A supramolecular approach to combining enzymatic and transition metal catalysis

Abstract

The ability of supramolecular host-guest complexes to catalyse organic reactions collaboratively with an enzyme is an important goal in the research and discovery of synthetic enzyme mimics. Herein we present a variety of catalytic tandem reactions that employ esterases, lipases or alcohol dehydrogenases and gold(I) or ruthenium(II) complexes encapsulated in a Ga(4)L(6) tetrahedral supramolecular cluster. The host-guest complexes are tolerated well by the enzymes and, in the case of the gold(I) host-guest complex, show improved reactivity relative to the free cationic guest. We propose that supramolecular encapsulation of organometallic complexes prevents their diffusion into the bulk solution, where they can bind amino-acid residues on the proteins and potentially compromise their activity. Our observations underline the advantages of the supramolecular approach and suggest that encapsulation of reactive complexes may provide a general strategy for carrying out classic organic reactions in the presence of biocatalysts.

Multi-pyridine decorated Fe(ii) and Ru(ii) complexes by Pd(0)-catalysed cross couplings: new building blocks for metallosupramolecular assemblies

“…Electrochemical measurements were performed with an Eco Chemie Autolab PGSTAT 20 system using glassy carbon working and platinum auxiliary electrodes with a silver wire as a pseudoreference electrode; purified MeCN was used as the solvent and 0.1 M [nBu 4 N][PF 6 ] as the supporting electrolyte; ferrocene was added at the end of each experiment as an internal reference. Compounds 4′-(3,5-dibromophenyl)-2,2′:6′,2″-terpyridine (5), 21 4-ethynylpyridine, 22 4-pyridineboronic acid pinacol ester 23 and Ru(DMSO) 4 Cl 2 24 were prepared by literature methods.…”

“…Pd(PPh 3 ) 4 (50 mg, 0.04 mmol, 20%) were added quickly and bubbled with argon for another 10 min. The solution was stirred at reflux for 24 h. The solvent was removed to give a yellow sludge which was dissolved in ethyl acetate (30 mL) 6 (0.32 g, 1.9 mol) was dissolved in degassed DMF (20 mL). The solution was bubbled with argon for 10 min.…”

“…The complexes are packed to form 2D sheets (Fig. 8) via close stacking between the pendant arms of adjacent complexes and voids are occupied by solvent and anions, with short non-classical CH⋯F hydrogen bonds formed between tpy CH groups and PF 6 − anions (see Fig. 8 caption for details).…”

“…11). 6 , with a glassy carbon working electrode, platinum counter electrode, Ag + /AgCl reference and potentials quoted are versus Fc + /Fc. All processes are reversibly, except where noted qr = quasi-reversible (reduction peak given), irr = irreversible.…”

“…6 Incorporating the rich chemistry of metal complexes into larger structures remains a key goal for materials and supramolecular chemists. The 'expanded ligand' 7 approach employs complexes decorated with pendant binding sites to achieve this objective.…”