A new self-assembled inorganic-organic hybrid layered compound containing hexarhenium cluster: [MV][{Mn(CH3OH)2}{Re6Se8(CN)6}]

A new layered compound, [MV][{Mn(CH₃OH)₂}{Re₆Se₈(CN)₆}] (1) consists of a layer alternately knitted by hexarhenium cluster and Mn complex, and MV²⁺ cations (methyl viologen dication = 1,1′-dimethyl-4,4′-bipyridilium dication) reside between the layers. The title compound 1 is the first layered framework containing cyano-hexarhenium clusters with photoactive guest molecules, MV²⁺. The MV²⁺ can be partly exchanged by H₂TMB²⁺ (N,N,N′,N′-tetramethylbenzidine dication) to form a compound [H₂TMB²⁺]_x[MV²⁺]_1−x [{Mn(CH₃OH)₂}{Re₆Se₈(CN)₆}] (2) showing an electronic interaction between the layered framework and [H₂TMB]²⁺ cation.     

Synthesis and properties of red emitter Ru(II) complexes based on 6,6′-disubstituted-4,4′-bipyrimidine

Heteroleptic complexes [Ru(bpy)₂(R₂bpm)]²⁺, where bpy = 2,2′-bipyridine and R₂bpm = 6,6′-diaryl-4,4′-bipyrimidine, have been synthesized and characterized, together with the homoleptic complex [Ru(R₂bpm)₃]²⁺, in which R₂bpm = 6,6′-diphenyl-4,4′-bipyrimidine. The substituent aryl on the bipyrimidine has significant effects on the properties of these complexes as compared to the parent [Ru(bpy)₂(bpm)]²⁺ complex. The complexes exhibit Ru-to-bpm charge transfer (CT) absorptions centered at about 540 nm and Ru-to-bpy CT absorptions centered at about 435 nm. The assignment of the low energy absorptions is supported by the relative ease of the reduction of the new complexes as compared to [Ru(bpy)₃]²⁺. The new complexes exhibit a relatively intense emission at room temperature, with lifetimes in the 10-50 ns range, with the homoleptic species exhibiting the higher-energy (maximum at 724 nm) and the longest-lived (τ = 48 ns) emission among the complexes. Luminescence lifetimes and quantum yields are governed by the energy gap law, indicating that direct deactivation to the ground state is the dominant relaxation pathway for 1-6, while thermally activated processes are inefficient.     

Synthesis, characterization, and aqueous chemistry of cytotoxic Au(III) polypyridyl complexes

This work reports the synthesis, characterization, and aqueous chemistry of a series of cytotoxic [Au(polypyridyl)Cl₂]PF₆ complexes {(where polypyridyl = dipyrido[3,2-f:2′,3′-h] quinoxaline (DPQ), dipyrido[3,2-a:2′,3′-c] phenazine (DPPZ) and dipyrido[3,2-a:2′,3′-c](6,7,8,9-tetrahydro) phenazine (DPQC))}. The crystal structure of [Au(DPQ)Cl₂]PF₆ was determined as example of the series and exhibits the anticipated square planar geometry common for d⁸ coordination complexes. The crystals of the complex belong to the space group P2₁/n with a = 7.624(2) Å, b = 18.274(5) Å, c = 14.411(14) Å, β = 98.03(3)°, and Z = 4. In ¹H NMR studies of these compounds in the presence of aqueous buffer, all four complexes rapidly converted to the dihydroxy species [Au(polypyridyl)(OH)₂] in a stepwise fashion. However, the [Au(polypyridyl)]³⁺ fragment believed to impart cytotoxicity in human ovarian cancer cell lines (A2780) remained intact and appeared stable for days. It was also noted that these Au(III) complexes were readily reduced in the presence of the common biological reducing agents, reduced glutathione and sodium ascorbate. How solution and redox stability may affect the biological activity of these novel Au(III) complexes is discussed.     

