Department of Biophysical Chemistry and Molecular Oncology, Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic.
Department of Synthesis, Institute of Inorganic Chemistry of the Czech Academy of Sciences, Hlavní 1001, 250 68 Řež, Czech Republic.
Molecules. 2022 Mar 8;27(6):1761. doi: 10.3390/molecules27061761.
In this study we explore the effect on the electrochemical signals in aqueous buffers of the presence of hydrophilic alkylhydroxy and carboxy groups on the carbon atoms of cobalta bis(dicarbollide) ions. The oxygen-containing -skeletal substituents of cobalta bis(dicarbollide) ions belong to the perspective building blocks that are considered for bioconjugation. Carbon substitution provides wider versatility and applicability in terms of the flexibility of possible chemical pathways. However, until recently, the electrochemistry of compounds substituted only on boron atoms could be studied, due to the unavailability of carbon-substituted congeners. In the present study, electrochemistry in aqueous phosphate buffers is considered along with the dependence of electrochemical response on pH and concentration. The compounds used show electrochemical signals around -1.3 and +1.1 V of similar or slightly higher intensities than in the parent cobalta bis(dicarbollide) ion. The signals at positive electrochemical potential correspond to irreversible oxidation of the boron cage (the C2B9 building block) and at negative potential correspond to the reversible redox process of (CoIII/CoII) at the central atom. Although the first signal is typically sharp and its potential can be altered by a number of substituents, the second signal is complex and is composed of three overlapping peaks. This signal shows sigmoidal character at higher concentrations and may be used as a diagnostic tool for aggregation in solution. Surprisingly enough, the observed effects of the site of substitution (boron or carbon) and between individual groups on the electrochemical response were insignificant. Therefore, the substitutions would preserve promising properties of the parent cage for redox labelling, but would not allow for the further tuning of signal position in the electrochemical window.
在这项研究中，我们探讨了亲水性烷基羟和羧基在钴双(二卡宾)离子碳原子上的存在对水溶液缓冲液中电化学信号的影响。钴双(二卡宾)离子的含氧-骨架取代基属于被认为可用于生物偶联的潜在构建块。碳取代提供了更广泛的多功能性和适用性，因为可能的化学途径具有更大的灵活性。然而，直到最近，由于缺乏碳取代同系物，只能研究仅在硼原子上取代的化合物的电化学。在本研究中，我们考虑了在磷酸盐缓冲水溶液中的电化学以及电化学响应对 pH 值和浓度的依赖性。所使用的化合物在约-1.3 和+1.1 V 处显示出电化学信号，其强度与母体钴双(二卡宾)离子相似或略高。正电化学势下的信号对应于硼笼（C2B9 构建块）不可逆氧化，而负电化学势下的信号对应于中心原子处(CoIII/CoII)的可逆氧化还原过程。尽管第一个信号通常很尖锐，其电位可以被许多取代基改变，但第二个信号很复杂，由三个重叠的峰组成。该信号在较高浓度下呈现出阶跃特性，可作为溶液中聚集的诊断工具。令人惊讶的是，取代位置（硼或碳）和各个基团对电化学响应的影响并不显著。因此，取代将保留母体笼在氧化还原标记方面的有前途的性质，但不会允许在电化学窗口中进一步调整信号位置。
