Imidazole derivatives of binuclear copper (II) and nickel (II) complexes incorporating bis(1,4,7-triazacyclononan-1-yl) ligands

A series of new binuclear copper (II) and nickel (II) complexes of the macrocyclic ligands bis(1,4,7-triazacyclononan-1-yl)butane (L^but) and bis(1,4,7-triazacyclononan-1-yl)-m-xylene (L^mx) have been synthesized: [Cu₂L^butBr₄] (1), [Cu₂L^but(imidazole)₂Br₂](ClO₄)₂ (2), [Cu₂L^mx(μ-OH)(imidazole)₂](ClO₄)₃ (3), [Cu₂L^but(imidazole)₄](ClO₄)₄ · H₂O (4), [Cu₂L^mx(imidazole)₄](ClO₄)₄ (5), [Ni₂ L^but(H₂O)₆](ClO₄)₄ · 2H₂O (6), [Ni₂L^but(imidazole)₆](ClO₄)₄ · 2H₂O (7) and [Ni₂L^mx (imidazole)₄(H₂O)₂](ClO₄)₄ · 3H₂O (8). Complexes 1, 2, 7 and 8 have been characterized by single crystal X-ray studies. In each of the complexes, the two tridentate 1,4,7-triazacyclononane rings of the ligand facially coordinate to separate metal centres. The distorted square-pyramidal coordination sphere of the copper (II) centres is completed by bromide anions in the case of 1 and/or monodentate imidazole ligands in complexes 2, 4 and 5. Complex 3 has been formulated as a monohydroxo-bridged complex featuring two terminal imidazole ligands. Complexes 6-8 feature distorted octahedral nickel (II) centres with water and/or monodentate imidazole ligands occupying the remaining coordination sites. Within the crystal structures, the ligands adopt trans conformations, with the two metal binding compartments widely separated, perhaps as a consequence of electrostatic repulsion between the cationic metal centres. The imidazole-bearing complexes may be viewed as simple models for the coordinative interaction of the binuclear complexes of bis (tacn) ligands with protein molecules bearing multiple surface-exposed histidine residues.     

Polynuclear and polymeric metal complexes based upon 1,2,4-triazolyl functionalized adamantanes

A series of coordination compounds [Cd₂(trad)₇Br₂][Cd(trad)Br₃]₂ (1), [Cd₃(trad)₆{N(CN)₂}₄(H₂O)₂](N(CN)₂)₂ (2), [{Cd₂(trad)₅}{Cd(N(CN)₂)₆}]·3CH₃OH (3), [{Cd₃(trad)₆(SeCN)₂}{Cd(SeCN)₄}₂] (4), [Cd₂(trad)₃(NCS)₄] (5), [Cd₃(tr₂ad)₃(μ-NCS)₃](NCS)₃ (6), [Cd₃(tr₂ad)₆](NO₃)₆·22H₂O (7), [Cu₃(tr₂ad)₄(SO₄)(H₂O)₃](SO₄)₂·34H₂O (8) and [Cu₂(OH)(tr₂ad)₂](NO₃)₃·4H₂O (9) (trad = 4-(adamantan-1-yl)-1,2,4-triazole; tr₂ad = 1,3-bis(1,2,4-triazol-4-yl)-adamantane) revealed the potential of 1,2,4-triazolyl functionalized adamantanes for design of metal-organic polymers incorporating polynuclear coordination units as multiconnected nodes. Structures 1-5 are based upon characteristic di- and trinuclear clusters involving triple triazole bridges [M(μ₂-trad)₃M] (M = Cd), while doubling of the ligand functionality (tr₂ad) allows integration of the clusters into 3D polymeric frameworks 6-9 (M = Cd, Cu).     

