Octahedral Coordination Environment Research Articles

Ligand-dependent redox-coupled spin crossover of a five coordinate cobalt salen complex

The electrochemical and spectroscopic behavior of a five-coordinate cobalt (III) salen (CoIIISalen+), where Salen is N,N′-bis(3,5-di-tert-butyl-2-hydroxybenzyliden)-1,7-diamino-4-methyl-4-azaheptane, is examined in the presence of a series of exogenous ligands. In non-coordinating solvents, and in the absence of suitable ligands, CoIIISalen+ prefers a high-spin configuration (S = 2/2) and has trigonal bipyramidal geometry. The binding of pyridyl- or imidazole-based ligands generate an octahedral complex that is low-spin (S = 0). X-ray crystallographic structures are reported for [CoIIISalen-ampy]Cl, [CoIIISalen-ampy](SbF6), and [CoIIISalen-cnpy](SbF6), all confirming the octahedral coordination environment. In the absence of exogenous ligands, CoSalen displays an electrochemically quasi-reversible redox wave in cyclic voltammograms for the CoII/III couple (E1/2 = −0.37 V vs Fc0/+). The addition of various ligands (L) to the electrolyte induces a pronounced increase in the anodic–cathodic peak splitting (Epa,hs – Epc,ls) due to a redox-coupled spin-crossover (RCSCO) mechanism. The reduction potential of CoIIISalen-L+ (Epc,ls) is highly dependent on the nature and charge of L. To better understand the relationship between ligand properties and the observed electrochemical shift, we performed spectroscopic binding studies of CoIISalen and CoIIISalen+ to establish a correlation of the observed redox potentials to well-established thermodynamic parameters, including Hammett parameters of para-substituted pyridines and gas phase basicity (GPB) of all ligands. The broad range of anodic/cathodic peak splitting generated by this series of ligands with CoIIISalen-L+ highlights the ability to tune the RCSCO properties and redox bistability of a complex through coordination changes with exogenous ligands.

Octahedral Co2+‐O‐Co3+ in Mixed Cobalt Spinel Promotes Active and Stable Acidic Oxygen Evolution

AbstractCobalt (Co)‐based oxides show promising activity as precious metal‐free catalysts for the oxygen evolution reaction in proton exchange membrane water electrolysis, but the dissolution of Co has limited the durability of Co3O4 at industrially relevant current densities. This work demonstrates that cation in an octahedral coordination environment accounts for the oxygen evolution activity. Using a mixed inverse‐normal phase spinel CoxGa(3‐x)O4 as a proof‐of‐concept example, the designed Co2+‐O‐Co3+ motifs in octahedral sites trigger oxygen evolution through a kinetically favorable radical coupling pathway. Furthermore, lattice oxygen exchange, a leading factor in catalyst structural degradation for normal Co3O4, is suppressed, as evidenced by isotopic labeling experiments and theoretical calculations. With the optimized catalyst, Co1.8Ga1.2O4, an overpotential of 310 mV at 10 mA cm−2 is reported, with stable operation at 200 mA cm−2 for 200 h in a three‐electrode setup, and a proton exchange membrane electrolyzer operating at 200 mA cm−2 for 450 h.

Bis(ethyl-enedi-ammonium) μ-ethyl-enedi-aminetetra-acetato-1κ3 O,N,O':2κ3 O'',N',O'''-bis-[tri-oxidomolybdate(VI)] tetra-hydrate.

The title compound, (C2H10N2)2[(C10H12N2O8)(MoO3)2]·4H2O, which crystallizes in the monoclinic C2/c space group, was obtained by mixing molybdenum oxide, ethyl-enedi-amine and ethyl-enedi-amine-tetra-acetic acid (H4edta) in a 2:4:1 ratio. The complex anion contains two MoO3 units bridged by an edta4- anion. The midpoint of the central C-C bond of the edta4- anion is located on a crystallographic inversion centre. The independent Mo atom is tridentately coordin-ated by a nitro-gen atom and two carboxyl-ate groups of the edta4- ligand, together with the three oxo ligands, producing a distorted octa-hedral coordination environment. In the three-dimensional supra-molecular crystal structure, the dinuclear anions, the organo-ammonium counter-ions and the solvent water mol-ecules are linked by N-H⋯Ow, N-H⋯Oedta and O-H⋯O hydrogen bonds.

