New Dinuclear Cobalt(II) and Zinc(II) Complexes of a Carboxylate-Rich Dinucleating Ligand: Synthesis, Structure, Spectroscopic Characterization, and Their Interactions with Sugars

Sugar–metal ion interactions in aqueous medium are involved in many biochemical processes such as the transport and storage of metals, the function and regulation of sugar-metabolizing metalloenzymes, the mechanism of action of metal-containing pharmaceuticals, and toxic metal metabolism. To understand such interactions we synthesized and fully characterized two new dinuclear cobalt­(II) and zinc­(II) complexes as carbohydrate binding models for xylose/glucose isomerases (XGI). Synthesis of the dicobalt complex, Na₃[Co₂(ccdp)­(μ-HCO₂)]­BF₄·9H₂O·2CH₃OH (<b>1</b>), was performed in methanol with stoichiometric amounts of Co­(BF₄)₂·6H₂O and the dinucleating ligand, H₅ccdp (H₅ccdp <i>= N,N′</i>-bis­[2-carboxybenzomethyl]-<i>N,N′</i>-bis­[carboxymethyl]-1,3-diaminopropan-2-ol), in the presence of NaOH at ambient temperature in an argon glovebox. Similarly, the dizinc complex, [NMe₄]₂[Zn₂(ccdp)­(μ-OAc)]·CH₃OH (<b>2</b>), was synthesized from Zn­(OAc)₂·2H₂O and H₅ccdp in the presence of NMe₄OH at ambient temperature in methanol. Binding of the complexes with carbohydrates was investigated under different reaction conditions. In aqueous alkaline media, complexes <b>1</b> and <b>2</b> showed chelating ability towards the biologically important sugars, d-glucose and d-xylose, and a polyalcohol enzyme inhibitor (xylitol). In solution, each complex forms a 1:1 complex-substrate bound product with specific binding constant values. Synthesis, characterization details, and substrate binding using spectroscopic techniques and single-crystal X-ray diffraction are reported

Inorganic Phosphate and Arsenate within New Tetranuclear Copper and Zinc Complexes: Syntheses, Crystal Structures, Magnetic, Electrochemical, and Thermal Studies

Three, PO₄^3–/HPO₄^2– and AsO₄^3–-incorporated, new tetranuclear complexes of copper­(II) and zinc­(II) ions have been synthesized and fully characterized. In methanol–water, reactions of H₃cpdp (H₃cpdp = <i>N</i>,<i>N</i>′-Bis­[2-carboxybenzomethyl]-<i>N</i>,<i>N</i>′-Bis­[2-pyridylmethyl]-1,3-diaminopropan-2-ol) with copper­(II) chloride in the presence of either NaOH/Na₂HPO₄·2H₂O or KOH/Na₂HAsO₄·7H₂O lead to the isolation of the tetranuclear complexes Na₃[Cu₄(cpdp)₂(μ₄-PO₄)]­(OH)₂·14H₂O (<b>1</b>) and K₂[Cu₄(cpdp)₂(μ₄-AsO₄)]­(OH)·16²/₃H₂O (<b>2</b>), respectively. Similarly, the reaction of H₃cpdp with zinc­(II) chloride in the presence of NaOH/Na₂HPO₄·2H₂O yields a tetranuclear complex, Na­(H₃O)₂[Zn₄(cpdp)₂(μ₄-HPO₄)]­Cl₃·12¹/₂H₂O (<b>3</b>). All complexes are characterized by single-crystal X-ray diffraction and other analytical techniques, such as Fourier transform infrared and UV−vis spectroscopy, thermogravimetric and electrochemical studies. The solid-state molecular framework of each complex contains two monocationic [M₂(cpdp)]⁺ (M = Cu, Zn) units, which are exclusively coordinated to either phosphate/hydrogen phosphate or arsenate groups in a unique mode. All three complexes exhibit a μ₄:η¹:η¹:η¹:η¹ bridging mode of the PO₄^3–/HPO₄^2–/AsO₄^3– groups, with each bridging among four metal ions. The thermal properties of all three complexes have been investigated by thermogravimetric analysis. Low-temperature magnetic studies of complexes <b>1</b> and <b>2</b> disclose moderate antiferromagnetic interactions mediated among the copper centers through alkoxide and phosphate/arsenate bridges. Electrochemical studies of complexes <b>1</b> and <b>2</b> in dimethylformamide using cyclic voltammetry reveal the presence of a fairly assessable one-electron metal-based irreversible reduction and one quasireversible oxidation couple

