Spectroelectrochemical Properties and Catalytic Activity in Cyclohexane Oxidation of the Hybrid Zr/Hf-Phthalocyaninate-Capped Nickel(II) and Iron(II) tris-Pyridineoximates and Their Precursors.

Yan Z Voloshin,Michal Malček,Svetlana A Belova,Denisa Darvasiová,Corina-Mihaela Manta,Daniel Gherca,Peter Rapta,Dumitru Samohvalov,Maria-Andreea Lungan,Samuel M Meier-Menches,Luísa M D R S Martins,Vladimir B Arion,Semyon V Dudkin,Armando J L Pombeiro

doi:10.3390/molecules26020336

Abstract

The in situ spectroelectrochemical cyclic voltammetric studies of the antimony-monocapped nickel(II) and iron(II) tris-pyridineoximates with a labile triethylantimony cross-linking group and Zr(IV)/Hf(IV) phthalocyaninate complexes were performed in order to understand the nature of the redox events in the molecules of heterodinuclear zirconium(IV) and hafnium(IV) phthalocyaninate-capped derivatives. Electronic structures of their 1e-oxidized and 1e-electron-reduced forms were experimentally studied by electron paramagnetic resonance (EPR) spectroscopy and UV−vis−near-IR spectroelectrochemical experiments and supported by density functional theory (DFT) calculations. The investigated hybrid molecular systems that combine a transition metal (pseudo)clathrochelate and a Zr/Hf-phthalocyaninate moiety exhibit quite rich redox activity both in the cathodic and in the anodic region. These binuclear compounds and their precursors were tested as potential catalysts in oxidation reactions of cyclohexane and the results are discussed.

Highlights

We report on spectroelectrochemical studies of metal(IV) phthalocyaninatecapped iron(II) and nickel(II) tris-pyridineoximates along with their precursors shown in Scheme 2
The Hf-Fe complex 12 led to the highest KA oil yield at 60 ◦ C after 6 h reaction, suggesting a synergic effect on the catalytic activity of the heterodinuclear species
All reactions were performed under inert atmosphere using the standard Schlenk techniques

Summary

Introduction

The covalent and coordination molecular assemblies with several electronically coupled metal centers are intensively studied [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26] because of their prospective application in molecular electronics and light-harvesting (supra)molecular systems. Hybrid multicentered inorganic and organometallic transition metal arrays with relatively isolated π- and σ-electronic systems, which belong to different metal-centered frameworks, have received a relatively little attention up to date These polytopic compounds have proven to be potentially useful building blocks for the design of redox- and photoredox-driven molecular electronic devices and artificial photosynthetic systems with long-lived charge separation states [27,28,29,30,31,32,33]. This class of hybrid transition metal complexes includes zirconium(IV) and hafnium(IV), as well as lutetium(III) phthalocyaninate-capped iron(II). To corroborate the experimental electrochemical assignments and the theoretical density functional theory (DFT) calculations, the spectroelectrochemical experiments for the hybrid complexes 1−3 (Scheme 1)

Methods

Results

Conclusion