C3v-Symmetric tripodal nitrophenylurea based anion receptors built on structurally preorganized trindane scaffold

C3v-Symmetric tripodal anion receptors with three urea or thiourea recognition motifs were synthesized from C3v-symmetric cis,cis,cis-2,5,9-tri-p-bromobenzyltrindane molecular skeleton via Hartwig amination and then formation of urea compounds with the corresponding isocyanate. The anion receptors recognized halide and oxo anions with C3-symmetry through the hydrogen bonding interactions between anions and the NH protons of urea or thiourea groups. The receptors 2 and 3 showed a significant binding affinity toward H2PO4- in DMSO-d6; 392 and 305 M−1, respectively. The strong affinity of H2PO4- anion may be attributed to its tetrahedral geometry and the basicity of H2PO4- anion, allowing it to form stronger hydrogen-bonding.