Inorganics, Volume 11, Issue 10 (October 2023) – 44 articles

Three Eu³⁺ complexes containing a neutral tripodal ligand possessing a predictable coordination mode have been obtained and studied. The trispyrazolylmethane complexes have an aqua ligand in the coordination sphere, forming both the mononuclear species [Eu(HCPz₃)H₂O(NO₃)₃] and the dimer [Eu(HCPz₃)H₂O(CF₃SO₃)₃]₂, having a Chinese lantern structure, whereas the use of the methylated tripod leads to the water-free complex, [Eu(HC(Pz^Me₂)₃)(NO₃)₃]. A qualitative analysis of the magnetic susceptibility of polycrystalline samples demonstrated that the magnetic properties can be described using a simple Van Vleck formula with spin–orbit coupling parameter (λ = 383 ÷ 406 cm⁻¹) close to the values for free Eu³⁺ ions. The stereochemical analysis of the coordination environment of [Ln(HC(Pz^Me₂)₃)(NO₃)₃] has shown that these complexes can be used as diamagnetic model systems to obtain information on the crystal field effects in the paramagnetic monoradical complexes, [LnRad(NO₃)₃], since both types of compounds have the same type of coordination polyhedron (symmetry point group D_3h) and very close Ln–donor atom distances. Full article

Two novel silver(I) coordination polymers, [Ag(4BP)(SCN)]_n (1) and {(4BPH)⁺[Ag(SCN)₂]⁻}_n (2) (4BP = 4-benzoyl pyridine), have been synthesized. The two complexes were prepared using almost the same reagents, which were AgNO₃, 4BP and NH₄SCN. The only difference was the presence of 1:1 (v/v) HNO₃ in the synthesis of 2. In the two complexes, the Ag(I) has distorted tetrahedral coordination geometry. The structure of both complexes and the involvement of the thiocyanate anion as a linker between the Ag(I) centers were confirmed using single-crystal X-ray diffraction. 4BP participated as a monodentate ligand in the coordination sphere of complex 1, while in 2 it is found protonated (4BP-H)⁺ and acts as a counter ion, which balances the charge of the anionic [Ag(SCN)₂]⁻ moiety. The thiocyanate anion shows different coordination modes in the two complexes. In complex 1, the thiocyanate anion exhibits a µ_1,1,3 bridging mode, which binds three Ag(I) ions to build a boat-like ten-membered ring structure leading to a two-dimensional coordination polymer. In 2, there are mixed µ_1,1 and µ_1,3 bridging thiocyanate groups, which form the one-dimensional polymeric chain running in the a-direction. Several interactions affected the stability of the crystal structure of the two complexes. These interactions were examined using Hirshfeld surface analysis. The coordination interactions (Ag-S and Ag-N) have a great impact on the stability of the polymeric structure of the two complexes. Additionally, the hydrogen-bonding interactions are crucial in the assembly of these coordination polymers. The O…H (10.7%) and C…H (34.2%) contacts in 1 as well as the N···H (15.3%) and S···H (14.9%) contacts in 2 are the most significant. Moreover, the argentophilic interaction (Ag…Ag = 3.378 Å) and π- π stacking play an important role in the assembly of complex 2. Full article

In recent years, there have been intense studies on hybrid organic–inorganic compounds (HOIPs) due to their tunable and adaptable features. This present study reports the vibrational, structural, and elastic properties of mixed halide single crystals of MA_xFA_1-xPbCl₃ at room temperature by introducing the FA cation at the A-site of the perovskite crystal structure. Powder X-ray diffraction analysis confirmed that its cubic crystal symmetry is similar to that of MAPbCl₃ and FAPbCl₃ with no secondary phases, indicating a successful synthesis of the MA_xFA_1-xPbCl₃ mixed halide single crystals. Structural analysis confirmed that the FA substitution increases the lattice constant with increasing FA concentration. Raman spectroscopy provided insight into the vibrational modes, revealing the successful incorporation of the FA cation into the system. Brillouin spectroscopy was used to investigate the changes in the elastic properties induced via the FA substitution. A monotonic decrease in the sound velocity and the elastic constant suggests that the incorporation of large FA cations causes distortion within the inorganic framework, altering bond lengths and angles and ultimately resulting in decreased elastic constants. An analysis of the absorption coefficient revealed lower attenuation coefficients as the FA content increased, indicating reduced damping effects and internal friction. The current findings can facilitate the fundamental understanding of mixed lead chloride perovskite materials and pave the way for future investigations to exploit the unique properties of mixed halide perovskites for advanced optoelectronic applications. Full article

