A novel dicationic room temperature ionic liquid, 1,1′-(5,14-dioxo-4,6,13,15-tetraazaoctadecane-1,18-diyl) bis(3-(sec-butyl)-1H-imidazol-3-ium) bis((trifluoromethyl)-sulfonyl) imide has been synthesized and fully characterized. Its thermal and electrochemical analyses along with transport properties have been studied. We propose it as a potential nominal additive to the commonly used conventional organic carbonate electrolyte mixture and study its adaptability in Lithium-ion batteries which are the prime power sources for ultraportable electronic devices. We have compared the performance characteristics of the full cells made without and with this ionic liquid. The cells comprise lithium nickel cobalt manganese oxide cathode, graphite anode and ethylene carbonate - dimethyl carbonate (1:1, v/v + LiPF₆) mixture electrolyte with nominal amount of ionic liquid as additive. The major concern with conventional electrolytes such as degradation of the materials inside batteries has been addressed by this electrolyte additive. Additionally, this additive is safer at relatively higher temperature. In its presence, the overall battery life is enhanced and it shows good cycling performance and coulombic efficiency with better discharge capacities (22% higher) after 100 cycles. Even after the increase in current rate from 10 mA/g to 100 mA/g, the cell still retains around 73% of capacity.

A summary of Fe³⁺ detection by luminescent MOFs and their mechanistic approaches are highlighted in this article based on recent publications.

Anaerobic reaction of Co(O₂CMe)₂·4H₂O with the thioether-containing acyclic pyrazine amide hexadentate ligand 1,4-bis[o-(pyrazine-2-carboxamidophenyl)]-1,4-dithiobutane (H₂L¹1) (–CH₂CH₂– spacer between the two pyrazine amide tridentate coordination units) furnishes [Co^II(L¹1)]·MeOH (1a) having CoN₂(pyrazine)N′₂(amide)S₂(thioether) coordination. It exhibits an eight-line EPR spectrum, attesting to a low-spin (S = 1/2) state of Co^II. A similar reaction in air, however, furnishes [Co^III(L^3a3a)(L^3b3b)]·2MeOH (2a) (S = 0), resulting from a C–S bond cleavage reaction triggered by an acetate ion as a base, having CoN₂(pyrazine)N′₂(amide)S(thioether)S′(thiolate) coordination. On the other hand, the reaction of Co(O₂CMe)₂·4H₂O with 1,4-bis[o-(pyrazine-2-carboxamidophenyl)]-1,5-dithiopentane (H₂L²2) (–CH₂CH₂CH₂– spacer between the two pyrazine amide tridentate coordination units) in air affords a cobalt(II) complex [Co^II(L²2)]·MeOH (1b·MeOH) (S = 1/2); its structurally characterized variety has the composition 1b·C₆H₆. Interestingly, 1b·MeOH undergoes facile metal-centred oxidation by aerial O₂–H₂O₂–[Fe(η⁵-C₅H₅)₂][PF₆], which led to the isolation of the corresponding cobalt(III) complex [Co^III(L²2)][ClO₄] (2b). When treated with methanolic KOH, 2b affords a low-spin (S = 0) organocobalt(III) complex [Co^III((L^2′2′)] (3). Structures of all complexes, except 1a, have been authenticated by X-ray crystallography. A five-membered chelate-ring forming ligand L¹1(2–) effects C–S bond cleavage and a six-membered chelate-ring forming ligand L²2(2–) gives rise to Co–C bond formation, in cobalt(III)-coordinated thioether functions due to α C–H bond activation by the base. A rationale has been provided for the observed difference in the reactivity properties. The spectroscopic properties of the complexes have also been investigated. Cyclic voltammetry experiments in MeCN–CH₂Cl₂ reveal facile metal-centred reversible-to-quasireversible Co^IV–Co^III (or a ligand-centred redox process; 2a), Co^III–Co^II (1a, 1b·MeOH, 2a, 2b and 3), Co^II–Co^I (1a, 1b·MeOH, 2a and 2b), and Co^I–Co⁰ (1a, 1b·MeOH and 2b) redox processes.

Using an acyclic hexadentate pyridine amide ligand, containing a –OCH₂CH₂O– spacer between two pyridine-2-carboxamide units (1,4-bis[o-(pyrydine-2-carboxamidophenyl)]-1,4-dioxabutane (H₂L⁹), in its deprotonated form), four new complexes, [Co^II(L⁹)] (1) and its one-electron oxidized counterpart [Co^III(L⁹)][NO₃]·2H₂O (2), [Ni^II(L⁹)] (3) and [Cu^II(L⁹)] (4), have been synthesized. Structural analyses revealed that the Co^II centre in 1 and the Ni^II centre in 3 are six-coordinate, utilizing all the available donor sites and the Cu^II centre in 4 is effectively five-coordinated (one of the ether O atoms does not participate in coordination). The structural parameters associated with the change in the metal coordination environment have been compared with corresponding complexes of thioether-containing hexadentate ligands. The μ_eff values at 298 K of 1–4 correspond to S = 3/2, S = 0, S = 1 and S = 1/2, respectively. Absorption spectra for all the complexes have been investigated. EPR spectral properties of the copper(II) complex 4 have been investigated, simulated and analyzed. Cyclic voltammetric experiments in CH₂Cl₂ reveal quasireversible Co^III–Co^II, Ni^III–Ni^II and Cu^II–Cu^I redox processes. In going from ether O to thioether S coordination, the effect of the metal coordination environment on the redox potential values of Co^III–Co^II (here the effect of spin-state as well), Ni^III–Ni^II and Cu^II–Cu^I processes have been systematically analyzed.

Acyclic pyrazine-2-carboxamide and thioether containing hexadentate ligand 1,4-bis[o-(pyrazine-2-carboxamidophenyl)]-1,4-dithiobutane (H₂bpzctb), in its deprotonated form, has afforded light brown [Ni^II(bpzctb)] (1) (S = 1) and green [Cu^II(bpzctb)] (2) (S = 1/2) complexes. The crystal structures of 1·CH₃OH and 2·CH₂Cl₂ revealed that in these complexes the ligand coordinates in a hexadentate mode, affording examples of distorted octahedral M^IIN₂(pyrazine)N′₂(amide)S₂(thioether) coordination. Each complex exhibits in CH₂Cl₂ a reversible to quasireversible cyclic voltammetric response, corresponding to the Ni^III/Ni^II (1) and Cu^II/Cu^I (2) redox process. The E_1/2 values reveal that the complexes of bpzctb(2−) are uniformly more anodic by 0.2 V than those of the corresponding complexes with the analogous pyridine ligand, 1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane (H₂bpctb), attesting that compared to pyridine, pyrazine is a better stabilizer of the Ni(II) or Cu(I) state. Coulometric oxidation of the previously reported complex [Ni^II(bpctb)] and 1 generates [Ni^III(bpctb)]⁺ and [Ni^III(bpzctb)]⁺ species, which exhibit a LMCT transition in the 470–480 nm region and axial EPR spectra corresponding to a tetragonally elongated octahedral geometry. Complex 2 exhibits EPR spectra characteristic of the d_z² ground state.