Luminescent probes for indole-binding proteins derived from ruthenium(II) polypyridine complexes

We report here the synthesis, characterisation, electrochemical, photophysical and protein-binding properties of four luminescent ruthenium(II) polypyridine indole complexes [Ru(bpy)₂(L1)](PF₆)₂ (1), [Ru(bpy)₂(L2)](PF₆)₂ (2), [Ru(L1)₃](PF₆)₂ (1a), and [Ru(L2)₃](PF₆)₂ (2a) (bpy = 2,2′-bipyridine; L1 = 4-(N-(2-indol-3-ylethyl)amido)-4′-methyl-2,2′-bipyridine; L2 = 4-(N-(6-N-(2-indol-3-ylethyl)hexanamidyl)amido)-4′-methyl-2,2′-bipyridine). Their indole-free counterparts, [Ru(bpy)₂(L3)](PF₆)₂ (3) and [Ru(L3)₃](PF₆)₂ (3a) (L3 = 4-(N-(ethyl)amido)-4′-methyl-2,2′-bipyridine), have also been synthesised for comparison purposes. Cyclic voltammetric studies revealed ruthenium-based oxidation at ca. +1.3 V versus SCE and diimine-based reductions at ca. −1.20 to −2.28 V. The indole moieties of complexes 1, 2, 1a and 2a displayed an irreversible wave at ca. +1.1 V versus SCE. All the ruthenium(II) complexes exhibited intense and long-lived orange-red triplet metal-to-ligand charge-transfer ³MLCT (dπ(Ru) → π*(L1-L3)) luminescence upon visible-light irradiation in fluid solutions at 298 K and in alcohol glass at 77 K. The binding of the indole-containing complexes to bovine serum album (BSA) has been studied by quenching experiments and emission titrations.     

Syntheses, characterization, and DFT investigation of new mononuclear acetonitrile- and chloro-ruthenium(II) terpyridine complexes

A series of mononuclear acetonitrile complexes of the type [Ru(CH₃CN)(L)(terpy)]²⁺ {L = phen (1), dpbpy (3), and bpm (5)}, and their reference complexes [RuCl(L)(terpy)]⁺ {L = phen (2), dpbpy (4), and dpphen (6)} were prepared and characterized by electrospray ionization mass spectrometry, UV-vis spectroscopy, and cyclic voltammograms (CV). Abbreviations of the ligands (Ls) are phen = 1,10-phenanthroline, dpbpy = 4,4′-diphenyl-2,2′-bipyridine, bpm = 2,2′-bipyrimidine, dpphen = 4,7-diphenyl-1,10-phenanthroline, bpy = 2,2′-bipyridine, and terpy = 2,2′:6′,2″-terpyridine. The X-ray structures of the two complexes 2 and 3 were newly obtained. The metal-to-ligand charge transfer (MLCT) bands in the visible region for 1, 3, and 5 in acetonitrile were blue shifted relative to those of the reference complexes [RuCl(L)(terpy)]⁺. CV for all the [Ru(CH₃CN)(L)(terpy)]²⁺ complexes showed the first oxidation wave at around 0.95 V, being more positive than those of [RuCl(L)(terpy)]⁺. The time-dependent-density-functional-theory approach (TDDFT) was used to interpret the absorption spectra of 1 and 2. Good agreement between computed and experimental absorption spectra was obtained. The DFT approach also revealed the orbital interactions between Ru(phen)(terpy) and CH₃CN or Cl⁻. It is demonstrated that the HOMO-LUMO energy gap of the acetonitrile ligand is larger than that of the Cl⁻ one.     

Communication of metal ions in the dinuclear ruthenium complexes containing 4,4′-bipyridine, 1,4-diisocyanobenzene, and pyrazine bridging ligands: Synthesis, characterization and structure determination

Reaction of [Ru(2,2′-bipyridine)(2,2′:6′,2″-terpyridine)Cl]PF₆ (abbreviated to [Ru(bipy)(terpy)Cl]PF₆) with 0.5 equiv of the bidentate ligand L produces the dinuclear complexes [{Ru(bipy)(terpy)}₂(μ-L)](PF₆)₄ (L = 4,4′-bipyridine 1, 1,4-diisocyanobenzene 2 and pyrazine 3) in moderate yields. Treating [Ru(bipy)(terpy)Cl]PF₆ with equal molar of 1,4-diisocyanobenzene affords [Ru(bipy)(terpy)(CNC₆H₄NC)](PF₆)₂ (2a). These new complexes have been characterized by mass, NMR, and UV-Vis spectroscopy, and the structures of 1-3 determined by an X-ray diffraction study. Cyclic voltammetric studies suggest that metal communication between the two ruthenium ions increases from 1 to 2 to 3.     

