Aurophilic Interactions in Multi‐Radical Species: Electronic‐Spin and Redox Properties of Bis‐ and Tris‐[(Nitronyl Nitroxide)‐Gold(I)] Complexes with Phosphine‐Ligand Scaffolds

Abstract

Multinuclear AuI complexes with two or three nitronyl nitroxide‐2‐ide radical anion and phosphine‐ligand scaffolds, (NN‐Au)2‐1 o, (NN‐Au)2‐1 m, and (NN‐Au)2‐1 p, have been synthesized to investigate the influence of AuI−AuI (aurophilic) interactions on the properties of multispin molecular systems. The desired complexes were successfully prepared in moderate yields in a one‐pot synthesis from the corresponding phosphine ligand, AuI source, parent NN, and sodium hydroxide. Among the prepared complexes, (NN‐Au)2‐1 o, in which an aurophilic interaction was clearly observed by crystal structure analysis, showed characteristic spin−spin interactions, electrochemical properties, and solvatochromic behavior. The results from theoretical calculations also suggested that the differences in properties between complex (NN‐Au)2‐1 o and the other complexes are due to intramolecular aurophilic interactions.

Au–Au Chemical Bonding in Nitronyl Nitroxide Gold(I) Derivatives

“…For this process, forward and reverse peak potentials (without the effect of uncompensated resistance) and half-wave potential are E Ox = 0.134, E Red = 0.072 V, and E 1/2 = 0.103 V, respectively. As for the peaks corresponding to irreversible processes, there are several: on the oxidation curve at a potential of 2.29 V and on the reduction curve at −1.64 and −2.95 V. On the whole, excellent agreement was observed between the oxidation potentials of 1i,j (Table ) and those of previously studied nitronyl nitroxide–gold derivatives. ,, …”

“…As for the peaks corresponding to irreversible processes, there are several: on the oxidation curve at a potential of 2.29 V and on the reduction curve at −1.64 and −2.95 V. On the whole, excellent agreement was observed between the oxidation potentials of 1i,j (Table 2) and those of previously studied nitronyl nitroxide−gold derivatives. 13,14,26 Single crystals of complexes NN−Au−P n Bu 3 (1i) and NN− Au−P F Ph 3 (1j) (as crystallohydrate 1j•2H 2 O) were obtained by recrystallization from a mixture of CH 2 Cl 2 with n-heptane or a mixture of acetone with n-heptane, respectively. Inspection of the crystallographic data for the presence of the Au(I)••• Au(I) bonding in the crystal structures of 1i and 1j uncovered the formation of dimerized molecules.…”

“…Among the prepared complexes, the orthosubstituted derivatives in which Au(I)−Au(I) bonds are clearly observed in an analysis of the crystal structure show characteristic spin−spin interactions, electrochemical properties, and solvatochromic behavior. 26 It can be assumed that the geometry of diphosphine ligands in ortho-substituted derivatives (Scheme 1) is the driving force ■ EXPERIMENTAL AND COMPUTATIONAL DETAILS Chemicals and General Methods. 4,4,5,5-Tetramethyl-4,5dihydro-1H-imidazole-3-oxide-1-oxyl 27 was synthesized as reported earlier.…”

“…To study Au–Au bonding, Japanese chemists have developed various dinuclear gold complexes with o -, m -, and p -phenylene linkers (Scheme ). Among the prepared complexes, the ortho-substituted derivatives in which Au­(I)–Au­(I) bonds are clearly observed in an analysis of the crystal structure show characteristic spin–spin interactions, electrochemical properties, and solvatochromic behavior …”

A Molecule Having 13 Unpaired Electrons: Magnetic Property of a Gadolinium(III) Complex Coordinated with Six Nitronyl Nitroxide Radicals

“…The synthetic route for Gd 3+ ·(1 – ) 3 is shown in Scheme . This method is similar to our previously reported method for preparing a series of organometallic nitronyl nitroxide (NN) radicals. ,− After the generation of an NN anion upon treatment of NN-H with sodium hydroxide, the resulting mixture was allowed to react with AuCl­(THT) (THT = tetrahydrothiophene) to afford Na + ·1 – (CCDC 2090754). Compound Na + ·1 – was converted to Gd 3+ ·(1 – ) 3 by treatment with gadolinium­(III) nitrate.…”