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Herein, we designed Er3+-incorporated zincate-based nanomaterials via a rapid, low-cost, and environmentally friendly urea-combustion route. X-ray powder diffraction (XRPD) profiles revealed their orthogonal crystalline structure. Electron microscopy showed nanoscale (48–70 nm) non-uniform agglomerated particles. The presence of [BaO11] and [ZnO5] structural units in the present samples was shown by Fourier-transform infrared (FT-IR) spectroscopy. Emission spectra yielded a characteristic peak at 551 nm, which contributed to their bright-green light. The optimal nanomaterial had 3.0 mol% of Er3+ content, and it exhibited excellent bright-green light. Exchange-type multipolar inter-linkages via cross-relaxation predominantly direct the quenching of luminescence post x = 0.03 Er3+ content, as shown by the Inokuti-Hirayama (I-H) model. The optical bandgap and Urbach energy were obtained from experimental data-fitting with Tauc’s hypothesis and an empirical correlation. Excellent color-purity (87.86%) and color temperature (6916 K) with chromaticity coordinates (0.2531, 0.6106) of the optimized nanomaterial were similar to National Television Standards Committee (NTSC) and NICHIA Corporation fabricated light-emitting diode (LED) green standards. Hence, the developed nanomaterials appear to be a good candidates for generating cool-green light in high-performance blue/green/red (B/G/R) white-light-emitting diodes (wLEDs), sensors, and laser applications.

Difunctionalization of strained cyclic alkynes presents a powerful strategy to build richly functionalized cyclic alkenes in an expedient fashion. Herein we disclose an efficient and flexible approach to achieve carbohalogenation, dicarbofunctionalization, aminohalogenation and aminocarbonation of readily available cyclohexenyl triflates. We have demonstrated the novel use of zincate base/nucleophile system for effective formation of key cyclohexyne intermediates and selective addition of various carbon and nitrogen nucleophiles. Importantly, leveraging the resulting organozincates enables the incorporation of a broad range of electrophilic partners to deliver structurally diverse cyclohexene motifs. The importance and utility of this method is also exemplified by the modularity of this approach and the ease in which even highly complex polycyclic scaffolds can be accessed in one step.

Acta crystallographica / Section E 77(6), 629-633 (2021). doi:10.1107/S2056989021004989, Published by International Union of Crystallography, Chester

Amido-zincates containing hydrides are underexplored yet potentially useful complexes. Attempts to access this type of zincate through combining amido-organo zincates and pinacolborane (HBPin) via Zn–C/H–BPin exchange led instead to preferential formation of amide–BPin and/or [amide–BPin(Y)]− (Y = Ph, amide, H), when the amide is hexamethyldisilazide or 2,2,6,6-tetramethylpiperidide and the hydrocarbyl group was phenyl or ethyl. In contrast, the use of a dipyridylamide (dpa) based arylzinc complex led to Zn–C/H–BPin metathesis being the major outcome. Independent synthesis and full characterisation of two LnLi[(dpa)ZnPh2] (L = THF, n = 3; L = PMDETA, n = 1) complexes, 1 and 3, respectively, enabled reactivity studies that demonstrated that these species display zincate type reactivity (by comparison to the lower reactivity of the neutral complex (Me-dpa)ZnPh2, 4, Me-dpa = 2,2′-dipyridyl-N-methylamine). This included 1 performing the rapid deprotonation of 4-ethynyltoluene and also phenyl transfer to α,α,α-trifluoroacetophenone in contrast to neutral complex 4. Complex 1 reacted with one equivalent of HBPin to give predominantly PhBPin (ca. 90%) and a lithium amidophenylzincate containing a hydride unit, complex 7-A, as the major zinc containing product. Complex 7-A transfers hydride to an electrophile preferentially over phenyl, indicating it reacts as a hydridozincate. Attempts to react 1 with >1 equivalent of HBPin or with catecholborane led to more complex outcomes, which included significant borane and dpaZn substituent scrambling, two examples of which were crystallographically characterised. While this work provides proof of principle for Zn–C/H–BPin exchange as a route to form an amido-zincate containing a hydride, amido-organozincates that undergo more selective Zn–C/H–BPin exchange still are required., Careful tuning of the nature of the amide ligand in amido-zincates allows for selective Zn–C over Zn–N exchange with HBPin affording a hydride containing amido-zincate. The mixed hydrido-phenyl zincate preferentially transfers hydride over phenyl.