Synthesis, structures, and magnetic properties of dicopper(II) and dinickel(II) complexes with a new bis(macrocycle), 7,7-(2-hydoxypropane-1,3-diyl)bis{3,7,11,17-tetraazabicyclo[11.3.1]- heptadeca-1(17),13,15-triene}

A new bis(macrocycle) ligand, 7,7^′-(2-hydoxypropane-1,3-diyl)-bis{3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene} (HL), and its dicopper(II) ([Cu₂(HL)Cl₂](NO₃)₂ · 4H₂O (4a), [Cu₂(HL)I₂]I₂ · H₂O (4b)) and dinickel(II) ([Ni₂(L)(OH₂)](ClO₄)₃ (5a), [Ni₂(L)(OH₂)]I₃ · 2H₂O (5b), [Ni₂(L)N₃](N₃)₂ · 7H₂O (5c)) complexes have been synthesized. The alkoxide bridged face-to-face structure of the dinickel(II) complex 5c has been revealed by X-ray crystallography, as well as the “half-opened clamshell” form of the bis(macrocyclic) dicopper(II) complex 4b. Variable temperature magnetic susceptibility studies have indicated that there exists intramolecular antiferromagnetic coupling (J=−33.8 cm⁻¹ (5a), −32.5 cm⁻¹ (5b), and −29.7 cm⁻¹ (5c)) between the two nickel(II) ions in the nickel(II) complexes.     

Two new 3D (3,8)-connected metal-organic frameworks based on zinc-triazole secondary building units and benzenetricarboxylate linkers

Two new zinc-triazole-carboxylate frameworks constructed from secondary building units (SBUs), [Zn₅(trz)₄(btc)₂(DMF)₂(H₂O)₂]·2H₂O·DMF (1) and [Zn₄(trz)₃(btc)₂(CH₃CN)(H₂O)]·5H₂O·(Bu₄N) (2), [Htrz = 1,2,4-triazole, H₃btc = 1,2,4-benzenetricarboxylate, Bu₄N = tetrabutylammonium], have been synthesized by solvothermal reactions and characterized by single-crystal X-ray diffraction analyses, X-ray power diffraction, elemental analyses, infrared spectra and thermogravimetric analyses. Both compounds 1 and 2 exhibit 3D (3,8)-connected tfz-d nets with {4³}₂{4⁶.6¹⁸.8⁴} topology symbol built from rod-shaped {[Zn₅(trz)₄]⁶⁺}_n SBUs (1) and {[Zn₄(trz)₃]⁵⁺}_n SBUs (2). In two compounds, rodlike units are connected by btc ligands via different modes. Additionally, solid state fluorescent emission spectra of two compounds show fluorescent properties at room temperature.     

Supramolecular assembly driven by hydrogen-bonding and π-π stacking interactions based on copper(II)-terpyridyl complexes

Six 2D and 3D supramolecular complexes [Cu(L1)(O₂CCH₃)₂] · H₂O (1), [Cu₂(L2)₂(μ₂-O₂CCH₃)₂](BF₄)₂ (2), [Cu₂(L1)₂(BDC)(NO₃)₂] · 0.5H₂O (3) [Cu₂(L2)₂(BDC)(NO₃)₂] (4), [Cu₂(L3)₂(BDC)(NO₃)₂] · 0.5H₂O (5) and [Cu₂(L2)₂(BDC)(H₂O)₂](BDC) · 8H₂O (6) (L1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, L2 = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine, L3 = 4′-phenyl-2,2′:6′,2″-terpyridine, BDC = 1,4-benzenedicarboxylate), have been prepared and structurally characterized by X-ray diffraction crystallography. In complexes 1, 3, and 4, 1D channels are formed through C-H?O and C-H?N hydrogen-bonding interactions, and further linked into 3D structure via C-H?O and O-H?O interactions. Complex 2 is a 2D layer constructed from intermolecular C-H?F and π-π stacking interactions. In the structure of 6, the BDC²⁻ ions and solvent water molecules form a novel 2D layer containing left- and right-handed helical chains via hydrogen-bonds, and an unusual discrete water octamer is formed within the layer. In 2, 4, 6 and [Ag₂(L2)₂](PF₆)₂ (7) the bonding types of pendent pyridines of L2 depending on the twist about central pyridines are involved in intramolecular (2 and 4), intermolecular (6) or coordination bonds (7) in-twist-order of 5.8°, 3.7°, 28.2° and 38.0°, respectively. Differently, the pendent pyridines of L1 in 1 and 3 form intermolecular hydrogen bonds despite of distinct corresponding twist angles of 25.1° (1) and 42.6°(3). Meanwhile, π-π stacking interactions are present in 1-6 and responsible for the stabilization of these complexes.     

