Coordination Of Cu Research Articles

Stability constants and molecular modeling of Cu(II)/AcO and Cu(II)/diclofenac complexes in ethanol

The speciation of diclofenac and copper complexes in ethanolic solutions is investigated. Current studies of coordination of Cu(II) and nonsteroidal anti-inflammatory drugs (NSAID) successfully describe structural features of Cu(II)/NSAID compounds in their solid state; however, stability of species in solution has been less explored. In order to approach the Cu(II)/Diclofenac speciation, the model system Cu(II)/Acetate was also investigated. A chemical model, which consists of a number of chemical equilibriums that involve the more stable species formed in solution, is proposed and proved to be consistent with experimental UV–Vis spectrums. Thermodynamic stability constants are reported, for the global complexation equilibriums iCu2++jL↔CuiLj2i-j, where L = Acetate or Diclofenac; for i=1, j=2 and for i=2, j=2,3,4. Molecular modeling, by applying quantum chemistry methods, based on density functional theory, is carried out to structurally characterize the neutral species present in the systems. Gibbs free energies in solution for the dimerization process 2CuL2→Cu2L4 were evaluated by means of thermodynamic cycles based on theoretical chemistry protocols. Although reduced solubility of diclofenac limits the use of water for speciation studies, results from experiments in ethanol might provide useful structural information to discuss the nature of Cu(II)/Dic complexes.

Synthesis and Cu(I)/Mo(VI) Reactivity of a Bifunctional Heterodinucleating Ligand on a Xanthene Platform.

In an effort to probe the feasibility of a model of Mo-Cu CODH (CODH = carbon monoxide dehydrogenase) lacking a bridging sulfido group, the new heterodinucleating ligand LH2 was designed and its Cu(I)/Mo(VI) reactivity was investigated. LH2 ((E)-3-(((5-(bis(pyridin-2-ylmethyl)amino)-2,7-di-tert-butyl-9,9-dimethyl-9H-xanthen-4-yl)imino)methyl)benzene-1,2-diol) features two different chelating positions bridged by a xanthene linker: bis(pyridyl)amine for Cu(I) and catecholate for Mo(VI). LH2 was synthesized via the initial protection of one of the amine positions, followed by two consecutive alkylations of the second position, deprotection, and condensation to attach the catechol functionality. LH2 was found to exhibit dynamic cooperativity between two reactive sites mediated by H-bonding of the catechol protons. In the free ligand, catechol protons exhibit H-bonding with imine (intramolecular) and with pyridine (intermolecular in the solid state). The reaction of LH2 with [Cu(NCMe)4]+ led to the tetradentate coordination of Cu(I) via all nitrogen donors of the ligand, including the imine. Cu(I) complexes were characterized by multinuclear NMR spectroscopy, high-resolution mass spectrometry (HRMS), X-ray crystallography, and DFT calculations. Cu(I) coordination to the imine disrupted H-bonding and caused rotation away from the catechol arm. The reaction of the Cu(I) complex [Cu(LH2)]+ with a variety of monodentate ligands X (PPh3, Cl-, SCN-, CN-) released the metal from coordination to the imine, thereby restoring imine H-bonding with the catechol proton. The second catechol proton engages in H-bonding with Cu-X (X = Cl, CN, SCN), which can be intermolecular (XRD) or intramolecular (DFT). The reaction of LH2 with molybdate [MoO4]2- led to incorporation of [MoVIO3] at the catecholate position, producing [MoO3(L)]2-. Similarly, the reaction of [Cu(LH2)]+ with [MoO4]2- formed the heterodinuclear complex [CuMoO3(L)]-. Both complexes were characterized by multinuclear NMR, UV-vis, and HRMS. HRMS in both cases confirmed the constitution of the complexes, containing molecular ions with the expected isotopic distribution.