In this work, we used the low temperature solution growth Successive Ionic Layer Adsorption and Reaction (SILAR) for a deposition of the nanostructured undoped and indium doped (ZnO and ZnO:In) thin films on flexible polyimide (PI) substrates for their use as cheap non-toxic thermoelectric materials in the flexible thermoelectric modules of planar type to power up portable and wearable electronics and miniature devices. The use of a zincate solution in the SILAR method allows to obtain ZnO:In film, which after post-growth annealing at 300 °C has low resistivity ρ ≈ 0.02 Ω m, and high Seebeck coefficient −147 μV/K and thermoelectric power factor ~1 μW K−2 m−1 at near-room temperatures. As evidence of the operability of the manufactured films as the basis of the TE device, we have designed and tested experimental lightweight thin-film thermoelectric module. This TE module is able to produce specific output power 0.8 μW/m2 at ΔT = 50 K.

The solid-phase synthesis of oxygen-deficient perovskite La(Al0.5Zn0.5)O2.75 is performed for the first time. The perovskite crystallizes in space group Pm3m with a lattice parameter of 3.7932 A. The cationic composition of the phase is confirmed via chemical analysis. It is shown that lanthanum alumina zincate has a mixed type of conductivity in the region of high oxygen partial pressures and temperatures above 500°C, while oxygen-ion transport predominates at temperatures below 400°C. Introducing zinc into the B-sublattice of perovskite allows high-density ceramics (>95%) to be obtained.

The decomposition rate of supersaturated zincate electrolytes based on 6 mol·dm-3 KOH was measured and the effect of additives used for reducing zincate solubility (KF, K2CO3, K3PO4) was evaluated. The electrolytes were studied after being aged for 5 years at room temperature. Powder morphology was obtained as a result of recrystallization processes were evaluated. Results indicate that the presence of 1 mol·dm-3 PO4 3- ions reduced the speed of decomposition to less than half. A study of ZnO recrystallization revealed the changes in particle sizes for all additives. Despite the long time of recrystallization processes, ZnO particles grew to different sizes depending on the type of low solubility electrolyte (LSE) used. While the presence of PO4 3- and F- ions promote the particle growth in all directions and thus influence both particle lengths and widths. The presence of carbonate ions CO3 2- reduce the particle sizes and thus could contribute to the growth of a larger active area of electrodes after long-term aging.

Alkaline zinc-manganese dioxide (Zn-MnO2) batteries are well suited for grid storage applications because of their inherently safe, aqueous electrolyte and established materials supply chain, resulting in low production costs. With recent advances in the development of Cu/Bi-stabilized birnessite cathodes capable of the full 2-electron capacity equivalent of MnO2 (617 mA h/g), there is a need for selective separators that prevent zincate (Zn(OH)4)2- transport from the anode to the cathode during cycling, as this electrode system fails in the presence of dissolved zinc. Herein, we present the synthesis of N-butylimidazolium-functionalized polysulfone (NBI-PSU)-based separators and evaluate their ability to selectively transport hydroxide over zincate. We then examine their impact on the cycling of high depth of discharge Zn/(Cu/Bi-MnO2) batteries when inserted in between the cathode and anode. Initially, we establish our membranes' selectivity by performing zincate and hydroxide diffusion tests, showing a marked improvement in zincate-blocking (DZn (cm2/min): 0.17 ± 0.04 × 10-6 for 50-PSU, our most selective separator vs 2.0 ± 0.8 × 10-6 for Cellophane 350P00 and 5.7 ± 0.8 × 10-6 for Celgard 3501), while maintaining similar crossover rates for hydroxide (DOH (cm2/min): 9.4 ± 0.1 × 10-6 for 50-PSU vs 17 ± 0.5 × 10-6 for Cellophane 350P00 and 6.7 ± 0.6 × 10-6 for Celgard 3501). We then implement our membranes into cells and observe an improvement in cycle life over control cells containing only the commercial separators (cell lifetime extended from 21 to 79 cycles).