Rerefinement of the crystal structure of BiF5.

The crystal structure of bis-muth penta-fluoride, BiF5, was rerefined from single-crystal data. BiF5 crystallizes in the α-UF5 structure type in the form of colorless needles. In comparison with the previously reported crystal-structure model [Hebecker (1971 ▸). Z. Anorg. Allg. Chem. 384, 111-114], the lattice parameters and fractional atomic coordinates were determined to much higher precision and all atoms were refined anisotropically, leading to a significantly improved structure model. The Bi atom (site symmetry 4/m..) is surrounded by six F atoms in a distorted octa-hedral coordination environment. The [BiF6] octa-hedra are corner-linked to form infinite straight chains extending parallel to [001]. Density functional theory (DFT) calculations at the PBE0/TZVP level of theory were performed on the crystal structure of BiF5 to calculate its IR and Raman spectra. These are compared with experimental data.

Exploring magnetic space groups of [formula omitted] MXene and its connection to vibrational and electronic properties

The vibrational, electronic, and magnetic properties of two-dimensional Cr2N MXene were investigated. Two crystal cells (hexagonal and monoclinic) were considered with their respective magnetic space groups. In the absence of experimental data to fine-tune the Ueff (Hubbard correction), we utilized cell parameters and magnetic moment as a reference window, derived from meta-GGA calculations performed with the SCAN functional. A value of Ueff (1.25 eV) was determined, which does not overestimate the lattice parameters and magnetic moment values. Phonon scattering was calculated, and the vibrational modes were indexed. According to the density of states, the observed splitting in the eg and t2g orbitals, and the crystal field analysis, we deduce that chromium in the MXene Cr2N predominantly adopts an octahedral coordination environment, a combination of octahedral and tetrahedral coordination results in the splitting of the d orbitals. Finally, using Monte Carlo simulation, the critical temperature (Tc) for each space group with different functionals was obtained.

Synthesis, crystal structures and urease inhibition of nickel(II), copper(II), zinc(II) and molybdenum(VI) complexes derived from N,n’-bis(4-bromosalicylidene)-1,3-propanediamine

Three new trinuclear complexes containing either nickel(II), copper(II) or zinc(II), [Ni3L2(NO3)2(CH3OH)2]·2CH3OH (1), [Cu3Br2L2] (2), [Zn3L2(NCS)2(CH3OH)2]·0.5CH3OH·0.5H2O (3), and a new dioxidomolybdenum(VI) complex, [MoO2L] (4), have been prepared from the bis-Schiff base N,N’-bis(4-bromosalicylidene)-1,3-propanediamine (H2L) with various metal salts in methanol. The complexes were characterized by elemental analysis, IR and UV–Vis spectra. Molecular structures were confirmed by single crystal X-ray diffraction experiments. The Ni ions in 1 adopt an octahedral coordination environment, bridged by phenolate oxygen and nitrate ligands. The Cu ions in 2 are square pyramidal and square planar, and the Zn ions in 3 are square pyramidal and octahedral. The metal atoms in 2 and 3 are bridged by phenolate oxygen donors. The Mo ion in 4 is octahedral. The Schiff base ligand coordinates to the metal atoms through two phenolate O and two imino N donors. Biological assays revealed that the nickel and copper complexes have effective urease inhibition.