Syntheses, structures and magnetic properties of tetranuclear and trinuclear nickel(II) complexes with β-diketone-functionalized pyridinecarboxylate ligand

The new β-diketone-functionalized pyridinecarboxylate ligand 2-(3-oxo-3-phenyl-propionyl)-6-pyridinecarboxylic acid (H₂L) has been synthesized and fully characterized. Its tetranuclear and trinuclear nickel(II) coordination compounds [Ni₄L₄(DMF)(H₂O)₃]·2.5DMF·3H₂O (1) and [Ni₃L₂(OAc)₂(DMF)₂ (H₂O)₂]·DMF·H₂O (2) have also been synthesized and characterized by single crystal X-ray diffraction. Compound 1 has a [2 × 2] molecular grid structure and 2 is a trinuclear structure. The magnetic properties study of 1 and 2 revealed the intramolecular antiferromagnetic exchange coupling between the Ni(II) ions exists.     

Keggin polyoxometalates-supported assembly of 2D supramolecular isomers: Synthesis, crystal structures and characteristics of two novel hybrid host-guest complexes

Two novel hybrid host-guest architectures based on metal-organic fragments and Keggin polyoxometalates, namely [α-Cu₁₂(trz)₈][PMo₁₂O₄₀] · H₂O (1) and [β-Cu₁₂(trz)₈][PMo₁₂O₄₀] · 2H₂O (2) (trz = 1,2,4-triazole), have been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction (XRD), elemental analysis, powder XRD, ESR, FT-IR, UV-Vis, and thermogravimetric analysis (TGA). The [Cu₁₂(trz)₈]⁴⁺ hosts in compounds 1 and 2 are two-dimensional (2D) supramolecular isomers, which present 4⁴ topology based on Cu₄(trz)₄ cyclic units and 6³ topology based on Cu₃(trz)₃ cyclic units, respectively. The metalmacrocyclic Cu₈(trz)₈ and Cu₉(trz)₉ rings represent the largest examples in the coordination chemistry of 1,2,4-triazole. 2D metal-organic fragments and Keggin anions both are connected via hydrogen bonds and Cu?O short contacts to form interesting 3D host-guest architectures of 1 and 2.     

Europium (III) complexes derived from carboxylic-substituted polychlorotriphenylmethyl radicals

Two europium (III) complexes (3 and 4) have been obtained reacting europium (III) nitrate and two polychlorotriphenylmethyl radicals properly functionalized with one (PTMMC⁻, 1) and six (PTMHC⁶⁻, 2) carboxylate groups, respectively. While complex 3 reveals a lamellar polar-apolar separated ion pair structure alternating PTM-based bilayers with nonaaquaeuropium cations ([Eu(H₂O)₉](PTMMC)₃(PTMMCH)₃ · 7H₂O · 6EtOH), complex 4 shows a one-dimensional chain-like structure with formula [Eu₂(PTMHC)(H₂O)₁₃] · 16H₂O · EtOH. Magnetic properties of both complexes were studied in the 2-300 K range, and show the presence of weak inter-radical antiferromagnetic interactions below 5 K.     

