Single-crystal Synchrotron X-ray Diffraction Research Articles

Electronic Structure of a Single-Component Molecular Conductor [Pd(dddt)2] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) under High Pressure

We examined high-pressure electronic structure of a single-component molecular conductor [Pd(dddt)$_2$] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) at room temperature, based on the crystal structure determined by single crystal synchrotron X-ray diffraction measurements at 5.9 GPa. The monoclinic unit cell contains four molecules that form two crystallographically independent molecular layers. A tight-binding model of 8 $\times$ 8 matrix Hamiltonian gives an electronic structure as a Dirac electron system. The Dirac point describes a loop within the first Brillouin zone, and a nodal line semimetal is obtained. The noticeable property of the Dirac cone with a linear dispersion is shown by calculating density of states (DOS). The Dirac cone in this system is associated with the crossing of HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) bands, which originates from the direct interaction between different molecular layers. This is a newly found mechanism in addition to the indirect one [J. Phys. Soc. Jpn., {\bf 86}, 064705 (2017)]. The Dirac points emerge as a line, when the HOMO and LUMO bands meet on the surface and the HOMO-LUMO couplings are absent. Such a mechanism is verified using a reduced model of 4 $\times$ 4 matrix Hamiltonian. The deviation of the band energy ($\delta E$) at the Dirac point from the Fermi level is very small ($\delta E < $ 0.4meV). The nodal line is examined by calculating the parity of the occupied band eigen states at TRIM (Time Reversal Invariant Momentum) showing that the topological number is 1.

Crystal Structure and Non-Hydrostatic Stress-Induced Phase Transition of Urotropine Under High Pressure.

High-pressure behavior of hexamethylenetetramine (urotropine) was studied in situ using angle-dispersive single-crystal synchrotron X-ray diffraction (XRD) and Fourier-transform infrared absorption (FTIR) spectroscopy. Experiments were conducted in various pressure-transmitting media to study the effect of deviatoric stress on phase transformations. Up to 4 GPa significant damping of molecular librations and atomic thermal motion was observed. A first-order phase transition to a tetragonal structure was observed with an onset at approximately 12.5 GPa and characterized by sluggish kinetics and considerable hysteresis upon decompression. However, it occurs only in non-hydrostatic conditions, induced by deviatoric or uniaxial stress in the sample. This behavior finds analogies in similar cubic crystals built of highly symmetric cage-like molecules and may be considered a common feature of such systems. DFT computations were performed to model urotropine equation of state and pressure dependence of vibrational modes. The first successful Hirshfeld atom refinements carried out for high-pressure diffraction data are reported. The refinements yielded more realistic C-H bond lengths than the independent atom model even though the high-pressure diffraction data are incomplete.

Constraining the density evolution during destruction of the lithospheric mantle in the eastern North China Craton

The thermoelastic properties of minerals in mantle xenoliths combined with the thermal states can provide an integrated understanding of the petrophysics of the lithospheric mantle. Here, we conducted high-pressure and high-temperature experiments on the main minerals (e.g. olivine, orthopyroxene, clinopyroxene, spinel, and garnet) in peridotite xenoliths from basalt of the eastern North China Craton (NCC) using in situ synchrotron single-crystal X-ray diffraction combined with diamond anvil cells. The pressure-temperature-volume data were fitted to the third-order Birch-Murnaghan equations of state and yielded the thermoelastic parameters that included bulk modulus, pressure and temperature derivatives, and thermal expansion coefficients. The density profiles of the eastern NCC during the destruction process since the Mesozoic are presented from the temporal and spatial aspects. The lithospheric density dramatically decreased during destruction, and high heat flow may have been a trigger. The spatially distributed density profile also provides firm evidence for lateral heterogeneities in the eastern NCC. This may suggest that the present mantle is characterized by heterogeneous destruction of the NCC.

High-pressure sapphire capillary cell for synchrotron single-crystal X-ray diffraction measurements to 1500 bar

A new sapphire capillary pressure cell for single-crystal X-ray diffraction measurements at moderate pressures (200−1500 bar; 1 bar = 100 kPa) has been developed and optimized for use on beamline I19 at Diamond Light Source. The three-component cell permits optical centring of the crystal andin situpressure modification to a precision of 1 bar. Compression of hexamethylenetetramine and its deuterated analogue to 1000 bar was performed, showcasing the accuracy and precision of the measurements, and highlighting evidence of a geometric isotope effect.