In this work, a number of new porphyrin dimers coupled with spacers based on α,α’-dibromo-o-xylene were synthesized and characterized by ¹H, ¹³C NMR, ¹H-¹H COSY NMR, UV-vis-spectroscopy, and MALDI-TOF mass spectrometry. The initial A3B-type hydroxy-substituted porphyrins form dimer structures with high yields of 80–85%, while the use of amino-substituted porphyrins as starting compounds leads to the heterocyclization and formation of N-heterocycle fused porphyrins. For porphyrin dimers, photophysical properties and quantum yields of singlet oxygen were investigated. The peripheral alkoxy-substituents increase fluorescence quantum yield in comparison with the unsubstituted compounds. Also, it was found that dimers are characterized by lower singlet oxygen quantum yields compared to the corresponding monomers. Model aggregation experiments in micellar systems demonstrate stabilization of the photoactive monomolecular form of all the porphyrins, using nonionic surfactant Triton X-100. Cytotoxicity of received dimers shows high inhibition against HEK293T cells in the absence of light. Full article

A hydride of Yb₂Pd₂Sn could be synthesized with approximately 2 H atoms per f.u. The hydrogenation leads to a volume expansion while preserving the tetragonal symmetry (P4/mbm). The lattice reaction is strongly anisotropic, and the 5% expansion in c is partly compensated by the 0.5% compression in a. The hydride is paramagnetic at least down to 0.5 K. Yb remains at or very close to the 3+ (4f¹³) state, as in Yb₂Pd₂Sn. Specific heat C/T vs. T shows an upturn existing already in Yb₂Pd₂Sn, but it is much more pronounced in the hydride (1.8 J/mol f.u. K² for T → 0, i.e., more than twice higher than in its precursor). This is interpreted as lowering the Kondo temperature due to H bonding. Full article

A mixture of nonlabeled (¹⁴N₂H₄) and ¹⁵N labeled hydrazine (¹⁵N₂H₄) in an aqueous solution is oxidized to ¹⁵N₂, ¹⁴N₂, and ¹⁴N¹⁵N molecules, indicating the intermediate existence of the ¹⁴NH₂-¹⁴NH-¹⁵NH-¹⁵NH₂ with subsequent hydrogen transfers and splitting of side N-N bonds. The structures, thermodynamics and electron characteristics of various N₄H₆ molecules in aqueous solutions are investigated using theoretical treatment at the CCSD/cc-pVTZ level of theory to explain the crucial part of the hydrazine oxidation reaction. Most N₄H₆ structures in aqueous solutions are decomposed during geometry optimization. Splitting the bond between central nitrogen atoms is the most frequent method, but the breakaway of the side nitrogen is energetically the most preferred one. The N-N fissions are enabled by suitable hydrogen rearrangements. Gibbs free energy data indicate the dominant abundance of NH₃... N₂... NH₃ species. The side N atoms have very high negative charges, which should support hydrogen transfers in aqueous solutions. The only stable cyclo-(NH)₄…H₂ structure has a Gibbs energy that is too high and breaks the H₂ molecule. The remaining initial cyclic structures are split into hydrazine and HN≡NH or H₂N≡N species, and their relative abundance in aqueous solutions is vanishing. Full article

Three Schiff base ligands, NQ, CQ and HQ, were prepared from the reaction of quinoline-3-carbohydrazide with 2-nitrobenzaldehyde, 2-chlorobenzaldehyde and 2,4-dihydroxybenzaldehyde, respectively, and were investigated for their coordination to Cu (II), Ni(II), Co(II), Cd(II), Cr(III) and Fe(III) chlorides. The NQ preparation and the X-ray structure of NQ and CQ, as well as the transition metal complexes of NQ, CQ and HQ, were reported for the first time. FTIR, 1H-NMR, magnetic susceptibility and elemental analysis were used to study the coordination of ligands to the metal ions. Based on the magnetic susceptibility and elemental analysis results, octahedral structures of the complexes such as [CuL2Cl(OH)], [FeL2Cl2(OH)] and [CoL2Cl(OH)] were proposed for L = NQ, CQ and HQ. The relatively large Cd(II) exhibited [CdL3(OH)2]. The FTIR study revealed that NQ and CQ are coordinated to the metal ions via azomethine nitrogen and carbonyl oxygen while HQ through azomethine nitrogen and phenolic oxygen. Despite the high solvation power of DMSO solvent in 1H-NMR experiments, the azomethine HC=N peak at 9.3 ppm is the most affected by complexation with metal ions. On the other hand, quinoline nitrogen seems to be a weaker coordinating site than the azomethine nitrogen. The HQ ligand, containing phenolic groups, and its complexes with Cu and Ni were found to have inhibitory effects on human breast adenocarcinoma MCF-7 and human chronic myelogenous leukemia K562. Nevertheless, metal ions did not exhibit a significant synergistic effect on the antiproliferative activity of the ligands investigated. Full article

