Iridium Complexes with BIAN-Type Ligands: Synthesis, Structure and Redox Chemistry

Abstract

A series of iridium complexes with bis(diisopropylphenyl)iminoacenaphtene (dpp-bian) ligands, [Ir(cod)(dpp-bian)Cl] (1), [Ir(cod)(NO)(dpp-bian)](BF4)2 (2) and [Ir(cod)(dpp-bian)](BF4) (3), were prepared and characterized by spectroscopic techniques, elemental analysis, X-ray diffraction analysis and cyclic voltammetry (CV). The structures of 1–3 feature a square planar backbone consisting of two C = C π-bonds of 1,5-cyclooctadiene (cod) and two nitrogen atoms of dpp-bian supplemented with a chloride ion (for 1) or a NO group (for 2) to complete a square-pyramidal geometry. In the nitrosyl complex 2, the Ir-N-O group has a bent geometry (the angle is 125°). The CV data for 1 and 3 show two reversible waves between 0 and -1.6 V (vs. Ag/AgCl). Reversible oxidation was also found at E1/2 = 0.60 V for 1. Magnetochemical measurements for 2 in a range from 1.77 to 300 K revealed an increase in the magnetic moment with increasing temperature up to 1.2 μB (at 300 K). Nitrosyl complex 2 is unstable in solution and loses its NO group to yield [Ir(cod)(dpp-bian)](BF4) (3). A paramagnetic complex, [Ir(cod)(dpp-bian)](BF4)2 (4), was also detected in the solution of 2 as a result of its decomposition. The EPR spectrum of 4 in CH2Cl2 is described by the spin Hamiltonian Ĥ = gβHŜ with S = 1/2 and gxx = gyy = 2.393 and gzz = 1.88, which are characteristic of the low-spin 5d7-Ir(II) state. DFT calculations were carried out in order to rationalize the experimental results.

Effects of Bis(imino)acenaphthene (Bian)-Derived Ligands on the Cytotoxicity, DNA Interactions, and Redox Activity of Palladium(II) Bipyridine Complexes

“…As part of metal complexes, acenaphtheneimine derivatives can exist in neutral, radical-anion, and dianion redox states . As a result, metal complexes with Bian ligands are typically characterized by rich redox chemistry incliding the redox isomerism (reversible intramolecular electron transfer), − which enables their use for various applications. For example, metal complexes with Bian ligands can be used in multielectron activation processes of small molecules and catalytic reactions based on redox transformations. ,− In particular, square-planar Pd­(II) complexes of the [Pd II X 1 X 2 (Bian)] type, where X 1 and X 2 are Cl, CH 3 , OH, etc., have been investigated as catalysts for olefin polymerization reactions (Brookhart catalysts). − …”

Gold(i) complexes with redox active BIAN and MIAN ligands: synthesis, structure and electrochemistry

“…The coordination chemistry of bis(arylimino)acenaphthenes (BIANs) has been actively developed in recent decades. 1–5 The increased interest in such compounds is primarily due to their unique redox properties. The coordinated BIANs can be in neutral, anion-radical and dianionic redox states.…”

Mono(arylhydrazino)acenaphthenones as a platform for the design of NIR chromophores based on Pd(ii)-BIAN complexes

“…Ar-bians are exocyclic diimines based on an extended p-system of acenaphthene, which provides rigidity for the carbon backbone and high chemical stability for the compounds. 1,[11][12][13][14][15] Being strong s-donors and p-acceptors, Ar-bians effectively coordinate most metal ions in various oxidation states. Their key feature is the ability to accept up to four electrons and reversibly exchange them with the coordinating metal, which makes it possible to trigger various redox transformations.…”