Synthesis, X-ray Crystallographic, Electrochemical, and Spectroscopic Studies of Bis-(1,10-phenanthroline)(2,2′-bipyridine)cobalt(III) Hexafluorophosphate

Abstract

The synthesis, X-ray crystallographic, electrochemical, and spectroscopic studies of bis-(1,10-phenanthroline)(2,2 0 -bipyridine)cobalt(III) hexafluorophosphate with acetone solvent of crystallization ([Co(phen) 2 (bpy)](PF 6 ) 3 Á1.6(CH 3 ) 2 CO) is reported. The compound crystallized in a monoclinic space group P2(1)/n with a = 13.215 (3) The cobalt(III) metal center has a slightly distorted octahedral geometry. 1,10-Phenanthroline and 2,2 0 -bipyridine ligands were generally planar, and did not exhibit p-p overlap. The packing of the cations was stabilized by hydrogen bonding with hexafluorophosphate anions. The electrochemical studies revealed the Co III/II , Co II/I and Co I/0 redox couples at E 1/2 = ?0.32, -0.91 and -1.61 V (vs AgCl/Ag) respectively in acetonitrile. 59 Co NMR spectroscopic studies revealed that the [Co(phen) 2 (bpy)](PF 6 ) 3 Á0.5 (C 2 H 5 ) 2 O species has a chemical shift of 6900 ppm in DMSO-d 6 . GraphicalAbstract The mononuclear complex, [Co(phen) 2 (bpy)](PF 6 ) 3 Á1.6(CH 3 ) 2 CO) was synthesized and characterized, but more revealing 59 Co NMR spectroscopic studies on the complex revealed interesting species in DMSO-d 6 .

Computational, electrochemical, and spectroscopic studies of two mononuclear cobaloximes: the influence of an axial pyridine and solvent on the redox behaviour and evidence for pyridine coordination to cobalt(i) and cobalt(ii) metal centres

“…In these systems, para-substituted pyridine linkers have been employed as important templates in the syntheses of photocatalytic systems reported for the reduction of protons to form hydrogen. 44,62,63 For many years, we have been interested in the development of transition metal complexes that contain at least one cobalt metal centre, 44,[64][65][66][67][68][69][70][71] and also inorganic reaction mechanisms that involve electron transfer processes. 64,65,[72][73][74] Recently, 44 [Ru(Me 2 bpy) 2 (L-pyr)Co-(dmgBF 2 ) 2 (OH 2 )](PF 6 ) 2 (where Me 2 bpy = 4,4′-dimethyl-2,2′bipyridine), and [Ru( phen) 2 (L-pyr)Co(dmgBF 2 ) 2 (OH 2 )](PF 6 ) 2 for hydrogen evolution in acidic acetonitrile.…”

“…For many years, we have been interested in the development of transition metal complexes that contain at least one cobalt metal centre, 44,64–71 and also inorganic reaction mechanisms that involve electron transfer processes. 64,65,72–74 Recently, 44 we reported the synthesis, characterization, and photocatalytic studies of novel mixed-metal binuclear ruthenium(II)–cobalt(II) photocatalysts [Ru(pbt) 2 (L-pyr)Co(dmgBF 2 ) 2 (H 2 O)](PF 6 ) 2 (where pbt = 2-(2′-pyridyl)benzothiazole, L-pyr = (4-pyridine) oxazolo[4,5- f ]phenanthroline), [Ru(Me 2 bpy) 2 (L-pyr)Co-(dmgBF 2 ) 2 (OH 2 )](PF 6 ) 2 (where Me 2 bpy = 4,4′-dimethyl-2,2′-bipyridine), and [Ru(phen) 2 (L-pyr)Co(dmgBF 2 ) 2 (OH 2 )](PF 6 ) 2 for hydrogen evolution in acidic acetonitrile.…”

Assessing the stability of the Co(I) species of two mononuclear dichlorocobalt compounds bearing 2,2′-bipyridine and trans-2-(2′-quiolyl)methylene-3-quinuclidione via 59Co NMR spectroscopy, electrochemical, and catalyzed proton electroreduction studies

“…Simulation of the cyclic voltammograms for the Co II/I and Co I/0 redox couples as quasireversible couples using DigiSim® ( Figure S10), estimated rate constants for the homogenous reactions occurring to be 0.01 and 0.2 s -1 at the Co(I) and Co(0) species, respectively. This quasi-reversibility is suspected to be related to (partial) deligation of the reduced metal centre [54,55]. The chemical reduction of cobalt species by borohydride salts are known to produce the corresponding cobalt(I) species [56,57].…”

SNS versus SNN Pincer Ligands: Electrochemical Studies and Their Palladium(II) Complexes as Electro‐Catalyst for Proton Reduction

“…Our interest in the electron transfer processes involving transition metal complexes,, as well as the electro‐catalytic reduction of protons and other small molecules,, has led to the development of these pincer ligands, bearing sulfur and nitrogen coordination sites. In this report, we outline the rich electrochemistry of two pincer ligand systems, along with the electro‐catalytic behavior of the Pd(II) coordination complexes of these systems containing “κ 3 ‐SNS” and “κ 3 ‐SNN” coordination modes, respectively, towards the reduction of protons in DMF.…”