Tetranuclear Copper Complex Research Articles

Chiral 1,8-naphthyridine based ligands: Syntheses and characterization of Di- and tetranuclear copper (I) and silver (I) complexes

Oxazoline and camphor-pyrazole units are introduced on the 1,8-naphthyridine scaffold to access chiral ligands L1, L2 and L3. Metalation of these chiral ligands with Cu(I) and Ag(I) precursors afforded di- and tetranuclear complexes [Cu4I4(L1)2] (1), [Cu4I4(L2)2] (2), [Cu2I2(L3)] (3), [Cu2I(L2)2](OTf) (4), [Ag2(L1)2](OTf)2 (5) and [Ag4(L2)4Br](OTf)3 (6), containing [M4Xn] (n = 1,4 and X = Br, I) or [M2Xn] (n = 0, 1, 2 and X = I) core. All complexes are structurally characterized. Naphthyridine-derived ligands reveal bridge-chelate coordination motif and hold two metal centers in close proximity. The tetranuclear complexes are dimer of dinuclear complexes bridged by the halides. Electronic absorption and emission spectra of copper complexes are reported. Catalytic utility of all complexes are examined for asymmetric transformations but they showed poor activity probably due to limited solubility and coordinative saturation at the metal centers. The best results are obtained with [L3/Cu salt] combination for cyclopropanation of styrene, NH bond insertion and nitroaldol (Henry) reactions with very low enantioselectivity.

Synthesis, Photophysical Properties, and Computational Analysis of Di- and Tetranuclear Alkyne Complexes of Copper(I) Supported by a Highly Fluorinated Pyrazolate

This work describes the reaction of a cyclic trinuclear complex, {[3,5-(CF3)2Pz]Cu}3, with internal alkynes to construct di- and tetranuclear copper(I) complexes with short cuprophilic contacts and the study of their intriguing bonding and photophysical properties, both experimentally and theoretically. For comparison, we have also investigated the related copper(I) trifluoroacetate 3-hexyne complexes so as to deduce and isolate the role played by the supporting pyrazolate ligand on the luminescence of these and related complexes. Some adducts reported herein feature bridging (i.e., μ2–η2,η2-) alkyne coordination modes, which is rare for copper(I)–alkyne complexes documented in the literature. Raman data show red shifts in the average υC≡C stretching frequency from 2260 cm–1 in free 3-hexyne to 2050 cm–1 in the terminal η2-/2e-donor alkyne adduct Cu2(μ-[3,5-(CF3)2Pz])2(EtC≡CEt)2 (1) and, more drastically, to 1874 cm–1 in the bridged μ2–η2,η2-/4e-donor adduct Cu4(μ-[3,5-(CF3)2Pz])4(μ-EtC≡CEt)2 (2). The te...

Peroxidative Oxidation of Alkanes and Alcohols under Mild Conditions by Di- and Tetranuclear Copper (II) Complexes of Bis (2-Hydroxybenzylidene) Isophthalohydrazide.

Bis(2-hydroxybenzylidene)isophthalohydrazide (H4L) has been used to synthesize the dinuclear [Cu2(1κNO2:2κN′O′2-H2L)(NO3)2(H2O)2] (1) and the tetranuclear [Cu4(μ-1κNO2:2κN′O2-H2L)2(μ-NO3)2(H2O)4]·2C2H5OH (2) complexes. The solvent plays an important role in determining the ligand behaviour in the syntheses of the complexes. An ethanol-acetonitrile mixture of solvents favours partials enolization in the case of 2. Both complexes have been characterized by elemental analysis, infrared radiation (IR), single crystal X-ray crystallography and electrochemical methods. The variable temperature magnetic susceptibility measurements of 2 show strong antiferromagnetic coupling between the central nitrato-bridged Cu (II) ions. The catalytic activity of both 1 and 2 has been screened toward the solvent-free microwave-assisted oxidation of alcohols and the peroxidative oxidation of alkanes under mild conditions. Complex 1 exhibits the highest activity for both oxidation reactions, leading selectively to a maximum product yield of 99% (for the 1-phenylethanol oxidation after 1 h without any additive) and 13% (for the cyclohexane oxidation to cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone after 3 h).