Single crystal electron paramagnetic resonance (EPR), powder X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) and UV–Visible (UV–Vis) spectroscopy studies of Cu(II) doped in hexaaquazinc(diaquabismalonto)zincate (HZDMZ) have been investigated at room temperature. Angular variation of copper hyperfine lines in the three orthogonal planes shows the presence of a single site in substitutional position, with spin Hamiltonian parameters calculated from EPR spectra are gxx = 2.3940; gyy = 2.0919; g-zz = 2.0700; A–xx = 13.85 mT; Ayy = 1.79 mT; Azz = 1.39 mT. Molecular orbital coefficients β2 = 0.765 and e2 = 0.275 have been calculated, which reveal a moderately covalent metal–ligand bond. Optical and EPR data have been collaborated to obtain crystal field parameters, admixture and molecular orbital coefficients. Powder XRD, FT-IR and UV–Vis data confirms the structure of host complex and presence of the dopant.

Removal of metal compounds from wastewater using processes where metals can be removed and valuable chemicals recycled is of significant industrial importance. Chelating surfactants are an interesting group of chemicals to be used in such applications. Carboxylated polyamines are a promising group to be used in such processes. To apply carboxylated polyamines as chelating surfactants, detailed knowledge of the solution chemistry, including complex formation, kinetics and structures of pure fundamental systems, is required. In this study zinc(II) alkyl-N-iminodiacetate systems with varying length of the alkyl chain have been studied. Acidic and stability constants have been studied by potentiometry, and the structures of both solids and aqueous solutions have been determined by EXAFS. Zinc(II) forms two strong complexes with alkyl-N-iminodiacetates in aqueous solution. In an attempt to determine the acidic constants of these complexes, the deprotonation of the nitrogen atom in the complex bound ligands, it was observed that this reaction is very slow and no accurate values could be obtained. The bis(alkyl-N-iminodiacetato)zincate(II) complexes take, however, up two protons in the pH region 3–7, which means that this complex is approximately singly protonated in the pH region 3–7 and doubly protonated at pH n-hexyl-N-iminodiacetato)zincate(II) complex at pH = 13 has a distorted octahedral configuration with four short strong Zn–O bonds at 2.08(1) Å, while the Zn–N bonds are weaker at much longer distance, 2.28(2) Å. Similar configurations are also found in most reported structures of zinc(II) complexes with carboxylated amines/polyamines. The singly protonated complex seems to be five-coordinate, with four Zn–O bond distances at ca. 2.03 Å, and a single Zn–N bond distance in the range 2.15–2.25 Å. The relationship between the structure of the protonated bis(n-hexyl-N-iminodiacetato)zincate(II) complex and the slow kinetics in the region pH = 3–7 are discussed.

In this focused review, I present an overview of our recent research on the zincate complex dilithium tetra-tert-butylzincate (TBZL)-catalyzed ring-opening polymerization (ROP) of e-caprolactone, efficient acylation and transesterification of alcohols with vinyl acetate and carboxylic esters, and polymer synthesis with a high transesterification ability. In the first part of this report, the ROP of e-caprolactone catalyzed by TBZL in toluene is described. In a subsequent study of the ROP of e-caprolactone in the presence of 2-hydroxyethyl methacrylate (HEMA), TBZL was found to act not only as an anionic initiator but also as a transesterification catalyst. In the second part of this report, the acylation and transesterification of alcohols with vinyl acetate and carboxylic esters catalyzed by TBZL are summarized. The acylation proceeded quantitatively at 0 °C within 1 h. A wide range of combinations of esters and alcohols were suitable for the transesterification at 0 to −40 °C. In addition, the transesterification proceeded chemoselectively even in the presence of H2O and amines. Next, TBZL-catalyzed polycondensations of diphenyl carbonate (DPC) with diols are discussed. Irreversible polycondensations catalyzed by TBZL occurred to yield aliphatic polycarbonates under atmospheric pressure. In the last part of this report, the transesterifications of poly(phenyl methacrylate) (PPhMA) side chains with alcohols catalyzed by TBZL are described. The transesterification reaction not only with alkyl alcohols but also with fluoroalcohols occurred. By changing the reaction solvent and temperature, the degree of conversion could be controlled. The present system permits the partial, quantitative, or terminal conversion of polymethacrylates. Our recent studies on the zincate complex dilithium tetra-tert-butylzincate-catalyzed transesterification and polymerization are reviewed. In the first part of this report, the ROP of e-caprolactone catalyzed by TBZL is described. In the second part of this report, the acylation and transesterification of alcohols with vinyl acetate and carboxylic esters catalyzed by TBZL are summarized. Next, TBZL-catalyzed polycondensations of diphenyl carbonate (DPC) with diols are discussed. In the last part of this report, the transesterifications of poly(phenyl methacrylate) (PPhMA) side chains with alcohols catalyzed by TBZL are described.

