Cyanostar binds anions throughhydrogen bonding from the C–H bonds, as the hydrogen has a positiveelectrostatic potential.[3] It is the first binder to make use of cyanostilbene's electropositive CH groups. The CH bonds create an electropositive region in the center of the macrocycle, creating abinding pocket. Cyanostar strongly binds anions that usually can only be bound weakly. The increased binding arises from the formation of a 2:1 complex, with two cyanostars sandwiching the anion on each side.[3] An extended version of this structural pattern is a 4:3 alternating stack of cyanostar molecules complexing a hydrogen-bonded chain ofdihydrogen phosphate units.[4]
Two cyanostars can be threaded onto aphosphate diester structure, forming arotaxane. Because they have a high affinity for the central phosphate group only when it is in its anionic form, there is a substantial and reversible structural change in response to acid–base changes in solution.[5]
^abcLee, Semin; Chen, Chun-Hsing; Flood, Amar H. (2013). "A Pentagonal Cyanostar Macrocycle with Cyanostilbene CH Donors Binds Anions and Forms Dialkylphosphate [3]Rotaxanes".Nature Chemistry.5 (8):704–710.Bibcode:2013NatCh...5..704L.doi:10.1038/nchem.1668.PMID23881503.