Lanthanide complexes of monosubstituted Calix[4]arene-ligands: Synthesis, structures, and magnetic properties of [Ln2(L)2(MeOH)4] (Ln = La, Gd, Tb, Tm) (H3L = mono-O-propargyl-calix[4]arene)

The ability of the propargylated calix[4]arene ligand H3L (= 25-(2-propynyloxy)-26,27,28-trihydroxy-calix[4]arene) to bind lanthanide ions has been studied. The triply deprotonated ligand was found to support dinuclear neutral complexes of composition [Ln2L2(MeOH)4] (Ln= La (1), Gd (2), Tb (3), Tm (4)). Spectroscopic data for 1–4 as well as X-ray crystallographic analysis of single crystals of 1∙(MeOH)2 and 2∙(MeOH)2 reveal that two [LnL] entities dimerize via two phenolato groups to generate a centrosymmetric (MeOH)2O3Ln(μ-O)2LnO3(OHMe)2 core structure. The Ln3+ ions reside in a distorted mono-capped octahedral coordination environment. Squid magnetic measurements for the Gd3+ and Tb3+ complexes agree with the formulation as dinuclear compounds, and reveal the presence of very weak antiferromagnetic exchange interactions (J < 0.1 cm−1). The ability of the La3+ complex to react with azides in a click reaction is also demonstrated.

Multi-color luminescent material with Mn2+/Mn4+ non-stoichiometric ratio doped octahedra and its anti-counterfeiting applications

Mn ions in different valence states can emit light of different colors in an octahedral coordination environment, which is conducive to the development of a single matrix with multi-color luminescence and applications in the field of anti-counterfeiting. The dual mode multi-color luminescent material CaSb2O6: Mn has been successfully synthesized using a single Mn source in the atmosphere. The CaSb2O6 matrix itself can also absorb 285 nm UV light, emit blue light, and show a long afterglow phenomenon. Both Mn4+ and Mn2+ ions will appear in the [SbO6] octahedra, whether the Mn source adopts MnCO3 or MnO2. The Mn4+ ion exhibits red emission upon UV excitation at 347 nm. The Mn2+ ion can emit a bright green light at 285 nm excitation while exhibiting a long afterglow phenomenon. In this study, the Mn2+ doped octahedron showed unique green emission and broadens the range of its photoluminescence (PL) wavelength. The performance of the material's long afterglow properties on the digital codes demonstrates its potential for dynamic anti-counterfeiting.

Inducing Ferrimagnetic Exchange in 1D-FeSe2 Chains Using Heteroleptic Amine Complexes: [Fe(en)(tren)][FeSe2]2.

[Fe(en)(tren)][FeSe2]2 (en = ethylenediamine, C2H8N2, tren = tris(2-aminoethyl)amine, C6H18N4) has been synthesized by a mixed-ligand solvothermal method. Its crystal structure contains heteroleptic [Fe(en)(tren)]2+ complexes with distorted octahedral coordination, incorporated between 1D-FeSe2 chains composed of edge-sharing FeSe4 tetrahedra. The twisted octahedral coordination environment of the Fe-amine complex leads to partial dimerization of Fe-Fe distances in the FeSe2 chains so that the FeSe4 polyhedra deviate strongly from the regular tetrahedral geometry. 57Fe Mössbauer spectroscopy reveals oxidation states of +3 for the Fechain atoms and +2 for the Fecomplex atoms. The close proximity of Fe atoms in the chains promotes ferromagnetic nearest neighbor interactions, as indicated by a positive Weiss constant, θ = +53.8(6) K, derived from the Curie-Weiss fitting. Magnetometry and heat capacity reveal two consecutive magnetic transitions below 10 K. DFT calculations suggest that the ordering observed at 4 K is due to antiferromagnetic intrachain interactions in the 1D-FeSe2 chains. The combination of two different ligands creates an asymmetric coordination environment that induces changes in the structure of the Fe-Se fragments. This synthetic strategy opens new ways to explore the effects of ligand field strength on the structure of both Fe-amine complexes and surrounding Fe-Se chains.

Substituent effects on spin-crossover Fe(II)N4O2 pyrenylhydrazone complexes.

