Synthesis of New Phenanthroline‐Based Heteroditopic Ligands – Highly Efficient and Selective Fluorescence Sensors for Copper(II) Ions

Abstract

AbstractThe heteroditopic phenanthroline derivatives 5,6‐bis(2‐pyridylcarboxamido)‐1,10‐phenanthroline (H2L1) and 5,6‐bis[(4‐methoxy‐2‐pyridyl)carboxamido]‐1,10‐phenanthroline (H2L2) have been prepared and characterized, together with their luminescent ruthenium(II) complexes [Ru(bpy)2(H2L1,2)](PF6)2 and [Ru(H2L1)3](PF6)2 and the corresponding iron(II) complex [Fe(H2L1)3](PF6)2. In these complexes, the metal ion is coordinated by the bidentate phen site of H2L. The luminescence of the ruthenium complexes (λex = 450 nm, λem ca. 620 nm) is completely quenched by Cu2+ ions in the micromolar concentration range and, to a lesser extent, by other metal ions. At pH 5, the response of the luminescent sensors is highly Cu2+‐selective. Heterodinuclear complexes [Ru(bpy)2(LM)](PF6)2, [Ru(LM)3](PF6)2, and [Fe(LM)3](PF6)2 have been isolated for M = Cu2+, Ni2+, Co2+, and Pd2+. It is suggested that M is coordinated to the tetradentate N4 site of L by two deprotonated amide N atoms and two pyridyl groups. This coordination type is confirmed by the EPR spectrum of the compound [RuII(bpy)2(L1CuII)](PF6)2.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)