Novel deep eutectic solvent made from sulfonic acid with acetamide, an ATR-IR characterization of different mole compositions and physicochemical properties of 1:6 mol ratios with electrodeposition of copper

Interest in DES is leveling up with increasing need for providing additional knowledge on their behavior and comparability with other type of solvents. In- addition cheap and environmental safe DES are emerging as attractive solvents in many applications. A novel deep eutectic solvent was made by simple mixing different mole ratios of sulfonic acid with acetamide. The effect of mole ratio on the interaction between the DES components was observed by ATR-IR with gradual color changes of formed DES. At 1 to 2 mol ratio respectively a different vibrational interactions is recorded. The least viscose DES of sulfonic acid with acetamide (1:6) shows temperature dependents of conductivity, viscosity and density with similar behaviors of other DESs. The cyclovolatammograms of 1:6 mol ratio of DES or its copper sulfate solution were measured and indicate a one-step reduction and oxidation of copper (Cu+2 to Cu0). Less than 75 nm copper was electrodeposited from its solution in DES with round particles on zinc substrate. DES and its solution with Copper sulfate was investigated by UV-visible spectroscopy suggested an Oh coordination of Cu2+ to DES.

Diaminoterephthalate‐EDTA and ‐EGTA Conjugates – “Turn on” Fluorescence Sensors for Zinc Ions

AbstractA highly effective “turn‐on” fluorescence sensor with high selectivity for Zn2+ ions is reported. Its constitution simply consists of two units of the fluorescence dye diaminoterephthalate (DAT) and the chelate ligand EDTA. In total, four products (DAT)2EDTA and (DAT)2EGTA were prepared by conjugation of DATs with chelate ligands EDTA and EGTA as sensors for metal ions in solution. The fluorescence of all four compounds is strongly quenched by coordination of Cu2+ and Ni2+ ions. For one EDTA‐derivative, the fluorescence quantum yield is increased by the factor of five with ten equivalents of ScCl3. For both EDTA derivatives, the fluorescence quantum yield increased by the factor of five with one equivalent Zn(OAc)2. Therefore, the (DAT)2EDTA structures constitute fluorescence sensors with a high selectivity for Zn2+ accompanied by a strong “turn‐on” effect with Zn2+ ions. Furthermore, the coordination geometry of (DAT)2EDTA with Zn2+ was elucidated by X‐ray single crystal structure analysis of the trinuclear complex [ZnCl2]{Zn(OH2)[(DAT)2EDTA – 2 H]}2 ⋅ 6.5 H2O.

Removal of Copper from Aqueous Solutions with Zeolites and Possible Treatment of Exhaust Materials

AbstractThe mechanism of Cu2+ loading into commercially available natural HEU‐type and synthetic LTA‐type zeolites for their possible use in environmental processes, such as water and air treatment applications, was studied. Elemental analysis, SEM/EDXS, XRD, XAS and XPS analyses revealed 4‐fold coordination of Cu2+ cations with oxygen atoms in the pores, a predominant location of copper atoms on the surface of crystallites and retained crystallinity of zeolites throughout the processes. The post‐treatment of Cu2+‐loaded samples with HCl and/or NaCl solutions confirmed the predominantly reversible sorption of copper on zeolites from aqueous solutions by ion‐exchange mechanism and, therefore, excellent regeneration possibilities for both types of zeolites. Furthermore, with the calcination of exhaust metal‐loaded zeolites, catalysts for total toluene oxidation reaction, as a model VOC pollutant, were obtained.

On the contribution of Pair Distribution Function (PDF) to the characterization of nanocrystalline MOFs: The case of M-MOF-74

Nanoporous Metal-Organic Frameworks (MOFs) have a great potential in so many industrial applications including heterogeneous catalysis and gas storage/capture/separation. MOF-74 is one of the most interesting MOFs in an academic context, as it contains open metal sites, possesses high versatility in metal nature, and can be prepared with so small crystal size. As a consequence, the catalytic activity of these nanocrystalline materials is superior to that given by their conventional counterparts. However, their characterization by conventional X-ray diffraction (XRD) is insufficient. In this work, we present a joint study of XRD and Pair Distribution Function (PDF) -both acquired under synchrotron radiation- of a series of nanocrystalline M-MOF-74 materials (M = Mg, Co, Ni, Cu or Zn) prepared at room temperature. Whereas the XRD continues being lacking for an adequate structural characterization, PDF provides key structural information at medium and short range and, therefore, is ideal for studying such nano-domains. It was confirmed that these materials are exclusively composed by MOF-74 phase and that their poor ability to diffract is due solely to their eminent nanocrystallinity, which resulted to be even more pronounced than it has been previously estimated. Beyond Scherrer-like approaches, PDF can give direct information about the range of crystal size in nanocrystalline materials. Moreover, the technique is also able to detect slight structural deviations in short-range environments, just like it is made clear in the case of Cu-MOF-74 compared with the rest of M-MOF-74 materials, which possesses a marked Jahn-Teller effect in the octahedral coordination of Cu.