The regioselective, direct alkylation of electron-deficient N-heteroarenes is, in principle, a powerful and efficient way of accessing alkylated N-heteroarenes that are important core structures of many biologically active compounds and pharmaceutical agents. Herein, we report a ZnMe2-promoted, direct C2- or C4-selective primary and secondary alkylation of pyridines and quinolines using 1,1-diborylalkanes as alkylation sources. While substituted pyridines and quinolines exclusively afford C2-alkylated products, simple pyridine delivers C4-alkylated pyridine with excellent regioselectivity. The reaction scope is remarkably broad, and a range of C2- or C4-alkylated electron-deficient N-heteroarenes are obtained in good yields. Experimental and computational mechanistic studies imply that ZnMe2 serves not only as an activator of 1,1-diborylalkanes to generate (α-borylalkyl)methylalkoxy zincate, which acts as a Lewis acid to bind to the nitrogen atom of the heterocycles and controls the regioselectivity, but also as an oxidant for rearomatizing the dihydro-N-heteroarene intermediates to release the product.

Organic cation salts with homoleptic zincate and stannanide anions, Ph4P [Zn(ESiMe3)3] (E = S (1a), Se (1b)) and Cat [Sn(ESiMe3)3] (Cat = Ph4P+ (E = S (2a-Ph4P); Cat = PPN+ (E = S 2a-Ph4P, Se (2a)) are presented and structurally characterized. Efforts to isolate neutral thermally metastable stannane precursors [Sn(ESiMe3)4] (E = S (3), Se(4)) are reported as well. The thermal decomposition of the presented precursors to yield binary sulfides and selenides of zinc and tin is investigated. Furthermore, the potential of using the title anions as precursors in solution-based low-temperature synthesis of Cu2ZnSnS4 (CZTS) by coprecipitation with [Cu(tmtu)3]PF6 and subsequent annealing is discussed.

Metal-air batteries have exhibited unlimited potential and economic value because of their considerably high energy density. However, under repeated cycling, air cathodes undergo a well-known problem, the deposition of metal oxide, clogging the active surface and ultimately leading to the severe degradation of the cyclic performance. Herein, we address this challenge in a zinc-air battery by introducing ketone as the Lewis base into the air catalyst. As illustrated by in situ X-ray diffraction observations, the ketone-enriched material could generate an ultrahigh negative potential to prevent the access of negatively charged zincate ions and thus enable the nondeposition of zinc oxide on the air cathode because of the strong electrostatic repulsion. Using this strategy, we demonstrate 650 highly stable cycles of a zinc-air battery under a high rate (25 mA cm-2). Such a Lewis-base-assisted method opens up new avenues to prevent air cathodes from being poisoned for highly durable metal-air batteries.

The lithiacarborane [Li-CB11 H11 ]- plays a central role in carborane chemistry, as it is a key intermediate to achieve the selective functionalization of the monocarba-closo-dodecaborate [CB11 H12 ]- for applications in various fields. Also, it is an organometallic species of fundamental interest because it represents a 3D analogue of phenyllithium featuring an exo C-Li bond in addition to the delocalized negative endo charge of the spherical cluster. For the first time, the elusive and highly reactive endo/exo formal dianion [CB11 H11 ]2- has been isolated as its lithiate as well as zincate in pure form and fully characterized. DFT calculations corroborate the experimental findings and underscore the remarkably high reactivity of the lithiacarborane. Subsequent derivatizations demonstrate the relevance of its initial clean formation.

This paper will look at surface treatment of aluminium and its alloys and explore what steps are required in order to successfully electroplate onto it to achieve a sound adherent finish.

In order to replace the highly poisonous cyanide zincate process of Al alloy, an eco-friendly approach was developed, i.e., electrodeposition of Cu-Zn coating from ionic liquid/ethanol mixed bath. It was demonstrated that the Cu5Zn8 alloy produced from 1-ethyl-3-methylimidazolium trifluoromethylsulfonate (EMImTfO) and 20% (Volume percent) ethanol mixtures under optimal conditions showed cauliflower-shaped structure with a (330) preferred orientation, which could significantly improve the corrosion resistance of Al substrate in Watts bath, thereby elevating Ni coating quality. The overall property of Cu-Zn intermediate layer and its subsequent coating, including compactness, adhesive strength and corrosion resistance is approximately the same as that of cyanide zincate layer and its surface coating, suggesting that the new method is an ideal alternative to conventional zincate treatment.