Supramolecular architectures of cadmium(II) built of 2,2′-biimmidazole and bifunctional carboxylates: Syntheses, crystal structure and properties

A series of four new supramolecular complexes of cadmium(II), {[CdBr(H₂biim)(PyCO₂)(H₂O)](H₂O)}_∞ (1) (H₂biim = 2,2′-biimidazole, PyCO₂ = isonicotinate), [Cd(H₂biim)₂(HBDC)₂] (2) (H₂BDC = terephthalic acid), [Cd(H₂biim)₂(H₂O)₂](BDC) (3) and [Cd(H₂biim)₂(H₂O)₂](PyCO₂)₂ · 4H₂O (4) have been prepared and characterized by X-ray crystallography, IR, fluorescence spectra and thermogravimetric analysis. Compound 1 exhibits an infinite chain-like structure through bridging isonicotinate. Strong interchain hydrogen bonds between isonicotinate and H₂biim result in the robust 2-D sheet structure, responsible for the insolubility. The similar hydrogen bonds between H₂biim and the coordinated 1,4-bdc and complementary hydrogen bonds between monoprotonated bdc are responsible for the robust 2-D layered structure of 2 that is insoluble in aqueous solution. 1,4-Bdc becomes uncoordinated in the soluble complex 3, although it has hydrogen bonded 2-D structure as well.     

Syntheses, crystal structures and magnetic properties of trinuclear and [3 × 1 + 1 × 2] pentanuclear complexes derived from a compartmental ligand: Role of solvent on nuclearity and number of components

Reaction of [Cu^IIL⊂(H₂O)] (H₂L = N,N′-ethylenebis(3-ethoxysalicylaldimine)) with nickel(II) perchlorate in 1:1 ratio in acetone produces the trinuclear compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂ (1). On the other hand, on changing the solvent from acetone to methanol, reaction of the same reactants in same ratio produces the pentametallic compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)]·2MeOH (2A), which loses solvated methanol molecules immediately after its isolation to form [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)] (2B). Clearly, formation of 1 versus 2A and 2B is solvent dependent. Crystal structures of 1 and 2A have been determined. Interestingly, compound 2A is a [3 × 1 + 1 × 2] cocrystal. The cryomagnetic profiles of 1 and 2B indicate that the two pairs of copper(II)···nickel(II) ions in the trinuclear cores in both the complexes are coupled by almost identical moderate antiferromagnetic interaction (J = −22.8 cm⁻¹ for 1 and −26.0 cm⁻¹ for 2B).     

Pyrazolato-bridged 1-D Co(II) coordination polymer and dinuclear Ni(II) and Cu(II) complexes: Syntheses, crystal structures and magnetic properties

Three complexes of composition [Co₃(Hdcp)₂(phen)₃(H₂O)₂]_n · nH₂O (1), [Ni₂(Hdcp)₂(H₂O)₄](Im)₂ (2) and [Cu₂(Hpca)₂(H₂O)₂(Im)₂] (3) (H₃dcp = 3,5-pyrazoledicarboxylic acid, H₂pca = 1H-pyrazole-5-carboxylic acid, Im = imidazole and phen = 1,10-phenanthroline) have been synthesized via hydrothermal reactions and their structures have been characterized. Complex 1 is mainly constructed by Hdcp and ancillary ligand 1,10-phenanthroline and exhibits one-dimensional linear chain structure. Complexes 2 and 3 are pyrazolato-bridged dinuclear complexes. The ancillary imidazole ligand was not involved in the coordination and stacked to the lattice of the complex in 2. In the process of synthesis 3, imidazole ligand was coordinated to the metal centre; with one of the carboxylic group of the H₃dcp ligand was eliminated to form [Cu₂(Hpca)₂(H₂O)₂(Im)₂] (3) in situ. The results of magnetic susceptibility measurements indicate that there exist antiferromagnetic interactions between Co(II) and Ni(II) centres in compounds 1 and 2, respectively.     

