Bis(2,2′-bipyridine)cobalt(III) complexes containing asymmetric ligands: Synthesis,DNA-binding and photocleavage studies

Three new Co^III complexes: [Co(bpy)₂(pdtb)]³⁺ (1), [Co(bpy)₂(pdta)]³⁺ (2) and [Co(bpy)₂(pdtp)]³⁺ (3) have been synthesized and characterized. The DNA binding behavior of the Co^III complexes has been investigated by spectroscopic methods and viscosity measurements. The results indicate that the size and shape of the intercalated ligand have a marked effect on the binding affinity of complexes involving CT-DNA. Complexes (2) and (3) have been found to promote cleavage of plasmid pBR 322 DNA from the supercoiled form I to the open circular form II upon irradiation. Photocleavage mechanisms are proposed.     

Syntheses,crystal structures,and characterization of three metal–organic complexes with 2,2′-biphenyldicarboxylic acid and phenanthroline ligands

Three complexes constructed with 2,2′-biphenyldicarboxylic acid, multidentate nitrogen donors, and metal salts, {[Cd(2,2′-dpdc)(tppp)(H₂O)]₂?·?2H₂O} _n (1), {[Pb(2,2′-dpdc)(pyphen)]₂} _n (2), and {[Pb(2,2′-dpdc)(dppz)]} _n (3) (H₂dpdc = 2,2′-diphenyldicarboxylic acid; tppp = 4-(1H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)phenol; pyphen?=?pyrazino[2,3-f]-[1,10]phenanthroline; and dppz = dipyrido[3,2-a:2′,3′-c]phenazine), are synthesized under hydrothermal conditions. These complexes are characterized by single-crystal X-ray diffraction, elemental analysis, IR, TGA, and photoluminescence. In 1, two 2,2′-dpdc ions bridge two Cd(II) ions to form an isolated cluster with Cd?···?Cd distance of 5.023(4)?Å. These clusters are further linked by intermolecular hydrogen bonds, yielding a 2-D supramolecular structure. Complex 2 contains two crystallographically independent Pb(II) ions in the asymmetric unit. Pb1 ions are bridged by 2,2′-dpdc anions to form a chain along the x-axis. Two Pb2 ions are coordinated by two 2,2′-dpdc anions and two pyphen ligands to form a cluster. These clusters are linked by π–π interactions to yield a 1-D supramolecular chain along the y-axis. In 3, neighboring Pb(II) atoms are bridged by 2,2′-dpdc anions to form a 1-D chain structure. Further, the chains are linked into a 3-D supramolecular network through aromatic π–π interactions.     

Mixed-ligand complexes of iron(II), iron(III), copper(II), and cobalt(II) with pyrazolonic and 2,2′-bipyridine ligands

New mixed-ligand complexes, [M₂(BAMP)(bipy)₂][MCl₄]₂, M=Co⁺²(1), Cu⁺²(2), [M₂(TAMEN)(bipy)₂][MCl₄]₂, M=Fe⁺²(3), Co²⁺(4), and [Fe₂(TAMEN)(bipy)₂][FeCl₆]₂ (5), where BAMP and TAMEN stand for the Mannich bases N,N′-bis(antipyryl-4-methylene)-piperazine and N,N′-tetra(antipyryl-4-methylene)-1,2-ethane-diamine, respectively, have been obtained and characterized by elemental analyses, conductometric and magnetic susceptibility measurements at room temperature, mass spectrometry, UV-Vis, infrared, and mass spectroscopy, and ¹H NMR spectra for the ligands.     