CU(II) Complex with Nicotine and Carcinogenicity of Raw Medical Tobacco

Unusual coordination of Cu(II) with the pyrrolidine N atom of nicotine in aqueous solution that could promote the formation of carcinogenic N-nitrosonornicotine in raw medical tobacco was shown using circular dichroism.

Application of polymer-bound Cu(II) complex of 2-phenylbenzimidazole towards oxidative bromination and oxidative esterification of organic substrates

Application of polymer immobilized Cu(II)(PS-Cu(II)PBMZL) complex of 2-phenylbenzimidazole in oxidative bromination and oxidative esterification of organic compounds is reported. The complex has been characterized by CHNS analysis, UV-Vis/DRS, FT-IR, ESR spectroscopic studies, magnetic moment measurements and TG analysis. A shift in νC=N in the polymer-bound complex compared with the ligand indicates its complexation to Cu(II) center. A distorted octahedral coordination of Cu(II) in PS-Cu(II)PBMZL is confirmed by the electronic spectral data and the efficient binding of PBMZL is ascertained by adecrease in the intensity of νCH2Cl peak in the PS-PBMZL compared to the polymer support. An array of experiments has been carried out to assess the influence of various reaction parameters on the performance of PS-Cu(II)PBMZL. The activity of the polymer-bound complex is higher than the unbound complex. In the case of oxidative bromination, PS-Cu(II)PBMZLH displayed a 65% phenol conversion with 61% 2-bromophenol selectivity. The % benzaldehyde conversion and methyl benzoate selectivity in the case of oxidative esterification has been found to be 79 and 82%. Compiling all these results along with the knowledge obtained regarding the most probable reactive species, tentative mechanisms have been proposed.

Effects of precursor concentration on morphologies of Cu2O micro/nanocrystals and properties of CO self-sustained catalytic combustion

The self-sustained catalytic combustion is one of the most effective ways to remove high concentration CO at low temperature. In this paper, Cu2O micro/nanocrystals with different morphologies were successfully synthesized by changing the precursor concentration using liquid phase reduction method. The obtained Cu2O were characterized using SEM, XRD, XPS, H2-TPR and O2-TPD, and the relationship between the catalytic performance and morphology was analyzed based on CO-TPD-MS and activity evaluation results. It was found that high precursor concentration leads to more exposure of active crystal planes of Cu2O. Compared with Cu2O-1 exposing only (100) crystal planes, Cu2O-5, the precursor concentration of which is 5 times of Cu2O-1, exposes (100) and (110) crystal planes. Cu2O-9, with 9 times of precursor concentration of Cu2O-1, exposes (100), (110) and (111) crystal planes simultaneously. All the obtained Cu2O with different precursor concentrations can achieve self-sustained CO catalytic combustion, and the catalytic activity increases with increasing precursor concentration (Cu2O-1 < Cu2O-5 < Cu2O-9). The results prove that unsaturated coordination of Cu and O on the (111) and (110) planes can enhance the corresponding reducibility, adsorption and activation of gaseous oxygen, consequently promoting the CO oxidation to CO2 over Cu2O-9.

The suppression of lone-pair stereoactivity in [Cu+(As3+O3)4] clusters in dixenite: A tribute to Paul B. Moore

Abstract The crystal structure of dixenite, ideally Cu+Fe3+Mn142+(As5+O4)(As3+O3)5(SiO4)2(OH)6, from Långban, Sweden, was refined to an R1-index of 1.58%, and the structure proposed by Araki and Moore (1981) was confirmed and details elucidated. The structure, crystallizing in space group R3 with a = 8.2204(3) and c = 37.485(3) Å, consists of layers of (Mn2+,Fe3+)(O,OH)6 octahedra linked by (As5+O4) and (SiO4) tetrahedra, (As3+O3) trigonal pyramids, and (CU+As43+) tetrahedra. There are five distinct layers in the repeat unit of the cell, four of which are very similar to the layers in mcgovernite. An unusual aspect of one of the trimers of octahedra is that there is a triangular-prismatic hole through the center of the cluster. The (CU+As43+) tetrahedra are parts of larger clusters: [Cu+(As3+O3)4] in which four (As3+O3) groups link to a central Cu+ that occupies the positions normally taken by the stereoactive lone-pairs of electrons that generally characterize As3+ in triangular-pyramidal coordination by O. Thus, the stereoactive lone-pair behavior that is characteristic of (As3+O3) trigonal pyramids is suppressed by the coordination of Cu+ by four As3+ ions.