A series of thirty novel tetracarboxylatoplatinum(IV) complexes in trans-configuration featuring combinations of mixed ammine, methylamine, dimethylamine, and cyclopentylamine ligands as well as acetato/propanoato and trifluoropropanoato ligands was synthesised. The platinum(IV) complexes were characterised by one- and two-dimensional multinuclear NMR spectroscopy (¹H, ¹³C, ¹⁵N, ¹⁹F, ¹⁹⁵Pt), ESI-MS, elemental analysis, and X-ray diffraction. Additional parameters such as reduction behaviour and lipophilicity were measured via NMR spectroscopy and RP-HPLC, revealing slow reduction and a broad spectrum of log k_w values in line with the respective ligand combination. In order to determine structure–activity relationships, cytotoxic activity was evaluated via the MTT assay in three human cancer cell lines (CH1/PA-1, ovarian teratocarcinoma, SW480, colon adenocarcinoma, A549, non-small-cell lung carcinoma). The induction of apoptosis and necrosis was determined in SW480 cells via the flow-cytometric annexin V/PI assay. In general, a tendency of higher lipophilicity leading to higher cytotoxicity was noticed. In contrast, lipophilicity alone plays a subordinate role for the induction of apoptosis, which strongly depends on the combination of am(m)ine and trifluoropropanoato ligands. Full article

The possibility of deep radiochemical purification of Li₂CO₃ has been examined in the context of the purification program of the AMoRE collaboration. In this experiment, commercial Li₂CO₃ was converted into LiNO₃. Co-precipitation with inorganic salt-based carriers followed by membrane filtration and sorption using MDM inorganic sorbent methods were tested for the removal of alkaline-earth and transition metals, potassium, magnesium, aluminum, uranium, thorium, and radium. The calcium molybdate-based carrier was the most efficient for removing Th, U, and K. Subsequently, the radium, calcium, and barium contamination was removed with MDM sorbent. After the impurities’ removal, the final Li₂CO₃ product was synthesized with NH₄HCO₃ sludge. The separation factors were derived by means of ICP-MS and HPGe analyses of the initial material and the intermediate and final products. The study showed the optimum conditions of co-precipitation and sorption to reach a high yield and radiopurity of lithium carbonate used for low-radioactive-background experiments. The developed method is an important step toward performing next-generation large-scale (1-ton) neutrino experiments using Li-containing detectors. Full article

Silver nanowires (AgNWs) are a potential alternative to conventional transparent conductive materials for various applications, such as flexible and transparent electrodes in optoelectronic devices, including touch screens, solar cells, and flexible displays. However, AgNW electrodes face degradation due to environmental factors, electrical instability, and mechanical stress. To overcome these challenges, strategies to protect AgNW-based electrodes via the incorporation of polymeric materials were widely investigated to improve the durability and stability of AgNW-based electrodes. This review paper gives a comprehensive overview of the incorporation of polymeric materials with AgNW electrodes, emphasizing their performance, and applications. We compare the different polymeric materials and their effect on the electrical, optical, and mechanical properties of AgNW electrodes. Furthermore, we evaluate the key factors affecting the choice of protective layers, such as their compatibility with AgNWs, and also we present current challenges and future opportunities for the development of polymeric materials for AgNW electrodes in emerging technologies. Full article

For the first time, a thiosemicarbazone-type ligand containing a paracetamol structural unit was synthesized. Five new coordination compounds based on copper(II) salts: [Cu(L)CH₃COO] (1), [{Cu(L)Cl}₂]·H₂O (2), [Cu(L)H₂O·DMF]NO₃ (3), [Cu(L)Br] (4), [Cu(L)H₂O]ClO₄ (5), were obtained, where HL is N-[4-({2-[1-(pyridin-2-yl)ethylidene]hydrazinecarbothioyl}amino)phenyl]acetamide. The new HL was characterized by NMR, FTIR, spectroscopy, and X-ray crystallography. All copper(II) coordination compounds were characterized by elemental analysis, FTIR, EPR spectroscopy, and molar electrical conductivity. Furthermore, single crystal X-ray diffraction analysis elucidated the structures of thiosemicarbazone HL as well as complexes 1–3. All compounds were tested for antimicrobial, antifungal, and antioxidant activities, and their toxicity to Daphnia magna was studied. Biological evaluation has revealed that most of the synthesized compounds demonstrate promising antibacterial, antifungal, and antioxidant activities. In many cases, their antibacterial/antifungal activity is comparable to that of certain drugs used in medicine for these purposes, and in some cases, even surpasses them. HL and complexes 2–5 exhibit antioxidant activity that surpasses that of Trolox. Furthermore, HL and complex 2 display virtually no toxicity to D. magna. Full article

