Spectroelectrochemical behaviour in dimethylformamide of pseudo-oxocarbons dianions derived from the croconate dianion

A “Pretender” Croconate-Bridged Macrocyclic Tetraruthenium Complex: Sizable Redox Potential Splittings despite Electronically Insulated Divinylphenylene Diruthenium Entities

“…In this particular case, however, an alternative scenario, where one of these composite waves originates from the first oxidations of opposite croconate linkers, is also conceivable, such that the loci of the individual oxidations remain to be verified. One should note here that neutral C 5 O 5 is only stable in water, forming leuconic acid, i.e., the pentaketone pentahydrate C 5 O 5 ·5H 2 O, whereas in other solvents the two-electron oxidized form is chemically unstable [ 54 , 68 ]. In spite of the presence of two kinds of electroactive building blocks, which are both capable of losing two electrons each, no further charging processes could be observed within the potential windows of the used electrolytes.…”

“…While the spectroscopic responses expected of Ru 2 Ph-based redox processes are amply known, we also conducted similar studies on (NBu 4 + ) 2 croc 2 − [ 80 ], which is soluble in CH 2 Cl 2 . Due to the inability of CH 2 Cl 2 to form strong hydrogen bonds, only the first oxidation is reversible (see Figure S10 of the Supplementary Materials ) [ 54 ]. Accompanying spectroscopic changes in the IR spectrum are displayed in Figure S11 of the Supplementary Materials and entail the bleaching of the strong band at 1520 cm −1 and the emergence of a new, weaker band at 1552 cm −1 as the most characteristic changes.…”

“…Quantum chemical studies however indicate that its degree of aromaticity is considerably lower than that of ordinary arenes [44,46]. Moreover, the croconate dianion undergoes two reversible one-electron oxidations at similarly low potentials as divinylarylene-bridged diruthenium complexes [23,[47][48][49][50][51][52] (e.g., E 1/2 2−/− = −240/−310 mV, E 1/2 −/0 = 5/100 mV against the ferrocene/ferrocenium redox couple FcH/FcH + in DMF as the solvent, depending on the supporting electrolyte) [53,54]. Electroactivity is usually also maintained on complexation with concomitant shifts to more anodic potentials as a result of electron donation to the metal ions [55].…”

Oxocarbonos, pseudo-oxocarbonos e esquaraínas

“…Carré, Fabre e colaboradores obtiveram os espectros eletrôni-cos para estes radicais-diânions sendo que neste estudo os mesmos foram gerados eletroquimicamente em dimetilformamida. 17,18 Nestes trabalhos os autores estudaram a oxidação eletroquímica dos ácidos oxocarbônicos utilizando eletrodos de platina em solução de ácido perclórico e propuseram que o mecanismo para o processo oxidativo ocorre em duas etapas de transferência de carga dos compostos na superfície do eletrodo, seguido de dessorção do produto de oxidação que sofre, em seguida, uma reação de hidratação no eletrodo. 19 Os íons oxocarbonos são muito empregados como fotorreceptores, compostos orgânicos semicondutores e em materiais com propriedades óticas não-lineares.…”

Raman spectra of a pseudo‐oxocarbon anion in ionic liquids

“…This system presents coordination properties, acceptor sites for hydrogen bonds, and the possibility of π-stacking interaction, so that it is an interesting species for supramolecular chemistry. [3,4] In previous works, Raman spectra of CV crystals with different alkali cations have been reported, [5,6] and also with the large tetrabutylammonium cation. [7] Resonant Raman spectra of diluted aqueous solution of potassium CV, together with semiempirical quantum chemistry calculations, elucidated the two chromophoric moieties responsible for electronic absorption bands at ca 440 and 530 nm, respectively, due to CN and π → π * transitions.…”