Inorganic Phosphate and Arsenate within New Tetranuclear Copper and Zinc Complexes: Syntheses, Crystal Structures, Magnetic, Electrochemical, and Thermal Studies

Three, PO₄^3–/HPO₄^2– and AsO₄^3–-incorporated, new tetranuclear complexes of copper­(II) and zinc­(II) ions have been synthesized and fully characterized. In methanol–water, reactions of H₃cpdp (H₃cpdp = <i>N</i>,<i>N</i>′-Bis­[2-carboxybenzomethyl]-<i>N</i>,<i>N</i>′-Bis­[2-pyridylmethyl]-1,3-diaminopropan-2-ol) with copper­(II) chloride in the presence of either NaOH/Na₂HPO₄·2H₂O or KOH/Na₂HAsO₄·7H₂O lead to the isolation of the tetranuclear complexes Na₃[Cu₄(cpdp)₂(μ₄-PO₄)]­(OH)₂·14H₂O (<b>1</b>) and K₂[Cu₄(cpdp)₂(μ₄-AsO₄)]­(OH)·16²/₃H₂O (<b>2</b>), respectively. Similarly, the reaction of H₃cpdp with zinc­(II) chloride in the presence of NaOH/Na₂HPO₄·2H₂O yields a tetranuclear complex, Na­(H₃O)₂[Zn₄(cpdp)₂(μ₄-HPO₄)]­Cl₃·12¹/₂H₂O (<b>3</b>). All complexes are characterized by single-crystal X-ray diffraction and other analytical techniques, such as Fourier transform infrared and UV−vis spectroscopy, thermogravimetric and electrochemical studies. The solid-state molecular framework of each complex contains two monocationic [M₂(cpdp)]⁺ (M = Cu, Zn) units, which are exclusively coordinated to either phosphate/hydrogen phosphate or arsenate groups in a unique mode. All three complexes exhibit a μ₄:η¹:η¹:η¹:η¹ bridging mode of the PO₄^3–/HPO₄^2–/AsO₄^3– groups, with each bridging among four metal ions. The thermal properties of all three complexes have been investigated by thermogravimetric analysis. Low-temperature magnetic studies of complexes <b>1</b> and <b>2</b> disclose moderate antiferromagnetic interactions mediated among the copper centers through alkoxide and phosphate/arsenate bridges. Electrochemical studies of complexes <b>1</b> and <b>2</b> in dimethylformamide using cyclic voltammetry reveal the presence of a fairly assessable one-electron metal-based irreversible reduction and one quasireversible oxidation couple

Inorganic Phosphate and Arsenate within New Tetranuclear Copper and Zinc Complexes: Syntheses, Crystal Structures, Magnetic, Electrochemical, and Thermal Studies