Multifunctional magnetic materials have broad application prospects in molecular switches and information storage. In this study, four mononuclear Fe(II) complexes are synthesized using a series of pyrenylhydrazone ligands HL1-4. Two deprotonated ligands are coordinated to the iron(II) ions in an enolic form, leading to neutral complexes FeII(Lx)2·xsol with a FeIIN4O2 octahedral coordination environment. Magnetic measurements suggest that complex Fe(L1)2·2ACE (1·2ACE, ACE = acetone) is mainly low spin below 300 K and complex Fe(L3)2·ACE (3·ACE) is high spin, whereas complexes Fe(L2)2 (2) and Fe(L4)2·6H2O (4·6H2O) exhibit gradual spin crossover behavior. The spin states of complexes 1-4 are confirmed by single-crystal X-ray diffraction analysis. The substituent effect on the magnetic properties of the complexes is significant in this system. Temperature-dependent fluorescence emission spectra show the coexistence but no coupling effect of spin crossover and fluorescence for complexes 2 and 4·6H2O.

Anomalous Pressure Response of Temperature-Induced Spin Transition and a Pressure-Induced Spin Transition in Two-Dimensional Hofmann Coordination Polymers.

Spin transition (ST) compounds have been extensively studied because of the changes in rich physicochemical properties accompanying the ST process. The study of ST mainly focuses on the temperature-induced spin transition (TIST). To further understand the ST, we explore the pressure response behavior of TIST and pressure-induced spin transition (PIST) of the 2D Hofmann-type ST compounds [Fe(Isoq)2M(CN)4] (Isoq-M) (M = Pt, Pd, Isoq = isoquinoline). The TISTs of both Isoq-Pt and Isoq-Pd compounds exhibit anomalous pressure response, where the transition temperature (T1/2) exhibits a nonlinear pressure dependence and the hysteresis width (ΔT1/2) exhibits a nonmonotonic behavior with pressure, by the synergistic influence of the intermolecular interaction and the distortion of the octahedral coordination environment. And the distortion of the octahedra under critical pressures may be the common behavior of 2D Hofmann-type ST compounds. Moreover, ΔT1/2 is increased compared with that before compression because of the partial irreversibility of structural distortion after decompression. At room temperature, both compounds exhibit completely reversible PIST. Because of the greater change in mechanical properties before and after ST, Isoq-Pt exhibits a more abrupt ST than Isoq-Pd. In addition, it is found that the hydrostatic properties of the pressure transfer medium (PTM) significantly affect the PIST due to their influence on spin-domain formation.

Synthesis, crystal structure and Hirshfeld surface analysis of diaquabis(o-phenylenediamine-κ2 N,N′)nickel(II) naphthalene-1,5-disulfonate

The reaction of o-phenylenediamine (OPD), sodium naphthalene1,5-disulfonate (Na2NDS) and nickel sulfate in an ethanol–water mixture yielded the title compound, [Ni(OPD)2(H2O)2]·NDS or [Ni(C6H8N2)2(H2O)2](C10H6O6S2). This salt consists of a complex [Ni(OPD)2(H2O)2]2+ cation with two bidentate OPD ligands and trans aqua ligands, and a non-coordinating NDS2– anion, which is the double-deprotonated form of H2NDS. The NiII atom is situated at a center of inversion and exhibits a slightly tetragonally distorted {O2N4} octahedral coordination environment, with four shorter equatorial Ni—N bonds [2.0775 (17) and 2.0924 (18) Å] and a longer axial Ni—O bond [2.1381 (17) Å]. The OPD ligand is located about an inversion center and is nearly coplanar with the NiN4 plane [dihedral angle 0.95 (9)°]. In the crystal, the cations and anions are connected by charge-assisted intermolecular N—H...O and O—H...O hydrogen-bonding interactions into the tri-periodic network structure. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H...H (44.1%), O...H/H...O (34.3%), C...H/H...C (14.8%) C...C (6.5%) (involving the cations) and O...H/H...O (50%), H...H (25%), C...H/H...C (15.3%), C...C (8.2%) (involving the anions) interactions.

Tetravalent Terbium Chelates: Stability Enhancement and Property Tuning.