Thermal and compressional behavior of the natural borate kurnakovite, MgB3O3(OH)5·5H2O

The thermal and compressional behaviors of kurnakovite, a potential B-rich aggregate in neutron radiation-shielding concretes, were studied by in situ single-crystal synchrotron X-ray diffraction (100–393 K, 0–13.36(5) GPa). Above 393 K, the crystal structure collapses in response to dehydration. The bulk thermal expansion coefficient is αV(298K) = 5.18(1)∙10−5 K−1. Volume compressional trend modelled with a Birch-Murnaghan equation of state yields a bulk modulus of KP0,T0 = 35(3) GPa. A phase transition occurs between 9.23(5) and 11.11(5) GPa, leading to a triclinic high-P polymorph (with triple unit-cell volume) and to an increase in coordination of one third of the trigonal-planar boron sites to a tetrahedral geometry.

Charge density of difluorides from synchrotron diffraction data and investigation of bonding in low valent binary fluorides

The experimental charge density analysis of two isostructural transition metal difluorides, CoF2 and NiF2 has been performed using single crystal synchrotron X-ray diffraction data. The multipole and MEM models of electron density and the thermal vibration parameters suggest that the difluoride of nickel is a hard molecule with more shared shell interaction nature than the difluoride of cobalt. In the course of study, a comparative study on fluorine bonding in low valent binary fluorides with metal cations of oxidation states, ranging from +1 to +3 have been accomplished and thoroughly analysed. The explored topological features derived from the Bader's theory of Atoms In Molecules (AIM) approach reveals the existence of ionic nature of bonding at +1 valence state of metal, as viewed in LiF and NaF and as the oxidation on metals ascends, intermediate interaction with increase in covalent nature is evidenced.

High-pressure behaviour and phase stability of Ca2B6O6(OH)10·2(H2O) (meyerhofferite)

The high-pressure behaviour of meyerhofferite [ideally Ca2B6O6(OH)10·2(H2O), with a ~ 6.63 Å, b ~ 8.34 Å, c ~ 6.47 Å, α = 90.8°, β = 102°, γ = 86.8°, Sp. Gr. P\(\overline{1}\)], a B-bearing raw material (with B2O3 ≈ 46 wt%) and a potential B-rich aggregate, has been studied by single-crystal synchrotron X-ray diffraction up to 9 GPa, under hydrostatic conditions. Meyerhofferite undergoes a first-order phase transition to meyerhofferite-II, likely iso-symmetric, bracketed between 3.05 and 3.48 GPa, with a spectacular unit-cell volume discontinuity (i.e., ΔV ~ 30 Å3). The isothermal bulk modulus (KV0 = β−1P0,T0, where βP0,T0 is the volume compressibility coefficient) of meyerhofferite, was found to be KV0 = 31.6(5) GPa, and a marked anisotropic compressional pattern, with K(a)0: K(b)0: K(c)0 ~ 1.5:1:3, was observed. The bulk modulus of meyerhofferite-II increases to 55(2) GPa and, differently to the majority of the borates studied at high pressure so far, the anisotropic compressional pattern of meyerhofferite decreases markedly in the high-pressure form. The P-induced deformation mechanisms controlling, at the atomic scale, the bulk compression of meyerhofferite are here described. Considerations about the use of meyerhofferite as a potential B-based aggregate in concretes, mortars or resins, are provided.

Pressure-Induced Polymerization of Polycyclic Arene-Perfluoroarene Cocrystals: Single Crystal X-ray Diffraction Studies, Reaction Kinetics, and Design of Columnar Hydrofluorocarbons.

