Recent advances in the development of ferrocene based electroactive small molecules for cation recognition: A comprehensive review of the years 2010–2020

Cations are ubiquitous for biological systems and play a very critical role in our cellular level, extracellular fluids (mostly monovalent cations) and in central nervous system. Electroanalytical sensors, mostly based on ferrocene, are very sensitive, selective, economic, and easy-to-make probes for the detection of these various metal cations. Ferrocene based chemosensors have emerged as a significant field of research in the last few decades. The inclusion of ferrocene to these sensor molecules has added another dimension in the sensing procedure due to its unique reversible redox properties. The present review summarizes the advances produced over a period of last 10 years on ferrocene based derivatives which are being able to detect various metal ions along with their chemical structures (wherever applicable). We will confine our discussion to ferrocene based cation sensors with a specific focus on their properties in terms of electrochemical studies, emission profile, binding units and stoichiometries with the metal ions. In the last 10 years, a huge number of publications have emerged on this topic; however, we witness a lack of a comprehensive review to cover up all the results under one umbrella. For the sake of legibility at a glance, all the ligands (nearly 172) and their different sensing parameters (detection limits, binding sites, reproducibilities and binding constant values) and their relative changes in the output signals (change of color, electrochemical potential and emission profile) upon interaction with different metal ions, are described and collected in tabular format. This review aims to be a comprehensive, authoritative, critical, and accessible review of general interest to the chemistry community because to the best of our knowledge, this is the first survey in the contemporary time to cover the complete literature of ferrocene based cation sensors over the last decade. We believe that, this collection and comparisons will facilitate the chemical community to build up more effective and potential electrochemical chemosensors conveniently in the upcoming period.