Coordination chemistry of rare-earth elements has been dominated by the +3 oxidation state. Complexes with higher-valence lanthanide ions are synthetically challenging but are of fundamental research interest and significance as advanced molecular materials. Herein, four tetravalent terbium complexes (2-5) of the common formula [Tb(OSiPh3)4L] (L = ethylene glycol dimethyl ether (DME), 2,2'-bipyridine (bpy), 2,2'-bipyrimidine (bpym), and 1,10-phenanthroline (phen)) are reported. Crystallographic analyses reveal in each of these complexes a hexacoordinate Tb(IV) ion situated in a distorted octahedral coordination environment formed by four triphenylsiloxido ligands and a bidentate chelating ligand. The use of chelating ligands enhances the stability of the resulting complexes over their THF solvate precursor. More significantly, the aromatic N-chelating ligands have been found to tune effectively the electronic structures of the complexes, as evidenced by the sizable potential shifts observed for the quasi-reversible redox Tb(IV/III) process and by the changes in their absorption spectra. The experimental findings are augmented with quantum theoretical calculations in which the ligand π-donation to the 5d orbitals of the Tb(IV) center is found to be primarily responsible for stability enhancement and the corresponding changes of physical properties observed. Magnetic measurements and results from electron paramagnetic resonance studies produced small absolute values of zero-field splittings of these complexes, ranging from 0.1071(22) to 1.1484(112) cm-1 and comparable to the values reported for analogous Tb(IV) complexes.

Structural and computational studies on a quenchable high-temperature polymorph of magnesium tungstate (MgWO4-II)

Single-crystals of a quenchable high-temperature polymorph of magnesium tungstate (MgWO4-II) have been grown using the flux method. Polycrystalline material of the same compound could be obtained from solid-state reactions performed at 1200 °C. Basic crystallographic data of the previously unknown modification are as follows: space group P1‾, a = 6.5525(6) Å, b = 7.5883(7) Å, c = 7.6976(6) Å, α = 119.064(9)°, β = 95.545(7)°, γ = 107.645(8)°, V = 304.84(5)3 Å and Z = 4. The crystal structure was solved from single-crystal diffraction using direct methods and refined to a residual value of R1 = 2.16%. Both cation species exhibit an octahedral oxygen coordination environment. By sharing common edges and corners, the octahedra form a three-dimensional network, which can be built from infinite rod-like elements running along [010] having a 2 × 2 octahedra wide cross section. MgWO4-II is topologically equivalent to the VO2(HT) structure-type. A detailed analysis of the relationships with other ABO4-compounds is presented. Solid-state characterization has been supplemented by micro-Raman spectroscopy. Interpretation of the spectroscopic data, including the allocation of the bands to certain vibrational species, has been aided by DFT-calculations. The thermal expansion tensor between ambient temperature and about 700 °C has been determined. The calculations indicate quasi-two-dimensional expansion behavior.

Pyrovskite: A software package for the high-throughput construction, analysis, and featurization of two- and three-dimensional perovskite systems.

The increased computational and experimental interest in perovskite systems comprising novel phases and reduced dimensionality has greatly expanded the search space for this class of materials. In similar fields, unified frameworks exist for the procedural generation and subsequent analysis of these complex condensed matter systems. Given the relatively recent rise in popularity of these novel perovskite phases, such a framework is yet to be created. In this work, we introduce Pyrovskite, an open source software package, to aid in both the high-throughput and fine-grained generation, simulation, and subsequent analysis of this expanded family of perovskite systems. Additionally, we introduce a new descriptor for octahedral distortions in systems, including, but not limited to, perovskites. This descriptor quantifies diagonal displacements of the B-site cation in a BX6 octahedral coordination environment, which has been shown to contribute to increased Rashba-Dresselhaus splitting in perovskite systems.