The present work describes the effects of dimethyl sulfoxide (DMSO) in KOH aqueous electrolyte on the performance of a zinc-air flow battery. Aqueous electrolytes containing 7 M KOH and (0 to 20)% v/v DMSO were studied revealing a critical role of DMSO on the dissolution and deposition of zinc. The anodic zinc dissolution process was studied via cyclic voltammetry, Tafel polarization and electrochemical impedance spectroscopy (EIS). The presence of DMSO showed improved zinc dissolution performance with the highest peak of zinc dissolution being the electrolyte containing 5% v/v DMSO. Tafel analysis demonstrated a significant decrease in polarization resistance and an increase in corrosion rate due to the introduction of DMSO to the electrolyte. This suggests that DMSO has the ability to suspend zinc oxide in the electrolyte, thus preventing passivation of the zinc surface. EIS results revealed that by adding DMSO to the electrolyte, charge transfer resistance increased. This is attributed to the formation of passive layers having arisen from DMSO adsorption, the formation of zincate ions in the vicinity of the zinc surface, and the deposition of discharged products. A difference in Nyquist plots was observed for 20% v/v DMSO/KOH and 0% v/v DMSO/KOH electrolytes implying non-Debye relaxation behavior taking place due to the surface effects. The electrolytes were implemented in a zinc-air flow battery. Maximum power densities of 130 mW/cm2 (5% v/v DMSO) and 125 mW/cm2 (20% v/v DMSO) were obtained and were observed to be about 43% and 28% higher than that of the DMSO-free electrolyte. Results indicated that when 20% v/v DMSO was added to KOH solution, there was 67% zinc utilization efficiency (550 mAh/g) which provided 20% improvement in discharge capacity. Further, the battery with 20% v/v DMSO demonstrated excellent cyclability. Overall, DMSO shows great promise for enhancement of zinc dissolution/deposition in zinc-air batteries.

This report details the development of several suitable noncryogenic metalation conditions for the synthesis of oxazole zincate. Subsequent rounds of high-throughput catalyst screening ultimately led to the identification of several suitable Pd sources that can be used for the Negishi coupling of unsubstituted oxazole. The scope and generality for one of the reported conditions is also presented.

Supramolecular structure exhibits good nonlinear optical (NLO) properties due to the enhanced proton transfer process. Semiorganic Bis(4-methylbenzylammonium) tetrabromido zincate (4MLTBZ) crystal was developed by functionalizing 4-methylbenzylamine (4MLBA) with hydrobromic acid and zinc bromide. Amine group of 4MLBA gets protonated by H+ cation of hydrobromic acid. Zinc bromide was linked with 4MLBA through C H ⋯Br and N H ⋯Br interactions which forms supramolecular structure and crystallized noncentrosymmetric space group Pna21. Raman and FTIR spectral analysis provides the evidence for the protonation of amine (NH3+) group. Raman spectrum reveals the coordination of ZnBr4 in 4MLTBZ crystal structure through the observed Zn Br vibrations between 50 and 400 cm−1. The impact over the shift in vibrational frequencies of NH and CH functional groups due to C H ⋯Br and N H ⋯Br interactions were discussed. The ‘Carbon Hydrogen’ frame work of 4MLTBZ crystal was established by 1H NMR and 13C NMR spectroscopy. The UV–Vis–NIR spectrum of 4MLTBZ showed very good transparency in the region from 260 nm to 1100 nm. The enhanced SHG efficiency and third order nonlinear optical susceptibility (χ3) are interpreted through hydrogen bonds.

Nickel-catalyzed asymmetric cross-coupling of secondary alkyl electrophiles with different nucleophiles represents a powerful strategy for the construction of chiral tertiary carbon centers. Yet, the use of aryl Grignard reagents or aryl zinc halides in many reactions typically resulted in low enantioselectivity, mainly due to their slow transmetalation step in the catalytical cycle and consequently the requirement of relatively high temperature. Here we report that the use of lithium aryl zincate [Ph2ZnBr]Li facilitates the transmetalation step of the nickel-catalyzed cross-coupling reaction. Based on this discovery, a highly enantioselective construction of fluoroalkyl-substituted stereogenic center by a nickel-catalyzed asymmetric Suzuki-Miyaura coupling of α-bromobenzyl trifluoro-/difluoro-/mono- fluoromethanes with a variety of lithium aryl zincates [Ph2ZnBr]Li that were in situ generated from the reaction of lithium organoboronate with 1.0 equivalent of ZnBr2 was described., Fluoroalkyl groups are widely found in pharmaceutical products. Here, the authors report a highly enantioselective nickel-catalyzed cross coupling method for the construction of fluoromethylated stereogenic centers via a highly reactive zincate species facilitating the transmetalation step in the nickel catalytic cycle.

