Synthesis, crystal structure and photoelectric property of Mn(II/IV) coordination complexes

Three novel coordination complexes [Mn(tpha)(phen)]_n (1); [Mn(na)₂(H₂O)₂]_n (2); {[Mn(phen)₂(OH)Cl] · Cl · (OH) · (C₉H₁₁NO₂) · 2H₂O} (3) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction (H₂tpha = terephthalic acid, Hna = nicotinic acid, phen = 1,10-phenanthroline). The tpha groups in complex 1 bridge the Mn(II) ions to an infinite 3D framework. Complex 2 exhibits a 2D network structure in which the Mn(II) ions are linked by nicotinic groups. Complex 3 is connected to a 2D coordination supramolecule by hydrogen bonds. The results of surface photovoltage spectra (SPS) of complexes 1-3 indicate that they all exhibit positive surface photovoltage (SPV) responses in the range of 300-800 nm. However, the intensity, position and numbers of SPV responses are obviously different. The distinctions can be mainly attributed to their structures, valences and coordination environments of the manganese ions in the three complexes. Moreover the external field induced surface photovoltage spectra (FISPS) of the three complexes have been measured.     

Manganese(II) and zinc(II) compounds via amino acid derivatives: Effects of temperature and solvents

To investigate the influence of temperature and the ratios of solvents on the design and synthesis of metal-organic frameworks (MOFs), we have synthesized and structurally characterized a series of supramolecular assemblies based on different amino acid derivatives and nitrogen-containing heterocyclic ligands, namely [Mn(phen)₂(phth)(H₂O)]·4H₂O (1), [Mn(phen)₂(HL1)₂]·3.5H₂O (2), [Zn(bpp)₂(L-Me)₂] (3), and [Zn(bpp)(L-Me)₂] (4) (H₂phth = phthalic acid, H₂L¹ = phthalyl-l-valine, H₂L = (+)-N-tosyl-l-glutamic acid, phen = 1,10-phenanthroline, bpp = 1,3-bis(4-pyridyl)propane, and L-Me = C₁₂H₁₃NO₆S-CH₃). Compounds 1 and 2, which are assembled through noncovalent interactions, were obtained by controlling the temperature. In 1, π-π stacking and hydrogen-bonding interactions lead to stacking in a 3D supramolecular network, while in 2, π-π stacking interactions form 1D chains that extend along the c-axis. Depending on the solvents employed, compounds 3 and 4 could be generated, with a 1D bpp-connected Zn-bpp-Zn double chain that is further hydrogen-bonded into a 2D network that extends parallel to the ac plane in 3, and a single chain in 4.     

Zinc complexes with tricarballylic acid and Lewis bases with zero- and two-dimensional structures

Three ternary zinc complexes of the open chain polycarboxylic acid, tricarballylic (1,2,3-propane-tricarboxylic) acid (PTCH₃) have been isolated and characterized with crystallographic and physicochemical techniques. [Zn(PTCH)(phen)(H₂O)]₂ · 4H₂O (1) (where phen = 1,10-phenanthroline) has a unique dinuclear structure, while [Zn(PTCH)(bpy)]_n · 3nH₂O (2) and [Zn(PTCH)(epy)]_n · 4nH₂O (3) (where bpy = 4,4′-bipyridine and epy = 1,2-bis(4-pyridine)ethane) have 2D polymeric structures. The bis-deprotonated ligand, in all three complexes, uses for coordination only two oxygen atoms, which belong to the same carboxylate in 1, and to two different carboxylates in 2 and 3.     

A series of d transition metal coordination complexes: Structures and comparative study of surface electron behaviors (n = 9, 8, 7, 6, 5)