Co(III) N,N′-diarylformamidine dithiocarbamate complexes: Synthesis,characterization, crystal structures and biological studies

Three symmetric N,N-diarylformamidine dithiocarbamates, N,N′-bis(2,6-dimethylphenyl)formamidine dithiocarbamate (DTL1), N,N′-bis(2,6-disopropylphenyl)formamidine dithiocarbamate (DTL2) and N,N′-dimesitylformamidine dithiocarbamate (DTL3), and three unsymmetric ones, N′-(2,6-dichlorophenyl-N-(2,6-dimethylphenyl)formamidine dithiocarbamate (DTL4), N′-(2,6-dichlorophenyl)-N-(2,6-diisopropylphenyl)formamidine dithiocarbamate (DTL5) and N′-(2,6-dichlorophenyl)-N-mesitylformamidine dithiocarbamate (DLT6), were reacted with chloridocobalt(III) in water to give Co-(DTL1)₃ ( 1 ), Co-(DTL2)₃ ( 2 ), Co-(DTL3)₃ ( 3 ), Co-(DTL4)₃ ( 4 ), Co-(DTL5)₃ ( 5 ) and Co-(DTL6)₃ ( 6 ). All the dithiocarbamates and complexes were characterized using ¹H NMR, ¹³C NMR, Fourier transform infrared, UV–visible and mass spectra and the purity confirmed by elemental analysis. In addition, crystal structures of complexes 1 , 2 , 4 and 5 were determined, confirming the formation of mononuclear species in which the Co(III) centers coordinated to six sulfur atoms from three dithiocarbamate ligands resulting in distorted octahedral geometries. All complexes showed moderate to good antibacterial activities against Gram-negative bacteria Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae and Pseudomonas aeruginosa even at low concentrations. None of the six were active against Gram-positive bacterium methicillin-resistant Staphylococcus aureus and only active against S. aureus at high concentrations. Complexes 5 and 6 were found to be more active than ciprofloxacin against S. typhimurium, E. coli, P. aeruginosa and K. pneumoniae and complexes with chloro-substituted ligands generally had enhanced activities. Antioxidant activities of the dithiocarbamate salts and their Co(III) complexes were also investigated using DPPH assay and the complexes were found to be more efficient. Complex 2 with an IC₅₀ value of 2.84 × 10⁻⁴ mM displayed the highest activity of all compounds tested, even outdoing ascorbic acid. The radical scavenging ability of the complexes followed the order 2 > 1 > ascorbic acid > 3 > 4 > 6 > 5 .     

Synthesis,characterization and photophysical properties of homoleptic platinum(II) complexes with 2,2′-biimidazole-based ligands

Eight pairs of cis–trans isomeric homoleptic platinum(II) complexes based on N-alkyl- or aryl-substituted 2,2′-biimidazole ligands were synthesized, and their photophysical properties were investigated. The cis and trans isomers readily interconvert at slightly elevated temperature, implying that the activation barrier for this process is low. Single crystal X-ray diffraction analysis revealed that the complexes have an ideal square-planar geometry. Their UV–Vis spectra showed lower energy absorption bands in the range of 345–378 nm, which are assigned to the typical MLCT mixed with LC transitions. In frozen glass solution at 77 K and also in the powder state, these complexes exhibit green emission ranging from 440 to 540 nm with photoluminescence quantum yields of 3.3–24.4%. The emitting excited state is dominated by ³ππ* character with some contributions from ³MLCT according to the excitation spectra.     

Synthesis,characterization, and cytotoxicity of Pt(IV) complexes containing 1,10-phenanthroline and 2,2′-bipyridine and diaminocyclohexane ligands