Supramolecular Structure and Antimicrobial Activity of Ni(II) Complexes with s-Triazine/Hydrazine Type Ligand

The two complexes, [Ni(DPPT)2](NO3)2*1.5H2O (1) and [Ni(DPPT)(NO3)Cl].EtOH (2), were synthesized using the self-assembly of (E)-2,4-di(piperidin-1-yl)-6-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)-1,3,5-triazine (DPPT) with Ni(NO3)2*6H2O in the absence and presence of NiCl2*6H2O, respectively. In both cases, the neutral tridentate DPPT ligand is found coordinated to the Ni(II) via three N-atoms from the hydrazone, pyridine and s-triazine rings. Hence, the homoleptic complex 1 has a NiN6 hexa-coordination environment while two NO3− are counter anions in addition to one-and-a-half crystallized hydration water molecules are found acting as an outer sphere. The heteroleptic complex 2 has a NiN3O2Cl coordination sphere where the coordination environment of the Ni(II) is completed by one bidentate nitrate and one chloride ion leading to a neutral inner sphere while the outer sphere contains one crystallized ethanol molecule. Both complexes have distorted octahedral coordination environments around the Ni(II) ion. Using Hirshfeld analysis, the intermolecular contacts H…H and O…H in 1 and the Cl…H, O…H, N…H, H…H, C…H and C…C in 2 are found to be the most important for crystal stability. The antimicrobial activity of complexes 1 and 2 was assessed against different bacterial and fungal strains, and the results were compared with the free ligand as well as the antibacterial (Gentamycin) and antifungal (Ketoconazole) positive controls. Both Ni(II) complexes are better antibacterial and antifungal agents than the free ligand. Interestingly, both Ni(II) complexes have similar antifungal activity against C. albicans compared to Ketoconazole.

Structural and Magnetic Properties of the {Cr(pybd)3[Cu(cyclen)]2}(BF4)4 Heteronuclear Complex

Heterotopic ligands containing chemically different binding centers are appealing candidates for obtaining heteronuclear metal complexes. By exploiting this strategy, it is possible to introduce different paramagnetic centers characterized by specific anisotropic magnetic properties that make them distinguishable when weakly magnetically coupled. This molecular approach has great potential to yield multi-spin adducts capable of mimicking logical architectures necessary for quantum information processing (QIP), i.e., quantum logic gates. A possible route for including a single-ion magnetic center within a finite-sized heterometallic compound uses the asymmetric (1-pyridyl)-butane-1,3-dione (pybd) ligand reported in the literature for obtaining Cr3+−Cu2+ metallo-cages. To avoid the formation of cages, we adopted the cyclen (1,4,7,10-tetraazacyclododecane) ligand as a “capping” agent for the Cu2+ ions. We report here the structural and magnetic characterization of the unprecedented adduct {Cr(pybd)3[Cu(cyclen)]2}(BF4)4, whose structure is characterized by a central Cr3+ ion in a distorted octahedral coordination environment and two peripheral Cu2+ ions with square-pyramidal coordination geometries. As highlighted by Continuous Wave Electron Paramagnetic Resonance (EPR) spectroscopy and Direct Current (DC) magnetometry measurements, this adduct shows negligible intramolecular magnetic couplings, and it maintains the characteristic EPR signals of Cr3+ and Cu2+ moieties when diluted in frozen solutions.

Anion effect on crystal structure of Zn-complexes of spironaphthopyran and their chromogenic properties in solution

Effect of the anion nature on crystal structure of Zn-complexes of spironaphthopyran and their chromogenic properties in solution were studied. Complexes with zinc chloride and zinc picrate exhibited tertahedral and octahedral coordination environment of the metal ion respectively. The structure of the complex with zinc picrate demonstrates a rare example of the co-crystallization of two types of complexes differing in the number of coordinated picrate anions. The composition, stability, and absorption properties of zinc complexes in acetone essentially depend on the counter anion nature. When the coordinating ability of the counter ion increases in the range BF4−, ClO4−, NO3–, Pic−, I−, Cl−, CH3COO–, (CH3)3CCOO– the complex stability is reduced from logK = 8.7 to 2.96. This is accompanied by the chromogenic effect which is related to the decrease in the spectral shift of the long-wavelength absorption band of the complex relative to the merocyanine ligand from 846 up to 168 cm−1. The complex photo-initiated processes include fluorescence and thermally reversible dissociation. Fluorescence is characterized by band maxima in the 622–637 nm region and normal Stokes shifts of 1087–1454 cm−1 with an efficiency being weakly dependent on the anion nature. In contrast, the negative photochromism of the complexes demonstrates a significant dependence of the photo-bleaching efficiency on the anion nature in the range 0.012–0.17. The presence of a chromogenic photochromic effect along with fluorescence makes it possible to consider the complex as fluorescent switch.