Pressure-induced polymerization of aromatic compounds leads to novel materials containing sp3 carbon-bonded networks. The choice of the molecular species and the control of their arrangement in the crystal structures via intermolecular interactions, such as the arene-perfluoroarene interaction, can enable the design of target polymers. We have investigated the crystal structure compression and pressure-induced polymerization reaction kinetics of two polycyclic 1:1 arene-perfluoroarene cocrystals, naphthalene/octafluoronaphthalene (NOFN) and anthracene/octafluoronaphthalene (AOFN), up to 25 and 30 GPa, respectively, using single-crystal synchrotron X-ray diffraction, infrared spectroscopy, and theoretical computations based on density-functional theory. Our study shows the remarkable pressure stability of the parallel arene-perfluoroarene π-stacking arrangement and a reduction of the interplanar π-stacking separations by ca. 19-22% before the critical reaction distance is reached. A further strong, discontinuous, and irreversible reduction along the stacking direction at 20 GPa in NOFN (18.8%) and 25 GPa in AOFN (8.7%) indicates the pressure-induced breakdown of π-stacking by formation of σ-bonded polymers. The association of the structural distortion with the occurrence of a chemical reaction is confirmed by a high-pressure kinetic study using infrared spectroscopy, indicating one-dimensional polymer growth. Structural predictions for the fully polymerized high-pressure phases consisting of highly ordered rods of hydrofluorocarbons are presented based on theoretical computations, which are in excellent agreement with the experimentally determined unit-cell parameters. We show that the polymerization takes place along the arene-perfluoroarene π-stacking direction and that the lateral extension of the columns depends on the extension of the arene and perfluoroarene molecules.

Novel sulfur hydrides synthesized at extreme conditions

The sulfur-hydrogen system is the first one in which superconductivity at temperatures over 200 K has been reported, albeit at high pressure. The particular phases causing the measured ${T}_{c}$ and their structures are not yet firmly identified. Here, synchrotron single-crystal x-ray diffraction studies of S-H samples were performed up to 150 GPa and revealed two previously unobserved and unpredicted sulfur-hydrogen phases---${\mathrm{H}}_{6\ifmmode\pm\else\textpm\fi{}x}{\mathrm{S}}_{5}$ with $x\ensuremath{\sim}0.4$, and ${\mathrm{H}}_{2.85\ifmmode\pm\else\textpm\fi{}y}{\mathrm{S}}_{2}$ with $y\ensuremath{\sim}0.35$. The crystallographic data obtained in this work, both for the new phases and for the previously identified ${\mathrm{H}}_{3}\mathrm{S}$ polymorphs, provide an unambiguous experimental proof of the chemical richness of the S-H system and the structural diversity of compounds forming at high pressures and high temperatures. Our results have profound implications for the interpretation of the resistance, superconductivity, and other physical properties measurements on the complex S-H system.

Quantification of the Magnetic Anisotropy of a Single-Molecule Magnet from the Experimental Electron Density.

Reported here is an entirely new application of experimental electron density (EED) in the study of magnetic anisotropy of single-molecule magnets (SMMs). Among those SMMs based on one single transition metal, tetrahedral CoII-complexes are prominent, and their large zero-field splitting arises exclusively from coupling between the d and dxy orbitals. Using very low temperature single-crystal synchrotron X-ray diffraction data, an accurate electron density (ED) was obtained for a prototypical SMM, and the experimental d-orbital populations were used to quantify the dxy-d coupling, which simultaneously provides the composition of the ground-state Kramers doublet wave function. Based on this experimentally determined wave function, an energy barrier for magnetic relaxation in the range 193-268 cm-1 was calculated, and is in full accordance with the previously published value of 230 cm-1 obtained from near-infrared spectroscopy. These results provide the first clear and direct link between ED and molecular magnetic properties.

U(H2O)2]{[(UO2)10O10(OH)2][(UO4)(H2O)2]}: A Mixed-Valence Uranium Oxide Hydrate Framework

A uranium oxide hydrate framework, [U(H2O)2]{[(UO2)10O10(OH)2][(UO4)(H2O)2]} (UOF1), was synthesized hydrothermally using schoepite as a uranium precursor. The crystal strucutre of UOF1 was revealed with synchrotron single-crystal X-ray diffraction and confirmed with transmission electron miscroscopy. The typical uranyl oxide hydroxide layers similar to those in β-U3O8 are further connected via double-pentagonal-bipyramidal uranium polyhedra to form a three-dimensional (3D) framework structure with tetravalent uranium species inside the channels. The presence of mixed-valence uranium was investigated with a combination of X-ray absorption near-edge structure and diffuse reflectance spectroscopy. Apart from the major hexavalent uranium, evidence for tetravalent uranium was also found, consistent with the bond valence sum calculations. The successful preparation of UOF1 as the first pure uranium oxide hydrate framework sheds light on the structural understanding of the alteration of UO2+x as either a mineral or spent nuclear fuel.