Ten transition metal coordination complexes [Cu₂(phen)(p-tpha)(μ-O)]_n1, [Cu(m-tpha)(imH)₂]_n2, [Ni(5-Haipa)₂(H₂O)₂]_n3, [Ni(phen)₂(H₂O)₂]·btc·[Ni(H₂O)₆]_0.5·9H₂O 4, [Co(2,5-pdc)(H₂O)₂]_n·nH₂O 5, [Co₂(2,5-pdc)₂(H₂O)₆]_n·2nH₂O 6, [Fe(2,5-Hpdc)₂(H₂O)₂]·H₂O 7, [Co(C₆H₄NO₂)₃]·H₂O 8, [Fe₂(μ₂-btec)(μ₂-H₂btec)(bipy)₂(H₂O)₂]_n9, [Mn(phen)(2,5-pdc)(H₂O)₂]·H₂O 10 (H₄btec = 1,2,4,5-benzenetetracarboxylic acid, phen = 1,10-phenanthroline, 2,5-H₂pdc = 2,5-pyridine-dicarboxylic acid, p-tpha = p-phthalic acid, m-tpha = m-phthalic acid, bipy = 2,2′-bipyridine, 5-H₂aipa = 5-aminoisophthalic acid, imH = imidazole, H₃btc = 1,3,5-benzenetricarboxylic acid) were synthesized through hydrothermal method. They were characterized by UV-Vis absorption spectra, single-crystal X-ray diffraction and surface photovoltage spectra (SPS). Structural analysis indicated that the complexes 1, 2, 3, 5, 6 and 9 were linked into infinite structures bridged by organic acid ligands. The other four complexes were molecular complexes and further connected to 2D or 3D structures by the hydrogen bonds. The SPS of complexes 1-10 indicate that there are positive response bands in the range of 300-800 nm showing different levels of photo-electric conversion properties. The intensity, position, shape and the number of the response bands in SPS are obviously different since the structure, species, valence, dⁿ electrons configuration and coordinated environment of the center metals are different. There are good relationships between SPS and UV-Vis spectra.     

Manganese(II) coordination polymers with bis(5-tetrazolyl)methane: Synthesis, structure and magnetic properties

Two new Mn(II) coordination polymers with bis(5-tetrazolyl)methane (H₂btm), [Mn(btm)(phen)(H₂O)] · H₂O (1) and [Mn(btm)(2,2′-bpy)] · 1.5H₂O (2), have been synthesized and their structures determined by X-ray diffraction. In complex 1, the btm ligands assume the μ₂-1,1′:4 coordination mode and interlink Mn(II) ions into infinite one-dimensional chains. The chains are assembled into a three-dimensional architecture via hydrogen bonds and π-π interactions. For 2, Mn(II) ions are connected by btm ligands in the μ₃-1,1′:2:3′ mode to produce two-dimensional (6,3) coordination network. Magnetic investigations revealed that interactions through the btm bridges in both 1 and 2 are antiferromagnetic.     

Synthesis, crystal structure and magnetic properties of new dinuclear Mn(III) compounds with 4-ClC6H4COO and 4-BrC6H4COO bridges

Four new dinuclear Mn(III) compounds have been synthesised: [{Mn(bpy)(H₂O)}₂(μ-4-ClC₆H₄COO)₂(μ-O)}](ClO₄)₂ (1), [{Mn(EtOH)(phen)}₂(μ-O)(μ-4-ClC₆H₄COO)₂](ClO₄)₂ (2), [{Mn(bpy)(EtOH)}(μ-4-BrC₆H₄COO)₂(μ-O){Mn(bpy)(ClO₄)](ClO₄) (3) and [{Mn(H₂O)(phen)}₂(μ-4-BrC₆H₄COO)₂(μ-O)](ClO₄)₂ (4). The crystal structures of 2 and 3 are evidence for the tendency of the ethanol and the perchlorate to act as ligands. Due to the coordination of these groups, the environment of the manganese ions is elongated in the monodentate ligand direction, and this distortion is more important when this ligand is the perchlorate. The magnetic properties of the four compounds have been analysed: compounds 1, 3 and 4 show antiferromagnetic behaviour, with J = −6.33 cm⁻¹ for 1, J = −6.76 cm⁻¹ for 3 and J = −3.08 cm⁻¹ for 4 (H = −JS₁·S₂), while compound 2 shows a very weak ferromagnetic coupling. For this compound, at low temperature the most important effect on the χ_MT data is the zero-field splitting of the ion, and the best fit was obtained with |D_Mn| = 2.38 cm⁻¹ and |E_Mn| = 0.22 cm⁻¹.     

