4-(4-Formyl-3-hydroxyphenoxy)phthalonitrile (3) and its condensation product with 2-aminophenol have been synthesized to reach 4-(3-hydroxy-4-(((2-hydroxyphenyl) imino)-methyl) phenoxy) phthalonitrile (5), a tridentate ligand possessing ONO binding sites. Subsequent condensation of phenylboronic acid with 5 afforded a novel boronic ester of a Schiff base with a phthalonitrile group (7). Boronate 7 displays high stability and can be handled in air due to the presence of coordinative B-N and covalent B-O bonds in its structure. The novel compounds were characterized by elemental analyses, IR, UV-vis, mass, H-1-, C-13- and B-11 NMR spectra. (C) 2011 Elsevier B.V. All rights reserved.