Inhibition of ligand arm hydrolysis and carboxylate coordination directed formation of μ4-oxido-bridged [Cu4] complexes: Synthesis, X-ray structure and functional activity

The dinuclear copper(II) complex [Cu2(µ–L2NH)2(OH2)2](ClO4)4 (1) was obtained following one imine side arm hydrolysis of HL1 (2,6-bis-[{3-(diethylamino)propylimino}methyl]-4-methylphenol). Introduction of carboxylates inhibited the hydrolysis and resulted in two tetranuclear copper(II) complexes [Cu4(µ4–O)(µ–L1)2(µ1,3–O2CCH3)4]·H2O (2a) and [Cu4(µ4–O)(µ–L1)2(µ1,3–O2CC2H5)4]·H2O (2b). Use of perchlorate and carboxylate salts of copper(II) for the reactions under study with HL1 has directed these reactions. Perchlorate anions in presence of H2O molecules, as hydrolytic nucleophiles, triggered imine arm hydrolysis and bridging carboxylate anions allowed transformation of copper(II) bound H2O molecule to μ4-oxido central nucleating group via hydroxido-bridge. The complexes were obtained from simultaneous chelation and bridging by the hydrolyzed and as used ligand anions L2NH− and HL1− respectively. These complexes have been characterized in the solid state by X-ray crystallography and FT-IR spectroscopy. Solution phase stability of Cu2-based fragments was studied by UV–vis absorption spectroscopy. Solution properties have been examined for substrate binding in catechol oxidase activity and binding affinity for biomacromolecules like DNA and Human Serum Albumin.

Magneto‐Structural and Computational Study of a Tetranuclear Copper Complex Displaying Carbonyl–π Interactions

A tetranuclear copper(II) complex (1) was synthesized using 2-hydroxy-N-(quinolin-8-yl)acetamide ligand. Single-crystal X-ray diffraction studies revealed that the complex consists of a distorted Cu 4 O 4 core in which the four copper(II) ions are linked by alkoxo bridges. X-ray analysis also evidenced intra-molecular noncovalent carbonyl-π interactions. Those interactions that are encountered between lone-pair electrons (of the amide oxygen atoms here) and π* orbitals of aromatic rings,

An unexpected μ4-oxido-bridged tetranuclear Cu(II) inverse coordination complex of a heptadentate bis(pyrazolyl)methane-based ligand: Synthesis, structure, spectroscopic properties, and catecholase activity

A new tetranuclear copper(II) complex, {But-C6H2(O)[CH = N-CH2-CH(pz)2]2}2Cu4(μ4-O)(OAc)4 (L2Cu4(μ4-O)(OAc)4, pz = pyrazolyl ring) has been prepared from the condensation reaction of 4-tert-butyl-2,6-diformylphenol with two equivalents of bis(pyrazolyl)ethanamine moieties in the presence of two equivalents of copper(II) acetate. The complex has been characterized by X-ray diffraction studies in solid state, as well as by UV–Vis, IR, and ESI spectroscopies. The structure of this inverse coordination complex consists of a central oxygen ion surrounded by four copper(II) cations residing in the corners of a distorted tetrahedron; the remaining coordination sites of the Cu2+ ions are filled by imine donors and acetate counter-ions, leaving the bis(pyrazolyl)methane donor groups uncoordinated to the copper(II) centers. In contrast to the solid-state structure, this compound was found to be dinuclear in solution, LCu2(OAc)2(OH). The complex catalyzes the oxidation of 3,5-di-tert-butylcatechol (DTBC) and 4-tert-butylcatechol (TBC) to their corresponding quinones. The catalytic mechanism was investigated using DTBC as a substrate, and it was found that the oxidation reaction occurs via two different pathways, one involving molecular oxygen and the other hydrogen peroxide as oxidants.