X-ray structure and magnetic properties of dinuclear and polymer iron(II) complexes

Five new octahedral iron(II) complexes [FeL2(4-dpa)]_n(EtOH) (1), [FeL2(bipy)]_n(DMF) (2), [FeL1(bpee)]_n (3), [Fe₂L3(1-meim)₄](1-meim)₄ (4) and [FeL1(DMAP)₂] (5), with L1 and L2 being tetradentate coordinating Schiff base like ligands (L1 = (E,E)-[{diethyl-2,2′-[1,2-phenylenebis(iminomethylidyne)]bis[3-oxobutanato](2-)-N,N′,O³,O³′}, L2 = (3,3′)-[{1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentane-dionato)(2-)-N,N′,O²,O²′}) and L3 being a octadentate dinucleating coordinating Schiff base like ligand ({tetraethyl-(E,E,E,E)-2,2′,2′′,2′′′-[1,2,4,5-phenylentetra(iminomethylidine)]tetra[3-oxobutanoato](2-)-N,N′,N′′,N′′′,O³,O³′,O³′′,O³′′′}); 4-dpa = di(4-picolyl)-amine, bipy = 4,4′-bipyridine, bpee = trans-1,2-bis(4-pyridyl)ethylene, 1-meim = 1-methylimidazole and DMAP = 4-dimethylaminopyridine, have been synthesized and characterised using X-ray structure analysis and T-dependent susceptibility measurements. Both methods indicate that all iron(II) centres are in the paramagnetic high-spin state over the whole temperature range investigated. The O-Fe-O angle, the so called bit of the equatorial ligand, is with an average of 111° in the region typical for high-spin iron(II) complexes of this ligand type. In the case of compound 1 an infinite two-dimensional hydrogen bond network can be found, for the compounds 2-4 no hydrogen bond interactions are observed between the complex molecules. A comparison of the curve progression obtained from the magnetic measurements of the mononuclear complex 5 and the polymeric complexes 1-3 leads to the conclusion that no magnetic interactions are mediated over the bridging axial ligands. For the dinuclear complex 4 weak antiferromagnetic interactions between the two iron centres are found.     

Synthesis, structure and electronic spectra of new three-coordinated copper(I) complexes with tricyclohexylphosphine and diimine ligands

Three new copper(I) complexes with tricyclohexylphosphine (PCy₃) and different diimine ligands, [Cu(phen)(PCy₃)]BF₄ (1) (phen = 1,10′-phennanthroline), [Cu(bpy)(PCy₃)₂]BF₄ (2) (bpy = 2,2′-bipyridine) and [Cu(MeO-CNN)(PCy₃)]BF₄ (3) (MeO-CNN = 6-(4-methoxyl)phenyl-2,2′-bipyridine), have been synthesized and characterized. X-ray structure reveals that complexes 1 and 3 are three-coordinated with trigonal geometry, while complex 2 adopts distorted tetrahedron geometry. Complexes 1 and 3 exhibit ligand redistribution reactions in chloromethane solution by addition of excess amount of PCy₃, in which three-coordinated 1 changes into four-coordinated [Cu(phen)(PCy₃)₂]⁺, and 3 leads to form [Cu(PCy₃)₂]BF₄ and CNN-OMe. All the three complexes display yellow ³MLCT emissions in solid state at room temperature with λ_max at 558, 564 and 582 nm for 1, 2 and 3, respectively, and red-shift to 605, 628 and 643 nm at 77 K in dichloromethane solution.     

