溶液是青铜/金色的，密度下降了大概30%.

溶剂化电子的标准电极电势是-2.77 V.^[8] 等效电导率是177 Mho cm²，与氢氧根离子相当。溶剂化电子在液氨中的扩散系数可以通过计时安培分析法（英语：chronoamperometry）测得。^[9]这一电导率对应的扩散率为4.75×10⁻⁵ cm²s⁻¹^[10]。

反应与应用

溶剂化电子可以与氧原子反应，形成超氧自由基（O₂^.−）。^[11]遇到一氧化氮，溶剂化电子可以形成羟基自由基（HO^.）。^[12]钠溶于液氨之后形成的具有溶剂化电子的溶液的通常应用是伯奇还原，而钠在乙醇中进行的布沃－布朗还原反应也被认为有溶剂化电子的作用。

参考文献

^ Schindewolf, U. Formation and Properties of Solvated Electrons. Angewandte Chemie International Edition in English. 1968, 7 (3): 190. doi:10.1002/anie.196801901.
^ Cotton, F.A; G. Wilkinson. Advanced Inorganic Chemistry. John Wiley and Sons Inc. 1972. ISBN 0-471-17560-9.
^ Kraus, Charles A. Solutions of Metals in Non-Metallic Solvents; I. General Properties of Solutions of Metals in Liquid Ammonia. J. Am. Chem. Soc. 1907, 29 (11): 1557–1571. doi:10.1021/ja01965a003.
^ Zurek, Eva. A Molecular Perspective on Lithium–Ammonia Solutions. Angew. Chem. Int. Ed. 2009, 48 (44): 8198–8232. doi:10.1002/anie.200900373.
^ Gibson, G. E.; Argo, W. L. The Absorption Spectra of the Blue Solutions of Certain Alkali and Alkaline Earth Metals in Liquid Ammonia and Methylamine. J. Am. Chem. Soc. 1918, 40 (9): 1327–1361. doi:10.1021/ja02242a003.
^ Dye, J. L. Electrons as Anions. Science. 2003, 301 (5633): 607–608. PMID 12893933. doi:10.1126/science.1088103.
^ Combellas, C; Kanoufi, F; Thiébault, A. Solutions of solvated electrons in liquid ammonia. Journal of Electroanalytical Chemistry. 2001, 499: 144. doi:10.1016/S0022-0728(00)00504-0.
^ Baxendale, J. H. (1964) , Radiation Res. Suppl., 114 and 139. [2018-09-07]. （原始内容存档于2021-12-19）.
^ 存档副本. [2018-09-05]. （原始内容存档于2019-06-05）.
^ Survey of Progress in Chemistry p 148
^ Hayyan, M.; Hashim M. A.; AlNashef I. M. Superoxide Ion: Generation and Chemical Implications. Chem. Rev. 2016, 116: 3029–3085. doi:10.1021/acs.chemrev.5b00407.
^ Janata, E.; Schuler, Robert H. Rate constant for scavenging eaq- in nitrous oxide-saturated solutions. J. Phys. Chem. 1982, 86 (11): 2078–84. doi:10.1021/j100208a035.