Photoluminescent coordination polymers of d metals with 4,4′-dipyridylsulfide (dps)

Reactions of AgClO₄, Zn(CH₃COO)₂ · H₂O and CuI with the ligand 4,4′-dipyridylsulfide (dps) in 1:1 ratio give rise to coordination polymers 1-3 and 5, the structures of which were characterized by X-ray crystallography. Polymers [Ag₂(dps)₂](ClO₄)₂ · MeCN (1) and [Ag₂(dps)₂(μ₂-MeCN)(MeCN)](ClO₄)₂ · MeCN · H₂O (2) are pseudo-supramolecular isomers, differing from each other in the coordination geometry of silver atom and the packing pattern. Both 1 and 2 are zigzag coordination polymers bridged by weak Ag?Ag, Ag?S or Ag?NC-CH₃ interactions to form double stranded coordination polymers. While [Zn(dps)(CH₃COO)₂] (3) is a zigzag single stranded coordination polymer, [Zn(dps)₂(H₂O)₂](ClO₄)₂ · H₂O (4) is an unusual mononuclear complex with a box-like structure. Interesting intermolecular hydrogen bonding present in the compounds 3 and 4 leads to 3D hydrogen-bonded network structure.Coordination polymer [Cu₂I₂(dps)₂] (5) is a non-interpenetrating (4,4) net. Photoluminescence properties of the compounds 1-5 have been examined in solid states at room temperature. These compounds have been found to exhibit yellow and blue photoluminescence.     

Metal-organic open frameworks with one-dimension channels assembled with pyridine 2,6-dicarboxylic acid and N-containing auxiliary ligands: Syntheses, crystal structures, and physical characterization

Four new complexes, {[Mn(imH)₂(pdc)]·H₂O}_n (1), [Zn₂(pdc)₂(H₂O)₅]·2H₂O (2), [Zn(imH)₂(pdc)]·H₂O (3), {[Zn₂(pdc)₂(bpy)(H₂O)₂]·5H₂O}_n (4) [imH = imidazole pdc = pyridine 2,6-dicarboxylate, bpy = 4,4′-bipyridine] have been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR, PXRD, single-crystal X-ray diffraction and thermogravimetric analyses. All the four complexes display a three-dimensional (3D) open framework with one-dimensional (1D) channels that are filled with lattice water molecules. Particularly, in 4, the lattice water molecules form an infinite water chain. Both 1 and 4 consist of 1D polymeric chains. While 2 contains a dinuclear Zn(II) unit, and 3 is a mononuclear complex. Further, the result of thermal analysis of 1 and 2 shows the robustness of the overall supramolecular three-dimensional architecture. Complexes 1, 3, and 4 exhibit strong fluorescent emissions in the solid state at room temperature and could be significant in the field of photoactive materials.     

Synthesis, structure and fluorescence of two novel manganese(II) and zinc(II)-1,3,5-benzene tricarboxylate coordination polymers: Extended 3D supramolecular architectures stabilised by hydrogen bonding

Two new coordination polymers {[Mn(H₂btc)(phen)(H₂O)₂]H₂btc · H₂O}_n (1) [H₃btc = 1,3,5-benzene tricarboxylic acid, phen = phenanthroline] and {[Zn₃(btc)₂(H₂O)₈](H₂O)₄}_n (2) have been synthesised and structurally characterised. Both the complexes crystallise as 1D chain, which further propagates through ligand-based hydrogen bonding interactions into a 3D supramolecular architecture. Supramolecular framework of 1 is constructed by [Mn(H₂btc)(phen)(H₂O)₂]⁺ as well as the constituent materials-uncoordinated H₂btc⁻ and water molecules. Complex 2 exists as a corrugated chain with both the bridging and terminal Zn²⁺ ions and each zinc centre is coordinated to four water molecules. Both 1 and 2 are stacked by mutual π-stacking of the ligands and exhibit strong fluorescence emission band at 414 and 400 nm, respectively.     

Construction of three low dimensional Zn(II) complexes based on different organic-carboxylic acids

Three new Zn(II) complexes based on different organic-carboxylic acids, [Zn(mba)₂(2,2′-bipy)] (1), [Zn(mpdaH)₂(H₂O)₄] · 4H₂O (2) and [Zn(cda)₂(H₂O)₂]_n (3) (Hmba = 4-methylbenzoic acid, H₂mpda = 2,6-dimethylpyridine-3,5-dicarboxylic acid and H₂cda = chelidonic acid) have been synthesized successfully under hydrothermal conditions. X-ray single crystal diffractions show that compounds 1 and 2 are the mononuclear and 3 is one-dimensional chain, in which the Zn(II) centers have different coordination geometries with octahedron for 1 and 2 and tetrahedron for 3. Through π-π stacking and/or hydrogen bonding (O-H?O and O-H?N) interactions, different supramolecular structures are assembled, namely, 2D supramolecular layer for 1 and 3D supramolecular networks for 2 and 3. Furthermore, the IR, TGA and luminescent properties are also investigated in this work.     