Sheaf-like manganese-doped zinc silicate (Mn-doped Zn₂SiO₄) was successfully synthesized without surfactant by hydrothermal route using manganese acetate, zinc nitrate, and sodium silicate as precursors. The structure, morphology, and optical properties were well investigated by various analytical techniques, such as X-ray diffraction (XRD), a scanning electron microscope (SEM), a transmission electron microscope (TEM), and photoluminescence (PL). The results showed the enhancement of crystallinity and an increase in the length of the as-prepared sample, which was achieved by prolonging the hydrothermal time. Based on the analysis of the XRD pattern, it can be stated that the sheaf-like Mn-doped Zn₂SiO₄ possesses a large lattice distortion compared to pure Zn₂SiO₄. Moreover, it was observed that hydrothermal times played a crucial role in the PL property. The PL peak intensity of samples located at 522 nm generally increased with the increase in reaction time in the range of 12–48 h. However, when the treating time reached 72 h, the property of PL decreased. The results of the PL spectra showed that Mn-doped Zn₂SiO₄ obtained by a hydrothermal time of 48 h displayed an efficient luminescent performance. The key to the high PL property mainly lies in the sheaf-like structure and large lattice distortion. Full article

In this paper, a series of K₅La_1-x(MoO₄)₄: xSm³⁺ and K₅La_0.86(MoO₄)₄: 0.07Sm³⁺, 0.07Ln³⁺ (Ln = Sc, Y or Gd) red phosphors were prepared by calcining the mixed raw powders at 600 °C. Meanwhile, the composition and fluorescence properties of the phosphors, especially for the thermal stability, were analyzed in detail. The results indicate that the K₅La_1-x(MoO₄)₄: xSm³⁺ phosphors can be effectively excited at 401 nm and emit red light with three main peaks at 561 nm, 600 nm and 646 nm, attributed to the ⁴G_5/2→⁶H_j/2 (j = 5, 7 and 9) energy transitions of the Sm³⁺ ion respectively, among which the K₅La_0.93(MoO₄)₄: 0.07Sm³⁺ exhibits the highest intensity. The quenching mechanism is ascribed to the dipole-dipole interaction. Ln³⁺ co-doping does not change the shape and peaking position of the excitation and emission spectra of K₅La_0.93(MoO₄)₄: 0.07Sm³⁺, but further increases the emission intensity in different degrees. Particularly, K₅La_0.86(MoO₄)₄: 0.07Sm³⁺, 0.07Gd³⁺ demonstrates a high quantum efficiency of 74.63%, a low color temperature (1753 K), and a high color purity of up to 99.97%. It is worth noting that all the phosphors have a good thermal stability, even a zero quenching phenomenon occurs, attributed to the electron traps confirmed by the TL spectrum. Full article

We present an investigation on the structures and chemical bonding of two Bi-doped boron clusters BiB_n⁻ (n = 4, 5) using photoelectron spectroscopy and theoretical calculations. The electron affinities of BiB₄ and BiB₅ are measured to be 2.22(2) eV and 2.61(2) eV, respectively. Well-resolved photoelectron spectra are obtained and used to compare with theoretical calculations to verify the structures of BiB₄⁻ and BiB₅⁻. Both clusters adopt planar structures with the Bi atom bonded to the periphery of the planar B_n moiety. Chemical bonding analyses reveal that the B_n moiety maintains σ and π double-aromaticity. The Bi atom is found to induce relatively small structural changes to the B_n moiety, very different from transition metal-doped boron clusters. Full article

The Pt^II isocyanide complex [Pt(ppy)Cl(CNC₆H₄-C≡C-Ph)] (1, Hppy=2-phenylpyridine) was co-crystallized with 1,4-diiodotetrafluorobenzene (1,4-DITFB), yielding 1·½(1,4-DITFB) adduct. The I···Cl halogen-bonding and π-π-stacking interactions combined with the rare π-hole(isocyano group)⋅⋅⋅d_z²[Pt^II] interactions were identified via analysis of X-ray diffraction data of the co-crystals. These two types of structure-determining interactions supplemented each other, and the system of I⋯Cl and π-hole(isocyano group)⋅⋅⋅d_z²[Pt^II] contacts achieved a 1D extended ladder-type architecture. The density functional theory calculations, employing a set of computational tools, verified the role of I⋯Cl and π-hole(isocyano group)⋅⋅⋅d_z²[Pt^II] noncovalent bonds in the spectrum of noncovalent forces. The solid-state photophysical study revealed an amplification of luminescence intensity in the co-crystals, which is attributed to the suppression of the nonradiative relaxation pathways due to an increase in the rigidity of the chromophore center. Full article