Interaction of Pt(II) and Pd(II) complexes of terpyridine with 1-methylazoles: A combined experimental and density functional study

The synthesis and characterization of several complexes of the composition [{M(terpy)}_n(L)](ClO₄)_m (M = Pt, Pd; L = 1-methylimidazole, 1-methyltetrazole, 1-methyltetrazolate; terpy = 2,2′:6′,2″-terpyridine; n = 1, 2; m = 1, 2, 3) is reported and their applicability in terms of a metal-mediated base pair investigated. Reaction of [M(terpy)(H₂O)]²⁺ with 1-methylimidazole leads to [M(terpy)(1-methylimidazole)](ClO₄)₂ (1: M = Pt; 2: M = Pd). The analogous reaction of [Pt(terpy)(H₂O)]²⁺ with 1-methyltetrazole leads to the organometallic compound [Pt(terpy)(1-methyltetrazolate)]ClO₄ (3) in which the aromatic tetrazole proton has been substituted by the platinum moiety. For both platinum(II) and palladium(II), doubly metalated complexes [{M(terpy)}₂(1-methyltetrazolate)](ClO₄)₃ (4: M = Pt; 5: M = Pd) can also be obtained depending on the reaction conditions. In the latter two compounds, the [M(terpy)]²⁺ moieties are coordinated via C5 and N4. X-ray crystal structures of 1, 2, and 3 are reported. In addition, DFT calculations have been carried out to determine the energy difference between fully planar [Pd(mterpy)(L)]²⁺ complexes Ip-IVp (mterpy = 4′-methyl-2,2′:6′,2″-terpyridine; L = 1-methylimidazole-N3 (I), 1-methyl-1,2,4-triazole-N4 (II), 1-methyltetrazole-N3 (III), or 3-methylpyridine-N1 (IV)) and the respective geometry-optimized structures Io-IVo. Whereas this energy difference is larger than 70 kJ mol⁻¹ for compounds I, II, and IV, it amounts to only 0.8 kJ mol⁻¹ for the tetrazole-containing complex III, which is stabilized by two intramolecular C-H?N hydrogen bonds. Of all complexes under investigation, only the terpyridine-metal ion-tetrazole system with N3-coordinated tetrazole appears to be suited for an application in terms of a metal-mediated base pair in a metal-modified oligonucleotide.     

Design,synthesis, DNA-binding affinity,cytotoxicity, apoptosis,and cell cycle arrest of Ru(II) polypyridyl complexes

A novel polypyridyl ligand CNPFIP (CNPFIP = 2-(5(4-chloro-2-nitrophenyl)furan-2-yl)-1H-imidazo[4,5f][1,10]phenanthroline) and its mononuclear Ru(II) polypyridyl complexes of [Ru(phen)₂CNPFIP]²⁺(1) (phen = 1,10-phenanthroline), [Ru(bpy)₂CNPFIP]²⁺(2) (bpy = 2,2′-bipyridine), and [Ru(dmb)₂CNPFIP]²⁺(3) (dmb = 4,4′-dimethyl-2,2′-bipyridine) have been synthesized successfully and characterized thoroughly by elemental analysis, UV/Vis, IR, NMR, and ESI-MS. The interaction of the Ru(II) complexes with calf thymus DNA (CT-DNA) was investigated by absorption titration, fluorescence, viscosity measurements. The experimental results suggest that three complexes bind to CT-DNA through an intercalative mode and the DNA-binding affinity of complex 1 is greater than that of complexes 2 and 3. The photocleavage of plasmid pBR322 DNA by ruthenium complexes 1, 2, and 3 was investigated. We have also tested three complexes for their antimicrobial activity against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. The in vitro cytotoxicity of these complexes was evaluated by MTT assay, and complex 1 shows higher cytotoxicity than 2 and 3 on HeLa cells. The induced apoptosis and cell cycle arrest of HeLa cells were investigated by flow cytometry for 24 h. The molecular docking of ruthenium complexes 1, 2, and 3 with the active site pocket residues of human DNA TOP1 was performed using LibDock.     