Phosphorescent iridium(III) complexes bearing l-alanine ligands: Synthesis, crystal structures, photophysical properties, DFT calculations, and use as chemosensors for Cu2+ ion

Two neutral iridium complexes with l-alanine as ancillary ligands, (thp)2Ir (l-alanine) (Ir1) (thp = 2-(thiophen-2-yl)pyridine) and (btp)2Ir (l-alanine) (Ir2) (btp = 2-(benzo[b]thiophen-2-yl)pyridine) were synthesized and investigated. The solid-state structures of the developed Ir1 and Ir2 were authenticated by single X-ray diffraction. Ir(III) complexes Ir1 and Ir2 exhibit intense yellow and red emission respectively with high quantum efficiencies (Φem = 0.88 for Ir1, Φem = 0.29 for Ir2) in oxygen-free acetonitrile solution at room temperature. Theoretical calculations were carried out to provide a further study of the orbital distributions and electronic states of the two complexes. The two complexes displayed significant reversible phosphorescence quenching upon binding to Cu2+ ion and the binding stoichiometry was approximately 1:1.1H NMR titration experiments indicated that coordination of Cu2+ to the nitrogen atoms of the l-alanine ligands of the complexes induce the significant variations in optical signals. This work showed that new phosphorescent probes based on iridium complexes could be realized by introducing simple amino acid ancillary ligands.

Synthesis, structure, Hirshfeld analysis and fluorescence properties of a new asymmetric salamo-based ligand and its Cu(II) complex involving oxime oxygen coordination

A new asymmetric salamo-based ligand (H2L) was synthesized and upon reaction with Cu(ClO4)2 an extremely rare dinuclear Cu(II) complex [Cu2(L)2] was formed and characterized by elemental analyses, infrared spectroscopy, UV–vis absorption spectroscopy, X-ray single crystal diffraction and Hirshfeld surface analyses. The Cu(II) complex consists of two Cu(II) ions and two fully deprotonated ligand (L)2– units. The Cu(II) is coordinated with the N2O2 cavity (N1, N2, O1 and O4) of L2– and the oxime oxygen (O3) of another L2– unit to form a uncommon dinuclear structure. The Cu(II) is five-coordinated, τ = 0.02, and has a configuration of slightly twisted tetragonal pyramidal geometry. The comparison between H2L and its Cu(II) complex through Hirshfeld surface analyses shows that the interaction of O-H/H-O is reduced, indicating that deprotonation of phenolic hydroxyl group and the coordination of Cu(II) forms a stable complex. In addition, fluorescence quenching of the Cu(II) complex compared to H2L further confirms the above experimental results.

Electrospun materials from polylactide and Schiff base derivative of Jeffamine ED® and 8-hydroxyquinoline-2-carboxaldehyde and its complex with Cu2+: Preparation, antioxidant and antitumor activities.

Novel fibrous materials from polylactide (PLA) and Schiff base from Jeffamine ED® and 8-hydroxyquinoline-2-carboxaldehyde (Jeff-8Q) or its complex with Cu2+ (Jeff-8Q.Cu2+) were successfully prepared by using one-pot electrospinning or electrospinning combined with dip-coating. These approaches enabled the fabrication of materials of diverse design: non-woven textile in which Jeff-8Q or Jeff-8Q.Cu2+ was predominantly in the fibers' bulk (type "in") or was deposited as a thin film on the surface of the fibers (type "on"). The morphology of the mats and chemical composition of their surface were analyzed by means of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The coordination of Cu2+ ions in Jeff-8Q.Cu2+/inPLA and Jeff-8Q.Cu2+/onPLA mats was examined by electron paramagnetic resonance (EPR) spectroscopy. It was found that the in vitro release of Jeff-8Q (Jeff-8Q.Cu2+) from the type "on" mats was more rapid than that of the type "in" mats. Enhancement of the antioxidant activity of the Jeff-8Q.Cu2+-containing fibrous mats as compared to mats containing Jeff-8Q was observed. In contrast to the neat PLA mat, the Jeff-8Q- and Jeff-8Q.Cu2+-containing mats (both type "in" and "on") displayed high in vitro antitumor activity against human cervical HeLa cells. The obtained materials are promising for use in local tumor treatment.