Four platinum(IV) complexes containing intercalating ligands [1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy)] and ancillary ligands [(1S,2S)-diaminocyclohexane (SS-DACH) and (1R,2R)-diaminocyclohexane (RR-DACH)] were synthesized and characterized by ¹H nuclear magnetic resonance, electrospray ionization mass spectrometry, X-ray crystal structure analysis, elemental analysis, ultraviolet absorption spectroscopy, circular dichroism spectroscopy, and electrochemical analysis. The reactions between [Pt(phen)(SS-DACH)Cl₂]²⁺ and glutathione and Ac-CPFC-NH₂ were investigated by high-performance liquid chromatography. [Pt(phen)(SS-DACH)Cl₂]²⁺ was reduced to its corresponding Pt(II) complex [Pt(phen)(SS-DACH)]²⁺, while glutathione and Ac-CPFC-NH₂ were oxidized to glutathione-disulfide and a peptide containing an intramolecular disulfide bond, respectively. The cytotoxicities of the Pt(IV) complexes against a human non-small cell lung cancer cell line (A549) and the corresponding cisplatin-resistant cell line (A549cisR) were evaluated. These Pt(IV) complexes showed a higher activity toward A549 and A549cisR than did cisplatin. Also, the cytotoxicities of the Pt(IV) complexes were higher for A549cisR than for A549 cells. Moreover, the cytotoxicities of the (SS-DACH)-liganded platinum complexes were higher than those of the (RR-DACH)-liganded platinum complexes in either A549 or A549cisR cells. Phen-liganded platinum complexes were more cytotoxic than the bpy-liganded platinum complexes. The cytotoxicities of these Pt(IV) complexes had no correlation with reduction potentials.     

Emissive mononuclear Eu(III) and Tb(III) complexes bearing deprotonated 2,2′-bipyridyl-1,2,4-triazole terdentate ligands

A series of new emissive mononuclear Ln(III) complexes with deprotonated 2,2?-bipyridyl-1,2,4-triazole terdentate ligands, [Ln(L)(DMF)₂(NO₃)₂]?n(solvent) (Ln = Eu (1 and 2), Tb (3 and 4), HL = 6-(5-trifluoromethyl-1,2,4-triazol-3-yl)-2,2′-bipyridine, 6-(5-trifluoromethyl-1,2,4-triazol-3-yl)-4,4′-dimethyl-2,2′-bipyridine), have been synthesized and characterized. As revealed by X-ray crystallography, each Ln(III) has a distorted tricapped trigonal prism generated by three nitrogens from one 2,2?-bipyridyl-1,2,4-triazolate chelate and six oxygens from two DMF molecules and two chelating nitrates, where 2,2?-bipyridyl-1,2,4-triazole serves as a mono-anionic tridentate chelate via deprotonation of the 1,2,4-triazolyl-NH. Complexes 1–4 are all emissive at room temperature in solution and solid states, and the introduction of two methyl groups into the 2,2?-bipyridyl ring is efficient in enhancing luminescence efficiencies of Ln(III) complexes.     

Synthesis,crystal structures,and magnetic properties of two manganese(II) coordination polymers bearing 1,1′-biphenyl-3,3′-dicarboxylate ligands

Two Mn(II) coordination polymers, namely [Mn(bpda)] _n (1) and [Mn(bpda)(bpy)_0.5] _n (2) (H₂bpda = 1,1′-biphenyl-3,3′-dicarboxylic acid and bpy = 4,4′-bipyridine), have been synthesized from H₂bpdc, bpy, and MnSO₄·2H₂O under hydrothermal conditions. The complexes were characterized by physicochemical and spectroscopic methods, as well as by X-ray crystallography. Compound 1 possesses a 3D structure consisting of carboxylate-bridged edge-sharing Mn–O–Mn double chains. Compound 2 features a 3D open structure with a dinuclear Mn(II) secondary building unit. Magnetic susceptibility measurements of compounds 1 and 2 exhibit antiferromagnetic interactions between the nearest Mn(II), with J = –11.3 cm⁻¹ and g = 2.12 for 1, and J = –13.5 cm⁻¹ and g = 2.12 for 2.     

pH-dependent syntheses and crystal structures, characterizations, and DFT calculations of complexes with 2,2′-biimidazole and terephthalic acid ligands