Synthesis, characterization, interaction with DNA and cytotoxicity in vitro of dinuclear Pd(II) and Pt(II) complexes dibridged by 2,2'-azanediyldibenzoic acid

The dinuclear complexes [Pd₂(L)₂(bipy)₂] (1), [Pd₂(L)₂(phen)₂] (2), [Pt₂(L)₂(bipy)₂] (3) and [Pt₂(L)₂(phen)₂] (4), where bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline and L = 2,2′-azanediyldibenzoic dianion) dibridged by H₂L ligands have been synthesized and characterized. The binding of the complexes with fish sperm DNA (FS-DNA) were investigated by fluorescence spectroscopy. The results indicate that the four complexes bound to DNA with different binding affinity, in the order complex 4 > complex 3 > complex 2 > complex 1, and the complex 3 binds to DNA in both coordination and intercalative mode. Gel electrophoresis assay demonstrates the ability of the complexes to cleave the pBR 322 plasmid DNA. The cytotoxic activity of the complexes was tested against four different cancer cell lines. The four complexes exhibited cytotoxic specificity and significant cancer cell inhibitory rate.     

Preparation and characterization of macrocyclic dinickel complexes coligated by monoalkyl- and dialkylcarbamates

The dinuclear nickel(II) complex [Ni₂L(Cl)]⁺ (1), where (L)²⁻ represents a 24-membered binucleating hexamine-dithiophenolate ligand, reacts readily with primary and secondary amines RR′NH in the presence of CO₂ (1 bar) to give dinuclear monoalkyl- and dialkylcarbamate complexes [Ni₂L(O₂CNRR′)]⁺ (R = H, R′ = CH₂Ph (2), R = H, R′ = n-Bu (3), R = H, R′ = n-Oct (4), R = H, R′ = CH₂CH₂OH (5), R = R′ = Et (6), and R = R′ = CH₂CH₂OH (7)). Complexes 2-7 can also be prepared by the reaction of 1 with CO₂(air)/amine. The carbamate complexes are hydrolyzed in methanolic solution to give the known alkylcarbonate complex [Ni₂L(O₂COMe)]⁺ (8). These conversions are less rapid than the transesterification reactions of 8, due to a less electron-demanding carboxyl C(carbamate) atom. All new complexes were either isolated as perchlorate or tetraphenylborate salts and fully characterized by elemental analysis, UV/Vis, and IR spectroscopy. The structures of 2[BPh₄] and 7[BPh₄] have also been determined by X-ray crystallography. They confirm the presence of μ_1,3-bridging alkylcarbamate units in the products.     

Synthesis and characterization of β-diketonato ruthenium(II) complexes with two 4-bromo or protected 4-ethynyl-2,2′-bipyridine ligands

Two new mononuclear mixed-ligand ruthenium(II) complexes with acetylacetonate ion (2,4-pentanedionate, acac) and functionalized bipyridine (bpy) in position 4, [Ru(bpyBr)₂(acac)](PF₆) (2; bpyBr = 4-Bromo-2,2′-bipyridine, acac = 2,4-pentanedionate ion) and [Ru(bpyOH)₂(acac)](PF₆) (3; bpyOH = 4-[2-methyl-3-butyn-2-ol]-2,2′-bipyridine) were prepared as candidates for building blocks. The ¹H NMR, ¹³C NMR, UV-Vis, electrochemistry and FAB mass spectral data of these complexes are presented.     

Effect of ancillary ligands on the photophysical properties of Ru(II) complexes bearing a highly conjugated diimine ligand: A density functional theory study

Two bis-heteroleptic Ru(II) complexes [Ru(bpy)₂(pcip)]²⁺ (1, bpy = 2,2′-bipyridine, pcip = 2-[4-phenylcarboxy]-1H-imidazol[4,5-f][1,10]phenanthroline) and [Ru(phen)₂(pcip)]²⁺ (2, phen = 1,10-phenanthroline), bearing highly conjugated diimine ligands, were prepared and isolated as their PF₆ salts. The bpy-derivative 1 showed better photophysical properties (emission quantum yield, lifetime of the emitting state, and the radiative decay rate constant) than the phen-compound 2. These results followed by theoretical calculations at DFT level established a comprehensive understanding between the structural parameters and the photophysical properties, as well as of the influence of π conjugation and the symmetry of the molecules on spectroscopic characteristics. These results provide fundamental photophysical data for selecting ancillary ligands in the design and improvement of Ru-based light-harvesting complexes.     