Tetranuclear Copper(II) Complexes with Simultaneous Phenoxo and Azido Bridges ‐ Synthesis, Structural and Magnetic Studies

AbstractTetradentate Schiff base ligands with multiple coordinaton sites are one of the best choice for the construction of multinuclear metal complexes. Coupled with auxiliary ligands under self assembling conditions, the scope for generating new structures increases manifold due to various structure directing factors in operation. Though, phenoxo or azido bridged copper(II) systems have been investigated thoroughly from structural and magnetic aspects, the literature is scanty with combined phenoxo and azido bridged systems. In a study on the effect of synthetic conditions on the structures generated and associated magnetic properties, two new tetranuclear copper complexes, viz., [Cu4(L1)2(μ‐N3)2(N3)2] (1) and [Cu4(L2)2(μ‐N3)2(N3)2] (2) where L1=N,N′‐Bis(salicylidene)diaminopropane (salpn) and L2=N,N′‐Bis(salicylidene)diaminobenzene (salophen) with both phenoxo and azido bridges are reported. The tetranuclear cluster is made of two inversion related dimers built of phenoxo bridged Cu1 and Cu2 with distorted square planar and square pyramidal geometries respectively. These dimers are bridged by symmetrically bridging azides leading to a tetranuclear core. The contrasting magnetic behavior inspite of same coordination environments, antiferromagnetic in 1 (J1=−2.17 cm−1; J2=−28.15 cm−1) and ferromagnetic in 2 (J1=−74.7 cm−1; J2=146.5 cm−1), is understood in terms of lower bridge angles and closer separation between copper centers in 2 than in 1.

Synthesis, crystal structure, DNA binding, molecular docking, cytotoxic activities and apoptosis of two copper (II) complexes constructed by 1,10-phen and semirigid bridge ligands

New di-and tetranuclear copper(II) complexes of formula [Cu (phen) (mqpa)]·2H2O·CH3CH2OH (1) and [Cu2(phen)2(ppa)2(H2O)2]·4H2O·CH3CH2OH (2) (phen = 1,10- phenanthroline, H2mqpa = 4-(2-methyl-quinolin-1-ium-8-yloxy) phthalic acid, H2ppa = 3-(pyridiium-3-yloxy) phthalic acid) have been synthesized and characterized by elemental analysis, infrared spectrum, and single X-ray diffraction. In complex 1, two [Cu(phen)] units are bridged by two mqpa ligands via carboxyl bridges, forming a binuclear compound with Cu…Cu distance of 3.329 Å. Through strong π…π and CH…π weak interaction, complex 1 molecules are assembled into 2D supramolecular structures. Compound 2 features a metallamacrocyclic assembly in which four [Cu(phen)(H2O)] species are linked together by four ppa bridge ligands in head to tail fashion with Cu…Cu distance of 8.713 and 8.528 Å. The adjacent tetranuclear complex 2 molecules stacked together through strong π…π. The Cu(II) ions in two compounds are all in square pyramidal geometry. The interaction of two complexes with FS-DNA was studied by electronic absorption titration and ethidium bromide displacement experiments, the result displayed both complexes interact with DNA in non-intercalation mode, molecular docking simulation displayed that complex 1 interacts with DNA with a partial intercalation mode and complex 2 favor binding to major groove. Both complexes exhibit cytotoxicity against HeLa cells and AGZY-83a cells, and complex 2 has similar anticancer activity toward HeLa cells with cisplatin. The results of apoptosis assays by flow cytometry shows complex 2 promotes more apoptosis in HeLa cell lines than complex 1.

