Supramolecular Assembly of Hypervalent Iodine Macrocycles and Alkali Metals

This study explores the solution- and solid-state assembly of phenylalanine based hypervalent iodine macrocycles (HIMs) with lithium and sodium cations. The metal cation binding of HIMs was evaluated by addition of lithium tetrakis(pentafluorophenyl)borate ethyl etherate (Li)BARF and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl] borate (Na)BARF. The relatively electron rich, outwardly projected carbonyl oxygens of the HIM co-crystalize with the cations into bent supramolecular architectures. Both crystal structures show a pattern of assembly between HIM and metal cation in 2:1 ratio. While association with sodium leads to a polymer-like network, the lithium crystal structure was limited to dimeric assemblies of HIM. In the lithium coordinating complex, the oxygen-lithium-oxygen bond angle is approximately 98.83°, displaying a closer arrangement of two HIMs. In contrast, the sodium complex exhibits a more open orientation of two HIMs with an oxygen-sodium-oxygen bond angle close to 167.98°. Lastly, a comparative study of association constants and binding energies for phenylalanine based HIM with (Li)BARF and (Na)BARF are presented.