Hydrogen-halide versus alkyl-halide oxidative addition in dimethyl platinum(II) complexes: Crystal structure of [PtBr2(bpy)]

Dimethyl platinum(II) complexes [PtMe₂(NN)] {NN = bu₂bpy (4,4′-di-tert-butyl-2,2′-bipyridine) (1a), bpy (2,2′-bipyridine) (1b), phen (1,10-phenanthroline) (1c)} reacted with commercial 3-bromo-1-propanol in the presence of 1,3-propylene oxide to afford cis, trans- [PtBrMe₂{(CH₂)₃OH}(NN)] (NN = bu₂bpy (2a), bpy (2b), phen (2c)). On the other hand, [PtMe₂(NN)] (1a)-(1b) reacted with the trace of HBr in commercial 3-bromo-1-propanol to give [PtBr₂(NN)] (NN = bu₂bpy (3a), bpy (3b)). The reaction pathways were monitored by ¹H NMR at various temperatures. Treatment of 1a-1b with a large excess of 3-bromo-1-propanol at −80 °C gave the corresponding methyl(hydrido)platinum(IV) complexes [PtBr(H)Me₂(NN)] (NN = bu₂bpy (4a), bpy (4b)) via the oxidative addition of dimethyl platinum(II) complexes with HBr. The complexes [PtBr(H)Me₂(NN)] decomposed by reductive elimination of methane above −20 °C for bu₂bpy and from −20 to 0 °C for bpy analogue to give methane and platinum(II) complexes [PtBrMe(NN)] (5a)-(5b) and then decomposed at about 0 °C to yield [PtBr₂(NN)] and methane. When the reactions were performed at a molar ratio of Pt:RX/1:10, the corresponding complexes [PtBrMe(NN)] (5a)-(5b) were also obtained. The crystal structure of the complex 3b shows that platinum adopts square planar geometry with a twofold axis through the platinum atom. The Pt…Pt distance (5.164 Å) is considerably larger than the interplanar spacing (3.400 Å) and there is no platinum-platinum interaction.     

Synthesis, spectral characterization, and single crystal X-ray structures of a series of manganese-2,2′-bipyridine complexes derived from substituted aromatic carboxylic acids

Reaction of [Mn(2,2′-bpy)₂(OAc)](ClO₄)(H₂O) with a series of aromatic carboxylic acids yields new Mn(II)carboxylates [Mn(2,2′-bpy)₂(L)](ClO₄)}₂ (1-3), [Mn(2,2′-bpy)₂(L)₂] (4-5) and [Mn(2,2′-bpy)₂(L)(H₂O)](ClO₄) (6) (L = 2-aminobenzoate (2-aba) (1), 4-hydroxybenzoate (4-hba) (2), thiophene-2-carboxylate (2-tca) (3), 2-hydroxynapthoate (2-hnapa) (4), 3,5-diisopropylsalicylic acid (dipsa) (5), 2,4,6-triisopropylbenzoate (tipba) (6)). The new compounds have been characterized with the aid of elemental analysis, spectroscopy, and single-crystal X-ray diffraction studies. Compounds 1-3, which have been synthesized from less bulky carboxylic acids, are dimeric in the solid-state. Compounds 4-6, which are derived from more bulkier aromaric carboxylic acids, exist as monomeric complexes. In the case of 6, where very bulky 2,4,6-triisopropyl benzoic acid is used as the starting material, only one carboxylate ligand binds to the metal, resulting in a cationic complex. Interestingly in all the six complexes, the C-H hydrogen atoms of the 2,2′-bpy ligands are involved in extensive hydrogen bonding with the carboxylate oxygen atoms of the adjacent molecules and hence form non-covalent 1-D or 2-D aggregates in the solid state.     