3D supramolecular network assembly and thermal decomposition of new copper(II) complexes with pyrazine-2,6-dicarboxylic acid

Four new Cu(II) complexes [Cu(pzda)(2,2′-bpy)(H₂O)] · 2.5H₂O (1), [Cu(pzda)(phen)(H₂O)] · H₂O (2), [Cu(pzda)(4,4′-bpy)] · H₂O (3) and [Cu(pzda)(bpe)_0.5(H₂O)] (4) were synthesized by hydrothermal reactions of copper salt (acetate or sulphate) with pyrazine-2,6-dicarboxylic acid (H₂pzda), and 2,2′-bipyridine (2,2′-bpy), 1,10-phenanthroline (phen), 4,4′-bipyridine (4,4′-bpy) or 1,2-bis(4-pyridyl)-ethane (bpe), respectively. For 1 and 2, they are both monomeric entities which are further assembled into 3D supramolecular networks by hydrogen bonds and π-π stacking interactions. Complex 3 has a 2D metal-organic framework which is connected into 3D supramolecular network by hydrogen bonds. However, for 4, the bpe ligand bridges two Cu(II) ions into binuclear unit, and then the binuclear molecules are assembled into 3D supramolecular network by hydrogen bonds between the coordination water molecule and the carboxylate oxygen atoms. The thermal decomposition mechanism of complexes 1 and 2 cooperated with powder XRD at different temperatures is discussed. The results reveal that once liberation of water molecules takes place the supramolecular network of 1 and 2 collapses.     

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.     

Synthesis, crystal structure and magnetic characterization of a series of four phenoxo-bridged binuclear manganese(III) Schiff base complexes

A family of four new phenoxo-bridged binuclear manganese(III) complexes of the general formula, [Mn(L)(X)]₂ where L = [N,N′-bis(salicylidene)]propane-1,2-diamine and X = salicylaldehyde anion (sal⁻) (1); NCS⁻ (2); NCO⁻ (3) and [Mn(L′)(N₃)]₂·2C₂H₅OH (4) where L′ = [N,N′-bis(2-hydroxyacetophenylidene)]propane-1,2-diamine has been prepared. The syntheses have been achieved by reacting manganese perchlorate with 1,2-diaminopropane and salicylaldehyde (or 2-hydroxyacetophenone for 4) or along with the respective pseudohalides so that the tetradentate Schiff base H₂L or H₂L′ is obtained in situ to bind the Mn(III) ion. The complexes have been characterized by IR spectroscopy, elemental analysis, crystal structure analysis and variable-temperature magnetic susceptibility measurements. The single crystal X-ray diffraction studies show that the compounds are isostructural containing dimeric Mn(III) units with bridging phenolate oxygen atoms. Low temperature magnetic studies indicate that the complexes 1-3 exhibit intradimer ferromagnetic exchange as well as single-molecule magnet (SMM) behavior while complex 4 is found to undergo an intradimer antiferromagnetic coupling.     

A series of metal-organic frameworks constructed with 2,2′-bipyridine-3,3′-dicarboxylate: Syntheses, structures, and physical properties

To determine the influence of metal ion and the auxiliary ligand on the formation of metal-organic frameworks, six new coordination polymers, {[Mn₂(bpdc)(bpy)₃(H₂O)₂] · 2ClO₄ · H₂O}_n (1), {[Mn(bpdc)(dpe)] · CH₃OH · 2H₂O}_n (2), {[Cu(bpdc)(H₂O)₂]}_n (3), {[Zn(bpdc)(H₂O)₂]}_n (4), {[Cd(bpdc)(H₂O)₃] · 2H₂O}_n (5), and {[Co(bpdc)(H₂O)₃] · 0.5dpe · H₂O}_n (6) (H₂bpdc = 2,2′-bipyridine-3,3′-dicarboxylic acid, bpy = 2,2′-bipyridine, dpe = 1,2-di(4-pyridyl) ethylene), have been synthesized and characterized. Compound 1 forms 1D helical chain structure containing two unique Mn^II ions. In 2, the bridging ligand dpe links Mn-bpdc double zigzag chains to generate a layer possesses rectangular cavities. In 3, bpdc²⁻ ligand connects to three metal centers forming a 2D network. Different from the above compounds, 4 displays a 1D double-wavelike chain. Compound 5 features a helical chain. Compound 6 also displays a helical chain with guest molecule dpe existing in the structure. These diverse structures illustrate rational adjustment of metal ions and the second ligand is a good method for the further design of helical compounds with novel structures and properties. In addition, the magnetic properties of 2, 3 and 6, the thermal stabilities and photoluminescence properties of 4 and 5 were also studied.     