An in-situ x-ray diffraction and infrared spectroscopic study of the dehydration of AlPO4-54

The dehydration of the large pore aluminophosphate AlPO4-54•xH2O was studied in situ as a function of vacuum pressure at room temperature by infrared spectroscopy and x-ray diffraction. On polycrystalline samples, under primary vacuum, the adsorbed water is removed very rapidly. The structural water in the AlO6 octahedra is then removed slowly with the quantity of the fully dehydrated form gradually increasing from 43 to 65% of the total material. This results in a two-phase mixture of fully dehydrated and a distinct partially dehydrated AlPO4-54•1/2H2O phase containing structural water. These phases have almost identical a cell parameters and very close c parameters. Secondary vacuum increases the amount of fully dehydrated material to more than 76%. Prolonged heating under vacuum increases the amount of fully dehydrated material to 90%. On single crystal samples, removal of adsorbed water is slower and results in a reduction in crystal quality, however prolonged exposure to primary vacuum yielded fully dehydrated material without the need for heating. The monoclinic structure of anhydrous AlPO4-54, space group Cm, with a doubled unit cell was confirmed using single crystal synchrotron x-ray diffraction data.

High-Pressure Polymeric Nitrogen Allotrope with the Black Phosphorus Structure.

Studies of polynitrogen phases are of great interest for fundamental science and for the design of novel high energy density materials. Laser heating of pure nitrogen at 140GPa in a diamond anvil cell led to the synthesis of a polymeric nitrogen allotrope with the black phosphorus structure, bp-N. The structure was identified insitu using synchrotron single-crystal x-ray diffraction and further studied by Raman spectroscopy and density functional theory calculations. The discovery of bp-N brings nitrogen in line with heavier pnictogen elements, resolves incongruities regarding polymeric nitrogen phases and provides insights into polynitrogen arrangements at extreme densities.

The seismically fastest chemical heterogeneity in the Earth's deep upper mantle—implications from the single-crystal thermoelastic properties of jadeite

Jadeite is a major mineral phase (up to 50 vol%) in the subducted sediments/crust with continental origin, which are one of the major heterogeneities and important enriched geochemical reservoirs (such as EM-1 and EM-2) for incompatible elements in the Earth's interior. Identifying and locating the enriched geochemical heterogeneities requires knowledge of the elastic properties of relevant mineral phases at high pressure-temperature conditions. Unfortunately, the single-crystal elastic properties of jadeite have never been measured at high-pressure conditions, partially due to its low crystal symmetry. In this study, we have experimentally determined the single-crystal elastic moduli of jadeite at high pressures for the first time up to 18 GPa at the ambient temperature condition using Brillouin spectroscopy. Fitting the third-order finite strain equation of state to the velocity-pressure data yields KS0′=3.9(1), G0′=1.09(4) with ρ0=3.302(5) g/cm3, KS0=138(3) GPa, and G0=84(2) GPa. In addition, we have also conducted synchrotron single-crystal X-ray diffraction experiments up to 25 GPa and 700 K. The fitting of a Holland-Powell type thermal-pressure Birch-Murnaghan equation of state yields KT0′=3.8(2) and α0=3.4(5) ×10−5 K−1. Based on the obtained thermoelastic parameters of jadeite, the density and seismic velocities of continent-derived sediments/crust are modeled at the depth range from 200 to 500 km. The seismic velocities of the subducted continental sediments/crust become extremely fast at depths greater than ∼300 km, up to 11.8% and 14.7% faster than the Vp and Vs of the ambient mantle, and 5.6% and 7.3% faster than the Vp and Vs of the subducted oceanic crust. The existence of even a small amount of the subducted continental sediments/crust can result in strong seismic anomalies in the Earth's interior.

Synthesis and single-crystal structure of sodium sulfide cationic cluster in the sodalite cavity of zeolite Y (FAU, Si/Al = 1.56)