Copper(II) complexes with monocarboxylate ligands bearing different substituent groups: Synthesis and spectroscopic studies

In our continuing efforts to explore the effects of substituent groups of ligands in the formation of supramolecular coordination structures, seven new Cu^II complexes formulated as [Cu₂(L¹)₄(DMF)₂] (1), {[Cu₂(L¹)₄(Hmta)](H₂O)_0.75}_∞ (2), [Cu₂(L²)₄(2,2′-bipy)₂] (3), [Cu₂(L³)₄(H₂O)₂] (4), [Cu₂(L³)₄(Hmta)]_∞ (5), [Cu₂(L³)₄(Dabco)]_∞ (6) and [Cu₂(L³)₄(Pz)]_∞ (7) with three monocarboxylate ligands bearing different substituent groups HL¹-HL³ (HL¹ = phenanthrene-9-carboxylic acid, HL² = 2-phenylquinoline-4-carboxylic acid, HL³ = adamantane-1-carboxylic acid, Hmta = hexamethylenetetramine, 2,2′-bipy = 2,2′-bipyridine, Dabco = 1,4-diazabicyclo[2.2.2] octane and Pz = pyrazine), have been prepared and characterized by X-ray diffraction. In 1, 2 and 4-7, each Cu^II ion is octahedrally coordinated, and carboxylate acid acts as a syn-syn bridging bidentate ligand. While each Cu^II ion in 3 is penta-coordinated in a distorted square-pyramidal geometry. 1 and 4 both show a dinuclear paddle-wheel block, while 2, 5, 6 and 7 all exhibit an alternated 1D chain structure between dinuclear paddle-wheel units of the tetracarboxylate type Cu₂-(RCO₂)₄ and the bridging auxiliary ligands Hmta, Dabco and Pz. Furthermore, 3 has a carboxylic unidentate and μ_1,1-oxo bridging dinuclear structure with the chelating auxiliary ligand 2,2′-bipy. Moreover, complexes 1-6 were characterized by electron paramagnetic resonance (EPR) spectroscopy.     

Hydrothermal synthesis, crystal structures and photoluminescent properties of four cadmium(II) coordination polymers derived from diphenic acid and auxiliary ligands

Four novel metal coordination polymers, [Cd(dpa)(H₂O)]_n (1), [Cd(dpa)(2,2′-bipy)]_n (2), {[Cd₂(dpa)₂(4,4′-bipy)₃](4,4′-bipy)(H₂O)₂}_n (3) and [Cd(dpa)(bim)₂(H₂O)]}_n (4) (H₂dpa = 2,4′-biphenyl-dicarboxylic acid, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, bim = benzimidazole), have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Single-crystal X-ray analyses reveal that the 2,4′-diphenic acids acts as bridging ligands, exhibiting rich coordination modes to link metal ions: bis-monodentate, bidentate chelating, chelating/bridging, monoatomic bridging and monodentate modes. In addition, the luminescent properties for compound 1-4 are also investigated in this work.     

Synthesis, characterization, X-ray structure and in vitro antimycobacterial and antitumoral activities of Ru(II) phosphine/diimine complexes containing the "SpymMe2" ligand, SpymMe2=4,6-dimethyl-2-mercaptopyrimidine

The reaction of cis-[RuCl₂(dppb)(N-N)], dppb = 1,4-bis(diphenylphosphino)butane, complexes with the ligand HSpymMe₂, 4,6-dimethyl-2-mercaptopyrimidine, yielded the cationic complexes [Ru(SpymMe₂)(dppb)(N-N)]PF₆, N-N = bipy (1) and Me-bipy (2), bipy = 2,2′-bipyridine and Me-bipy = 4,4′-dimethyl-2,2′-bipyridine, which were characterized by spectroscopic and electrochemical techniques and X-ray crystallography and elemental analysis. Additionally, preliminary in vitro tests for antimycobacterial activity against Mycobacterium tuberculosis H37Rv ATCC 27264 and antitumor activity against the MDA-MB-231 human breast tumor cell line were carried out on the new complexes and also on the precursors cis-[RuCl₂(dppb)(N-N)], N-N = bipy (3) and Me-bipy (4) and the free ligands dppb, bipy, Me-bipy and SpymMe₂. The minimal inhibitory concentration (MIC) of compounds needed to kill 90% of mycobacterial cells and the IC₅₀ values for the antitumor activity were determined. Compounds 1-4 exhibited good in vitro activity against M. tuberculosis, with MIC values ranging between 0.78 and 6.25 μg/mL, compared to the free ligands (MIC of 25 to >50 μg/mL) and the drugs used to treat tuberculosis. Complexes 1 and 2 also showed promising antitumor activity, with IC₅₀ values of 0.46 ± 0.02 and 0.43 ± 0.08 μM, respectively, against MDA-MB-231 breast tumor cells.     

