Electrochemistry of nickel(II) complexes with N,N′-bis(3,5-di-tert-butylsalicylidene)polymethylenediamines

The Influence of Electrolyte Type on Kinetics of Redox Processes in the Polymer Films of Ni(II) Salen-Type Complexes

Electrodes modified with polymers derived from the complexes [Ni(salcn)], [Ni(salcn(Me))] and [Ni(salcn(Bu))] were obtained in order to study the kinetics of electrode processes occurring in polymer films, depending on the thickness of the films, the type of electrolyte and the solvent. FTIR and EQCM methods were used to determine the type of mass transported into polymer films during anode processes and the number of moles of ions and solvent. The rate of charge transport through films was determined by the cyclic voltammetry method, by the quantity cD1/2. It was shown that the charge transport was determined by the transport of anions. The kinetics were most efficient for poly[Ni(salcn(Bu))] modified electrodes, obtained from TBAPF6 and working in TBAClO4 and TBABF4. It was also shown that a solvent with a higher DN value and lower viscosity (MeCN) facilitated the transport of the charge through polymer films.

The crystal structure of bis-[(E)-4-bromo-2-({[2-(pyridin-2-yl)eth-yl]imino}-meth-yl)phenol]nickel(II) bis-[(E)-4-bromo-2-({[2-(pyridin-2-yl)eth-yl]imino}-meth-yl)phenolato]nickel(II) bis(perchlorate) methanol monosolvate, a structure containing strong inter-species hydrogen bonds

The title compound, [Ni(C14H12BrN2O)2][Ni(C14H13BrN2O)2](ClO4)2·CH3OH consists of two mononuclear ([Ni(HL)2]2+ and [NiL2]) complex mol-ecules linked by strong hydrogen bonding [O⋯O separations of only 2.430 (5) Å], which is the shortest reported to date for such species. In one of the complexes, both the coordinated phen-oxy groups retain their protons and thus this is the cationic equivalent species of the other complex where both coordinated phen-oxy groups are deprotonated. In addition, perchlorate anions are present for charge balance, as well as methanol solvate mol-ecules. For the neutral NiL2 complex, each 2-ethyl-amine-pyridine arm is disordered over two equivalent conformations with occupancies of 0.750 (8):0.250 (8). The perchlorate anion is disordered over two equivalent conformations with occupancies of 0.602 (8):0.398 (8). The perchlorate ions also link to the H atoms on the methanol methyl and hydroxyl groups. These inter-actions link the moieties into a complex three-dimensional array. The crystal studied was refined as a two-component twin.

The mechanism of electropolymerization of nickel(ii) salen type complexes

Ni(ii) complexes with (±)-trans-N,N′-bis(salicylidene)-1,2-cyclohexanediamine ([Ni(salen)]), and its methyl ([Ni(salen(Me))]) and tert-butyl ([Ni(salen(Bu))]) derivatives have been synthesized.

Ligand-centred oxidative chemistry in sterically hindered salen complexes: an interesting case with nickel

Salen ligands are ubiquitous chelators, whose nickel complexes readily undergo a ligand-centred redox chemistry in non-coordinating solvents.

Synthesis, spectroscopy, magnetic and redox behaviors of copper(II) complexes with tert-butylated salen type ligands bearing bis(4-aminophenyl)ethane and bis(4-aminophenyl)amide backbones

New salen type ligands, N,N'-bis(X-3-tert-butylsalicylidene)-4,4'-ethylenedianiline [(X=H (1), 5-tert-butyl (2)] and N,N'-bis(X-3-tert-butylsalicylidene)-4,4'-amidedianiline [X=H (3), 5-tert (4)] and their copper(II) complexes 5-8, have been synthesized. Their spectroscopic (IR, (1)H NMR, UV/vis, ESR) properties, as well as magnetic and redox-reactivity behavior are reported. IR spectra of 7 and 8 indicate the coordination of amide oxygen atoms of 3 and 4 ligands to Cu(II). The solid state ESR spectra of 5-8 exhibits less informative exchange narrowed isotropic or anisotropic signals with weak unresolved low field patterns. The magnetic moments of 5 (2.92 μ(B) per Cu(II)) and 6 (2.79 μ(B) per Cu(II)) are unusual for copper(II) complexes and considerably higher than those for complexes 7 and 8. Cryogenic measurements (300-10 K) show weak antiferromagnetic exchange interactions between the copper(II) centers in complexes 6 and 8. The results of electrochemical and chemical redox-reactivity studies are discussed.

Synthesis, spectroscopic characterization and reactivity studies of oxovanadium(IV) complexes with bulky N,N'-polymethylenebis(3,5-(t)Bu(2)salicylaldimine) ligands

A series of new sterically hindered N,N'-polymethylenebis(3,5-(t)Bu(2)salicylaldimine) ligands (H(2)L(x)) VO(IV) complexes, [VO{(2-O-3,5-(t)Bu(2)C(6)H(2))CHN-R-NCH-(3,5-(t)Bu(2)-C(6)H(2)O-2)] (X), where R=-(CH(2))(3)- (3), -(CH(2))(4)- (4), -(CH(2))(5)- (5), -(CH(2))(6)- (6) and -CH(2)C(CH(3))(2)CH(2)- (7) and early reported -(CH(2))(2)- (1) and -CH(2)CH(CH(3))- (2), has been synthesized and characterized by spectroscopic (IR, UV/vis, (1)H NMR, EPR), electrochemical and magnetic susceptibility measurements. Complexes 1-7 are described a trigonal distorted pyramids. All seven compounds give nearly the same parallel hyperfine coupling constant (A(z)) regardless that the geometry of VO(IV) changes from square pyramidal to trigonal distorted pyramids. Chemical oxidation of 1-7 by one equiv Ce(IV) leads to the formation of stable [VO(V)L(x)](+) complexes. Cyclic voltammograms of 2-6 in DMSO along with a quasi-reversible VO(IV)/VO(V) redox couple also showed irreversible phenolate/phenoxyl responses. Each 1 and 7 shows only one reversible VO(IV) centered oxidation waves. Chemical oxidation of H(2)L(x) forms the stable [H(2)L(x)](+) radical species.