Silver(I) Coordination Polymers Based On Halogenated Cyanoformamidine: Roles Of Oxyanions And Halogen Atoms In The Structural Diversity

The reactions of asymmetrical N-(4-halophenyl)-N '-cyanoformamidine (L-X, X = F, Cl, Br or I) with AgClO4 and AgNO3 afforded six coordination polymers, including {[Ag(L-Cl)](ClO4)}(n) [(L-Cl = N-(4-chlorophenyl)-N '-cyanoformamidine)], 1; {[Ag(L-Br)](ClO4)}(n) [(L-Br = N-(4-bromophenyl)-N '-cyanoformamidine)], 2; {[Ag(L-I)(2)](ClO4)}(n) [(L-I = N-(4-iodophenyl)-N '-cyanoformamidine)], 3; {[Ag(L-F)](NO3)}(n) [(L-F = N-(4-fluorophenyl)-N '-cyanoformamidine)], 4; {[Ag(L-Cl)](NO3)}(n), 5 and {[Ag(L-Br)](NO3)}(n), 6. Complexes 1 and 2 are 1D helical chains, and 3 features a 2D layer with the (6(3))-hcb topology. Complexes 4-6 are 1D linear chains supported by Ag---O interactions, which are further linked through Ag---Ag interactions and N-H---O hydrogen bonds to form 3D supramolecular structures. Halogen substituents on ligands and oxyanions in complexes affect the structures of complexes due to differences in the electronegativity, volume and Ag---O strengths. Although fluorine, chlorine and bromine atoms exhibit a similar structural effect and the iodine atom has the opposite effect, the larger ClO4- anion hinders the formation of the argentophilic interaction and the smaller NO3- anion is involved in this interaction.