Trimetallic Iridium–Nickel–Iridium Bis(formazanate) Assemblies

Abstract

Formazans have attracted a lot of attention in coordination chemistry since the early 1940s because of their unique properties engendered by the nitrogen-rich conjugated backbone. Although many studies have been done using formazanates to chelate transition metals, research using formazanates as building blocks for polynuclear compounds and supramolecular chemistry remains rare. In this paper, we describe a synthetic strategy that uses a pyridylsubstituted bis(formazanato)nickel complex as a metalloligand to further assemble with two [Ir(C^N) 2 ] + centers (C^N is the cyclometalating ligand). The trimetallic complexes represent a new binding mode for flexidentate pyridyl-substituted formazanates and a new structural class of polynuclear formazanate complexes. This work expands the chemistry of polynuclear formazanate complexes, for the first time pairing 3d and 5d metals in the same assembly. The redox chemistry of these trimetallic complexes, evaluated via cyclic voltammetry, is described. The compounds described in this work are luminescent, and studies of bis-cyclometalated iridium model complexes lacking the formazanate bridge confirm that the phosphorescence arises from the iridium center.

Ratiometric oxygen sensors of cyclometalated iridium(iii) with enhanced quantum yields and variable dynamic ranges

“…To better understand the photophysical properties of the iridium–fluorophore constructs we also consider here the pyridine-terminated model complexes [Ir(C^N) 2 (pyridine)(Cl)] ( C^N-py ), prepared analogously. The two complexes F 2 ppy-py and piq-py were described previously by our group, 43 whereas btp-py is newly described here. The identity and purity of all new complexes were ascertained by multinuclear NMR spectroscopy (Fig.…”