In this study, O-amino benzenethiol (OABT) was oxidized in one pot using Fe(NO₃)₃ to produce a novel Fe₂S₃-Fe₂O₃/poly O-amino benzenethiol (POABT), which showed a highly uniform morphology. At the same time, from SEM analysis, highly wrinkled porous polypyrrole (Ppy) and porous ball-like POABT structures prepared from the K₂S₂O₈ route were evidenced by SEM and TEM analyses. A nanocomposite pseudo-supercapacitor (SC) was fabricated using Fe₂S₃-Fe₂O₃/POABT, and its performance was tested with and without incorporating Ppy in the paste. The results indicate that Ppy significantly increased the specific capacitance (C_S) values, indicating an enhancement in charge storage. At a current density of 0.2 A/g, the C_S values were 44 F/g and 161 F/g for the paste without and with Ppy, respectively. Additionally, the E was calculated, and the incorporation of Ppy resulted in a significant increase in E, reaching 30 W.h.kg⁻¹; this was significantly higher than the value of 8.18 W.h.kg⁻¹ observed without Ppy materials. This effect is likely due to the improved charge transfer facilitated by the presence of Ppy, as evidenced by the Nyquist plot, where the R_ct values were 1.1 Ω and 2.1 Ω with and without Ppy, respectively. Overall, the low cost and significant technical advantages of this capacitor make it a promising candidate for commercial applications. Full article

We present the first detailed study of optical absorption coefficients (OACs) in a GaAs quantum dot confined with a Woods–Saxon potential containing a hydrogenic impurity at its center. We use a finite difference method to solve the Schrödinger equation within the framework of the effective mass approximation. First, we compute energy levels and probability densities for different parameters governing the confining potential. We then calculate dipole matrix elements and energy differences, $E_{1p}-E_{1s}$, and discuss their role with respect to the OACs. Our findings demonstrate the important role of these parameters in tuning the OAC to enable blue or red shifts and alter its amplitude. Our simulations provide a guided path to fabricating new optoelectronic devices by adjusting the confining potential shape. Full article

Cobalt hydroxide is a widely studied electrode material for supercapacitor and alkaline zinc ion batteries. The large interlayer spacing of Co(OH)₂ is also attractive to store Zn ions. However, Co(OH)₂ is quite unstable in the acidic ZnSO₄ electrolyte due to its amphoteric nature. Herein, we synthesized a mixed phase of Co(OH)₂/CoOOH via a two-step electrochemical preparation. As the cathode material for an aqueous zinc ion battery (AZIB), Co(OH)₂/CoOOH delivered a maximum capacity of 164 mAh g⁻¹ at 0.05 A g⁻¹ and a high energy density of 275 Wh kg⁻¹. Benefiting from the low charge-transfer resistance, a capacity of 87 mAh g⁻¹ was maintained at 1.6 A g⁻¹, showing a good rate performance of the mixed phase. Various spectroscopy analyses and simulations based on the density functional theory (DFT) suggested a higher thermal stability of the mixed phase than pure Co(OH)₂, due to its less local structural disorder. The reduced Co-Co and Co-O shells increased the mechanical strength of the mixed phase to accommodate Zn²⁺ ions and endure the electrostatic repulsion, resulting in an enhanced cycling stability. The mixed phased also delivered a good stability at the current density of 0.05 A g⁻¹. After 200 cycles, a capacity retention of 78% was retained, with high Coulombic efficiencies. These results provide a new route to synthesize high-performance LDH for aqueous zinc ion batteries. Full article

Biaryl monophosphines are important precursors to active catalysts of palladium-mediated cross-coupling reactions. The efficiency of the phosphine-based transition metal complex catalyst has its origin in the electronic structure of the complex used and the sterical hindrance created by the ligand at an active catalyst site. The aim of this paper is to shed some light on the multiverse of coordination modes of biaryl monophosphine ligands. Here, we present the analysis of the X-ray single crystal structures of palladium(II) complexes of a family of biaryl monophosphine ligands and the first crystallographic report on a related phosphine sulfide. Despite the common biaryl monophosphine ligand motif, they show diverse coordination modes (i) starting from the activation of aromatic C atoms and producing a C,P metallacycle, through (ii) the O,P chelation to Pd(II) ions with a simultaneous demethylation reaction of one of the methoxy groups, ending up with (iii) the monodentate coordination to metal cations via P atoms or (iv) via S atoms in the case of phosphine sulfide. We relate our results to the crystal structures found in the Cambridge Structural Database to show the multiverse of coordination modes in the group of biaryl monophosphine ligands. Full article

