Anion detection and quantification remain always challenging due to their inherent strong hydration energy, complex geometries and pH dependence. Several techniques and methodologies have been developed for the recognition and sensing of anions. Among all such techniques, fluorescence spectroscopy has received special attention due to its highly convenient and accurate detection capacity. A number of different mechanisms are prevalent in the literature for the emission spectroscopy. Intramolecular charge transfer (ICT) is one of such predominant mechanisms, which is usually observed in molecules with D-π-A or D-A type of structural arrangement. When ICT based probes interact with the desired analyte, the electron density in the recognition group is altered (e.g., as a result of bond cleavage, substitution, or substrate coordination) which installs a ‘push-pull’ system in the molecule. In the past two decades, a huge number of publications have emerged on this topic. Keeping into account the vast number of reports on anion sensing relied upon ICT mechanism, we will confine our discussion to sensors that are developed in last 6 years. The structural features of all the selected probes (total 123 probes), developed in the last 6 years, will be discussed in the present review with the particular emphasis on the mechanism (ICT) responsible for the detection and recognition of various anions. Apart from the mechanistic details, information about the detection limit, selectivity and visible change of color/state, binding units and stoichiometries with anions have also been discussed thoroughly and collected in tabular format. For the sake of legibility, all the probes have been categorized according to the number of anions they detect and are subdivided into specific anion-based sensing and their mechanism. This review aims to be a comprehensive, convincing and reader-friendly review of general interest to the chemistry community. To the best of our knowledge, this is the first survey in the contemporary time to cover the complete literature of past six years about anion sensing exclusively based on ICT mechanism. Throughout the review we provide an illustrative overview about the design strategies that may be exploited for analyte sensing and their corresponding suitable molecular systems. We hope, this review will enhance the basic understanding of the subject of ICT based mechanism which will certainly help the researchers to generate new molecular architectures with superior anion sensing ability in future.

由于其固有的强水合能、复杂的几何形状和 pH 依赖性，阴离子检测和量化始终具有挑战性。已经开发了几种用于识别和感测阴离子的技术和方法。在所有这些技术中，荧光光谱因其高度方便和准确的检测能力而受到特别关注。许多不同的机制在发射光谱的文献中很普遍。分子内电荷转移 (ICT) 是此类主要机制之一，通常在具有 D-π-A 或 DA 类型结构排列的分子中观察到。当基于 ICT 的探针与所需的分析物相互作用时，识别组中的电子密度会发生变化（例如，由于键断裂、取代或底物配位），在分子中安装了“推拉”系统。在过去的二十年里，出现了大量关于这个主题的出版物。考虑到大量关于依赖 ICT 机制的阴离子传感的报告，我们将讨论仅限于过去 6 年开发的传感器。在本综述中将讨论过去 6 年开发的所有选定探针（总共 123 个探针）的结构特征，特别强调负责检测和识别各种阴离子的机制 (ICT)。除了机械细节、关于检测限、选择性和颜色/状态的可见变化的信息，阴离子的结合单位和化学计量也已被彻底讨论并以表格形式收集。为了清晰起见，所有探针都根据它们检测到的阴离子数量进行了分类，并细分为特定的基于阴离子的传感及其机制。这篇评论旨在对化学界的普遍兴趣进行全面、有说服力和读者友好的评论。据我们所知，这是当代第一次涵盖过去六年关于完全基于 ICT 机制的阴离子传感的完整文献的调查。在整个审查中，我们提供了有关可用于分析物传感及其相应合适分子系统的设计策略的说明性概述。我们希望，