Silver() coordination polymers based on halogenated cyanoformamidine: roles of oxyanions and halogen atoms in the structural diversity

• Published in: CrystEngComm 2021-03, Vol.23 (9), p.1961-1968
• Main Authors: Cheng, Fu-Hung, Liu, Yu-Hsiang, Lee, Wei-Te, Hu, Ji-Hong, Hu, Hui-Ling, Mahat Chhetri, Pradhumna, Chen, Jhy-Der
• Format: Article
• Language: English
• Subjects: Absorption spectra; Anions; Atomic structure; Bromine; Chlorine; Coordination compounds; Coordination polymers; Crystallography; Electronegativity; Fluorine; Halogenation; Hydrogen bonds; Iodine; Silver nitrate; Surface analysis (chemical); Topology
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/d1ce00025j

The reactions of asymmetrical N -(4-halophenyl)- N ′-cyanoformamidine (L-X, X = F, Cl, Br or I) with AgClO 4 and AgNO 3 afforded six coordination polymers, including {[Ag(L-Cl)](ClO 4 )} n [(L-Cl = N -(4-chlorophenyl)- N ′-cyanoformamidine)], 1 ; {[Ag(L-Br)](ClO 4 )} n [(L-Br = N -(4-bromophenyl)- N ′-cyanoformamidine)], 2 ; {[Ag(L-I) 2 ](ClO 4 )} n [(L-I = N -(4-iodophenyl)- N ′-cyanoformamidine)], 3 ; {[Ag(L-F)](NO 3 )} n [(L-F = N -(4-fluorophenyl)- N ′-cyanoformamidine)], 4 ; {[Ag(L-Cl)](NO 3 )} n , 5 and {[Ag(L-Br)](NO 3 )} 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 ClO 4 − anion hinders the formation of the argentophilic interaction and the smaller NO 3 − anion is involved in this interaction. Halogen substituents on cyanoformamidine ligands and oxyanions affect the structures of complexes due to differences in their electronegativity and volume.