Three, PO₄^3–/HPO₄^2– and AsO₄^3–-incorporated, new tetranuclear complexes of copper­(II) and zinc­(II) ions have been synthesized and fully characterized. In methanol–water, reactions of H₃cpdp (H₃cpdp = <i>N</i>,<i>N</i>′-Bis­[2-carboxybenzomethyl]-<i>N</i>,<i>N</i>′-Bis­[2-pyridylmethyl]-1,3-diaminopropan-2-ol) with copper­(II) chloride in the presence of either NaOH/Na₂HPO₄·2H₂O or KOH/Na₂HAsO₄·7H₂O lead to the isolation of the tetranuclear complexes Na₃[Cu₄(cpdp)₂(μ₄-PO₄)]­(OH)₂·14H₂O (<b>1</b>) and K₂[Cu₄(cpdp)₂(μ₄-AsO₄)]­(OH)·16²/₃H₂O (<b>2</b>), respectively. Similarly, the reaction of H₃cpdp with zinc­(II) chloride in the presence of NaOH/Na₂HPO₄·2H₂O yields a tetranuclear complex, Na­(H₃O)₂[Zn₄(cpdp)₂(μ₄-HPO₄)]­Cl₃·12¹/₂H₂O (<b>3</b>). All complexes are characterized by single-crystal X-ray diffraction and other analytical techniques, such as Fourier transform infrared and UV−vis spectroscopy, thermogravimetric and electrochemical studies. The solid-state molecular framework of each complex contains two monocationic [M₂(cpdp)]⁺ (M = Cu, Zn) units, which are exclusively coordinated to either phosphate/hydrogen phosphate or arsenate groups in a unique mode. All three complexes exhibit a μ₄:η¹:η¹:η¹:η¹ bridging mode of the PO₄^3–/HPO₄^2–/AsO₄^3– groups, with each bridging among four metal ions. The thermal properties of all three complexes have been investigated by thermogravimetric analysis. Low-temperature magnetic studies of complexes <b>1</b> and <b>2</b> disclose moderate antiferromagnetic interactions mediated among the copper centers through alkoxide and phosphate/arsenate bridges. Electrochemical studies of complexes <b>1</b> and <b>2</b> in dimethylformamide using cyclic voltammetry reveal the presence of a fairly assessable one-electron metal-based irreversible reduction and one quasireversible oxidation couple

Inorganic Phosphate and Arsenate within New Tetranuclear Copper and Zinc Complexes: Syntheses, Crystal Structures, Magnetic, Electrochemical, and Thermal Studies

Three, PO₄^3–/HPO₄^2– and AsO₄^3–-incorporated, new tetranuclear complexes of copper­(II) and zinc­(II) ions have been synthesized and fully characterized. In methanol–water, reactions of H₃cpdp (H₃cpdp = <i>N</i>,<i>N</i>′-Bis­[2-carboxybenzomethyl]-<i>N</i>,<i>N</i>′-Bis­[2-pyridylmethyl]-1,3-diaminopropan-2-ol) with copper­(II) chloride in the presence of either NaOH/Na₂HPO₄·2H₂O or KOH/Na₂HAsO₄·7H₂O lead to the isolation of the tetranuclear complexes Na₃[Cu₄(cpdp)₂(μ₄-PO₄)]­(OH)₂·14H₂O (<b>1</b>) and K₂[Cu₄(cpdp)₂(μ₄-AsO₄)]­(OH)·16²/₃H₂O (<b>2</b>), respectively. Similarly, the reaction of H₃cpdp with zinc­(II) chloride in the presence of NaOH/Na₂HPO₄·2H₂O yields a tetranuclear complex, Na­(H₃O)₂[Zn₄(cpdp)₂(μ₄-HPO₄)]­Cl₃·12¹/₂H₂O (<b>3</b>). All complexes are characterized by single-crystal X-ray diffraction and other analytical techniques, such as Fourier transform infrared and UV−vis spectroscopy, thermogravimetric and electrochemical studies. The solid-state molecular framework of each complex contains two monocationic [M₂(cpdp)]⁺ (M = Cu, Zn) units, which are exclusively coordinated to either phosphate/hydrogen phosphate or arsenate groups in a unique mode. All three complexes exhibit a μ₄:η¹:η¹:η¹:η¹ bridging mode of the PO₄^3–/HPO₄^2–/AsO₄^3– groups, with each bridging among four metal ions. The thermal properties of all three complexes have been investigated by thermogravimetric analysis. Low-temperature magnetic studies of complexes <b>1</b> and <b>2</b> disclose moderate antiferromagnetic interactions mediated among the copper centers through alkoxide and phosphate/arsenate bridges. Electrochemical studies of complexes <b>1</b> and <b>2</b> in dimethylformamide using cyclic voltammetry reveal the presence of a fairly assessable one-electron metal-based irreversible reduction and one quasireversible oxidation couple

