ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Mixed-ligand complexes of boric acid with organic biomolecules

Dursun Ali Köse and Birgül Zümreoglu-Karan

Department of Chemistry, Hitit University, Çorum, 19032 Turkey

E-mail: dalikose@hitit.edu.tr

Abstract: Boric acid forms meta-stable complexes with biomolecules like amino and hydroxy acids and stable complexes with the diol group containing carbohydrates, vitamins, and nucleotides, yielding mono-chelate (1: 1 complex) or bis-chelate (1: 2 complex) structures with negatively charged tetrahedral borate anions. Here we report water-soluble, bio-available mixed-ligand boron adducts for potential nutritional and/or pharmaceutical applications. The complexes were prepared by complete esterification of boric acid with a number of acyclic- and cyclic hydroxy-functionalized biomolecules employing sodium as the counter ion. Structural and thermal properties of the complexes were investigated using chemical analysis, ¹¹B NMR, FTIR, and TGA-DTA techniques. Complexes containing salicylic acid as one of the ligands displayed higher thermal and hydrolytic stabilities.

Keywords: boric acid complexes – boron adducts – borate esters – 11B NMR – mixed ligand complexes

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-011-0108-0

Chemical Papers 66 (1) 54–60 (2012)