Coordination compounds of copper exhibit cytotoxic activity and are suitable for the search for novel drug candidates for cancer treatment. In this work, we synthesized three copper(II) carboxylate complexes, [Cu₂(3-(4-hydroxyphenyl)propanoate)₄(H₂O)₂]·2H₂O (C1), [Cu₂(phenylpropanoate)₄(H₂O)₂] (C2) and [Cu₂(phenylacetate)₄] (C3), and characterized them by elemental analysis and spectroscopic methods. Single-crystal X-ray diffraction of C1 showed the dinuclear paddle-wheel arrangement typical of Cu–carboxylate complexes in the crystal structure. In an aqueous solution, the complexes remain as dimeric units, as studied by UV-visible spectroscopy. The lipophilicity (partition coefficient) and the DNA binding (UV visible and viscosity) studies evidence that the complexes bind the DNA with low K_b constants. In vitro cytotoxicity studies on human cancer cell lines of metastatic breast adenocarcinoma (MDA-MB-231, MCF-7), lung epithelial carcinoma (A549) and cisplatin-resistant ovarian carcinoma (A2780cis), as well as a nontumoral lung cell line (MRC-5), indicate that the complexes are cytotoxic in cisplatin-resistant cells. Full article

β-Ga₂O₃, with excellent bandgap, breakdown field, and thermal stability properties, is considered to be one of the most promising candidates for power devices including field-effect transistors (FETs) and for other applications such as Schottky barrier diodes (SBDs) and solar-blind ultraviolet photodetectors. Ohmic contact is one of the key steps in the β-Ga₂O₃ device fabrication process for power applications. Ohmic contact techniques have been developed in recent years, and they are summarized in this review. First, the basic theory of metal–semiconductor contact is introduced. After that, the representative literature related to Ohmic contact with β-Ga₂O₃ is summarized and analyzed, including the electrical properties, interface microstructure, Ohmic contact formation mechanism, and contact reliability. In addition, the promising alternative schemes, including novel annealing techniques and Au-free contact materials, which are compatible with the CMOS process, are discussed. This review will help our theoretical understanding of Ohmic contact in β-Ga₂O₃ devices as well as the development trends of Ohmic contact schemes. Full article

Four ligands based on the 2-tert-butyl-4-X-6-{Bis[(6-methoxy-pyridin-2-ylmethyl)-amino]-methyl}-phenol unit are synthesized: X = CHO (HL^CHO), putrescine-pyrene (HL^pyr), putrescine (HL^amine), and 2-tert-butyl-4-putrescine-6-{Bis[(6-methoxy-pyridin-2-ylmethyl)-amino]-methyl}-phenol (H₂L^bis). Complexes 1, 2, 3, and 4 are formed upon chelation to copper(II). The crystal structure of complex 1 shows a square pyramidal copper center with a very weakly bound methoxypridine moiety in the apical position. The pKa of the phenol moiety is determined spectrophotometrically at 2.82–4.39. All the complexes show a metal-centered reduction in their CV at E_p^c,red = −0.45 to −0.5 V vs. SCE. The copper complexes are efficient nucleases towards the ϕX174 DNA plasmid in the presence of ascorbate. The corresponding IC₅₀ value reaches 7 μM for 2, with a nuclease activity that follows the trend: 2 > 3 > 1. Strand scission is promoted by the hydroxyl radical. The cytotoxicity is evaluated on bladder cancer cell lines sensitive (RT112) or resistant to cisplatin (RT112 CP). The IC₅₀ of the most active complexes (2 and 4) is 1.2 and 1.0 μM, respectively, for the RT112 CP line, which is much lower than cisplatin (23.8 μM). Full article

A new Ag(I) adduct was synthesized by the reaction of 4-amino-4H-1,2,4-triazole (L) with AgNO₃. Its chemical structure was approved to be [Ag₂(L)₂(NO₃)]_n(NO₃)_n utilizing elemental analysis, FTIR spectra, and single crystal X-ray diffraction (SC-XRD). According to SC-XRD, there are two independent silver atoms which are coordinated differently depending on whether the nitrate anion is coordinated or not. The coordination geometry of Ag1 is a slightly bent configuration while Ag2 has a distorted tetrahedral structure. The 4-amino-4H-1,2,4-triazole ligand and one of the nitrate groups adopt bridging mode, which connects the crystallographically independent Ag1 and Ag2 atoms resulting in the formation of two-dimensional coordination polymer. Hirshfeld surface analysis displays that the intermolecular O···H (34.0%), Ag···N (10.6%), H···H (10.4%), Ag···O (9.3%), and N···H (9.0%) contacts are the most abundant interactions. Regarding anticancer activity, the [Ag₂(L)₂(NO₃)]_n(NO₃)_n demonstrates stronger cytotoxic efficacy against lung (IC₅₀ = 3.50 ± 0.37 µg/mL) and breast (IC₅₀ = 2.98 ± 0.26 µg/mL) carcinoma cell lines than the anticancer medication cis-platin. The [Ag₂(L)₂(NO₃)]_n(NO₃)_n complex showed interesting antibacterial and antifungal activities compared to the free components (AgNO₃ and 4-amino-4H-1,2,4-triazole). The investigated silver(I) complex exhibits remarkable antibacterial activity against E. coli (MIC = 6.1 µg/mL) that may be on par with Gentamycin (MIC = 4.8 µg/mL). As a result, the newly synthesized Ag(I) complex could be suggested for anticancer and antibacterial treatments. Full article