Synthesis, Structure, Spectroscopic Characterization, and Protein Binding Affinity of New Water-Soluble Hetero- and Homometallic Tetranuclear [Cu^II₂Zn^II₂] and [Cu^II₄] Clusters

Two new water-soluble hetero- and homometallic tetranuclear clusters, Na₄[Cu₂Zn₂(ccdp)₂(μ-OH)₂]·CH₃OH·6H₂O (<b>1</b>) and K₃[Cu₄(ccdp)₂(μ-OH)­(μ-OH₂)]·14H₂O (<b>2</b>), have been synthesized in methanol–water at room temperature by exploiting the flexibility, chelating ability, and bridging potential of a carboxylate-rich dinucleating ligand, <i>N</i>,<i>N</i>′-bis­(2-carboxybenzomethyl)-<i>N</i>,<i>N</i>′-bis­(carboxymethyl)-1,3 diaminopropan-2-ol (H₅ccdp). Complex <b>1</b> is obtained through the self-assembly of two monoanionic [CuZn­(ccdp)]⁻ fragments, which are, in turn, exclusively bridged by two μ-OH^– groups. Similarly, complex <b>2</b> is formed through the self-assembly of two monoanionic [Cu₂(ccdp)]⁻ species exclusively bridged by one μ-OH^– and one μ-OH₂ groups. Complexes <b>1</b> and <b>2</b> are fully characterized in the solid state as well as in solution using various analytical techniques including a single-crystal X-ray diffraction study. The X-ray crystal structure of <b>1</b> reveals that two Cu^II centers are in a distorted square-pyramidal geometry, whereas two Zn^II centers are in a distorted trigonal-bipyramidal geometry. The solid-state structure of <b>2</b> contains two dinuclear [Cu₂(ccdp)]⁻ units having one Cu^II center in a distorted square-pyramidal geometry and another Cu^II center in a distorted trigonal-bipyramidal geometry within each dinuclear unit. In the powder state, the high-field EPR spectrum of complex <b>1</b> indicates that two Cu^II ions are not spin-coupled, whereas that of complex <b>2</b> exhibits at least one noninteracting Cu^II center coordinated to a nitrogen atom of the ligand. Both complexes are investigated for their binding affinity with the protein bovine serum albumin (BSA) in an aqueous medium at pH ∼7.2 using fluorescence spectroscopy. Synchronous fluorescence spectra clearly reveal that complexes <b>1</b> and <b>2</b> bind to the active sites in the protein, indicating that the effect is more pronounced toward tyrosine than tryptophan. Density functional theory calculations have been carried to find the Fukui functions at the metal sites in complexes <b>1</b> and <b>2</b> to predict the possible metal centers involved in the binding process with BSA protein

Synthesis, Structure, Spectroscopic Characterization, and Protein Binding Affinity of New Water-Soluble Hetero- and Homometallic Tetranuclear [Cu^II₂Zn^II₂] and [Cu^II₄] Clusters

