The dynamics of formation of the O2-CoII bond in the cobalt(II) cyclidene complexes

Dioxygen Activation at a Single Copper Site: Structure, Bonding, and Mechanism of Formation of 1:1 Cu−O2 Adducts

“…This hypothesis is supported by previous work that established a connection between ∆S q and metal complex steric properties in oxygenation reactions. 72,75,76 Further insight into pathway A for the reaction of L 1 Cu-(MeCN) with O 2 was provided by a Hammett study of oxygenations performed in the presence of excess quantities of various para-substituted benzonitriles. The excellent correlation of k A with substituent σ p values ( Figure 8) represents a quantitative measure of the sensitivity of oxygenation rate constants to electronic effects across a mechanistically homogeneous series of metal complexes.…”

A Continuous Wave and Pulse EPR and ENDOR Investigation of Oxygenated Co(II) Corrin Complexes

“…At Q-band, the proton signals are shifted to higher frequency (the proton Zeeman frequency, ν H , is 14.9 MHz for B 0 ) 350 mT (typical field for X-band) and 53.2 MHz for B 0 ) 1250 mT (typical field for Q-band)). Figures 4a and 5a 12.57 MHz at B 0 ) 1250 mT, we expect the magnitude of the cobalt hyperfine interaction to vary from 35 to 75 MHz or from 85 to 125 MHz, depending on whether we are observing the upper frequency or the lower frequency set of ENDOR signals, respectively. From the partially resolved cobalt hyperfine splittings in the CW-EPR spectra at X-band (see Figure 1, 140 K, (2)), upper limits for the magnitude of the cobalt hyperfine couplings can be estimated, which confirm the first assumption (observation of upper-frequency set).…”

“…9,11 The kinetics of dioxygen binding and dissociation and the thermodynamics of the redox process have been studied in great detail. 12,13 Different models have been proposed to describe the electronic structure of the oxygen carriers and the nature of the bound O 2 . 14,15 Cobalt oxygen carriers have also been studied extensively for their use in industrial applications, in particular in gas separation processes, because of the highly selective transport of oxygen through polymer membranes 16 and their ability to act as electrocatalysts for the reduction of O 2 at graphite electrodes 17 and as electrochemical dioxygen generators.…”

“…28 Heptamethyl cobyrinate perchlorate, [Cob(II)ester]ClO 4 (1), 29,30 has the relevant structural features of base-off B 12r , the reduced Co(II) form of vitamin B 12 in which the intramolecular dimethylbenzimidazole is not coordinated to the cobalt (hence base-off). The corrin ligand of (1) is derived directly from B 12 and differs from that of base-off B 12r in the periphery only, where the six carboxamide substituents and the characteristic nucleotide function of base-off B 12r are replaced by methyl ester groups. However, the essential features of the geometry of the corrin ligand are retained.…”

Linker-dependent chromogenic control of the emission of polymethylene-vaulted trans-bis(salicylaldiminato)platinum(II) complexes

“…The effects of the linkers in a series of vaulted porphyrin [38,39] and cyclidene [40] metal complexes on the stoichiometric reactivity during the incorporation of molecular oxygen [39,40] and on the catalytic activity for the epoxidation of olefins with PhIO [38] have been investigated; since both phenomena are greatly affected by the size-selective inclusion of substrates in the reaction cavities of the vaulted complexes, which exhibit varying capacities. In addition, both the UV-vis absorbance wavelengths and Raman frequencies of vaulted porphyrin iron complexes are reportedly altered by varying the linker length, depending on the associated strain induced in the coordination planes [41].…”