Selective electroreduction of CO2 to acetone by single copper atoms anchored on N-doped porous carbon

Efficient electroreduction of CO2 to multi-carbon products is a challenging reaction because of the high energy barriers for CO2 activation and C–C coupling, which can be tuned by designing the metal centers and coordination environments of catalysts. Here, we design single atom copper encapsulated on N-doped porous carbon (Cu-SA/NPC) catalysts for reducing CO2 to multi-carbon products. Acetone is identified as the major product with a Faradaic efficiency of 36.7% and a production rate of 336.1 μg h−1. Density functional theory (DFT) calculations reveal that the coordination of Cu with four pyrrole-N atoms is the main active site and reduces the reaction free energies required for CO2 activation and C–C coupling. The energetically favorable pathways for CH3COCH3 production from CO2 reduction are proposed and the origin of selective acetone formation on Cu-SA/NPC is clarified. This work provides insight into the rational design of efficient electrocatalysts for reducing CO2 to multi-carbon products.

Effect of the Nuclearity and Coordination of Cu and Fe Sites in β Zeolites on the Oxidation of Hydrocarbons

Cu and Fe zeolites can activate oxygen for oxidative reactions of methane and stable hydrocarbon molecules. Here, we analyzed the activity of Cu and Fe sites with various nuclearities and coordinations in *BEA zeolites toward complete oxidation of methane, toluene, and ethanol by molecular oxygen. Spectral analysis of the interaction of methane with the individual Cu and Fe sites and a kinetic study show that the oxidation of methane is catalyzed by different active sites with different activation energies. In the low-temperature region (225–325 °C), the activity is primarily caused by reactive bridging oxygen atoms in dimeric Cu and Fe clusters. Isolated Fe3+-oxo ions in the octahedral coordination and Cu2+ partially charge-balanced by the framework with less rigid redox states contribute to the activity at higher temperatures of ≥350 °C. The isolated Fe3+-oxo ions tetrahedrally coordinated to the framework oxygen and the bare Cu2+ ions charge-balanced exclusively by the framework are strongly stabilized and cannot act as active sites. Oxidation of the hydrocarbons over both the dimeric and isolated Cu and Fe active sites is nonspecific with practically barrierless consecutive reactions of already activated molecules and therefore fully CO2-selective for all of the hydrocarbons in an excess of oxygen.

Facile fabrication of Cu(II) coordinated chitosan-based magnetic material for effective adsorption of reactive brilliant red from aqueous solution

In order to effectively remove reactive brilliant red (RBR) in aqueous solution, a novel Cu(II) coordinated chitosan-based magnetic composite (CTS-Cu@SiO2@Fe3O4) was prepared. The physicochemical properties of the resultant adsorbent were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), vibrating sample magnetometer (VSM) thermogravimetric (TG) analysis, scanning electron microscopy (SEM) and N2 adsorption-desorption. The adsorption capacity toward RBR was systematically investigated as a function of contact time, solution pH, initial concentration, ionic strength and temperature. Compared with CTS@SiO2@Fe3O4, CTS-Cu@SiO2@Fe3O4 showed better adsorption performance in removing RBR, reaching a maximum of 880.84 mg/g at pH 4, which confirmed that the coordination of Cu(II) can improve the adsorption capability. The adsorption kinetics of CTS-Cu@SiO2@Fe3O4 was found to follow the pseudo-second-order kinetic model, and the equilibrium adsorption data were well described by the Freundlich isotherm model. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic. XPS analysis confirmed that the adsorption was mainly controlled by electrostatic interaction between copper/amino cation and RBR anion. Furthermore, regeneration experiments demonstrated that CTS-Cu@SiO2@Fe3O4 can be used repeatedly. In a word, CTS-Cu@SiO2@Fe3O4 can be served as a promising adsorbent for dye wastewater scavenging.

