Investigation of potential hybrid capacitor property of chelated N-Heterocyclic carbene Ruthenium(II) complex

Abstract

The synthesis of chelated ruthenium(II) complex type Ru(η 6-HMB)(NHC)Cl (NHC=Nheterocyclic carbene, HMB=hexamethylbenzene) is presented. The ruthenium(II)-NHC complex 6 was obtained in good yield and was fully characterised by NMR spectroscopy, Xray diffraction and HRMS analysis. Electrochemical analysis by cyclic voltammetry (CV) revealed reversible redox behaviour at the ruthenium centre in 6. DFT studies and the catalytic activity of complex 6 on transfer hydrogenation reaction of aryl ketones are also presented. The potential hybrid capacitor applications of Ru-NHC complex is discussed and reported firstly in the literature. It was found that the highest performance was found at 20.1 F/g, which is a promising result for energy storage applications.

Comparison of the Spectroscopically Measured Catalyst Transformation and Electrochemical Properties of Grubbs’ First- and Second-Generation Catalysts

“…The band at 334 nm may be ascribed to the Ru–CHPh metal–ligand charge transfer (MLCT), in analogy to similar ruthenium benzylidenes. , Both catalyst species also showed weak absorption bands at longer wavelengths (514 and 502 nm for 1 and 2 , respectively). These can be attributed to the forbidden Ru=C ene visible metal to ligand charge transfer (MLCT). ,, The blue shift observed in the visible MLCT band when one of the PCy 3 ligands in 1 is replaced with an SIMes ligand in 2 implies that the energy gap between the orbitals involved in the transfer is larger in 2 compared to 1 , and that the Ru=C ene bond of 2 is thus weaker . For this band, 1 also shows a slightly larger extinction coefficient (ε) of 710 M –1 cm –1 in comparison to 590 M –1 cm –1 for 2 , implying that the transition for 1 has a higher degree of allowedness .…”

“…Various studies have recently been conducted, and investigations continue, to improve the Grubbs catalysts with regard to their activity, stability, catalyst lifetime, and selectivity. − These studies include DFT investigations, − ligand exchange research, − NMR investigations, − and mechanistic studies. ,,, However, no comparative electronic study (UV–vis, electrochemical) on the valence and core electrons of Grubbs’ first- or second-generation catalysts could be found. A few articles on the electrochemical behavior of ruthenium carbene complexes with structures similar to those of Grubbs’ catalysts − report a one-electron Ru II /Ru III oxidation that may be reversible or irreversible, depending on the compound. ,,, Investigations into the effect of different ligands on the electronic properties of the ruthenium center were anticipated to provide a feasible explanation for the slower initiation and higher activity of 2 when compared to 1 . , …”

“…A few articles on the electrochemical behavior of ruthenium carbene complexes with structures similar to those of Grubbs' catalysts 58−64 report a one-electron Ru II /Ru III oxidation that may be reversible or irreversible, depending on the compound. 57,59,62,64 Investigations into the effect of different ligands on the electronic properties of the ruthenium center were anticipated to provide a feasible explanation for the slower initiation 65 and higher activity of 2 when compared to 1. 23,63 Herein, we therefore report on the characterization of the Grubbs firstand second-generation catalysts and the decomposition thereof by NMR, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI− TOF MS), UV−visible spectroscopy (UV−vis), and attenuated total reflectance fourier transformed infrared (ATR− FTIR).…”

NHC‐Pd complex heterogenized on graphene oxide for cross‐coupling reactions and supercapacitor applications

“…Column chromatography was conducted on silica gel of 60-120 mesh purchased from Merck and thin layer chromatography (TLC) was carried out using 0.25 mm Merck TLC silica gel plates using UV light as a visualizing agent. Concentration in the vacuo refers to the removal of volatile solvent using a rotary solvent evaporator connected to a dry diaphragm pump (10)(11)(12)(13)(14)(15) followed by pumping to a constant weight with an oil pump (<300 mTorr). All the organic products were known and identified by comparison of their physical and spectral data with those of authentic samples.…”

“…[14] Akkoç et al prepared chelated Nheterocyclic carbene ruthenium(II) complex and obtained a capacitance of 20.1 F/g, revealing the occurrence of a redox reaction at the ruthenium center. [15] As a continuation of our previous studies using a green and sustainable approach in the field of catalysis, [16] in this study we have designed and developed a heterogeneous catalyst in which a N-heterocyclic carbene-palladium(II) complex was immobilized on graphene oxide (GO@NHC-Pd) and studied the activity of the prepared GO@NHC-Pd catalyst in Suzuki-Miyaura and Hiyama cross-coupling reactions. The newly synthesized GO@NHC-Pd catalyst was characterized using various spectroscopic, thermal, surface, and microscopic techniques, such as Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma optical emission spectrometry (ICP-OES), and powder X-ray diffraction (XRD) analysis.…”