INORGANIC CHEMISTRY FRONTIERS REVIEW Cite this: Inorg. Chem. Front., 2020, 7, 3735 Received 21st April 2020, Accepted 24th June 2020 DOI: 10.1039/d0qi00447b rsc.li/frontiers-inorganic Advances in ligand-unsupported argentophilic interactions in crystal engineering: an emerging platform for supramolecular architectures Amanpreet Kaur Jassal * a,b Functionality of silver metal ions in coordination chemistry in addition to in crystal engineering is one of the most important research topics. These compounds have been extensively examined thanks to their distinctive properties and various arrangements of structural designs, with the presence of important argentophilic interactions. Various compounds are useful both in the absence and presence of ligand- supported interactions, which are established to obtain appreciably diverse molecular/structural and physical/physicochemical characteristics from silver core-based compounds. In some cases, weak inter- actions have seen to be useful for Ag–Ag contacts and in some cases, Ag–Ag contacts cooperate in the erection of a variety of interactions and result in topological variations in molecular structures. The out- comes of various developmental studies are appraised herein, focusing on molecular structural systems in which more than two silver cores are accessible at a close distance, supporting the required structural characterization. This review describes examples of various ligand-unsupported argentophilic inter- actions, emphasizing reticular design methods, synthetic approaches, and characterization techniques for these materials. Introduction In the last couple of decades, the study of argentophilic interactions 1–8 in silver chemistry is one of the most rapidly growing fields in crystal engineering and supramolecular chemistry. 9–14 Silver ions can participate in argentophilic inter- actions, even at distances little more than the sum of their van der Waals radii (3.44 Å), 15 maintaining angular specificities. From the literature survey, it has been found that weak argen- tophilic interactions are speculated to result in double bonds within a distance of 4.2 Å. 16 Strongly bridging counter anions, like carboxylate ions, 17–22 bridge silver atoms very strongly, with observed Ag–Ag distances as short as 2.778 Å. Amid the weak bridging ions, NO 3 − ions 2,23,24 have shown more enhanced bridging capabilities than ClO 4 − , PF 6 − , and BF 4 − anions. 12,25–28 These interactions can be manipulated by various types of ligands used for the construction of com- pounds with Ag + ions. The nature of the ligand 29 has a note- worthy influence on the distance between silver atoms and the robustness of the argentophilic interactions. The role of the ligand in favoring and enforcing argentophilicity is vital, as shown by the large number of compounds containing “ligand- supported” interactions 20,30–32 in comparison with the rare “ligand-unsupported” examples (Table 1). 33–37 The above-men- tioned interactions are distinguished in earlier reported data as either unsupported or supported, depending on the pres- Amanpreet Kaur Jassal Dr Amanpreet Kaur Jassal received her Ph.D. from Guru Nanak Dev University Amritsar, India, in 2016. She was a recipi- ent of an INSPIRE Fellowship (DST-SERB) while pursuing her Ph.D. Later, she started working as a National Post-Doctoral Fellow (DST-SERB) at IIT Delhi. After that, she moved to Technion Israel Institute of Technology, Israel, for her post- doctoral studies. Currently, she is working as a women scientist (DST-WOSA) at IIT Delhi. Her research interests include crystal engineering, polyoxometalates, metal–organic frameworks, and organometallic compounds. She has published more than 45 peer- reviewed international articles, with a h-factor of 13 and 433 citations. a Schulich Faculty of Chemistry, Technion–Israel Institute of Technology, Haifa, Israel b Chemistry Department, Indian Institute of Technology Delhi, New Delhi, India. E-mail: amanpreetkaurjassal@gmail.com This journal is © the Partner Organisations 2020 Inorg. Chem. Front. , 2020, 7, 3735–3764 | 3735 Published on 07 July 2020. Downloaded on 2/19/2022 11:26:42 AM. View Article Online View Journal | View Issue