SYNTHESIS AND MOLECULAR-STRUCTURE OF NEW O N/O LIGANDS - BIS-PHENOL-PYRIDINE AND BIS-PHENOL-PYRAZOLE/

Two new heterocyclic ligands, 2,6-bis-(2'-hydroxyphenyl)pyridine 2 and 3,5-bis-(2'-hydroxyphenyl)pyrazole 4 have been prepared. The molecula r structures of 2,6-bis-(2'-methoxyphenyl)pyridine I, the tetrafluorob orate 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 me oriented so that the oxygen atoms of the methoxy group s re placed away front the nitrogen of the pyridine to overcome electr onic repulsion. In salt 3, intramolecular hydrogen bonds are found bet ween the pyridinium proton and the hydroxyl atoms which are involved i n 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 respon sible for the formation of chains. (C) 1997 Elsevier Science Ltd.