The extraframework sodium sulfide cationic cluster, Na4S2+, has been introduced into zeolite Y (FAU, Si/Al = 1.56). A single crystal of |Na73(Na4S2+)1.0|[Si117Al75O384]-FAU was prepared by allowing aqueous 0.1 M Na2S solution to flow past a |Na75|[Si117Al75O384]-FAU crystal, and followed by vacuum dehydration at 723 K. Its structure was determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd $$\overline{3}$$ m. The structure was refined using all intensities to the final error index R1/wR2 = 0.044/0.125. About 77 Na+ ions per unit cell are found at the crystallographically distinct positions, six. One Na+ ion per unit cell is at the center of double 6-ring. Two site-I′ positions are occupied by 26.5 and 4 Na+ ions, respectively, per unit cell. Thirty-two Na+ ions per unit cell are found at site II, in the supercage opposite single 6-rings. The remaining 4.5 and 9 Na+ ions per unit cell occupy two sites III′ near triple 4-rings in the supercage. Finally, one sulfide ion per unit cell, associated with Na+ ions, is found at the center of sodalite cavity. The 4 Na+ ions at site I′ coordinate to a sulfide ion at the center of sodalite cavity to give tetrahedral cationic cluster, Na4S2+. In |Na73(Na4S2+)1.0|[Si117Al75O384]-FAU, tetrahedral Na4S2+ ions center about 12.5% of the sodalite cavities.

Synthesis, crystal structure, polymorphism and microscopic luminescence properties of anthracene derivative compounds

Anthracene derivative compounds are currently investigated because of their unique physical properties (e.g. bright luminescence and emission tunability), which make them ideal candidates for advanced optoelectronic devices. Intermolecular interactions are the basis of the tunability of the optical and electronic properties of these compounds, whose prediction and exploitation benefit from knowledge of the crystal structure and the packing architecture. Polymorphism can occur due to the weak intermolecular interactions, requiring detailed structural analysis to clarify the origin of observed material property modifications. Here, two silylethyne-substituted anthracene compounds are characterized by single-crystal synchrotron X-ray diffraction, identifying a new polymorph in the process. Additionally, laser confocal microscopy and fluorescence lifetime imaging microscopy confirm the results obtained by the X-ray diffraction characterization, i.e. shifting the substituents towards the external benzene rings of the anthracene unit favours π-π interactions, impacting on both the morphology and the microscopic optical properties of the crystals. The compounds with more isolated anthracene units feature shorter lifetime and emission spectra, more similar to those of isolated molecules. The crystallographic study, supported by the optical investigation, sheds light on the influence of non-covalent interactions on the crystal packing and luminescence properties of anthracene derivatives, providing a further step towards their efficient use as building blocks in active components of light sources and photonic networks.

Large anisotropic negative thermal expansion in Cu-TDPAT metal-organic framework: A combined in situ X-ray diffraction and DRIFTS study

Cu-TDPAT (H6TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine), a stable nanoporous metal-organic framework with rht topology, has sparked broad interest as an adsorbent for several chemical separation processes. In this work, in situ synchrotron diffraction experiments followed by sequential LeBail refinements reveal that Cu-TDPAT shows unusually large anisotropic negative thermal expansion (NTE). The PASCal crystallography tool, used to analyze the magnitude of the NTE, reveals an average volumetric thermal expansion coefficient αv = −20.3 MK−1. This value is significantly higher than the one reported for Cu-BTC (also known as HKUST-1), which contains the same Cu-paddlewheel building unit, αv ≈ −12 MK−1. In situ synchrotron single crystal X-ray diffraction and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were employed to shed light on the NTE mechanism. Using these two methods, we were able to elucidate the three main structural motions that are responsible for the NTE effect. The more pronounced NTE behavior of Cu-TDPAT is attributed to the lower symmetry combined with the more complex ligand structure when compared to Cu-BTC. The knowledge obtained in this work is important for understanding the behavior of the adsorbent under transient variable temperature conditions in fixed adsorption beds.

Entropy-Driven Incommensurability: Chemical Pressure-Guided Polymorphism in PdBi and the Origins of Lock-In Phenomena in Modulated Systems.

Incommensurate order, in which two or more mismatched periodic patterns combine to make a long-range ordered yet aperiodic structure, is emerging as a general phenomenon impacting the crystal structures of compounds ranging from alloys and nominally simple salts to organic molecules and proteins. The origins of incommensurability in these systems are often unclear, but it is commonly associated with relatively weak interactions that become apparent only at low temperatures. In this article, we elucidate an incommensurate modulation in the intermetallic compound PdBi that arises from a different mechanism: the controlled increase of entropy at higher temperatures. Following the synthesis of PdBi, we structurally characterize two low-temperature polymorphs of the TlI-type structure with single crystal synchrotron X-ray diffraction. At room temperature, we find a simple commensurate superstructure of the TlI-type structure (comm-PdBi), in which the Pd sublattice distorts to form a 2D pattern of short and long Pd-Pd contacts. Upon heating, the structure converts to an incommensurate variant (incomm-PdBi) corresponding to the insertion of thin slabs of the original TlI type into the superstructure. Theoretical bonding analysis suggests that comm-PdBi is driven by the formation of isolobal Pd-Pd bonds along shortened contacts in the distorted Pd network, which is qualitatively in accord with the 18-n rule but partially frustrated by the population of competing Bi-Bi bonding states. The emergence of incomm-PdBi upon heating is rationalized with the DFT-Cemical Pressure (CP) method: the insertion of TlI-type slabs result in regions of higher vibrational freedom that are entropically favored at higher temperatures. High-temperature incommensurability may be encountered in other materials when bond formation is weakened by competing electronic states, and there is a path for accommodating defects in the CP scheme.

