Synthesis and molecular structure of new O/N/O ligands: bis-phenol-pyridine and bis-phenol-pyrazole

Article abstract of DOI:10.1016/S0040-4020(97)00733-3

Two new heterocyclic ligands, 2,6-bis-(2'-hydroxphenyl)pyridine 2 and 3,5-bis-(2'-hydroxyphenyl)pyrazole 4 have been prepared. The molecular structures of 2,6-bis-(2'-methoxyphenyl)pyridine 1, the tetrafluoroborate salt of 2,6-bis-(2'-hydroxyphenyl)pyridine 3 (a monohydrate) and that of compound 4 have been determined by X-Ray analysis. In 1, the phenyl rings are oriented so that the oxygen atoms of the methoxy groups are placed away from the nitrogen of the pyridine to overcome electronic repulsion. In salt 3, intramolecular hydrogen bonds are found between tile pyridinium proton and the hydroxyl atoms which are involved in strong O-H···O and O-H···F interactions. In addition, the water molecule participates in a bridging hydrogen bond network with the BF₄^-. The molecules in 4, are also held together by hydrogen bonds where the hydroxyl groups act as both a donor and an acceptor and are responsible for the formation of chains.