Syntheses, structures and magnetic properties of μ1,5-dicyanamide bridged di- and polynuclear manganese(II) complexes containing neutral N-donor Schiff bases: Control of coordination number and nuclearity by varying denticity

Two hexacoordinated dinuclear compounds [Mn(L1)(dca)]₂(ClO₄/PF₆)₂·CH₃OH (1/2) and two heptacoordinated coordination polymers [Mn(L2)(dca)]_n(ClO₄/PF₆)_n (3/4) [L1 = N,N′-(bis-(pyridin-2-yl)benzylidene)-1,3-propanediamine; L2 = N,N′-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine; dca = dicyanamide] are synthesized and characterized. Structures of 1-3 have been solved by X-ray diffraction measurements. Each manganese(II) center in 1/2 is located in a distorted octahedral environment with an MnN₆ chromophore coordinated by the four N atoms of L1 and two nitrile N atoms of bibridged μ_1,5 dca. Interestingly, the coordination polymer 3 forms a 1D chain through single Mn-(NCNCN)-Mn units in which each manganese(II) center adopts a pentagonal bipyramidal geometry with an MnN₇ chromophore occupied with five N atoms of L2 and two nitrile N atoms of monobridged μ_1,5 dca. Magnetic susceptibility measurements of 1-3 in the 2-300 K temperature range reveal weak antiferromagnetic interactions.     

Manganese(II) complexes with croconate and 2-(2-pyridyl)imidazole ligands: Syntheses, X-ray structures and magnetic properties

The mixed-ligand complexes of manganese(II) of formula [Mn(pyim)₂(C₅O₅)] (1) and [Mn(pyim)(H₂O)(C₅O₅)]_n · 2.5nH₂O (2) [pyim = 2-(2-pyridyl)imidazole and  = croconate (dianion of 4,5-dihydroxy-4-cyclopentene-1,2,3-trione)] have been prepared and their structures determined by X-ray crystallographic methods. Compound 1 is a tris-chelated mononuclear complex where the manganese atom is six-coordinate: four nitrogen atoms from two pyim molecules and two oxygen atoms from a croconate group build a somewhat distorted octahedral surrounding around the metal atom. The resulting neutral mononuclear units are linked to each other through double bridges which are constituted by the imidazole N-H and the metal-coordinated croconate-oxygen atom, the metal-metal separation through this supramolecular pathway being 7.6856(11) Å. Compound 2 is a croconato-bridged manganese(II) uniform chain with an intrachain metal-metal distance of 7.5118(9) Å. A bidentate pyim group, a water molecule and four oxygen atoms from two bis-bidentate croconate ligands build an irregular seven-coordination polyhedron around each manganese atom in 2. The investigation of the magnetic properties of 2 in the temperature range 1.9-295 K has shown the occurrence of a weak antiferromagnetic interaction [J = −0.066 cm⁻¹ with the Hamiltonian defined as H = −J ∑_i S_i · S_i+1] through the bis-bidentate croconate. The ability of the bis-chelating croconate to mediante magnetic interactions between paramagnetic first-row transition metal ions is discussed and compared to that of the related oxalate ligand.     

