Unique Crystal\nStructure of a Self-Assembled Dinuclear\nCu Peptoid Reveals an Unusually Long Cu···Cu Distance

Studies on a series of molecular dicopper peptoid complexes\nshowed\nthat the Cu···Cu distances measured in X-ray single-crystal\ndiffraction are typically in the range of 4.2–6.9 Å. Herein,\nwe designed a new peptoid, <b>L1</b>, having 2,2′-bipyridine,\npropyl, and pyridyl side chains and discovered that although it forms\na typical dicopper self-assembled structure (complex <b>1</b>), the Cu···Cu distance is exceedingly long −8.043\nÅ. By analyzing its structure and surface properties in comparison\nto a control Cu-peptoid complex (<b>2</b>), in which the pyridyl\nside chain is modified by an ethanolic side chain, we suggest that\nthe long Cu···Cu distance is contributed by the hydrophilic–hydrophobic\ninteraction influenced by the pyridyl side chain and the steric hindrance\nof the propyl side chain. This result may motivate the use of dinuclear\nCu peptoid complexes for wider applications, such as cooperative catalysis\nand luminescence.