Several approaches have been tried to reduce Al corrosion in primary and secondary alkaline batteries. The most successful to date has been the addition of ZnO to the electrolyte, which results in the spontaneous deposition of a protective metallic Zn film on the Al surface. However, there is a limited understanding in the literature of the structure of this Zn film and how that structure (i) influences the protection of Al, and (ii) is influenced by the electrolyte composition. This work aims to develop a fundamental understanding of the protection mechanism against Al corrosion when zincate is added to KOH electrolytes. This was accomplished through morphological studies of the resulting Zn film using SEM, XRD, N2 adsorption, and measurements of H2 gas evolution as well as electrochemical characterization during discharge. It was found that adding saturated ZnO to KOH electrolytes provides the most protective Zn film with good adherence and high density, which can lower the Al corrosion rate by 2 orders of magnitude. Moreover, configurations with a capacity near the Al theoretical capacity were achieved.

Physico-chemical properties of NaOH and KOH electrolytes are studied as possible state of charge indicators for the alkaline zinc-air redox flow battery. In order to predict the available energy of the battery and to prevent degradation as the result of unsuitable operating conditions, its state of charge has to be known. The state of charge is directly related to the composition of the negative electrolyte. A battery charging operation is simulated by electrodepositing zinc on a rotating cylinder electrode from NaOH electrolyte, while the simulation of a discharging operation is accomplished by dissolving ZnO in KOH electrolyte. The refractive index, conductivity, and density of NaOH- and KOH-electrolytes as well as the rest potential of the zinc electrode in these media are measured for different zincate and alkali concentrations at several temperatures. The electrolyte density and electrolyte conductivity are both linearly correlated with the zincate concentration. A linear correlation is found also between the rest potential and the logarithmic concentration term in the Nernst equation for the zinc half-cell reaction. These indicators permit a simple and straightforward monitoring of the state of charge of alkaline zinc-air redox flow batteries.

A dramatic increase in UV endurance of polycarbonate (PC) films were achieved via thoughtful intercalation of cesium zincate (Cs2ZnO2) nanoparticles (NPs). The augmented UV endurance of PC/Cs2ZnO2 nanocomposite (NC) films were analyzed via yellowing index quantification and Fourier Transform Infrared (FTIR) measurements at 1713 cm−1. The foundation for improved UV stability was owed to Cs2ZnO2 NPs induced lessening of undesirable photo-degradation reactions. Moreover, the introduced NPs act to dissipate the high energy UV photons via polymer-nano metal oxide induced synergistic spectral down-conversion. The novel spectral down-conversion abilities and patina-green light emitting properties of PC/Cs2ZnO2 NC films were valued with UVA-transilluminator coupled fluorescence microscopic studies. Eventually, the synergistic combination of Cs2ZnO2 NPs with PC host, wherein the metal oxide offers protection against undesirable photo-degradation reactions, while the polymeric host guards the luminescence centers of nanostructured metal oxides are highly desirable for various photonic and opto-electronic applications.

Discharge behavior of the Zn negative electrode was investigated to elucidate the effects of Li+ as an additive in Zn batteries. Li+ influenced the dissolution of Zn as well as the formation of ZnO (passivation). The dissolution reaction was enhanced by Li+; step-flow dissolution at the Zn surface changed to dissolution from the entire surface. SEM observations of the ZnO formed due to the supersaturation of zincate ions showed morphological changes from acicular crystals to particulate clusters upon introduction of Li+; also, ZnO peaks in XRD patterns decreased. These changes indicated that Li+ suppressed the growth of ZnO, which was caused by the adsorption or incorporation of Li+ into the ZnO crystallites. In situ Raman analysis was carried out to monitor such a difference in the nucleation and growth processes. An E2 mode corresponding to crystalline wurtzite ZnO was dominant in the solution without Li+, while this mode diminished and an E1 (LO) mode corresponding to excess Zn in the interstitial sites of ZnO became strong in the presence of Li+. It was suggested that the Zn excess was introduced due to dominance of nucleation (reactions between zincate species) over the growth process (zincate decomposition at the surface).

