Influence of Functionalized Substituents on the Electron‐Transfer Abilities of Copper Guanidinoquinoline Complexes

Abstract

The influence of functionalized ligands on the electron-transfer abilities of copper guanidinoquinoline complexes as entatic state models has been examined. An electron donating group (OCH 3 ) or electron withdrawing group (Br) was introduced in 6-position of the quinoline unit of the ligands TMGqu and DMEGqu. The electron self-exchange rates k 11 of the copper complexes with these ligands were determined using the Marcus cross relation. The k 11 values of the functionalized complexes are smaller or equal to the values of their unsubstituted forms. These results were complemented by the examination of the reorganization energies of the electron-transfer via Eyring theory and DFT calculations. The higher reorganization energies [a] 4998 Figure 2. Copper(I) and copper(II) guanidinoquinoline complexes C1-C8 with substituent in 6-position (X = Br, OMe) of the quinoline unit.

Encapsulation of tricopper cluster in a synthetic cryptand enables facile redox processes from CuICuICuI to CuIICuIICuII states

“…S20†). These fast ET rates approach the fastest synthetic mono- and dicopper system (10 5 to 10 6 M −1 s −1 ) 33,35–43 as well as Nature's blue copper ET protein 10 5 to 10 6 M −1 s −1 . 44,45 The corresponding reorganization energies for 4a / 4b and 4b / 4c were calculated to be 1.21(1) eV and 1.21(1) eV using eqn (1) ( Z = 10 11 M −1 s −1 , T = 298 K).…”

Low Reorganization Energy for Electron Self-Exchange by a Formally Copper(III,II) Redox Couple

“…Schematic representation of electron-transfer self-exchange properties of copper centers in proteins and model complexes (all experimentally determined, except those italicized with asterisks , ). Reorganization energies (eV) are given in blue, and self-exchange rate constants (M –1 s –1 , at 25 °C) are given in parentheses.…”

Increasing the Activity of Copper Guanidine Quinoline Catalysts: Substitution at the Quinoline Backbone Leads to Highly Active Complexes for ATRP

“…The ligands TMG6Brqu (L2) and TMG6Methoxyqu (L3) were synthesized according to the literature. [16] The guanidine synthesis of the ligands was accomplished according to a general procedure starting from amine precursors (Scheme 2). [17] The preparation of each differently substituted ligand follows individual synthetic routes (Scheme 3).…”

“…The formation of bischelate complexes of various TMGqu ligands including TMG6Methoxyqu with copper salts in solution has been described by our group in previous electrochemical studies. [16] All measurements were carried out threefold with four different sweep rates to determine the reversibility of the electrochemical reactions. As seen in Figure 3, the half potential E 1/2 was determined with respect to a Fc/Fc + internal standard and later recalculated to the SCE reference for simplified literature comparison.…”

“…[17a,b,30] The ligands TMG6Brqu and TMG6Methoxyqu were synthesized according to the literature. [16] General analytical methods FT IR: KBr FT IR spectra were measured with a ThermoFisher Avatar 360 (Resolution 2 cm À 1 ). ATR FT IR spectra where measured with a Shimadzu IRTracer 100 with CsI beamsplitter combined with a Specac Quest ATR unit (monolithic crystalline diamond, resolution 2 cm À 1 ).…”