engleski

NITROCHLORANILATE – A NOVEL HETEROSUBSTITUTED 2, 5-DIHYDROXYQUINOID LIGAND WITH A GREAT POTENTIAL FOR DESIGN OF COORDINATION POLYMERS

2, 5-dihydroxyquinones (anilic acids) are a class of versatile organic ligands interesting for design of novel coordination polymers and metal-organic frameworks. They are able to coordinate metals in terminal bidentate and bridging (bis)bidentate modes, and are thus able to form coordination polymers of various topologies [1]. The most commonly used ones are unsubstituted 2, 5-dihydroxyquinone [2] and its dichloro-analogue, chloranilic acid (3, 6-dichloro-2, 5-dihydroxyquinone) [3]. Substituents on positions 3 and 6 of the quinoid ring influence electronic structure of the ring through inductive effect, thus enhancing properties such as acidity, electronegativity (the rings may act as electron acceptors), optical properties (colour and possible luminescence) and capability to coordinate metals. The ligands are also able to mediate magnetic exchange interactions [1]. So far, all studied anilic acids were symmetrically substituted (i.e. substituents at positions 3 and 6 are identical), and pioneering work with the first asymmetrically substituted analogue, chlorocyananilic acid (3-chloro-6-cyano-2, 5-dihydroxyquinone) revealed interesting luminescent properties [4], promising for design of optoelectronic materials. Here we present a novel asymmetrically substituted ligand, nitrochloranilic acid (3-nitro-6-chloro-2, 5-dihydroxyquinone, NCA) and first of its transition metal complexes. In a mononuclear complex (Hpy)2[Mn(NCA)2(H2O)2] it behaves as a terminal bidentate ligand, while in 1D coordination polymers [Mn2(NCA)(H2O)5·3H2O]n, {;[Co(NCA)(phen)]·EtOH};n and [Cu(NCA)(H2O)2]n·H2O it acts as a bridging (bis)bidentate ligand. In the binuclear [Cu(NCA)(bpy)]2 it bridges two monomeric units [Cu(NCA)(bpy)] by bonding to Cu atom through its nitro group.

nitrochloranilate ; heterosubstituted ligand ; coordination polymer

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