The divalent transition metal complexes [Zn(L)₂(H₂O)₂](Tere) (I), [Cd(L)₂(H₂O)₂](Tere]) (II) and [Cd(L)₂(HTere)₂] (III) (L = 2,2’-biimidazole, Tere = terephthalate) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectrum, thermal analysis and single-crystal X-ray diffraction analysis. Complexes II and III have the same starting materials but possess different frame-works and are prepared from H₂Biim and H₂Tere under hydrothermal conditions with different pH values. The crystal structures show I and II have the same coordination circumstances and are coordinated by two H₂O molecules and two neutral bidentate 2,2′-biimidazole ligands. The terephthalate acts as the counter anion. In contrast, complex III contains protonated carboxylate groups coordinated to the metal centre to give neutral species. Furthermore, based on the optimized structures, molecular frontier orbitals, Mulliken charges and IR spetra of complex I and III are investigated by density functional theory. Calculated results show that the energy gap (ΔE _L-H) between HOMO and LUMO of complex III is bigger than that of I. It is revealed that complex III is more stable, and this calculated estimation corresponds with experimental analysis of TGA curves.     

Synthesis,structures, and catalytic oxidation of three aqua-coordinated and oxo-bridged diruthenium(III) complexes with sulfobenzoate and 2,2′-bipyridine

Three new diruthenium(III) complexes, [Ru₂O(2-sb)₂(2,2′-bipy)₂(H₂O)₂]·2.5H₂O (1), [Ru₂O(3-sb)₂(2,2′-bipy)₂(H₂O)₂]·9H₂O (2), and [Ru₂O (4-sb)₂(2,2′-bipy)₂(H₂O)₂]·9H₂O (3), where sb^2? is sulfobenzoate dianion and 2,2′-bipy is 2,2′-bipyridine, were synthesized using hydrothermal methods and characterized by IR, elemental analysis, thermogravimetric analysis, UV–vis, and fluorescence spectra. The single crystal X-ray analysis showed that each of these complexes has a dinuclear core stabilized by two bridging carboxylates and one bridging O^2?. Variable sb^2? ligands (2-sb, 3-sb, and 4-sb) in these complexes lead to diverse electronic spectroscopic behavior. The efficiency of activating methyl phenyl sulfide oxidation utilizing H₂O₂ in 3 equiv. was studied at 23?±?2?°C. The effect of the amount of catalyst and solvents on activities was investigated. Under optimized reaction conditions, the major product was sulfoxide. Complex 1 gave significant conversion of 100 and 98% selectivity for sulfoxide after 4?h.     

Synthesis,crystal structures,and photoluminescence of two new zinc complexes based on 2,2′-thiodibenzoic acid

{[Zn₂(tdba)₂(phen)₂(H₂O)₂]?·?2H₂O?·?2DMF} _n (1) and [Zn(tdba)(bpy)] _n (2) (H₂tdba?=?2,2′-thiodibenzoic acid, phen?=?1,10-phenanthroline, bpy?=?2,2′-bipyridine, DMF?=?dimethylformamide) were hydrothermally synthesized, and characterized by single-crystal X-ray diffraction analysis, FT-IR, and elemental analysis. The obtained complexes exhibit different structures. Compound 1 is 0-D with tdba connecting two Zn ions in a μ ₁–η ¹/μ ₁–η ¹ coordination forming a dinuclear molecule. Each molecule is further connected with neighbors via hydrogen-bonding and π?···?π interactions. Compound 2 displays a 1-D structure in which Zn²⁺ centers are connected via tdba anions into 1-D chains propagating along the a-axis; these chains are further packed via π?···?π interactions. In addition, photoluminescence for 1 and 2 has been investigated.     