Co-sorption of sulfamethoxazole and Cu onto several soils with different properties and their binding mechanism

The present study aims to investigate the co-sorption characteristic of Sulfamethoxazole (SMX) and Cu(II) onto two typical soils with different properties in China. The sorption of SMX and Cu(II) onto soil is carried out by batch method. The results indicated that Cu(II) co-presence significantly increased SMX adsorption on Black soils, but decreased SMX adsorption on Brown soils. The further kinetic models fitting found, however, that Cu(II) co-presence had little effect on the sorption process of SMX onto soils. The co-sorption of SMX and Cu(II) on soil mineral surface was confirmed by the X-ray photoelectron spectroscopy and Energy Spectrum Analysis based on the variation of elemental bonding energy after adsorption. The further Infrared Spectrometric Analysis proved that SMX and Cu(II) were bonded on soil mineral surface by coordination of Cu(II) with the N reactive groups of SMX. Finally, in view of the different sorption of SMX on Brown and Black soils after Cu(II) addition, it could conclude that the coordination is not favourable to SMX adsorption onto soil mineral phases.

A new chromenylium-cyanine chemosensor for switch-ON near-infrared copper (II) sensing

A highly selective and sensitive near-IR chemosensor having a chromenylium-cyanine backbone for the detection of Cu2+ in aqueous samples has been designed and synthesized. The sensor has exhibited linear optical response to copper ions at the range of 0–4.9 × 10−6 M in the presence of other competing metal ions, such as Na+, K+, Mg2+, Ca2+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Zn2+, Al3+, Cd2+, Ag+, Sr2+, Pb2+, Hg2+ and Ba2+. The limit of detection (LOD) was calculated as 1.28 × 10−8 M which was lower than that of previously reported analogues. The sensor allows detection of the copper(II) ion through the spirocyclic ring-opening reaction by coordination of Cu2+.

Copper(II) Coordination and Translocation in Luteolin and Effect on Radical Scavenging.

Luteolin differs as a radical scavenger dramatically from apigenin in response to Cu(II) coordination despite a minor structural difference. Coordination of Cu(II) increases the radical scavenging efficiency of luteolin, especially at low pH, while decreases the efficiency of apigenin at both low and higher pH as studied by ABTS•+ radical scavenging. Luteolin forms a 1:1 complex with Cu(II) binding to 4-carbonyl and 5-phenol for pH <6 and to 3',4'-catechol for pH >6. Apigenin forms a 1:2 complex independent of pH coordinated to 4-carbonyl and 5-hydroxylyl. Cu(II) coordinated to luteolin, as studied by pH jump stopped-flow, translocates with rate constants of 11.1 ± 0.3 s-1 from 4,5 to 3',4' sites and 1.0 ± 0.1 s-1 from 3',4' to 4,5 sites independent of Cu(II) concentration, pointing toward the dissociation of Cu(II) from an intermediate with two Cu(II) coordination as rate determining. 3',4'-Catechol is suggested to be a switch for Cu(II) translocation with deprotonation initiating 4,5 to 3',4' translocation and protonation initiating 3',4' to 4,5 translocation. For dicoordinated apigenin, the coordination symmetry balances an electron withdrawal effect of Cu(II) resulting in a decrease of phenol acidity and less radical scavenging efficiency compared to parent apigenin. Compared to that of parent luteolin, the radical scavenging rate of both 4,5 and 3',4' Cu(II)-coordinated luteolin is enhanced through increased phenol acidity by electron withdrawal by Cu(II), as confirmed by density functional theory (DFT) calculations. Coordination and translocation of Cu(II) accordingly increases the antioxidant activity of luteolin at pH approaching the physiological level and is discovered as a novel class of natural molecular machinery derived from plant polyphenols, which seems to be of importance for protection against oxidative stress.

Interaction with plasmid DNA of Hoechst-TACN conjugates

ABSTRACTA new family of conjugates between the Hoechst minor groove binder and the TACN metal ion ligand connected through hydrophobic alkyl or more hydrophilic oxyethyl linkers of different length has been prepared. The linkers are connected to the convex side of the Hoechst skeleton thus forcing the TACN ligand to exit the minor groove and interact with the phosphate backbone of DNA. The conjugates preserve the binding mode of Hoechst with an affinity influenced by the nature of the linker, the more hydrophobic being the more efficient. Coordination of Cu(II) or Zn(II) poorly affect these parameters. Nevertheless, the Zn(II) complex bearing a C6 linear alkyl linker induced a modest but reproducible acceleration of the hydrolytic cleavage of DNA which can be ascribed to the ability of the conjugate to deliver the hydrolytic subunit close to the DNA phosphodiester bonds.