Metal-controlled assembly and selectivity of a urea-based anion receptor

1-( 3-[ 1,10] phenanthrolin-2-yl-phenyl)-3-( 4-trifluoromethyl-phenyl)-urea ( 1) forms a solution-stable 1:2 complex with copper( I), [ Cu-I( 1)(2)](+), which behaves as an anion receptor in aprotic media. The [ Cu-I( 1)(2)](+) receptor may adopt a geometrical arrangement in which the two facing urea subunits give tetrafurcate H-bond interaction with a spherical anion ( halides and H2PO4-). In the presence of the Y-shaped acetate, the [ Cu-I(1)(2)](+) receptor rearranges to interact with two CH3COO- ions, according to two stepwise equilibria. Thus, in the presence of substoichiometric amounts of the anions, [ Cu-I( 1)(2)](+) discriminates H2PO4- over CH3COO-, inverting the basicity trend.