In this review, we present a timeline that shows the origin of mixed chelate copper (II) complexes, registered as Mark Title Casiopeínas^®, as the first copper (II) compounds proposed as anticancer drugs in 1988 and 1992. In the late twentieth century, the use of essential metals as anticancer agents was not even considered, except for their antifungal or antibacterial effects; also, copper, as gold salts, was used for arthritis problems. The use of essential metals as anticancer drugs to diminish the secondary toxic effects of Cisplatin was our driving force: to find less toxic and even more economical compounds under the rational design of metal chelate complexes. Due to their chemical properties, copper compounds were the choice to continue anticancer drug development. In this order of ideas, the rational designs of mixed chelate–copper (II) complexes (Casiopeínas, (Cas) homoleptic or heteroleptic, depending on the nature of the secondary ligand) were synthesized and fully characterized. In the search for new, more effective, and less toxic drugs, Casiopeína^® (Cas) emerged as a family of approximately 100 compounds synthesized from coordinated Cu(II) complexes with proven antineoplastic potential through cytotoxic action. The Cas have the general formula [Cu(N–N)(N–O)]NO₃ and [Cu(N–N)(O–O)]NO₃, where N–N is an aromatic substituted diimine (1,10-phenanthroline or 2,2′-bipyridine), and the oxygen donor (O–O) is acetylacetonate or salicylaldehyde. Lately, some similar compounds have been developed by other research groups considering a similar hypothesis after Casiopeína’s discoveries had been published, as described herein. As an example of translational medicine criteria, we have covered each step of the established normative process for drug development, and consequently, one of the molecules (Casiopeína III ia (CasIIIia)) has reached the clinical phase I. For these copper compounds, other activities, such as antibacterial, antiparasitic and antiviral, have been discovered. Full article

During the interaction of aqueous-ethanol or ethanol solutions AgNO₃, H[AuCl₄], and CuCl₂, as well as aqueous suspensions of slightly soluble copper(II) salts Cu(C₆H₄NO₂)₂·H₂O, Cu(C₇H₅O₂)₂∙3H₂O, and CuC₇H₄O₃∙H₂O with the ethanol solution of clotrimazole at pH of ~(5.0–5.5), the [Ag(C₂₂H₁₇ClN₂)₂]NO₃·2H₂O, [Au(C₂₂H₁₇ClN₂)Cl₃], [Cu(C₂₂H₁₇ClN₂)₂Cl₂]·5H₂O, Cu(C₂₂H₁₇ClN₂)₄(C₆H₄NO₂)₂, Cu(C₂₂H₁₇ClN₂)₄(C₇H₅O₂)₂, and Cu(C₂₂H₁₇ClN₂)₃(C₇H₄O₃)·2H₂O compounds are synthesised. They are characterised by elemental, thermal, thermogravimetric, and IR spectroscopic methods of analysis. The [Ag(C₂₂H₁₇ClN₂)₂]NO₃·2H₂O complex was shown to have a higher antimycotic activity against Saccharomyces cerevisiae fungi than that of AgNO₃ and C₂₂H₁₇ClN₂. Cocrystals/salts of the composition C₂₂H₁₇ClN₂·C₆H₅NO₂, C₂₂H₁₇ClN₂·C₇H₆O₂, 2C₂₂H₁₇ClN₂·C₇H₆O₃, and 2C₂₂H₁₇ClN₂·C₁₉H₁₉O₆N₇·H₂O are obtained from aqueous and aqueous ethanol suspensions containing nicotinic, benzoic, salicylic, and folic acids and clotrimazole (pH is 4.5–6.0). These cocrystals and salts were studied usin thermogravimetric, IR-spectroscopic methods. Diffraction patterns of the powders were obtained. The influence of the difference in the pK_a components on the ability to form cocrystals/salts was assessed. Full article

New sulfone 2-aminobenzimidazole derivatives were designed and synthesized. Their nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II) compounds were obtained and fully characterized by spectroscopic and analytical techniques. Single crystal X-ray structural analysis was performed in order to study the relevant intra and inter non-covalent interactions, mainly H···π, lone pair···π, and π···π, highlighting the difference between the terminal ethyl and phenyl groups in such interactions. Dimeric and trimeric supramolecular syntons were found for some of these compounds. Additionally, their antiproliferative activity was investigated, finding that the copper(II) compounds with the sulfone phenyl derivative were the most active. Full article

