Virtual Issue: Molecular Sensors**

A molecular sensor, also known as a chemosensor or probe, is a molecular or supramolecular-based system that is able to transform probe–analyte interactions into a signal which allows analyte sensing. The most common output signals are usually optical or electrochemical changes. In particular, optical responses have become very popular due to the possibility of using low-cost, widely available instrumentation and even the possibility of detecting target species with the naked eye. The design of these molecular sensors and probes has advanced and gained importance in the last years due to the progress made in the knowledge on the preparation of host–guest complexes and on studies on how this interaction can be used for the design of selective molecular probes. This is a very in-terdisciplinary filed that in many cases involves organic or inorganic synthesis, photo-physical studies, and analytical applications. In this context, the design of new molecular sensors to detect anions, cations, and neutral species has gained primary significance recently due to the importance to detect target analytes in environmental and biological samples. Molecular sensors for metal cations were developed more than two decades ago, whereas probes for anions and neutral species have been investigated more recently. Articles already accepted show diverse approaches for the design of chemical probes that are based on different sensing principles and display sensing features to a wide range of ana-lytes such as anions, cations, neutral molecules, and gases. Molina et al. (DOI: 10.1002/open.201402022) prepared aryl or heteroaryl 5-substituted imidazo-benzothiadiazole derivatives and found an interesting selective dual-channel sensing of mercury(II) cations and acetate anions. Moreover the probes also display sensing features in the presence of nitroaromatic compounds with a selective response to the explosive picric acid. In a close research approach to the design of sensing probes for target chemical substances that could be used as weapons, Martínez-MµÇez, Costero, and co-workers (DOI: 10.1002/open.201402014) designed a molecular sensor for the selective chromogenic recognition of diisopropylfluorophos-phate (DFP), a Sarin and Soman mimic, in 99:1 (v/v) water/ acetonitrile and in the gas phase. Anion sensing probes were studied in the works of Ito et al. and Yam and co-workers. Ito and Shinoda (DOI: 10.1002/open.201402049) prepared macrotricyclic octaden-tate cyclen dimer ligands that were able to afford cage-shaped dinuclear Na + complexes. The authors found an interesting selectivity for dicarboxylates of different length. For instance, N-Boc-Asp dianion was strongly coordinated inside the cavity of the receptor whereas N-Boc-Glu dianion, which …