Rational design and structural diversity of copper(II) complexes assembled from 3-sulfobenzoate and 2,2′-bipyridine

Abstract

Three new Cu II/3-sb/2,2′-bipy complexes, [Cu(2,2′-bipy) 2(3-sb)]·4 H 2O ( 1), {[Cu(2,2′-bipy)(3-sb)(H 2O) 2]·2. 5H 2O} n ( 2), and {[Cu(2,2′-bipy)(3-sb)(H 2O)]·2H 2O} n ( 3), in addition to the our previously reported {[Cu(2,2′-bipy)(3-sb)(H 2O)](H 2O)} n ( 4) and [Cu(2,2′-bipy) 2Cl](3-Hsb)·3H 2O ( 5) [3-sb = 3-sulfobenzoate dianion; 2,2′-bipy = 2,2′-bipyridine], have been synthesized by hydrothermal reactions or the combination of hydrothermal reactions and solution evaporation. The molecular structure of complex 1 is a monomer in which the 3-sb monodentately coordinates to the Cu II ion. Complexes 2– 4 exhibit one-dimensional infinite chain structures in which the 3-sb ligands serve as bridges. Complex 5 is a cation–anion species in which the 3-Hsb is non-coordinating. Five complexes exhibit four coordination geometries, irregular geometry between square pyramid and trigonal bipyramid in 1, distorted octahedron in 2, square pyramid in 3– 4, and trigonal bipyramid in 5. These complexes contain lattice and/or coordinated water molecules, therefore extensive hydrogen bonds occur. The extended hydrogen-bonding architectures are 1-D chains for 4 and 5, 2-D layers for 1 and 3, and 3-D network for 2. Complexes 3 and 4 have same crystal system and space group, and afford similar 1-D frameworks but have different lattice water molecules, therefore the addition lattice water molecule in complex 3 leads to more compact packing, longer metal–lattice water distance, and shorter Cu⋯Cu separation by 3-sb compared to those in complex 4. The fluorescent emissions of complexes 1– 3 are stronger than those of ligands, indicating the coordination of 3-sb and 2,2′-bipyridine can enhance the emissions.