Platinum(ii) complexes of mixed-valent radicals derived from cyclotricatechylene, a macrocyclic tris-dioxolene

Abstract

The redox series [1]0/1+/2+/3+ has been characterised by UV/vis/NIR spectroelectrochemistry, cw EPR, ENDOR and HYSCORE spectroscopies and DF calculations.

New sterically-hindered o-quinones annelated with metal-dithiolates: regiospecificity in oxidative addition reactions of a bifacial ligand to the Pd and Pt complexes

“…19 Comparing the HFS constant value at the nucleus of platinum in the binuclear complex 14 with those in the corres-ponding semiquinonate complexes, where the platinum nucleus is situated in close proximity of the unpaired electron containing dioxolene coordination site, one can easily see that the constant differs by less than two times (12.7-13.2 G in Pt semiquinonates). 19,20 This confirms a substantial delocalization of the spin density to the periphery of the binuclear complex.…”

Rigidification of a macrocyclic tris-catecholate scaffold leads to electronic localisation of its mixed valent redox product

“…The separation between the first two oxidation potentials in 2a and 2b E ½ = 0.16-0.17 V, yields the comproportionation constants K c = 6-8 × 10 2 between each oxidation level. 10,13 That is slightly smaller than for 1a and 1b E ½ = 0.18-0.22 V, K c = 1-5 × 10 3 ), 14 from 2a in this solvent at 253 K proceeds isosbestically, and leads to an increase in intensity for this peak, coupled to the ingrowth of a new shoulder near 23 × 10 3 cm -1 (Fig. 2).…”

“…Similar issues were also encountered with 1b. 14 Differential pulse voltammograms of 2a and 2b in CH 2 Cl 2 /0.1M NBu 4 PF 6 resemble those of 1a and 1b, in showing three closely spaced low-potential oxidations ( Fig. 1).…”

“…12 The three catecholate groups in these complexes are oxidised sequentially, leading to 2+ radical products showing class II mixed valency by UV/vis/NIR spectroscopy, 13 despite the absence of direct conjugation between their dioxolene redox centers. 14 The radical products of this work were too unstable to isolate however, and could only be handled in solution below room temperature. We reasoned this might reflect a lack of steric protection about the methylene groups of the oxidised [ctc] n macrocycle, since sq and other phenoxyl radicals are prone to atom abstraction or coupling reactions at such para substituents.…”

Generation of Aromatic (Dehydro)benzoannulene Dications Stabilized by Platinum Catecholate Complexes

“…The separations between the first and second oxidation potentials (Δ E 1 ) and between the second and the third (Δ E 2 ) of 2 are 0.22 and 0.70 V, respectively. The Δ E 2 value of 2 is significantly larger than that of the cyclotriveratrylene‐type complex 6 (Figure ), in which three nonconjugated platinum catecholates are oxidized stepwise, similarly to 2 , with Δ E 1 and Δ E 2 values of 0.25 and 0.20 V, respectively, indicating the stabilization of 2 2+ by the generation of an aromatic system.…”