Redox Reactions of Nickel, Copper, and Cobalt Complexes with “Noninnocent” Dithiolate Ligands: Combined in Situ Spectroelectrochemical and Theoretical Study

Abstract

The redox properties of copper, nickel, and cobalt complexes (MePh 3 P)[M(bdt) 2 ] with the ligand benzene-1,2-dithiolate (bdt) and synthesized complexes (MePh 3 P)[M(bdtCl 2 ) 2 ] with the ligand 3,6-dichlorobenzene-1,2-dithiolate (bdtCl 2 ) have been studied by cyclic voltammetry and in situ EPR−UV/vis/NIR spectroelectrochemistry. The addition of chlorine substituents to the 3-and 6-positions of the benzene ring not only facilitates the reduction of [M(bdtCl 2 ) 2 ] − complexes but also leads to the remarkable stabilization of [M(bdtCl 2 ) 2 ] 2− dianions in solution. In contrast to the EPR-silent copper complexes, the solutions of nickel samples exhibit a broad singlet EPR signal at room temperature which becomes anisotropic at 100 K with a characteristic rhombic pattern. Cathodic reduction of copper and cobalt complexes leads to paramagnetic species having an EPR signal with splitting from 63,65 Cu for copper and from 59 Co for cobalt samples, confirming a strong contribution of the central atom with substantial delocalization of the unpaired spin onto the central atom. B3LYP/6-311g*/pcm calculations of the monoanions as well as of their oxidized and reduced forms were performed. The spin density of all open-shell ground states calculated for the investigated complexes in different redox states corresponds well to the experimental spectroelectrochemical data.

Tuning the Mesomorphism and Redox Response of Anionic‐Ligand‐Based Mixed‐Valent Nickel(II) Complexes by Alkyl‐Substituted Quaternary Ammonium Cations

“…The oxidized product synthesized by chemical oxidation of NMe 4 Ni by using I 2 does not contain any ammonium cation, as is evident from IR and UV/Vis absorption spectroscopy (Figure S6), which indicates homovalency of the ligands, as in the case of [Ni II (DTBBdtSQ) 2 ] − . These results are thus consistent with the ligand‐based redox behavior of the complexes: one‐electron reduction processes should provide a dianionic [Ni II (Bdt) 2 ] 2− species, whereas one‐electron oxidation processes should provide a neutral [Ni II (BdtSQ) 2 ] species, as shown in Scheme …”

“…The decreases in cathodic and anodic currents during the repeated positive and negative scans, respectively, are attributed to the transfer of the electrochemically generated oxidized and reduced species into the electrolyte phase (Figure S9). The oxidation could involve the transfer of the NMe 2 C8,10 2 cation into the electrolyte phase to generate a neutral [Ni II (BdtSQ) 2 ] species, and on the other hand, the reduction could be accompanied by the transfer of cations between the condensed and electrolyte phases to compensate the additional anionic charges generated by the one‐electron reduction of the mixed‐valent Ni core (Scheme ) …”

Metal–ligand covalency enables room temperature molecular qubit candidates

“…The average bond distances between the metal ions and the ligand donor atoms, 2.372(11)Å and 2.279(2)Å for V-S and Cu-S bonds, respectively, agree well with prior crystal structures of other dithiolate species. 25 Comparison of the average M-L bond distances in 1 and 2 reveals that the metal-donor bond distances are all well below those computed using the Shannon-Prewitt ionic radii for Cu 2+ , V 4+ , and S 2À , with larger deviations observed for 2 relative to 1. 26 These short bond distances suggest enhanced metal-donor covalency in the copper complex relative to its vanadium counterpart.…”

Thiophene‐Extended Nickel Thiazoledithiolene: π‐Extended Fused‐Ring Metal Dithiolenes with Stabilized Frontier Orbitals

“…However, an alternate approach to tuning these complexes is through the fusion of aromatic rings to the dithiolene core. Common examples of fused‐ring metal dithiolenes have included the fusion of benzene ( 2 ) and thiophene ( 3 ),, , with ring fusion increasing molecule planarity and enhancing orbital overlap, thus maximizing electron delocalization into the organic ligands.…”