The synthesis and characterization of mixed ligand Ru(II) complexes with dipyrido(2,3-a:3′,2′-j)phenazine (dpop′) and 2,3,5,6-tetra(2-pyridyl)-pyrazine (tppz)

The synthesis of the mixed ligand mono metallic [Ru(dpop′)(tppz)]²⁺ and bimetallic [(dpop′)Ru(tppz)Ru(dpop′)]⁴⁺ (dpop′ = dipyrido(2,3-a:3′,2′-j)phenazine; tppz = 2,3,5,6 tetra-(2-pyridyl)pyrazine) complexes is described. The [Ru(dpop′)(tppz)]²⁺ complex display an intense absorption at 518 nm which is assigned to a Ru(dπ) → dpop′ (π∗) MLCT transition, and at 447 nm which is assigned to a Ru(dπ) → tppz(π∗) MLCT transition. It undergoes emission at RT in CH₃CN with λ_em = 722 nm. The bimetallic [(dpop′)Ru(tppz)Ru(dpop′)]⁴⁺ complex shows a low energy absorption shoulder near 635 nm assigned to a Ru(dπ) → tppz(π∗) MLCT transition and an intense peak at 542 nm due to Ru(dπ) → dpop′ (π∗) MLCT transition. The bimetallic complex also emits at RT in CH₃CN with λ_em = 785 nm. Cyclic voltammetry shows reversible Ru^+2/+3 oxidations at 1.68 V for the monometallic complex and Ru^+2/+3 oxidation couples at +1.94 and +1.70 V for the bimetallic complex.     

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.     

Preparation and properties of ruthenium (II) complexes of 2,2′:6′,2″-terpyridines substituted at the 4′-position with heterocyclic groups

Four ligands whose general formula is R-terpy with terpy = 2,2′:6′,2″ terpyridine bearing at the 4′-position a substituent R = 2-furyl, 2-pyrrolyl, 2-thienyl and 5-2,2′bithienyl were synthesised. The absorption spectra and the electrochemical behaviour of the corresponding homoleptic Ru(II) complexes were investigated and compared to those of the parent complex [Ru(terpy)]²⁺. Due to the donor effect of the grafted heterocyclic groups, the absorption and emission maxima are red-shifted and the energy levels of the HOMO Π(t_2g) metal orbitals are slightly higher. The incorporation of these heterocyclic moieties extends the electronic delocalisation over the corresponding ligands, leading to higher emission quantum yields. Cyclic voltammetric studies of pyrrolyl-, thienyl- and bithienyl-functionalised complexes show that an electroactive layer can be deposited on the electrode. Preliminary results point out that an electrodeposited film could be used as a photocathode in an aqueous electrolyte.     

Crystal structures of a type-1 ribosome inactivating protein from Momordica balsamina in the bound and unbound states

The ribosome inactivating proteins (RIPs) of type 1 are plant toxins that eliminate adenine base selectively from the single stranded loop of rRNA. We report six crystal structures, type 1 RIP from Momordica balsamina (A), three in complexed states with ribose (B), guanine (C) and adenine (D) and two structures of MbRIP-1 when crystallized with adenosine triphosphate (ATP) (E) and 2′-deoxyadenosine triphosphate (2′-dATP) (F). These were determined at 1.67 Å, 1.60 Å, 2.20 Å, 1.70 Å, 2.07 Å and 1.90 Å resolutions respectively. The structures contained, (A) unbound protein molecule, (B) one protein molecule and one ribose sugar, (C) one protein molecule and one guanine base, (D) one protein molecule and one adenine base, (E) one protein molecule and one ATP-product adenine molecule and (F) one protein molecule and one 2′-dATP-product adenine molecule. Three distinct conformations of the side chain of Tyr70 were observed with (i) χ¹ = − 66°and χ² = 165° in structures (A) and (B); (ii) χ¹ = − 95° and χ² = 70° in structures (C), (D) and (E); and (iii) χ¹ = − 163° and χ² = 87° in structure (F). The conformation of Tyr70 in (F) corresponds to the structure of a conformational intermediate. This is the first structure which demonstrates that the slow conversion of DNA substrates by RIPs can be trapped during crystallization.     