Construction of three one-dimensional zinc(II) complexes containing pyrazine-2,3-dicarboxylic acid

Three one-dimensional zinc complexes, namely, [Zn(pzdc) · 3H₂O] · H₂O (1), [Zn₂(pzdc)₂ · 4H₂O] · 2.5H₂O (2), and [Zn(pzdc)(phen) · 4H₂O]_n (3) (H₂pzdc, pyrazine-2,3-dicarboxylic acid, phen = 1,10-phenanthroline), have been synthesized successfully under hydrothermal condition. X-ray diffraction analyses reveal that complex 1 is a square-wave-like chain and complex 2 shows a 1D ladder-like infinite chain, while complex 3 has 1D zigzag chain structure. In all cases, the Zn(II) centers have octahedral coordination geometries. Through hydrogen bonding (such as O-H···O, O-H···N and C-H···O) and/or π-π stacking interactions, three-dimensional supramolecular networks are constructed in three complexes. Furthermore, the IR, TGA and luminescent properties are also investigated in this work.     

Assembly of two novel cadmium(II) supramolecular architectures constructed from pyridine-functionalized 1,10-phenanthroline ligand

Two novel cadmium(II) coordination polymers [Cd(pyip)(ox)]·H₂O (1) and [Cd₂(pyip)₂(ox)₂·(H₂O)][Cd(pyip)(ox)]·4(H₂O) (2) (pyip = 2-(pyridin-3-yl-1H-imidazo [4,5-f][1,10]phenanthroline, H₂ox = oxalic acid), have been hydrothermal synthesized and characterized by single crystal X-ray diffraction. Compound 1 is 1D zigzag chain, in which oxalate anion as bridging ligand is responsible for the formation of the main framework and pyip as chelating ligand grafts on two sides of the zigzag chain. Compound 2 contains two kinds of independent polymers [Cd₂(pyip)₂(ox)₂(H₂O)] (A) and [Cd(pyip)(ox)] (B) to form an interdigitated 1D + 1D structure, in which polymers A and B are paratactically assembled in an ABCD sequence. The fundamental unit of polymer B in 2 is the same as that in 1. For compounds 1-2, weak interactions, primarily hydrogen bonding and π?π stacking interactions, have greatly influence on the supramolecular motifs recognized in the crystal packing. Especially, the oxalate anions as bridging ligand simultaneously adopt multiform coordination modes in two compounds. In addition, 1 and 2 displayed a strong fluorescent emission in the solid state at room temperature.     

Two forms of a copper(II) complex of 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole: a six-coordinate monomer versus a five-coordinate polymer

The reaction of the new bidirectional ligand 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole (pyppt) with Cu(ClO₄)₂ · 6H₂O in a 2:1 molar ratio in EtOH affords the complex [Cu^II(pyppt)₂(ClO₄)₂] · H₂O (1) as a microcrystalline turquoise solid. Recrystallisation of complex 1 from MeCN by vapour diffusion of Et₂O gives blue crystals of the monomeric octahedral complex [Cu^II(pyppt)₂(ClO₄)₂] · MeCN (2). In contrast, addition of EtOH to a solution of complex 1 in MeCN followed by slow evaporation yields blue crystals of the five-coordinate polymeric complex {[Cu^II(pyppt)₂](ClO₄)₂ · EtOH}_∞ (3). The structures of both complexes have been determined by single crystal X-ray diffraction.     

