Copper(ii) complexes with 2-ethylpyridine and related hydroxyl pyridine derivatives: structural, spectroscopic, magnetic and anticancer in vitro studies

Physicochemical Analysis of Cu(II)-Driven Electrochemical CO2 Reduction and its Competition with Proton Reduction

The reduction of CO2 has become a key role in reducing greenhouse gas emissions in efforts to search for long-term responses to climate change. We report a couple of CO2-reducing molecular catalysts based on earth-abundant copper complexes. These are [Cu(DPA)(PyNAP)] (1) and [Cu(DPA)(PyQl)] (2) (where, DPA=pyridine-2,6-dicarboxylate, PyNAP=2-(pyridin-2-yl)-1,8-naphthyridine, and PyQl=2-(pyridin-2-yl)quinoline). The copper metal-catalysed 2-electron reduction of CO2 to CO in the presence of 2-protons is challenging. These catalysts exhibit the production of CO gas in DMF/water mixtures, achieving an impressive Faradaic efficiency of 84 % and 72 % for complex 1 and 2 at -1.7 V vs. SCE, respectively, for selective CO2 reduction. The production of H2 due to 2H++2e- was also observed as a byproduct through the competitive proton reduction reaction. This was cross-verified by online gas and mass analysis. A comprehensive series of electrochemical experiments have substantiated the homogeneous behaviour exhibited by these molecular electrocatalysts. Our investigations confirmed the stability of the electrocatalysts under the electrocatalytic conditions. The mechanistic pathways were proposed to work with the EECC and ECEC (E: electrochemical and C: chemical) mechanisms. A CO2 insertion into an in-situ generated hydride from the Cu-center generates CO through the favourable path. This critical path kinetically favors excess Faradaic efficiency in 1 than 2, which agrees with the computational investigation.

Deciphering Electrocatalytic Hydrogen Production in Water Through a Bioinspired Water-Stable Copper(II) Complex Adorned with (N2S2)-Donor Sites

Electrocatalytic hydrogen production stands as a pivotal cornerstone in ushering the revolutionary era of the hydrogen economy. With a keen focus on emulating the significance of hydrogenase-like active sites in sustainable H2 generation, a meticulously designed and water-stable copper(II) complex, [Cl-Cu-LN2S2]ClO4, featuring the N,S-type ligand, LN2S2 (2,2'-((butane-2,3-diylbis(sulfanediyl))bis(methylene))dipyridine), has been crafted and assessed for its prowess in electrocatalytic H2 production in water, leveraging acetic acid as a proton source. The molecular catalyst, adopting a square pyramidal coordination geometry, undergoes -Cl substitution by H2O during electrochemical conditions yielding [H2O-Cu-LN2S2]2+ as the true catalyst, showcases outstanding activity in electrochemical proton reduction in acidic water, achieving an impressive rate of 241.75 s-1 for hydrogen generation. Controlled potential electrolysis at -1.2 V vs. Ag/AgCl for 1.6 h reveals a high turnover number of 73.06 with a commendable Faradic efficiency of 94.2 %. A comprehensive analysis encompassing electrochemical, spectroscopic, and analytical methods reveals an insignificant degradation of the molecular catalyst. However, the post-CPE electrocatalyst, present in the solution domain, signifies the coveted stability and effective activity under the specified electrochemical conditions. The synergy of electrochemical, spectroscopic, and computational studies endorses the proton-electron coupling mediated catalytic pathways, affirming the viability of sustainable hydrogen production.

Adamantane-type clusters: compounds with a ubiquitous architecture but a wide variety of compositions and unexpected materials properties

The research into adamantane-type compounds has gained momentum in recent years, yielding remarkable new applications for this class of materials. In particular, organic adamantane derivatives (AdR4) or inorganic adamantane-type compounds of the general formula [(RT)4E6] (R: organic substituent; T: group 14 atom C, Si, Ge, Sn; E: chalcogenide atom S, Se, Te, or CH2) were shown to exhibit strong nonlinear optical (NLO) properties, either second-harmonic generation (SHG) or an unprecedented type of highly-directed white-light generation (WLG) - depending on their respective crystalline or amorphous nature. The (missing) crystallinity, as well as the maximum wavelengths of the optical transitions, are controlled by the clusters' elemental composition and by the nature of the organic groups R. Very recently, it has been additionally shown that cluster cores with increased inhomogeneity, like the one in compounds [RSi{CH2Sn(E)R'}3], not only affect the chemical properties, such as increased robustness and reversible melting behaviour, but that such 'cluster glasses' form a conceptually new basis for their use in light conversion devices. These findings are likely only the tip of the iceberg, as beside elemental combinations including group 14 and group 16 elements, many more adamantane-type clusters (on the one hand) and related architectures representing extensions of adamantane-type clusters (on the other hand) are known, but have not yet been addressed in terms of their opto-electronic properties. In this review, we therefore present a survey of all known classes of adanmantane-type compounds and their respective synthetic access as well as their optical properties, if reported.

