Supramolecular encapsulation of anions in a copper(I) complex

Mixed ligand copper(lI) complexes of 1,10-phenanthroline (phen) and 1,2-bis(diphenyl)phosphinoethane (dppe) have been prepared with different counter ions [ClO4- (1), BF4- (2), SO42- (3), NO3- (4)]. Based on the H-1 and P-31 NMR spectra of these complexes, it is seen that the solution equilibria of the sulfate complex is different from the rest and involves ligand dissociation. Competition experiments show that the nitrate ion is preferred by the cation in solution. Complex 4 has H-1 NMR features that are different from those observed in complexes 1 and 2. A Cambridge Structural Database study has been taken up to show the uniqueness of phenanthroline in interacting with anions, especially nitrate ions through a preferential (phen)C2-O(nitrate) interaction