Synthesis,chemical characterization,X-ray crystal structure and magnetic properties of oxalato-bridged copper(II) binuclear complexes with 2,2′-bipyridine and diethylenetriamine as peripheral ligands

Two new μ-oxalato binuclear copper(II) complexes, [{Cu(NO₃)(H₂O)(bipy)}₂(ox)] (1) and [{Cu(dien)}₂(ox)](NO₃)₂ (2), with ox=oxalate, dien=diethylenetriamine and bipy=2,2′-bipyridine, have been synthesized and their crystal and molecular structures have been determined by single-crystal X-ray diffraction methods. The crystal structure of 1 consists of centrosymmetric neutral dimers where the copper atoms lie in a strongly elongated octahedral environment, surrounded by two nitrogen atoms of a bipy molecule and two oxygen atoms of the bridging oxalato group in the equatorial plane and oxygen atoms of water molecules and nitrate ions in the axial positions. Crystal structure of 2 is made up of non-coordinated nitrate anions and asymmetric binuclear cations in which copper atoms are in a distorted square–pyramidal coordination with three atoms of a diethylenetriamine ligand and an oxygen atom of the asymmetrically coordinated oxalato bridge building the basal plane and the other oxygen atom of the oxalato ligand filling the apical position. Both compounds have been also characterized by Fourier transform infrared (FT-IR) and electron spin resonance (ESR) spectroscopies, thermal analysis and variable temperature magnetic susceptibility measurements. The two compounds exhibit antiferromagnetic exchange with a singlet–triplet separation of −382 and −6.5 cm⁻¹ for 1 and 2, respectively. Magnetic and ESR results are discussed with respect to the crystal structure of the compounds.     

Synthesis,crystal structures,and magnetic properties of cobalt(II) and nickel(II) complexes of 2,2′-bipyridine-6,6′-dicarboxylate: three three-dimensional networks formed via hydrogen bonding interactions

Three Co(II) and Ni(II) complexes, namely [Co(bpdc)(H₂O)₂] (1), [Ni(bpdc)(H₂O)₂] (2), and [Co₂(bpdc)₂(prz)_0.5(H₂O)₃]·0.5H₂O (3) (H₂bpdc = 2,2′-bipyridine-6,6′-dicarboxylic acid and prz = piperazine), have been synthesized from H₂bpdc and the corresponding metal salts under hydrothermal conditions. The complexes were characterized by physico-chemical and spectroscopic methods, as well as by X-ray crystallography. Compounds 1 and 2 both consist of neutral mononuclear molecules, of [Co(bpdc)(H₂O)₂] and [Ni(bpdc)(H₂O)₂], respectively. Compound 3 consists of a mononuclear molecule of [Co(bpdc)(H₂O)₂] and a binuclear molecule of [Co₂(bpdc)₂prz (H₂O)₂]. The discrete neutral complexes 1–3 further extend their structures into three-dimensional supramolecular architectures by intermolecular O–H⋯O and C–H⋯O hydrogen bonds as well as π–π stacking interactions. Magnetic susceptibility measurements show that complex 3 exhibits weak ferromagnetic interactions between the two Co(II) ions bridged by the prz ligand, with C = 5.41 cm³ mol⁻¹ K and θ = +27.6 K, respectively.     

Synthesis and characterization of lead(II) complexes with substituted 2,2′-bipyridines,trifluoroacetate, and furoyltrifluoroacetonate

Two substituted 2,2′-bipyridine lead(II) complexes, [Pb(5,5′-dm-2,2′-bpy)(tfac)₂] _n (1) (5,5′-dm-2,2′-bpy?=?5,5′-dimethyl-2,2′-bipyridine and tfac?=?trifluoroacetate) and [Pb₂(4,4′-dmo-2,2′-bpy)₂(ftfa)₄] (2) (4,4′-dmo-2,2′-bpy?=?4,4′-dimethoxy-2,2′-bipyridine and ftfa?=?furoyltrifluoroacetonate), have been synthesized and characterized by elemental analysis, IR, ¹H NMR, and ¹³C NMR spectroscopies, thermal behavior, and X-ray crystallography. Complexes 1 and 2 are 1D coordination polymer and dinuclear complex, respectively. The supramolecular features in these complexes are guided by weak directional intermolecular interactions.     