Steric hindrance, ligand ejection and associated photocytotoxic properties of ruthenium(II) polypyridyl complexes

Two ruthenium(II) polypyridyl complexes were prepared with the {Ru(phen)2}2+ moiety and a third sterically non-hindering bidentate ligand, namely 2,2′-dipyridylamine (dpa) and N-benzyl-2,2′-dipyridylamine (Bndpa). Hence, complexes [Ru(phen)2(dpa)](PF6)2 (1) and [Ru(phen)2(Bndpa)](PF6)2 (2) were characterized and their photochemical behaviour in solution (acetonitrile and water) was subsequently investigated. Compounds 1 and 2, which do not exhibit notably distorted octahedral coordination environments, contrarily to the homoleptic “parent” compound [Ru(phen)3](PF6)2, experience two-step photoejection of the dpa and Bndpa ligand upon irradiation (1050–430 nm) for several hours. DNA-binding studies revealed that compounds 1 and 2 affect the biomolecule differently upon irradiation; while 2 solely modifies its electrophoretic mobility, complex 1 is also capable of cleaving it. In vitro cytotoxicity studies with two cancer-cell lines, namely A549 (lung adenocarcinoma) and A375 (melanoma), showed that both 1 and 2 are not toxic in the dark, while only 1 is significantly cytotoxic if irradiated, 2 remaining non-toxic under these conditions.Graphical abstractLight irradiation of the complex cation [Ru(phen)2(dpa)]2+ leads to the generation of transient Ru species that is present in the solution medium for several hours, and that is significantly cytotoxic, ultimately producing non-toxic free dpa and [Ru(phen)(OH2)2]2+.

CRYSTAL AND MOLECULAR STRUCTURE OF THE ISLAND TETRANUCLEAR DIOXOMOLYBDENUM(VI) COMPLEX [MoO&lt;sub&gt;2&lt;/sub&gt;(&lt;i&gt;L&lt;/i&gt;&lt;sup&gt;1&lt;/sup&gt;)]&lt;sub&gt;4&lt;/sub&gt; (H&lt;sub&gt;2&lt;/sub&gt;&lt;i&gt;L&lt;/i&gt;&lt;sup&gt;1&lt;/sup&gt; IS ACETYLACETONE ISONICOTINOYLHYDRAZONE) WITH LARGE INTRA- AND INTERMOLECULAR CHANNELS

The solvated complex [МоО2(L1)]4dimethylformamide (I) was synthesized. Its structure wasdetermined by X-ray diffraction analysis. The crystal structure is composed of the tetranuclear complexes [МоО2(L1)]4 (Ia) as the structural units lying on crystallographic twofold axes. Both crystallographically independent molybdenum atoms are in a distorted octahedral coordination environment formed by two cis-О(oxo) ligands, two N(L1) atoms of two molecules Ia in trans positions to the О(oxo) ligands, and two О(L1) atoms of one complex molecule in cis positions to О(oxo) and trans to each other. Each (L1)2– ligand is coordinated to two Мо atoms in a tetradentate tridentate-chelating (2О, N) bridging (N) mode. The average bond lengths in complex Iа are as follows: Мо–О(oxo), 1.701 Å; Мо–N(L1), 2.460 (b) and 2.214 Å (c); Мо–О(L1), 1.980 Å. The О(oxo)–МоО–(oxo) bond angle is 105.6°. The ordered dimethylformamide molecule is located in a narrow channel in the structure. The strongly disordered (non-located) solvent molecules (methanol/dimethylformamide/water) occupy wide channels in the structure of I.