Synthetic Diversity and Luminescence Properties of ArN(PPh2)2‐Based Copper(I) Complexes

The dinuclear copper(I) complexes 1 and 2 were prepared by reacting PNP ligands ArN(PPh2)2, (Ar = 2,6‐Me2C6H3; L1) with CuCl and CuBr. By altering the position of the methyl substituents from ortho to meta (Ar = 3,5‐Me2C6H3; L2), trinuclear copper(I) complexes 3 and 4 were obtained, while the methyl substituent at the para position (Ar = 4‐MeC6H4; L3) led to the tetranuclear copper(I) complexes 5 and 6. Single crystal X‐ray studies show the different Cu···Cu interactions in complexes 1–6 ranging from 2.650 to 2.935 Å. The copper(I) complexes 3–6 were found to exhibit mechanochromic as well as thermochromic luminescent behavior presumably stemming from a decrease in their Cu···Cu distances.

Redox processes in the Cu/(phen)/[B12H12]2−/solv system: Selective preparation of copper(I), copper(II), and heterovalent copper(I/II) compounds

Abstract The complexation of copper and 1,10-phenanthroline (phen) in the presence of the [B12H12]2− anion is studied in organic solvents. The starting reagents contain copper(I) salts. The reactions are carried out in air and accompanied with oxidation of copper(I). Varying solvents and starting reagents, we succeeded in synthesizing selectively copper(I), copper(II), and heterovalent copper(I,II) complexes. Mononuclear, tetranuclear, and polymeric copper(II) complexes as well as a mononuclear copper(I) complex and a mixed cationic mononuclear copper(I)/copper(II) complexes are isolated and characterized by IR-spectroscopy and X-ray diffraction. The electronic structure of mononuclear copper(II) complex [CuII(phen)2Cl]2[B12H12] 2CH2I2 is studied by EPR.

Tetranuclear and dinuclear phenoxido bridged copper complexes based on unsymmetrical thiosemicarbazone ligands.

We report on the synthesis of new dinucleating phenol-based "end-off" compartmental ligands HLMeH and HLMe2 bearing two different binding sites, one bis(2-methylpyridyl)aminomethyl (BPA) and one thiosemicarbazone (TSC) site, and their corresponding copper(ii) complexes 1t and 2d. With the ligand HLMeH, a tetranuclear entity (1t) has been isolated in the solid state, whereas with HLMe2, which differs from HLMeH by a methyl substituent on the N-terminal amino group of the TSC arm, a dinuclear form (2d) is obtained. X-ray crystallography analysis shows that the nuclearity di vs. tetra is modulated by interactions between copper atoms and hydroxido bridges along with the sulphur atoms of TSC arms. From a magnetic point of view, 1t can be considered as an association of two dinuclear forms leading for both complexes to overall antiferromagnetic coupling. Analysis in acetonitrile solution of structure-property relationships has been carried out by comparing their UV/Vis, electrochemistry, ESI-MS, and NMR (variable temperature and DOSY = diffusion ordered spectroscopy) properties with trends from computational calculations (DFT). HRMAS-DOSY (High Resolution Magic Angle Spinning) NMR spectroscopy has been performed to evaluate the presence of different species in solution at room temperature.

Mono‐ and tetranuclear copper(I) complexes with N‐heterocyclic chelating and triphenylphosphine ligands: Crystal structures, luminescent and heterogeneous catalytic properties

N‐heterocyclic chelating and triphenylphosphine ligands react with cuprous halide to form a variety of copper(I) complexes, namely, mononuclear [Cu(PBO)(PPh3)Br].CH2Cl2 (1) and [Cu(PBM)(PPh3)I] (2) (PBO = 2‐(2′‐Pyridyl)benzoxazole, PBM = 2‐(2′‐Pyridyl)benzimidazole, PPh3 = triphenylphosphine) and tetranuclear [Cu4(μ2‐I)2(μ3‐I)2(PPh3)4].2CH2Cl2 (3) have been synthesized and characterized. Complexes 1 and 2 are basically alike; both of them are mononuclear and four‐coordinated, possessing a slightly distorted trigonal pyramidal geometry. Complex 3 is tetranuclear and the coordination numbers of the two copper(I) atoms are three and four, Cu(1) forming an approximate trigonal planar coordination environment, while Cu(2) is a slightly distorted trigonal pyramidal geometry, resulting in a distorted chair‐like conformation. Complexes 1 and 2 are emissive in the solid state at ambient temperature, with the maxima at 552 and 602 nm, respectively, due to a MLCT excited state. Moreover, complex 3 manifests promising heterogeneous catalytic activities for the degradation of methylene blue (MB), with degradation efficiency of 99% under ambient light.

