Isolable Cu(I) Complexes of Extremely Electron-Poor, Completely Unreduced o-Quinone and “Di-o-Quinone” Ligands Stabilized through π–π Interactions in the Secondary Coordination Sphere

Abstract

The copper–quinone interaction plays important roles in diverse fields such as biochemistry, catalysis, and optically/magnetically switchable materials. Despite this fact, the isolation and thorough characterization of copper­(I)-quinone complexes remains a highly challenging task owing to their intrinsic instability. We herein present systems where the stability imparted by the extended π-system of a pyrene ring is used to synthesize, isolate, and crystallographically characterize the first example of a dinuclear metal complex that is bridged by a completely unreduced “di-o-quinone”-type ligand. Additionally, we present the monocopper counterpart with the o-quinone–pyrene type of ligand. The copper complexes are redox-rich and display intriguing electrochemical, optical, and electron paramagnetic resonance (EPR) spectroscopic properties. The line-rich EPR spectra of the one-electron reduced copper­(I) complexes were simulated and analyzed via density functional theory calculations. The results presented here establish π–π stacking as a viable alternative to stabilize otherwise unstable redox-active compounds with possible consequences for sensing and redox catalysis.

How Solid Surfaces Control Stability and Interactions of Supported Cationic CuI(dppf) Complexes─A Solid-State NMR Study

“…− (BArF − ). 57 For example, 1-BF 4 (300.2 mg, 0.382 mmol, 1 eq) was dissolved in MeCN (7 mL). Upon the addition of Na(BArF) (1.015 g, 1.145 mmol, 3 eq), a yellow solid precipitated, while the suspension was stirred for 30 min.…”

“…The counter ions BF 4 – were exchanged according to the literature with B­[3,5-(CF 3 ) 2 C 6 H 3 ] 4 – (BArF – ) . For example, 1 -BF 4 (300.2 mg, 0.382 mmol, 1 eq) was dissolved in MeCN (7 mL).…”

Synthesis of Asymmetric Coupled Polymethines Based on a 7-Chloropyrido[1,2-a]benzimidazole-8,9-dione Core

“…4 Among many parameters relevant to the design of organic redox materials, the planarity or nonplanarity of the molecules is also an important factor. 5 Quinones can be used as ligands to design coordination complexes 6,7 or metal−organic frameworks 8 featuring original photophysical and redox properties. Functionalization of the quinone molecules and tuning the bonds formed between quinone ligands and metal ions as well as delocalized electron distributions endow the metal−organic frameworks (MOFs) with chemical and electrochemical stability, which are essential for organic electrode materials to have the desirable properties.…”

“…(7), 1,3-indandione analogues with differ-i v i d u a l n o t d i r e c t l y a s s o c i a t e d w i t h s c i t e i s p r o h i b i t e d .…”

Metal-directed supramolecular architectures based on the bifunctional ligand 2,5-bis(1H-1,2,4-triazol-1-yl)terephthalic acid

“…(Mondal et al, 2018;Wang et al, 2014;Ardila-Suá rez et al, 2019). In addition, various kinds of intermolecular weak interactions, such as hydrogen bonding, stacking, metal-metal interactions etc., are vital in the self-assembly process (Khavasi et al, 2010;Yang et al, 2009;Bala et al, 2013;Mikhalyova et al, 2015;Albold et al, 2019).…”