Synthetic chemists can use different solvents (for example, polar vs nonpolar) to affect solute–solvent interactions and therefore favor a particular reaction product. Using a different isotope of the same solvent to select the product, however, is uncommon. We find that water and heavy water (D₂O) can select different products in the hydrothermal syntheses of iron-containing solids. Under hydrothermal and anaerobic conditions, water oxidizes iron to evolve hydrogen gas and a mixture of Fe²⁺- and Fe³⁺-containing solids. When we replace D₂O for H₂O under identical hydrothermal conditions, we can select thermodynamic products in our syntheses of iron-containing solids, whether it be oxides or chalcogenides. To explain this remarkable difference in product selectivity, we discover an unexpected difference in a fundamental property between H₂O and D₂O: their standard reduction potentials. Through electrochemical measurements and under strongly basic conditions (pH = 14), we find that the reduction potential of D₂O is 109 mV lower than that of H₂O. This difference in the reduction potential cannot be explained by the simple Nernst formulation. The unique product selectivity of D₂O over H₂O allows us to prepare iron chalcogenides with structures relevant to the iron-based superconductors.

中文翻译：

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水热合成中H ₂ O和D ₂ O之间的同位素效应

合成化学家可以使用不同的溶剂（例如，极性溶剂与非极性溶剂）来影响溶质与溶剂的相互作用，因此偏爱特定的反应产物。然而，使用相同溶剂的不同同位素来选择产物并不常见。我们发现水和重水（D ₂ O）在含铁固体的水热合成中可以选择不同的产物。在水热和厌氧条件下，水将铁氧化以释放出氢气以及含Fe ²⁺和Fe ³⁺的固体混合物。当我们用D ₂ O代替H _2时在相同的水热条件下，我们可以在合成含铁固体中选择热力学产物，无论是氧化物还是硫属元素化物。为了解释这种产物选择性的显着差异，我们发现了H ₂ O和D ₂ O之间的基本性质之间的意外差异：它们的标准还原电位。通过电化学测量并在强碱性条件下（pH = 14），我们发现D ₂ O的还原电位比H ₂ O的还原电位低109 mV 。这种还原电位的差异无法通过简单的能斯特公式来解释。D ₂ O对H ₂的独特产物选择性O使我们可以制备具有与铁基超导体相关的结构的硫属硫化铁。