Tetranuclear copper(II) complex with the µ4-1,6-hexadicarboxylate linker: crystal structure and magnetic properties

Tetranuclear copper(II) complex [Cu4L2(OOC(CH2)6COO)] (I) based on bis(azomethine), condensation product of 1-phenyl-3-methyl-4-formylpyrazolone-5 with 1,3-diaminopropanol-2, is synthesized. The structure of its DMSO-adduct (Ia) is determined by X-ray diffraction analysis (CIF file CCDC 1447891). The complexes contain two binuclear fragments bonded by the µ4-1,6-hexadicarboxylate linker. The magnetic exchange interaction in complex I is antiferromagnetic (2J =–155 cm–1), whereas that in complex Ia is ferromagnetic (2J = 129 cm–1), which is due to different conformations of the metallochelate cycles.

The magnetic exchange interaction in bi- and tetranuclear copper(II) complexes with the bis-azomethine of 1,3-diaminopropanol-2 and 4-hydroxy-3-formylcoumarin with an azide exogenous bridge

By the reaction of Cu(II) perchlorate with the condensation product of 1,3-diamino-2-propanol and 4-hydroxy-3-formylcoumarin (H3L) in the presence of sodium azide, a tetranuclear copper(II) complex with the composition [Cu2L(μ2-1,1-N3)]2 (I) was obtained. On crystallization from a pyridine solution, the crystalline adduct [Cu2L(μ2-N3)(py)2] (II) (py=pyridine) was obtained and further characterized by XRD. The copper ions in (II) are coordinated by ONO’NO donor atoms of the triply deprotonated pentadentate ligand and the azide anion is coordinated in an asymmetric µ2-1,1 fashion, favoring a “roof”-like conformation of the molecule. The pyridine molecules are coordinated to each copper center, completing the distorted square-pyramidal coordination environment, but in a different way – for one copper ion the solvent molecule populates an apical position, for the other – a position in the basal plane. The tetranuclear complex is formed by linking two binuclear [Cu2L] units by two bridging μ2–1,1–N3 groups in a head-to-tail fashion. The temperature dependence of the magnetic susceptibility was studied for both I and II samples, showing a medium strength overall antiferromagnetic exchange for I and a weak ferromagnetic one with 2J=+5cm−1 for II. Two major superexchange pathways in I – through an alkoxide oxygen atom of the polydenate ligand and through the bridging azide-anion are characterized by opposite magnetic interaction characters – antiferromagnetic (2JO=−328cm−1) and ferromagnetic (2JN=+132cm−1), correspondingly. Quantum-chemical modeling using the broken symmetry approach was performed for II and possible binuclear isomers of I, differing in the azide-anion coordination mode and conformation of the polydentate ligand, and for two possible tetranuclear dimers.

Synthesis and crystal structures of N,N'-bis(5-methylsalicylidene)ethane-1,2-diamine and its bromido-, phenolato-, and dicyanoamido-cobridged polymeric copper(II) complex

