Synthesis and structural characterization of new N2O2-donor Schiff base macrocycles and their silver(I) coordination polymers

Abstract

Two N2O2-donor macrocyclic Schiff bases mD1 and mD2 (mD1=1,5-diaza-2,4:7,8:16,17-tribenzo-9,15-dioxa-cyclooctadeca-1,5-dien; mD2=1,5-diaza-2,4:7,8:15,16-tribenzo-9,14-dioxa-cycloheptadeca-1,5-dien) were prepared by the [1+1] cyclocondensation reaction of the corresponding dialdehyde and diamine. The reactions of the prepared macrocycles with silver nitrate led to formation of unique (regarding the N2O2-donors) silver coordination polymers, AgmD1 and AgmD2. All synthesized compounds were characterized by vibrational spectroscopy (IR), thermal methods (TG/DSC) and the ligands additionally by NMR. The crystal and molecular structures of the macrocycles and the silver coordination polymers were determined by the single crystal X-ray diffraction method. The molecular structure of the macrocycles is found to be rather similar, but with significant differences in the crystal packing arrangement due to slight deviations from planarity. In the complex AgmD1 each silver atom is coordinated by two imino nitrogen atoms of the neighboring ligand molecules and, with an oxygen atom of the nitrate group, thus producing an infinite zig-zag polymeric chain. The silver atoms in AgmD2 are tetrahedrally coordinated with two N-bound ligand molecules and two nitrate anions. This form of coordination produces an additional metallacyclic ring. The polymeric structure is formed through connection of the metallacyclic rings by bridging nitrate anions. Slight deviations in the conformation of the macrocyclic ligands have significant impact upon the coordination mode and topology of the silver coordination polymer structures.