Synthesis and characterization of copper(II) complexes with 3-methylpicolinic acid. Crystal and molecular structure of bis (3-methylpicolinato- N , O )(4-picoline)copper(II)

Abstract

Copper(II) complexes of 3-methylpicolinic acid (3-MepicH), namely [Cu(3-Mepic)2] · 2H2O (1) and [Cu(3-Mepic)2(4-pic)] (2) were prepared and characterized by IR spectroscopy and thermal analysis (TGA/DTA). Crystal structure for 2 was determined by X-ray crystal structure analysis. 1 was prepared by reaction of copper(II) sulfate pentahydrate and 3-methylpicolinic acid in aqueous solution, while 2 was prepared by recrystallization of 1 from 4-picoline solution. Structure analysis revealed square-pyramidal copper(II) coordination and N,O-chelating mode of 3-methylpicolinic acid in 2. Copper(II) is coordinated by two 3-Mepic ligands in the basal plane of a square pyramid and by 4-picoline in the apical position. Crystal packing of 2 is dominated by weak intermolecular C–H ··· O hydrogen bonds and π ··· π stacking interactions forming a complex three-dimensional supramolecular architecture.