Synthesis, characterization and crystal structures of manganese (Ⅱ) complexes containing nitronyl nitroxide and its reduced derivative

Two novel adducts of formula Mn(hfac)2( NITPhCl )2 (1) and [Mn(hfac)2(IMHPhCl)]2(NIT-PhCl)·0.5H2O (2), where hfac = hexafluoroacetylacetonate, NITPhCl = 2-(3-chlorophenyl)-4,4,5,5-tetram-ethylimidazolyl-1-oxyl-3-oxide, IMHPhCl = 2-(3-chlorophenyl)-4, 4, 5, 5-tetramethylimidazolyl-3-oxide, have been prepared by the reaction of Mn(hfac)2·2H2O with NITPhCl. Compound 1 is triclinic, space group P-1with a = 1.3003(3) nm, 6 = 1.3138(3) nm,c = 1.4931 (3) nm, α = 83.74(3)°, β = 77.77(3)°, γ = 60.59(3)°, V=2.171(1)nm3, Z = 2. Compound 2 is triclinic, space group P-1 with a = 1.2994(3) nm, b = 1.4841(3) nm, c = 2.1031 (4) nm, a = 92.30(3)° ,p = 98.68(3)°, γ = 97.89(3)°, V= 3.964(2)nm3, Z = 2. Each manganese atom is hexacoordinated in both compounds and compound 2 is organized inchains by hydrogen bonds between neighboring pairs of NITPhCl and IMHPhCl.     

Synthesis,crystal structure and properties of two terbium complexes with 2,2′-bipyridine

Two new complexes {[Tb(2-IBA)₃ · 2,2′-bipy]₂ · C₂H₅OH} (1) and [Tb(2-ClBA)₃ · 2,2′-bipy]₂ (2) (2-IBA = 2-iodobenzoate; 2-ClBA = 2-chlorobenzoate; 2,2′-bipy = 2,2′-bipyridine) were prepared and their crystal structures determined by X-ray diffraction. Complex 1 is composed of two types of binuclear molecules, [Tb(2-IBA)₃ · 2,2′-bipy]₂ (a) and [Tb(2-IBA)₃ · 2,2′-bipy]₂ (b), and an uncoordinated ethanol molecule. In molecule (a), two Tb³⁺ ions are linked by four 2-IBA groups, all bidentate-bridging. In molecule (b), two Tb³⁺ ions are held together by four 2-IBA groups in two coordination modes, bidentate-bridging and chelating-bridging. In the two molecules, each Tb³⁺ ion is further bonded to one chelating 2-IBA group and one chelating 2,2′-bipy molecule, resulting in coordination numbers of eight for (a) and nine for (b). The structural characteristics of 2 are similar to that of molecule (b) in 1. The two complexes, 1 and 2, both emit strong green fluorescence under ultraviolet light with the ⁵D₄ → ⁷F _j (j = 6–3) emission of Tb³⁺ ion observed.     

Synthesis,characterization, and crystal structures of two Ag (I) coordination polymers based on biphenyl-2,2′,4,4′-tetracarboxylate

In this article, [Ag₈(btc)₂(2,2′-bpy)₂] _n (1) and [Ag₄(btc)(phen)₂] _n (2) (H₄btc?=?biphenyl-2,2′,4,4′-tetracarboxylic acid, 2,2′-bpy?=?2,2′-bipyridine, phen?=?1,10-phenanthroline) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectra, thermogravimetric analyses, and single-crystal X-ray diffraction. Complex 1 shows a 3-D framework containing a 2-D bilayer network constructed from (btc)^4? with Ag (I), whereas 2 features a 2-D supramolecular bilayer network. The differences of the two complexes demonstrate that nitrogen-containing chelating ligands have a significant effect on the formation and structure of the resulting complexes. Electrochemistry properties of 1 were also studied.