Dinuclear terephthalato-bridged nickel(II) complexes. Structural characterization and magnetic properties

The dinuclear terephthalato-bridged nickel(II) complexes [Ni₂(cyclen)₂(μ-tp)](ClO₄)₂ (1) [Ni₂(trpn)₂(μ-tp)(H₂O)₂](ClO₄)₂ (2) and [Ni₂(3,3,3-tet)₂(μ-tp)(H₂O)₂](ClO₄)₂ · 2H₂O (3), where tp = terephthalate dianion, cyclen = 1,4,7,10-tetraazacyclododecane, trpn = tris(3-aminopropyl)amine and 3,3,3-tet = 1,5,9,13-tetraazatridecane, were synthesized and structurally characterized by X-ray crystallography. Their magnetic susceptibilities were also determined at variable temperatures over the range 2-300 K. The structures of these complexes consist of μ-tp bridging two Ni(II) centers in a bis(bidentate) bonding fashion in 1 and in bis(monodentate) bonding fashion in 2 and 3. The coordination geometry around the Ni(II) ions in these compounds has a distorted octahedral geometry with four nitrogen atoms from the amine ligand (cyclen, trpn or 3,3,3-tet) and two coordinated oxygen atoms supplied by the chelated carboxylate group of the bridged terephthalate ligand in 1, and by one tp-carboxylate-oxygen in 2 and 3. The sixth coordination site in the last two complexes 2 and 3 is achieved via an oxygen atom from a coordinated water molecule. The intradimer Ni…Ni distances in these complexes are 10.740, 11.428 and 11.537 Å for 1, 2 and 3, respectively. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Ni(II) centers. Also, the analysis of the infrared spectral data for the ν(COO⁻) stretching frequencies of the tp-carboxalato groups reveals the existence of the bis(bidentate) and bis(monodentate) coordination modes for the bridged terephthalate ligand in 1, 2 and 3, respectively. Despite the different coordination modes of the tp bridging ligand in these complexes, they all exhibit very weak antiferromagnetic coupling. The coupling constants J were found to be −2.2, −0.6 and −1.5 cm³ K mol⁻¹ for the complexes 1, 2 and 3, respectively. The structural and magnetic results of 1-3 are discussed in relation to the other related published μ-terephthalato dinuclear Ni(II) compounds.     

Synthesis, crystal structures, DNA-binding properties, cytotoxic and antioxidation activities of several new ternary copper(II) complexes of N,N′-(p-xylylene)di-alanine acid and 1,10-phenanthroline

Three novel ternary copper(II) complexes, [Cu₂(phen)₂(l-PDIAla)(H₂O)₂](ClO₄)₂·2.5H₂O (1), [Cu₄(phen)₆(d,l-PDIAla)(H₂O)₂](ClO₄)₆·3H₂O (2) and [Cu₂(phen)₂(d,l-PDIAla)(H₂O)](ClO₄)₂·0.5H₂O (3) (phen = 1,10-phenanthroline, H₂PDIAla = N,N’-(p-xylylene)di-alanine acid) have been synthesized and structurally characterized by single-crystal X-ray crystallography and other structural analysis. Spectrometric titrations, ethidium bromide displacement experiments, CD (circular dichroism) spectral analysis and viscosity measurements indicate that the three compounds, especially the complex 3, strongly bind to calf-thymus DNA (CT-DNA). The intrinsic binding constants of the ternary copper(II) complexes with CT-DNA are 0.89 × 10⁵, 1.14 × 10⁵ and 1.72 × 10⁵ M⁻¹, for 1, 2 and 3, respectively. Comparative cytotoxic activities of the copper(II) complexes are also determined by acid phosphatase assay. The results show that the ternary copper(II) complexes have significant cytotoxic activity against the HeLa (Cervical cancer), HepG2 (hepatocarcinoma), HL-60 cells (myeloid leukemia), A-549 cells (pulmonary carcinoma) and L02 (liver cells). Investigations of antioxidation properties show that all the copper(II) complexes have strong scavenging effects for hydroxyl radicals and superoxide radicals.