Two new water-soluble hetero- and homometallic tetranuclear clusters, Na₄[Cu₂Zn₂(ccdp)₂(μ-OH)₂]·CH₃OH·6H₂O (<b>1</b>) and K₃[Cu₄(ccdp)₂(μ-OH)­(μ-OH₂)]·14H₂O (<b>2</b>), have been synthesized in methanol–water at room temperature by exploiting the flexibility, chelating ability, and bridging potential of a carboxylate-rich dinucleating ligand, <i>N</i>,<i>N</i>′-bis­(2-carboxybenzomethyl)-<i>N</i>,<i>N</i>′-bis­(carboxymethyl)-1,3 diaminopropan-2-ol (H₅ccdp). Complex <b>1</b> is obtained through the self-assembly of two monoanionic [CuZn­(ccdp)]⁻ fragments, which are, in turn, exclusively bridged by two μ-OH^– groups. Similarly, complex <b>2</b> is formed through the self-assembly of two monoanionic [Cu₂(ccdp)]⁻ species exclusively bridged by one μ-OH^– and one μ-OH₂ groups. Complexes <b>1</b> and <b>2</b> are fully characterized in the solid state as well as in solution using various analytical techniques including a single-crystal X-ray diffraction study. The X-ray crystal structure of <b>1</b> reveals that two Cu^II centers are in a distorted square-pyramidal geometry, whereas two Zn^II centers are in a distorted trigonal-bipyramidal geometry. The solid-state structure of <b>2</b> contains two dinuclear [Cu₂(ccdp)]⁻ units having one Cu^II center in a distorted square-pyramidal geometry and another Cu^II center in a distorted trigonal-bipyramidal geometry within each dinuclear unit. In the powder state, the high-field EPR spectrum of complex <b>1</b> indicates that two Cu^II ions are not spin-coupled, whereas that of complex <b>2</b> exhibits at least one noninteracting Cu^II center coordinated to a nitrogen atom of the ligand. Both complexes are investigated for their binding affinity with the protein bovine serum albumin (BSA) in an aqueous medium at pH ∼7.2 using fluorescence spectroscopy. Synchronous fluorescence spectra clearly reveal that complexes <b>1</b> and <b>2</b> bind to the active sites in the protein, indicating that the effect is more pronounced toward tyrosine than tryptophan. Density functional theory calculations have been carried to find the Fukui functions at the metal sites in complexes <b>1</b> and <b>2</b> to predict the possible metal centers involved in the binding process with BSA protein

Synthesis, Structure, Spectroscopic Characterization, and Protein Binding Affinity of New Water-Soluble Hetero- and Homometallic Tetranuclear [Cu^II₂Zn^II₂] and [Cu^II₄] Clusters

Two new water-soluble hetero- and homometallic tetranuclear clusters, Na₄[Cu₂Zn₂(ccdp)₂(μ-OH)₂]·CH₃OH·6H₂O (<b>1</b>) and K₃[Cu₄(ccdp)₂(μ-OH)­(μ-OH₂)]·14H₂O (<b>2</b>), have been synthesized in methanol–water at room temperature by exploiting the flexibility, chelating ability, and bridging potential of a carboxylate-rich dinucleating ligand, <i>N</i>,<i>N</i>′-bis­(2-carboxybenzomethyl)-<i>N</i>,<i>N</i>′-bis­(carboxymethyl)-1,3 diaminopropan-2-ol (H₅ccdp). Complex <b>1</b> is obtained through the self-assembly of two monoanionic [CuZn­(ccdp)]⁻ fragments, which are, in turn, exclusively bridged by two μ-OH^– groups. Similarly, complex <b>2</b> is formed through the self-assembly of two monoanionic [Cu₂(ccdp)]⁻ species exclusively bridged by one μ-OH^– and one μ-OH₂ groups. Complexes <b>1</b> and <b>2</b> are fully characterized in the solid state as well as in solution using various analytical techniques including a single-crystal X-ray diffraction study. The X-ray crystal structure of <b>1</b> reveals that two Cu^II centers are in a distorted square-pyramidal geometry, whereas two Zn^II centers are in a distorted trigonal-bipyramidal geometry. The solid-state structure of <b>2</b> contains two dinuclear [Cu₂(ccdp)]⁻ units having one Cu^II center in a distorted square-pyramidal geometry and another Cu^II center in a distorted trigonal-bipyramidal geometry within each dinuclear unit. In the powder state, the high-field EPR spectrum of complex <b>1</b> indicates that two Cu^II ions are not spin-coupled, whereas that of complex <b>2</b> exhibits at least one noninteracting Cu^II center coordinated to a nitrogen atom of the ligand. Both complexes are investigated for their binding affinity with the protein bovine serum albumin (BSA) in an aqueous medium at pH ∼7.2 using fluorescence spectroscopy. Synchronous fluorescence spectra clearly reveal that complexes <b>1</b> and <b>2</b> bind to the active sites in the protein, indicating that the effect is more pronounced toward tyrosine than tryptophan. Density functional theory calculations have been carried to find the Fukui functions at the metal sites in complexes <b>1</b> and <b>2</b> to predict the possible metal centers involved in the binding process with BSA protein

