Importance of anions in electrodeposition of nickel from gluconate solutions

Electrodeposition of nickel from slightly acidic gluconate solutions containing chloride or/and sulfate ions was investigated. Electrochemical measurements correlated with bath speciations showed nickel chloride complex and nickel sulfate complexes as crucial species affecting cathodic reactions in a potential range up to −1.3V. At more negative potentials, nickel deposition was governed by a release of nickel cation from nickel-gluconate complex. This was further evidenced by differences in nucleation modes, morphology, and structure of the deposits. Wettability of as-plated and chemically modified nickel layers were determined and correlated with their morphology and corrosion resistance.

Spin Crossover in Nickel(II) Tetraphenylporphyrinate via Forced Axial Coordination at the Air/Water Interface

Coordination-induced spin crossover (CISCO) in nickel(II) porphyrinates is an intriguing phenomenon that is interesting from both fundamental and practical standpoints. However, in most cases, realization of this effect requires extensive synthetic protocols or extreme concentrations of extra-ligands. Herein we show that CISCO effect can be prompted for the commonly available nickel(II) tetraphenylporphyrinate, NiTPP, upon deposition of this complex at the air/water interface together with a ruthenium(II) phthalocyaninate, CRPcRu(pyz)2, bearing two axial pyrazine ligands. The latter was used as a molecular guiderail to align Ni···Ru···Ni metal centers for pyrazine coordination upon lateral compression of the system, which helps bring the two macrocycles closer together and forces the formation of Ni–pyz bonds. The fact of Ni(II) porphyrinate switching from low- to high-spin state upon acquiring additional ligands can be conveniently observed in situ via reflection-absorption UV-vis spectroscopy. The reversible nature of this interaction allows for dissociation of Ni–pyz bonds, and thus, change of nickel cation spin state, upon expansion of the monolayer.

Density-functional-theory-predicted symmetry lowering from cubic to tetragonal in nickel hexacyanoferrate

Density-functional-theory (DFT) computations on a Prussian blue analogue (PBA), nickel hexacyanoferrate, Ni2+ 3[Fe3+(CN)6]2·nH2O, predict the existence of a tetragonal (P 4 m2) crystal structure that is energetically degenerate with the previously reported cubic (F 43m) structure for this PBA. The proposed tetragonal structure satisfies observations, such as X-ray diffraction and magnetic measurements, that have been reported previously. A van der Waals corrected exchange-correlation functional is used in the DFT+U computations for an improved description of hydrogen bonding. The results provide strong support for a revised and simplified crystallographic description of Ni2+ 3[Fe3+(CN)6]2·nH2O, and show how H2O molecules stabilize the crystal structure and affect its magnetic and electronic properties. The symmetry lowering in nickel hexacyanoferrate is attributed to the hydration shell of the interstitial nickel cation. Calculations strongly suggest a maximum of n = 7 interstitial H2O molecules per formula unit for nickel hexacyanoferrate at room temperature, and a higher water content at temperatures below T ≃ 200 K. Since the symmetry lowering relies on the presence of interstitial H2O molecules, this revised crystallographic description may be applicable more generally to the large class of F 43m-structured PBAs.

A longitudinally expanded Ni-based metal–organic framework with enhanced double nickel cation catalysis reaction channels for a non-enzymatic sweat glucose biosensor

A longitudinally expanded Ni-Based metal–organic framework with enhanced double nickel cation catalysis reaction channels was used for a non-enzymatic sweat glucose biosensor.

Controlling the charge transfer flow at the graphene/pyrene–nitrilotriacetic acid interface

Tuning of the charge flow direction at the SAM–graphene interface by coordination of the SAM with a nickel cation.