Departamento de Química, Universidade Estadual de Londrina, Londrina, Brazil.
Departamento de Física-CCE, Universidade Estadual de Maringá, Maringá, Brazil.
Astrobiology. 2021 Sep;21(9):1121-1136. doi: 10.1089/ast.2020.2322.
Considered one of the most promising building blocks of life on primitive Earth, cyanide and its complexes are likely to have played an important role in the emergence of life on the planet. Investigation into cyanide on Earth has primarily considered high concentrations, but the cyanide concentration in the oceans of prebiotic Earth was exceptionally low. Thus, Bernal's hypothesis has allowed investigators to work around this problem. We observed, however, that cyanide does not adsorb onto several minerals; therefore, ferrocyanide could be used as a cyanide source when adsorbed onto mineral surfaces to promote the synthesis of molecules of biological significance. When adsorbed onto bentonite, a mineral that has Fe atoms in its interlayers, the formation of Prussian blue analog complexes occurs through endothermic reaction and with increased entropy. The adsorption of ferrocyanide onto kaolinite indicates an exothermic and outer-sphere interaction, which results in degeneracy breakdown for C ≡ N stretch energy into two new bands of FTIR-ATR spectrum. Magnetite, which has iron atoms in its structure, and ferrocyanide interactions have been observed by outer-sphere coordination as well as the formation of Prussian blue analogs, as confirmed by the appearance of a new doublet in the Mössbauer spectra and a broadband close to 750 nm at UV-visible spectroscopy. Magnetite and kaolinite experiments presented relevant results only when performed in seawater, which suggests the importance of seawater composition for prebiotic experiments. These obtained results prove that ferrocyanide interacts with minerals differently according to structure and composition and show that this complex, like the Prussian blue analogs, may have played a crucial role as a source of cyanide on primitive Earth.
氰化物及其配合物被认为是原始地球上最有前途的生命构建块之一，很可能在地球上生命的出现中发挥了重要作用。对地球上氰化物的研究主要考虑了高浓度，但原始地球海洋中的氰化物浓度异常低。因此，贝尔纳的假设使研究人员能够解决这个问题。然而，我们观察到氰化物不会吸附在几种矿物质上；因此，亚铁氰化物可以被用作吸附在矿物表面上的氰化物源，以促进具有生物意义的分子的合成。当吸附在蒙脱石上时，一种在层间具有 Fe 原子的矿物质，普鲁士蓝类似物的形成通过吸热反应和增加熵发生。亚铁氰化物在高岭石上的吸附表明是放热和外层空间相互作用，这导致 C≡N 伸缩能的简并分解为 FTIR-ATR 光谱的两个新带。具有铁原子结构的磁铁矿和亚铁氰化物之间的相互作用已通过外层空间配位以及普鲁士蓝类似物的形成得到证实，这一点通过穆斯堡尔光谱中出现新的双峰和紫外-可见光谱中接近 750nm 的宽带得到证实。只有在海水中进行磁铁矿和高岭石实验时才会得到相关结果，这表明海水成分对原始生命实验的重要性。这些结果证明，亚铁氰化物根据结构和组成与矿物质的相互作用不同，并且表明该配合物与普鲁士蓝类似物一样，可能在原始地球上作为氰化物的来源发挥了关键作用。