A bis-Schiff base N,N'-bis(5-methylsalicylidene)ethane-1,2-diamine (H2L) was prepared and characterized by elemental analysis, 1H NMR and 13C NMR spectra, MS, and single crystal X-ray diffraction (CIF file CCDC no. 1022761 (H2L)). Reaction of the Schiff base with copper bromide and sodium dicyanoamide in methanol gave a novel bromido-, phenolato-, and dicyanoamido-cobridged polymeric copper(II) complex, ({Cu2LBr[N(CN)2]}2)n (I). Structure of complex I was characterized by elemental analysis and single crystal X-ray diffraction (CIF file CCDC no. 1022762 (I)). The smallest repeat unit of complex I is a dicyanoamide bridged tetranuclear copper(II) complex moiety, {Cu2LBr[N(CN)2]}2, in which there possesses a crystallographic inversion symmetry. The tetranuclear moieties are further linked through Br atoms, forming a zigzag chain. The chains are further linked by dicyanoamide ligands, forming a 2D network. One Cu atom in complex I is coordinated by two N and two O atoms of the Schiff base ligand and one Br atom, forming square pyramidal geometry. The other Cu atom is coordinated by two N atoms of the Schiff base ligand, two N atoms of dicyanoamide ligands, and one Br atom, forming square pyramidal geometry. The bromido-, phenolato-, and dicyanoamido-cobridged Cu···Cu distances are 4.823(2), 2.955(1), and 7.121(3) A, respectively. The [Cu2L] units are linked by the bridging groups, to form 2D chains along the xy plane.

Synthesis and structure elucidation of new open cubane tetranuclear [CuII4] Cluster: Evaluation of the DNA/HSA interaction and pBR322 DNA cleavage pathway and cytotoxicity

New open–cubane tetranuclear copper(II) complex of formulation {[Cu4(HL)4(H2O)2]·(CH3OH)2·(H2O)5}(1) derived from Schiff base ligand 2–((E)–(1,3–dihydroxy–2–methylpropan–2–ylimino)methyl)–6–methoxyphenol (HL) was synthesized. The characterization of both ligand (HL) and tetranuclear Cu complex was carried out by analytical, spectroscopic and single crystal X–ray diffraction. The structure analyses revealed that in the tetranuclear core, the metal centers are mutually interconnected via two phenoxo oxygen and two alkoxo oxygen atoms of four H2L2− ligand to generate a distorted single–open [Cu4(μ3–O)2]6+ open cubane core with the four Cu atoms disposed in an extended “butterfly–like” arrangement. Binding of complex 1 with CT DNA was investigated by using vivid spectroscopic techniques to study the mode of the interaction of 1 towards CT DNA. The results obtained indicated that 1 avidly binds to CT DNA via electrostatic mode with an intrinsic binding constant, Kb value 4.63×104M–1. Complex 1 showed an impressive nuclease activity generating single–strand breaks and the mechanistic investigation confirms the contribution of the reactive oxygen species (ROS). Likewise, the interaction of 1 with human serum album (HSA) revealed the change in intrinsic fluorescence intensity of HSA and was supposed to be associated with the microenvironment of Trp residue. Furthermore, the interaction of complex 1 with DNA and HSA was further investigated by the molecular docking studies which corroborated well with above findings. We have also tested 1 for cytotoxicity against the PC3 (Prostate) and K562 (Leukemia) cancer cell lines. The results exhibited were moderate when compared to standard drug viz, adriamycin (ADR).

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

Three, PO43–/HPO42– and AsO43–-incorporated, new tetranuclear complexes of copper(II) and zinc(II) ions have been synthesized and fully characterized. In methanol–water, reactions of H3cpdp (H3cpdp = N,N′-Bis[2-carboxybenzomethyl]-N,N′-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 (1) and K2[Cu4(cpdp)2(μ4-AsO4)](OH)·162/3H2O (2), 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 (3). 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 PO43–/HPO42–/AsO43– 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 1 and 2 disclose moderate antiferromagnetic interactions mediated among the copper centers through alkoxide and phosphate/arsenate bridges. Electrochemical studies of complexes 1 and 2 in dimethylformamide using cyclic voltammetry reveal the presence of a fairly assessable one-electron metal-based irreversible reduction and one quasireversible oxidation couple.

A new stepped tetranuclear copper(II) complex: synthesis, crystal structure and photoluminescence properties.

