Uncommon coordination modes of 4-methylimidazole in [Zn(4-Meim)2(5-Meim)2]sq·3H2O

A novel Zn(II) complex, [Zn(4-Meim)2(5-Meim)2]sq·3H2O (1), (H2sq = squaric acid, 4-Meim = 4-methylimidazole and 5-Meim = 5-methylimidazole) has been synthesized and characterized by elemental, spectral (IR), thermal analyses and single crystal X-ray diffraction techniques. The Zn(II) ion center accommodates two binding types of the 4(5)-Meim ligand in same coordination sphere, which is a very unique example of the linkage isomers. The sq counterion interacts each other though water bridges by strong hydrogen bonds forming a zig-zag chain along the b-axis and generate image motif. The adjacent chains are connected by the water molecule forming a image aperture.