A phenoxo–azido assorted Schiff base copper(II) bridged dimer in trace level fluorescence sensing of a pesticide: a DFT supported phenomenon

<p>A binuclear phenoxo- and azido-bridged copper(II) Schiff base complex has been synthesized along with its mononuclear copper-Schiff base analog. The compounds have been characterized by IR spectroscopy and CHN elemental analysis. The single-crystal structure and variable temperature magnetic properties of the binuclear compound have been studied from the X-ray crystallographic data and superconducting quantum interference device magnetometry, respectively. The synthesized crystalline binuclear complex has interesting spectral features that allow it to act as a spectral sensor toward an organophosphorus pesticide which is a potential environmental toxicant coming to the environment as agricultural waste. Although both the mononuclear and binuclear complexes are suitable as sensors for the organophosphorus, the binuclear complex being crystalline is suitable for attaining structural and mechanistic details of the interaction. Density functional theory calculations and ESI MS analysis of the interactions with the binuclear complex suggest that the binding of organophosphorus substrate with <b>2</b> occurs through one copper center.</p

Unraveling Multicopper [Cu₃] and [Cu₆] Clusters with Rare μ₃‑Sulfato and Linear μ₂‑Oxido-Bridges as Potent Antibiofilm Agents against Multidrug-Resistant Staphylococcus aureus

In this research article, two multicopper [Cu3] and [Cu6] clusters, [Cu3(cpdp)(μ3-SO4)(Cl)(H2O)2]·3H2O (1) and [Cu6(cpdp)2(μ2-O)(Cl)2(H2O)4]·2Cl (2) (H3cpdp = N,N′-bis[2-carboxybenzomethyl]-N,N′-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol), have been explored as potent antibacterial and antibiofilm agents. Their molecular structures have been determined by a single-crystal X-ray diffraction study, and the compositions have been established by thermal and elemental analyses, including electrospray ionization mass spectrometry. Structural analysis shows that the metallic core of 1 is composed of a trinuclear [Cu3] assembly encapsulating a μ3-SO42– group, whereas the structure of 2 represents a hexanuclear [Cu6] assembly in which two trinuclear [Cu3] motifs are exclusively bridged by a linear μ2-O2– group. The most striking feature of the structure of 2 is the occurrence of an unusual linear oxido-bridge, with the Cu3–O6–Cu3′ bridging angle being 180.00°. Whereas 1 can be viewed as an example of a copper(II)-based compound displaying a rare μ3:η1:η1:η1 bridging mode of the SO42– group, 2 is the first example of any copper(II)-based compound showing an unsupported linear Cu–O–Cu oxido-bridge. Employing variable-temperature SQUID magnetometry, the magnetic susceptibility data were measured and analyzed exemplarily for 1 in the temperature range of 2–300 K, revealing the occurrence of antiferromagnetic interactions among the paramagnetic copper centers. Both 1 and 2 exhibited potent antibacterial and antibiofilm activities against methicillin-resistant Staphylococcus aureus (MRSA BAA1717) and the clinically isolated culture of methicillin-resistant S. aureus (MRSA CI1). The mechanism of antibacterial and antibiofilm activities of these multicopper clusters was investigated by analyzing and determining the intracellular reactive oxygen species (ROS) generation, lipid peroxidation, microscopic observation of cell membrane disruption, membrane potential, and leakage of cellular components. Additionally, 1 and 2 showed a synergistic effect with commercially available antibiotics such as vancomycin with enhanced antibacterial activity. However, 1 possesses higher antibacterial, antibiofilm, and antivirulence actions, making it a potent therapeutic agent against both MRSA BAA1717 and MRSA CI1 strains