The effect of organic acid on self-assembly process: Syntheses and characterizations of six novel cadmium(II)/zinc(II) complexes derived from mixed ligands

Using the principle of crystal engineering, six metal-organic coordination polymers, [Cd(bdc)(3-pytpy)]_n · 2nH₂O (1), [Cd(bdc)_0.5(3-pytpy)]_n · n(ClO₄) (2), Cd(ndc)_0.5(3-pytpy)]_n · n(ClO₄) (3), [Zn(ndc)(3-pytpy)]_n (4), [Cd(bqdc)(3-pytpy)]_n (5), and [Zn(pam)(3-pytpy)]_n · 2nH₂O (6) (H₂bdc = benzene-1,4-dicarboxylic acid, H₂ndc = naphthalene-2,6-dicarboxylic acid, H₂bqdc = 2,2′-biquinoline-4,4′-dicarboxylic acid, H₂pam = pamoic acid), were synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Compounds 1-6 crystallize in the presence of organic-acid linkers as well as multi-functional N-donor ligand 4′-(3-pyridyl)-2,2′:6′,2′′-terpyridine (3-pytpy). In complexes 1, 4, 5, and 6, the dicarboxylate as bridging ligand connects metal atoms to form the main body of 1D zigzag chains for 1 and 4, nearly linear chain for 5 and helical chain for 6, while 3-pytpy as tridentate chelating ligand is just like lateral arm grafting on both sides of these chains. In complexes 2 and 3, both the dicarboxylate and 3-pytpy as bridging ligands connect metal atoms into 2D polymeric structure for 2 and 1D chain of alternating loops and rods for 3. The weak interactions such as hydrogen bonding and π···π stacking were investigated on the formation of superamolecular structures and the influence of organic acid on the formation of the final structures was discussed. In addition, the photoluminescent properties of 1-6 were also determined.     

Synthesis and structures of three d metal coordination polymers constructed from flexible polycarboxylate and 1,10-phenanthroline ligands

Three novel d¹⁰ metal coordination polymers, {[Cd(H₂odpa)(phen)₂]·H₂O}_n (1), [Cd₂(odpa)(phen)(H₂O)₂]_n (2), {[Zn₄(odpa)₂(phen)₂(H₂O)₂]·H₂O}_n (3), (H₄odpa = 4,4′-oxydiphthalic acid, phen = 1,10-phenanthroline) were obtained with different metal/ligand ratios through hydrothermal method and characterized. Compound 1 forms a one dimensional zigzag chain, in which two phen ligands chelate to one cadmium atom. Compound 2 shows a three dimensional network structure comprised of new tetranuclear cadmium clusters as the nodes and (odpa)⁴⁻ anions as the linkers, exhibits an unusual topological structure. Compound 3 is an unprecedented three dimensional polymer based on octanuclear zinc clusters cross-linked by (odpa)⁴⁻ anions. In 1-3, central Cd^II/Zn^II ions and (odpa)⁴⁻ ligand display completely different coordination modes and conformations. In addition, the thermal stabilities and photoluminescence properties of 1-3 were also studied.     

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.     

Structural change of supramolecular coordination polymers of itaconic acid and 1,10-phenanthroline along lanthanide series

Five new supramolecular lanthanide coordination polymers with three different structures, {[La₂(IA)₃(phen)₂] · 2H₂O}_n (1), {[Ln(IA)_1.5(phen)] · xH₂O}_n [x = 1, Ln = Eu (2); x = 0.25, Ln = Dy (3)], and [Ln(IA)_1.5(phen)]_n [Ln = Er (4); Yb (5)], were prepared by hydro- and solvothermal reactions of lanthanide chlorides with itaconic acid (H₂IA) and 1,10-phenanthroline (phen), and structurally characterized by single crystal X-ray diffraction. 1 Comprises 1-D double-chains that are further assembled to a 3-D supramolecular structure via hydrogen bonds and π-π stacks between phen molecules. 2 and 3 have 2-D infinite networks which are further constructed to form 3-D supramolecular architectures with 1-D channels by π-π aromatic interactions. 4 and 5 have 2-D layer structures consisting of three types of rings which are further architectured to form 3-D supramolecular structures by C-H?O hydrogen bonds. The H₂IA ligands are all completely deprotonated and exhibit tetra-, penta-, and hexadentate coordination modes in the titled complexes. The high-resolution emission spectrum of 2 shows only one Eu³⁺ ion site in 2, which is in agreement with the result of X-ray diffraction. And the magnetic property and the thermal stability of 2 were also investigated.     

