Silva, WagnerZanatta, MarcileiaFerreira, Ana SofiaCorvo, Marta C.Cabrita, Eurico J.2021-03-192021-03-192020-10-191661-6596PURE: 26227474PURE UUID: df4cc931-f045-4277-a647-24a070d28a73Scopus: 85093650272PubMed: 33086771PubMedCentral: PMC7589445WOS: 000585561000001http://hdl.handle.net/10362/114137grant number 201863/2014-6 UIDB/04378/2020 UIDB/50025/2020-2023 POCI-01-0145-FEDER-007688 PTDC/QUI-QFI/31508/2017 FCT-(ROTEIRO/0031/2013-PINFRA/22161/2016 UIDB/04378/2020In the last few years, ionic liquids (ILs) have been the focus of extensive studies concerning the relationship between structure and properties and how this impacts their application. Despite a large number of studies, several topics remain controversial or not fully answered, such as: the existence of ion pairs, the concept of free volume and the effect of water and its implications in the modulation of ILs physicochemical properties. In this paper, we present a critical review of state‐of-the‐art literature regarding structure–property relationship of ILs, we re‐examine analytical theories on the structure–property correlations and present new perspectives based on the existing data. The interrelation between transport properties (viscosity, diffusion, conductivity) of IL structure and free volume are analysed and discussed at a molecular level. In addition, we demonstrate how the analysis of microscopic features (particularly using NMR‐derived data) can be used to explain and predict macroscopic properties, reaching new perspectives on the properties and application of ILs.3710075590engFree volumeIon pairIonic liquidPhysicochemical propertiesSupramolecular organizationTransport propertiesWaterCatalysisMolecular BiologySpectroscopyComputer Science ApplicationsPhysical and Theoretical ChemistryOrganic ChemistryInorganic Chemistryreview10.3390/ijms21207745https://www.scopus.com/pages/publications/85093650272