Two copper(II) complexes (Cu-L1, Cu-L2) derived from 2,3-substituted quinazolinone Schiff base ligands (L1, L2) were prepared to examine their anticancer activity. Compounds were characterized using various spectroscopic methods (FTIR, NMR, UV-vis) and quantum-chemical calculations. The biological effects of Cu(II) complexes bearing quinazolinone scaffolds were evaluated on two cancers’ cell lines (breast—MCF-7 and lung—A549), as well as on untransformed cells (keratinocytes—HaCaT). Copper complexes were highly cytotoxic, with IC₅₀ in the low micromolar range, while the quinazoline ligands L1 and L2 remained inactive in inhibiting cell proliferation. Antioxidant activity was investigated in the model systems using DPPH and FRAP assays. The Cu-L1 and Cu-L2 complexes exhibited enhanced DPPH free radical scavenging efficiency compared to the L1 and L2 ligands, but their reducing ability was comparable to that of the free ligands. Evaluation of oxidative stress in vitro carried out by staining cells with various ROS-specific indicators showed reduced production of superoxide anion radical and hydrogen peroxide after treatment of cells with copper complexes. Such a negative impact on ROS formation in cells can lead to cellular redox imbalance and consequent cell death, among others, by inducing apoptosis and/or necrosis, depending on the copper complex used. We hypothesize that the high cytotoxic activity of the investigated copper complexes is apparently the result of multiple mechanisms of action, and the imbalance in the cellular antioxidant system partly contributes to the overall cytotoxic effect. Full article

The treatment of N-Phenylmorpholine-4-carbothioamide (HPMCT) with bivalent metal ions in a 2:1 mol ratio without a base present affords [MCl₂(κ¹S-HPMCT)₂] {M = Cu(1), Pd(2), Pt(3), and Hg(4)} in a good yield. Furthermore, the reaction of two equivalents of HPMCT and one equivalent of bivalent metal ions in the presence of Et₃N has afforded [M(κ²S,N-PMCT)₂] {M = Ni(5), Cu(6), Pd(7), Pt(8), Zn(9), Cd(10), and Hg(11)}. Infrared, ¹H, ¹³C Nuclear Magnetic Resonance molar conductivity, and elemental analysis were used to characterize the synthesized complexes. The results suggest that HPMCT is bonded as monodentate via an S atom in Complexes (1–4), whereas linkage as a bidentate chelating ligand via S and N atoms gives two chelate rings. Moreover, the synthesized ligand and the complexes were screened for antibacterial activity, which displayed that the very best antibacterial activities for Complexes (1), (6), and (3). In addition, the cytotoxic activity of the HPMCT ligand, [PdCl₂(HPMCT)₂] (2), and [PtCl₂(HPMCT)₂] (3) were screened on breast cancer cell lines (MCF-7), and Complex (3) reveals the most promising activity with an IC₅₀ value 12.72 ± 0.4 μM. Using the B3LYP method and 6-311++G(d,p) basis sets for the ligand and the SDD basis set for the central metal, the synthesized complexes utilizing the prepared ligand were optimized. Various quantum parameters such as hardness, electron affinity, dipole moment, vibrational frequencies, and ionization energy for the ligand and its complexes have been calculated. In general, a favorable agreement was found between the experimental results and the obtained theoretical results. Full article

Recent advancements in the study of the protein complex photosystem II have clarified the sequence of events leading to the formation of oxygen during the S₃ → S₄ → S₀ transition, wherein the inorganic Mn₄Ca(µ-O)₆(OH_x)₄ cluster finishes photo-catalyzing the water splitting reaction (Greife et al., Nature 2023, 617, 623–628; Bhowmick et al., Nature 2023, 617, 629–636). During this final step, a tyrosine radical (Tyr_Z), stable for a couple of milliseconds, oxidizes a cluster-bound oxygen while the hydrogen bonding patterns of nearby waters shift a proton away. A treatment of this redox reaction within the context of accepted transition state theories predicts rate constants that are significantly higher than experimentally recovered values (10¹² s⁻¹ versus 10³ s⁻¹). In an effort to understand this disparity, temperature-dependent experiments have revealed large entropic contributions to the rates with only a moderate enthalpy of activation. We suggest that the entropic source may be related to the observed proton rearrangements, and further possible near isoenergetic variations in the nearby extended H-bonding network delaying the realization of an ‘ideal’ transition state. In the following, we explore this relation in the context of Eyring’s transition state theory and Marcus’ electron transfer theory and evaluate their compatibility with the experimental evidence. Full article