Sagar, D. M.; Colin; Bain, D.; Verlet, Jan R. R. Hydrated Electrons at the Water/Air Interface. J. Am. Chem. Soc. 2010, 132 (20): 6917–6919. doi:10.1021/ja101176r.
Martyna, Glenn. Electronic states in metal-ammonia solutions. Physical Review Letters. 1993, 71 (2): 267. Bibcode:1993PhRvL..71..267D. doi:10.1103/physrevlett.71.267.
Martyna, Glenn. Quantum simulation studies of singlet and triplet bipolarons in liquid ammonia. Journal of Chemical Physics. 1993, 98 (1): 555–563. Bibcode:1993JChPh..98..555M. doi:10.1063/1.464650.
Martyna, Glenn. Quantum simulation studies of metal–ammonia solutions. Journal of Chemical Physics. 1994, 100 (10): 7590–7601. Bibcode:1994JChPh.100.7590D. doi:10.1063/1.466852.
Solvated Electron. Advances in Chemistry 50. 1965. ISBN 978-0-8412-0051-7. doi:10.1021/ba-1965-0050.
Anbar, Michael. Reactions of the Hydrated Electron. Solvated Electron. Advances in Chemistry 50. 1965: 55. ISBN 0-8412-0051-3. doi:10.1021/ba-1965-0050.ch006.
Abel, B.; Buck, U.; Sobolewski, A. L.; Domcke, W. On the nature and signatures of the solvated electron in water. Phys. Chem. Chem. Phys. 2012, 14 (1): 22–34. Bibcode:2012PCCP...14...22A. PMID 22075842. doi:10.1039/C1CP21803D.
Determination of the Chemical Solvation Energy of the Solvated Electron. Journal of Electroanalytical Chemistry 129. 1981. doi:10.1016/S0022-0728(81)80027-7.
Survey of Progress in Chemistry, chapter 5, 129, 1969 [first page https://www.sciencedirect.com/sdfe/pdf/download/eid/1-s2.0-B9780123957061500108/first-page-pdf] and content preview [1] （页面存档备份，存于互联网档案馆）
The electrochemistry of the solvated electron Technische Universiteit Eindhoven https://pure.tue.nl/ws/files/2089318/388448.pdf （页面存档备份，存于互联网档案馆）
IAEA On the Elextrolytic Generation of Hydrated Electron [2] （页面存档备份，存于互联网档案馆）
Fundamentals of Radiation Chemistry, chapter 6, p 145-198, Academic Press, 1999 [3] （页面存档备份，存于互联网档案馆）

[1] Schindewolf, U. Formation and Properties of Solvated Electrons. Angewandte Chemie International Edition in English. 1968, 7 (3): 190. doi:10.1002/anie.196801901.

[c&w-2] Cotton, F.A; G. Wilkinson. Advanced Inorganic Chemistry. John Wiley and Sons Inc. 1972. ISBN 0-471-17560-9.

[3] Kraus, Charles A. Solutions of Metals in Non-Metallic Solvents; I. General Properties of Solutions of Metals in Liquid Ammonia. J. Am. Chem. Soc. 1907, 29 (11): 1557–1571. doi:10.1021/ja01965a003.

[4] Zurek, Eva. A Molecular Perspective on Lithium–Ammonia Solutions. Angew. Chem. Int. Ed. 2009, 48 (44): 8198–8232. doi:10.1002/anie.200900373.

[5] Gibson, G. E.; Argo, W. L. The Absorption Spectra of the Blue Solutions of Certain Alkali and Alkaline Earth Metals in Liquid Ammonia and Methylamine. J. Am. Chem. Soc. 1918, 40 (9): 1327–1361. doi:10.1021/ja02242a003.

[6] Dye, J. L. Electrons as Anions. Science. 2003, 301 (5633): 607–608. PMID 12893933. doi:10.1126/science.1088103.

[7] Combellas, C; Kanoufi, F; Thiébault, A. Solutions of solvated electrons in liquid ammonia. Journal of Electroanalytical Chemistry. 2001, 499: 144. doi:10.1016/S0022-0728(00)00504-0.

[8] Baxendale, J. H. (1964) , Radiation Res. Suppl., 114 and 139. [2018-09-07]. （原始内容存档于2021-12-19）.

[9] 存档副本. [2018-09-05]. （原始内容存档于2019-06-05）.

[10] Survey of Progress in Chemistry p 148

[11] Hayyan, M.; Hashim M. A.; AlNashef I. M. Superoxide Ion: Generation and Chemical Implications. Chem. Rev. 2016, 116: 3029–3085. doi:10.1021/acs.chemrev.5b00407.

[12] Janata, E.; Schuler, Robert H. Rate constant for scavenging eaq- in nitrous oxide-saturated solutions. J. Phys. Chem. 1982, 86 (11): 2078–84. doi:10.1021/j100208a035.

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