Mononuclear manganese(III) catechol compounds as substrate adduct complexes for manganese-substituted intradiol cleaving catechol dioxygenases

The complexes [Mn(L₁)(tcc)] (1), [Mn(L₂)(tcc)] · H₂O · 0.5CH₃OH (2), [Mn(L₃)(tcc)] · CH₂Cl₂ (3), [Mn(L₄)(tcc)] · 1.5CH₂Cl₂ (4), [Mn(L₅)(tcc)] (5), and (HN(C₂H₅)₃)[Mn(L₆)(tcc)] · CH₂Cl₂ (6) have been synthesized using the ligands HL₁ (2-[(bis(pyridin-2-ylmethyl)amino)methyl]phenol), HL₂ (2-[[((6-methylpyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino]methyl] phenol), HL₃ (2-[[((6-methylpyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino]methyl]-4-nitrophenol), HL₄ (2-[(bis(pyridin-2-ylmethyl)amino)methyl]-4-bromophenol), HL₅ (2-[(bis(pyridin-2-ylmethyl)amino)methyl]-6-methoxyphenol) and H₂L₆ ([(bis(2-hydroxy-5-nitrobenzyl))(pyridin-2-ylmethyl)]amine) and characterized by X-ray crystallography, mass spectrometry, IR, UV-Vis spectroscopy, cyclic voltammetry, and elemental analysis. Compounds 1 and 6 crystallize in the monoclinic space groups P2₁/n and P2₁/c, respectively, whereas the crystal structures of complexes 2, 3, and 4 were solved in the triclinic space group . Complex 5 crystallizes in the orthorhombic space group P2₁2₁2₁. Complexes 1-6 are structural related to the proposed active site of intradiol cleaving catechol dioxygenase exhibiting a distorted octahedral N₃O₃ (1-5) and N₂O₄ (6) donor set, respectively. Complexes 1-6 can be regarded as structural manganese analogous for substituted forms of iron-containing intradiol cleaving catechol dioxygenases, where the substrate tetrachlorocatechol (tcc) is asymmetrically bound to the metal center.     

Lanthanide complexes with disulfide ligand generated in situ: Syntheses, crystal structures and fluorescent properties

Five new lanthanide complexes [Ln₂(DTDN)₄(phen)₄]·7H₂O·2H₃O⁺ (Ln = Nd (1), Sm (2), Eu (3), Tb (4), Dy (5), H₂DTDN = 2,2′-dithiodinicotinic acid, phen = 1,10-phenanthroline) have been solvothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, and TG analyses. By in situ oxidation of 2-mercaptonanicotinic acid (2-H₂MN), the expected ligand H₂DTDN was generated. All crystals are isostructural and crystallize in monoclinic system with space group C2/c. The metal center is eight-coordinated completely by four carboxylic oxygen atoms from four different DTDN²⁻ ligands, and four nitrogen atoms from two phen molecules with a distorted square-antiprismatic geometry. The structures can be considered as two-dimensional (2D) structures and further linked by hydrogen bonds into the final trinodal 4-connected network. Photoluminescence studies revealed that complexes 2-5 exhibit strong fluorescent emission bands in the solid state at room temperature.     

Two new supermolecular structures of organic-inorganic hybrid compounds: [Zn(phen)(SO4)(H2O)2]n and [Cu(phen)(H2O)2] · SO4 (phen = 1,10-phenanthroline)

Two new organic-inorganic hybrid compounds [Zn(phen)(SO₄)(H₂O)₂]_n (1) and [Cu(phen)(H₂O)₂] · SO₄ (2) have been prepared by conventional aqueous solution synthesis and characterized by single-crystal X-ray diffraction, IR spectroscopy, thermal gravimetric analysis (TGA) and fluorescent spectroscopy. In compound 1, the sulfate group adopts bidentate mode to coordinate with two Zn(II) ions to form one-dimensional polymer. The one-dimensional polymers are further linked together via the intermolecular hydrogen-bonding and π-π stacking interactions to form a 3D supramolecular framework. Compound 2 is build up of discrete [Cu(phen)(H₂O]²⁺ cations and SO₄²⁻ anions to form a three-dimensional framework via hydrogen-bonding and π-π stacking interactions. Furthermore, the luminescent properties of both 1 and 2 were studied. The complexes 1 and 2 excited at 280 nm wavelength produced characteristic luminescence features, arising maybe due to the π-π transitions.     

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.