Binuclear and tetranuclear copper(II) complexes are of interest because of their structural, magnetic and photoluminescence properties. Of the several important configurations of tetranuclear copper(II) complexes, there are limited reports on the crystal structures and solid-state photoluminescence properties of `stepped' tetranuclear copper(II) complexes. A new CuII complex, namely bis{μ3-3-[(4-methoxy-2-oxidobenzylidene)amino]propanolato}bis{μ2-3-[(4-methoxy-2-oxidobenzylidene)amino]propanolato}tetracopper(II), [Cu4(C11H13NO3)4], has been synthesized and characterized using elemental analysis, FT-IR, solid-state UV-Vis spectroscopy and single-crystal X-ray diffraction. The crystal structure determination shows that the complex is a stepped tetranuclear structure consisting of two dinuclear [Cu2(L)2] units {L is 3-[(4-methoxy-2-oxidobenzylidene)amino]propanolate}. The two terminal CuII atoms are four-coordinated in square-planar environments, while the two central CuII atoms are five-coordinated in square-pyramidal environments. The solid-state photoluminescence properties of both the complex and 3-[(2-hydroxy-4-methoxybenzylidene)amino]propanol (H2L) have been investigated at room temperature in the visible region. When the complex and H2L are excited under UV light at 349 nm, the complex displays a strong blue emission at 469 nm and H2L displays a green emission at 515 nm.

New cyclic tetranuclear copper(II) complexes containing quadrilateral cores: Synthesis, structure, spectroscopy and their interactions with DNA in aqueous solution

Three new cyclic tetranuclear copper(II) complexes, Tetrakis{3-[(2-pyridylmethyl)-amino]-propionato}(tetrachloro)tetracopper(II)methanolhydrate (1·CH3OH·H2O), Tetrakis{3-[(2-pyridylmethyl)-amino]-propionato}(tetrathiocyanato)tetracopper(II) (2) and Tetrakis{3-[(2-pyridylmethyl)-amino]-propionato}(tetraazido)tetracopper(II) (3) have been synthesized by exploiting the chelating ability and bridging potential of a carboxyamine functionalized tridentate ligand, HL (HL = 3-[(2-Pyridylmethyl)-amino]-propionic acid). Complexes 1, 2 and 3 have been synthesized by carrying out reaction of the ligand HL with stoichiometric amounts of CuCl2·2H2O, CuCl2·2H2O/NH4SCN, and CuCl2·2H2O/NaN3, respectively, in the presence of NMe4OH at ambient temperature. Various analytical techniques have been employed to characterize the complexes, including single crystal X-ray diffraction study of 1. Structures of complexes 2 and 3 have been optimized by DFT calculation at B3LYP/6-311G level. Analysis of X-ray crystal structure reveals that the metallic core of complex 1 contains four distorted square pyramidal Cu(II) ions. The Cu(II) ions in each complex are arranged at the corners of a quadrilateral showing a μ2:η1:η1syn-anti bidentate bridging mode of four carboxylate groups of L− ligands with each bridging between two Cu(II) ions. These complexes represent a new family of 16-MCCuII-4 metallocoronates with repeating -[CuIIOCO]- units. In aqueous solution (pH∼7.5), the interactions of complexes with DNA have been investigated by UV–Vis and fluorescence titration spectroscopy, and viscosity measurements.

Synthesis, crystal structure, and magnetic property of a stepped tetranuclear copper(II) complex of 3,5-diisopropylpyrazole-1-methoxide

Reaction of copper(II) chloride dihydrate in methanol with deprotonated 3,5-diisopropylpyrazole-1-methanol (dippmOH) led to the tetranuclear copper(II) complex [(dippmO)CuCl]4 (1). The crystal structure of 1 indicates that two copper(II) ions connect via the oxygen atoms of dippmO− ligands each other in which two dimeric units are formed. Furthermore, one of the coordinated oxygen atoms in a dimer is bonded to an adjacent copper(II) ion positioned other dimer, which gives rise to a stepped tetranuclear structure. 1 shows strong antiferromagnetic interactions through the oxo groups within the dimeric units (J1=−239cm−1) and weak antiferromagnetic couplings between the dimers (J2=−15cm−1).