Ligand influence on the formation of exo-coordinated silver(I) complexes with N2O2 Schiff base macrocycles and the role of anion in supramolecular aggregation

Abstract

Three novel silver(I) complexes with N2O2-donor macrocyclic Schiff bases L1 and L2 (L1 = 1,5-diaza-2,4:7,8:17,18-tribenzo-9,16-dioxa-cyclononadeca-1,5-dien; L2 = 1,5-diaza-2,4:7,8:18,19- tribenzo-9,17-dioxa-cycloeicosa-1,5-dien) were prepared by the reaction of the corresponding macrocycles with silver nitrate and silver perchlorate in 1:1 stoichiometric ratio. The reactions of macrocyclic ligands (L1 and L2) with silver perchlorate led to the formation of unusual (regarding donor set atoms) silver coordination polymers, AgL1ClO4, and (AgL2ClO4)2·CH2Cl2. The reaction of L2 with silver nitrate resulted in a formation of discrete binuclear silver complex (AgL2NO3)2. In all three compounds, silver ions are exo-coordinated due to the presence of rigid CN bond in the molecular structure of ligands in which nitrogen atom non-bonding electron pairs are exo- oriented. All synthesized compounds were characterized by vibrational spectroscopy (IR) and thermal methods (TG/DSC). The crystal and molecular structures of silver complexes were determined by the single crystal X-ray diffraction method. In the complex AgL1ClO4, each silver atom is coordinated by two ligand molecules and one perchlorate anion (T-shaped geometry). The coordination geometry around the silver atom can be described as T-shaped, resulting in a formation of the 1D zig-zag polymeric chain. In (AgL2ClO4)2·CH2Cl2 two distinct coordination surroundings of silver ions that can be divided into cationic (linear geometry) and anionic (square planar geometry) part. The topology of the polymeric chain can be described as a 1D zig-zag. The silver atoms in (AgL2NO3)2 are tetrahedrally coordinated with two N-bound ligand molecules and one nitrate anion (bidentate). This form of coordination produces a discrete bimetallic silver complex with an additional metallacyclic ring. The anion and ligand influence on the chain structure is attributed to the presence of rigid imine double bond and partly to the coordination ability of counter ions.