III-V Clathrate Semiconductors with Outstanding Hole Mobility: Cs8In27Sb19 and A8Ga27Sb19 (A = Cs, Rb).

Three novel unconventional clathrates with unprecedented III-V semiconducting frameworks have been synthesized: Cs8In27Sb19, Cs8Ga27Sb19, and Rb8Ga27Sb19. These clathrates represent the first examples of tetrel-free clathrates that are completely composed of main group elements. All title compounds crystallize in an ordered superstructure of clathrate-I in the Ia3̅ space group (No. 206; Z = 8). In the clathrate framework, a full ordering of {Ga or In} and Sb is observed by a combination of high-resolution synchrotron single-crystal and powder X-ray diffraction techniques. Density functional theory (DFT) calculations show that all three clathrates are energetically stable with relaxed lattice constants matching the experimental data. Due to the complexity of the crystal structure composed of heavy elements, the reported clathrates exhibit ultralow thermal conductivities of less than 1 W·m-1·K-1 at room temperature. All compounds are predicted and experimentally confirmed to be narrow-bandgap p-type semiconductors with high Seebeck thermopower values, up to 250 μV·K-1 at 300 K for Cs8In27Sb19. The latter compound shows carrier concentrations and mobilities, 1.42 × 1015 cm-3 and 880 cm2 ·V-1·s-1, which are on par with the values for parent binary InSb, one of the best electronic semiconductors. The high hole carrier mobility is uncommon for complex bulk materials and a highly desirable trait, opening ways to design semiconducting materials based on tunable III-V clathrates.

From solid state to in vitro anticancer activity of copper(II) compounds with electronically-modulated NNO Schiff base ligands.

The copper(ii) complexes of general formula [Cu(GL)(Cl)] (1-3, G = OMe, H and NO2, respectively), bearing tridentate Schiff base ligands (GL-) and a chloride as a fourth labile one, are here reported. The Schiff bases derive from the monocondensation of ethylenediamine and substituted salicylaldehyde, where the electronic properties are modulated by the releasing or withdrawing power of the G group. The compounds were structurally characterized through single crystal Synchrotron X-ray diffraction experiments in the solid state, revealing that 1 (OMe) and 2 (H) adopt a dimeric assembly [Cu(μ-Cl)(GL)]2 through apical interaction of the chloride ions of two monomeric units, while 3 embraces a 1D polymeric chain structure [Cu(μ-Cl)(NO2L)]n with a similar bridging fashion, all supported by extended intramolecular or intrachain hydrogen bonds. The redox properties of the complexes were also studied by cyclic voltammetry with no marked effect of the substituent on the potential of the CuII/CuI redox system. UV/Vis spectroscopic studies in mimicked physiological conditions highlighted the intactness and stability of the coordinated NNO tridentate ligand in 1-3 and the lability of the coordinated chloride ion with the formation of the aquo-complexes [Cu(GL)(H2O)]+ in aqueous solution, as confirmed by conductance measurements with a 1 : 1 electrolyte molar conductivity. In vitro tests on cell viability were conducted on malignant cell lines typical for their poor prognosis and curability, revealing time-dependent and differential cytotoxicity given by the substituent G. All compounds were capable of formation of intracellular reactive oxygen species and DNA intercalation, acting as nuclease and producing double-strand DNA breaks. This is especially effective for 3 (NO2), which revealed the highest anticancer activity against malignant triple-negative breast cancer MDA-MB-231 cells, with a two-to-four-fold cytotoxicity enhancement with respect to 1 (OMe) and 2 (H), and, most important, substantial differentiation of cytotoxicity with respect to healthy endothelial HUVEC cell line.