Studies of zinc electrode oxidation under the conditions of limited volume of alkaline electrolyte are carried out. It is shown, that at anodic polarization below 7–8 mV the zinc surface is covered by phase layer of zinc oxides and hydroxides. The last ones hinder diffusion of ions participating in electrochemical reactions. Then, formation of zincate complex [ $$\rm{Zn}(OH)\begin{array}{c}2-\\ 4\end{array}$$ ] starts, with the slow diffusion stage of hydroxide ions to the anode surface. At polarization from 0.08 to 0.12 V formation of supersaturated zincate electrolyte occurs, and its decomposition with formation of the loose zinc oxide layer. At polarization above 0.12 V, nonporous oxide film is formed on zinc surface; zinc oxidation process proceeds by solid-phase mechanism.

Each CrIII cation in the title compound is coordinated by the six N atoms from two 1,4,7-tri­aza­cyclo­nonane (tacn) ligands, displaying a distorted octa­hedral environment. The crystal packing is stabilized by extensive hydrogen-bonding inter­actions involving the N—H groups of the tacn ligands, O—H groups or O atoms of the water mol­ecules and Cl atoms of the [ZnCl4]2− anions., The structure of the title compound, [Cr(tacn)2]2[ZnCl4]3·H2O (tacn is 1,4,7-tri­aza­cyclo­nonane; C6H15N3), has been determined from synchrotron X-ray data. Each CrIII cation is coordinated by the six N atoms from the two tacn ligands, displaying a distorted octa­hedral geometry. Three distorted tetra­hedral [ZnCl4]2− anions and one lattice water mol­ecule lie outside this coordination sphere. The Cr—N bond lengths are in the range 2.0621 (11) to 2.0851 (12) Å, while the mean inner N—Cr—N bond angle is 82.51 (5)°. The crystal packing is stabilized by hydrogen-bonding inter­actions with the N—H groups of the tacn ligands and the water O—H groups acting as donors, and the O atoms of the water mol­ecules and Cl atoms of the [ZnCl4]2− anions as acceptors. Overall these contacts lead to the formation of a three-dimensional network.

Treatment of two equivalents of N,N′-bis(X-phenyl)oxamides (1) with one equivalent of [Zn(OAc)2(H2O)2] (2) in the presence of four equivalents of [nBu4N]OH produce the corresponding bis(N,N′-substituted oxamate) zincate(II) complexes with the general formula (nBu4N)2[Zn(X-phenyloxamide)2] (3) (a, X = 3-NO2; b, X = 4-NO2; c, X = 2,6 CH3; d, X = 3,4-CH3; e, X = 2-Br; f, X = 4-Br; g, X = 2-F; h, X = 4-F; i, X = 2-Cl; j, X = H). Complexes 3a–j have been characterized by elemental analysis, NMR (1H, 13C{1H}) and IR spectroscopy. In addition, 3a and 3f have been characterized by single crystal X-ray crystallography. The zinc (II) ion in the later complexes is four-coordinate with two ethanediamide-nitrogen atoms from two bidentate N,N′-disubstituted oxamate ligands at each metal center. In addition, the calculated electrostatic potentials of 3f rationalize the formation of chain structures via the Br…Br interaction. Complexes 3a–j showed a characteristic LLCT (π → π*) band in the UV-Vis spectra, which was confirmed by TD-DFT calculations. DFT calculations show that the Zn(II) orbitals are neither contributing to the HOMO nor to the LUMO, i.e. the HOMO and LUMO are mainly located on the ligands. The emission spectra analyses for Zn(II) complexes 3a–j show enhanced intensity and blue shifted emission compared to ligands 1a−j. The cyclic voltammetry measurements of complexes 3a–j showed reversible electrochemical processes for the (N,N′-substituted oxamate−2/−3) between −1.52 and −1.77 V using [NnBu4][B(C6F5)4] as the supporting electrolyte. It was found that the 3-nitro- (3a) and 4-nitro-functionalized (3b) derivatives resulted in a significantly higher Fc/Fc+ redox potential (E0′) compared to the more electron-rich 3, 4-dimethyl (3c) and 2,6-dimethyl (3d) derivatives.