Syntheses, structures, and magnetic properties of heterobimetallic Fe2M (M = Cu, Mn) chains based on tetracyanometallic building block

Using the tetracyanometalate precursor [Fe(4,4′-dmbipy)(CN)₄]^- (4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine) as the building block, two new cyano-bridged one-dimensional heterobimetallic coordination polymers, [M(CH₃OH)₂Fe₂(4,4′-dmbipy)₂(CN)₈]_n (M = Cu, 1; Mn, 2), have been synthesized and structurally characterized. X-ray crystallography reveals that complexes 1 and 2 consist of heterobimetallic chains of squares, and the central M^II ion is six-coordinated as an elongated distorted octahedral geometry. Magnetic studies show ferromagnetic coupling between Fe^III and Cu^II ions in complex 1. Complex 2 exhibits ferrimagnetic behavior caused by the noncompensation of the local interacting spins (S_Mn = 5/2 and S_Fe = 1/2), which interact antiferromagnetically through bridging cyanide groups. magpack program has been employed to investigate the magnetic nature of squares chain structure.     

DNA-binding and photocleavage studies of mixed polypyridyl ruthenium(II) complexes with calf thymus DNA

New mixed polypyridyl {NMIP = 2′-(2″-nitro-3″,4″-methylenedioxyphenyl)imidazo-[4′,5′-f][1,10]-phenanthroline, dmb = 4,4′-dimethyl-2,2′-bipyridine, bpy = 2,2′-bipyridine} ruthenium(II) complexes [Ru(dmb)₂(NMIP)]²⁺ (1) and [Ru(bpy)₂(NMIP)]²⁺ (2) have been synthesized and characterized. The binding of these complexes to calf thymus DNA (CT-DNA) has been investigated with spectroscopic methods, viscosity and electrophoresis measurements. The experimental results indicate that both complexes could bind to DNA via partial intercalation from the minor/major groove. In addition, both complexes have been found to promote the single-stranded cleavage of plasmid pBR 322 DNA upon irradiation. Under comparable experimental conditions compared with [Ru(phen)₂(NMIP)]²⁺, during the course of the dialysis at intervals of time, the CD signals of both complexes started from none, increased to the maximum magnitude, then no longer changed, and the activity of effective DNA cleavage dependence upon concentration degree lies in the following order: [Ru(phen)₂NMIP]²⁺ > complex 2 > complex 1.     

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.     

Synthesis, characterizations and crystal structures of antimony(III) complexes with nitrogen-containing ligands

Six antimony adducts with N-donor neutral ligands (1,10-phenanthroline, 4,4′-bipyridine) have been obtained following the reaction of antimony halides with phenanthroline and 4,4′-bipyridine. By changing the solvent and stoichiometry, we obtained six different complexes, Sb(phen)Cl₃ (1), Sb(phen)Br₃ (2), Sb₂(phen)₄Br₈ (3) and Sb(bpy)Cl₃ (4), Sb(bpy)₂Cl₃ (5), Sb(bpyH · bpyH₂)Br₆ (6) (where phen = 1,10-phenanthroline, bpy = 4,4′-bipyridine). All the complexes have been characterized via elemental analysis, FT-IR and NMR (¹H, ¹³C) spectroscopy. The crystal structures of complexes 2, 3 and 6 have been determined by X-ray single crystal diffraction.The structural analysis show that the coordination sphere around antimony atom in complex 2 is a distorted square pyramid, coordinated by three bromine atoms and two nitrogen atoms from phen. In complex 3, the central antimony atom is six-coordinated through four bromine atoms and two nitrogen atoms forming a distorted octahedral geometry. Besides that, there are also uncoordinated 1,10-phenanthroline bonded by hydrogen bonds and π-π stacking interactions, which is rarely observed in previous reports. The crystal structure of complex 6 consists of bpyH · bpyH₂ trications and hexabromoantimonate trianions. The antimony atom in the anion has a distorted octahedral environment. Additionally, all complexes present a 3D framework built up by N-H?Br, C-H?Br and C-H?Cl weak hydrogen bonds interactions.