Copper perchlorate catalyzed oxidative cyclisation of a novel bishydrazone ligand, formation of an unusual copper complex and in vitro biological implications

A novel hexadentate bishydrazone ligand, 1,10-bis(di(2-pyridyl)ketone) adipic acid dihydrazone (H2L1) is synthesized and characterized. With copper perchlorate as a catalytic oxidant, the ligand undergoes oxidative cyclisation and resulted in the formation of an unusual copper complex [Cu(L1a)2Cl]ClO4 (1), where L1a is 3-(2-pyridyl)triazolo[1,5-a]-pyridine. The Cu(II) complex was characterized physicochemically, while the molecular structure was confirmed by single crystal X- ray diffraction. In the complex cation, copper(II) is in a distorted trigonal bipyramidal coordination environment, surrounded by two triazolo nitrogen atoms and two pyridyl nitrogen atoms of L1a and a chloride atom. The relevant non covalent intermolecular interactions of the complex quantified using Hirshfeld surface analysis reveals that the O···H/ H···O (27.2%) contacts has the highest contribution. The solution phase bandgaps of the compounds were calculated using Tauc plot, whereas the solid-state band gaps were calculated by Kubelka-Munk model. DFT studies of the compounds indicate that the theoretical calculations corroborate with the experimental data. DPPH antioxidant activity assay of the synthesized compounds showed that the proligand H2L1 has a lower IC50 value (24.1 μM) than that of complex 1 (29.7 μM). The in vitro antibacterial activity was evaluated against Escherichia coli and Staphylococcus aureus, which revealed that complex 1 have excellent activity against E. coli, much as the standard ciprofloxacin. The cytotoxic efficacy investigation of the compounds against A549 (lung) adenocarcinoma cells suggested that H2L1 has more anticancer activity (IC50 value of 149.08 μM) than that of complex 1(IC50 value of 176.70 μM).

Cuproptosis: emerging biomarkers and potential therapeutics in cancers

The sustenance of human life activities depends on copper, which also serves as a crucial factor for vital enzymes. Under typical circumstances, active homeostatic mechanisms keep the intracellular copper ion concentration low. Excess copper ions cause excessive cellular respiration, which causes cytotoxicity and cell death as levels steadily rise above a threshold. It is a novel cell death that depends on mitochondrial respiration, copper ions, and regulation. Cuproptosis is now understood to play a role in several pathogenic processes, including inflammation, oxidative stress, and apoptosis. Copper death is a type of regulatory cell death(RCD).Numerous diseases are correlated with the development of copper homeostasis imbalances. One of the most popular areas of study in the field of cancer is cuproptosis. It has been discovered that cancer angiogenesis, proliferation, growth, and metastasis are all correlated with accumulation of copper ions. Copper ion concentrations can serve as a crucial marker for cancer development. In order to serve as a reference for clinical research on the product, diagnosis, and treatment of cancer, this paper covers the function of copper ion homeostasis imbalance in malignant cancers and related molecular pathways.

Magneto-structural maps and bridged-ligand effect for dichloro-bridged dinuclear copper(ii) complexes: a theoretical perspective

Theoretical understanding of magneto-structural correlations in dichloro-bridged dicopper(ii) complexes can guide the design of magnetic materials having broad-scale applications. However, previous reports suggest these correlations are complicated and unclear. To clarify possible correlations, magnetic coupling constants (J _calc) of variants of a representative {Cu-(μ-Cl)₂-Cu} complex A were calculated through BS-DFT. The variation of the Cu-(μ-Cl)-Cu angle (α), Cu⋯Cu distance (R ₀), and Cu-Cl-Cu-Cl dihedral angle (τ) followed by structural optimization and calculation of the magnetic coupling constant (J _calc) revealed several trends. J _calc increased linearly with R ₀ and τ, and initially increased and then decreased with α. Further, bridging ligand effects on J _calc for dicopper(ii) complexes were evaluated through BS-DFT; the results revealed that J _calc increased with increasing ligand field strength (I^- < Br^- < Cl^- < N₃ ^- < F^-). Furthermore, a linear relationship was found between the spin density of the bridging ligand and J _calc.