[Cu4(H2O)4(dmapox)2(btc)]n · 10nH2O: The first two-dimensional polymeric copper(II) complex with bridging μ-trans-oxamidate and μ4-1,2,4,5-benzentetracarboxylato ligands: Synthesis, crystal structure and DNA binding studies

A two-dimensional copper(II) polymer with formula of [Cu₄(H₂O)₄(dmapox)₂(btc)]_n · 10nH₂O, where dmapox is the dianion of N,N′-bis[3-(dimethylamino)propyl]oxamide and btc is the tetra-anion of 1,2,4,5-benzenetetracarboxylic acid, was synthesized and characterized by elemental analysis, conductivity measurement, IR and electronic spectral studies. The crystal structure of the complex has been determined by X-ray single-crystal diffraction. The structure consists of crystallized water molecules and neutral two-dimensional copper(II) coordination polymeric networks constructed both by the bis-tridentate μ-trans-dmapox and tetra-monodentate μ₄-btc bridging ligands. Each btc ligand links four trans-dmapox-bridged binuclear copper(II) building blocks [Cu₂(H₂O)₂(trans-dmapox)]²⁺ and each binuclear copper(II) building block attaches to two btc ligands forming an infinite 2D layer which consists of 4+4 grids with dimensions of 13.563(5) × 15.616(5) Å. The environment around the copper(II) atom can be described as a distorted square-pyramid and the Cu?Cu separations through μ-trans-dmapox and μ₄-btc bridging ligands are 5.225 Å (Cu1-Cu1ⁱ), 5.270 Å (Cu2-Cu2ⁱⁱ), 6.115 Å (Cu1-Cu2), 9.047 Å (Cu1-Cu2ⁱⁱⁱ) and 10.968 Å (Cu1-Cu1ⁱⁱⁱ), respectively. Abundant hydrogen bonds among the crystallized, the coordinated water molecules, and the uncoordinated carboxyl oxygen atoms cross-link the two-dimensional layers into an overall three-dimensional channel-like framework. The interaction of the copper(II) polymer with calf thymus DNA (CT-DNA) has been investigated by using absorption, emission spectral and electrochemical techniques. The results indicate that the copper(II) polymer interacts with DNA strongly (K_b = 4.8 × 10⁵ M⁻¹ and K_sv = 1.1 × 10⁴) and the interaction mode between the copper(II) polymer and DNA may be the groove binding. To the best of our knowledge, this is the first report about the crystal structure and DNA-binding studies of a two-dimensional copper(II) polymer bridged both by the trans-oxamidate and btc ligands.     

A two-dimensional copper(II) polymer with bridging μ-trans-oxamidate and μ2-picrate ligands: Synthesis, crystal structure and DNA binding studies

A two-dimensional copper(II) polymer with formula of [Cu₂(dmapox)(pic)₂]_n · nCH₃OH, where dmapox is the dianion of N,N′-bis[3-(dimethylamino)propyl]oxamide and pic is picrate, was synthesized and characterized by elemental analysis, conductivity measurement, IR and electronic spectra studies. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. It crystallizes in monoclinic, space group P2₁/c with crystallographic data: a = 14.076(7) Å, b = 13.896(7) Å, c = 9.278(5) Å, β = 106.909(6)° and Z = 2. The structure consists of uncoordinated methanol molecules and two-dimensional copper(II) polymeric coordination network constructed by the bis-tridentate trans-dmapox and tridentate picrate ligands. The environment around the copper(II) atom can be described as a distorted octahedron and the Cu?Cu separations through μ-trans-oxamidate and μ₂-picrate bridges are 5.227 Å and 8.359 Å, respectively. The copper(II) complex presents as a polymer in solid state, whereas in solution it presents as discrete neutral binuclear copper(II) species [Cu₂(dmapox)(pic)₂] due to the weak interactions between the copper(II) atoms and the para-nitro oxygens of the adjacent picrate ligands. The fluorescence titration and the ethidium bromide (EB) fluorescence displacement experiments reveal that the binding mode between the binuclear copper(II) complex [Cu₂(dmapox)(pic)₂] and Herring Sperm DNA might be intercalation.     

Organolanthanide constrained geometry complexes modified for catalysis: synthesis, structure, and aminoalkene hydroamination properties of a pyrrolidine-substituted constrained geometry organolutetium complex

The reaction of the organolutetium complex (CGC′)LuCl₃Li₂(THF), (1; CGC′ = [Me₂Si(3-pyrrolidinyl-1-η⁵-indenyl)(^tBuN)]²⁻) with NaN(TMS)₂ provides a straightforward route to the halide-free organolutetium amido complex, (CGC′)LuN(TMS)₂(THF) (2). These new complexes were characterized by standard analytical methodology. The monomeric complex 2 crystallizes in the monoclinic space group P2₁/c with four molecules in a cell of dimensions a = 11.1566(6) Å, b = 14.9805(8) Å, c = 22.18007(12) Å, and β = 90.0620(10)°. Complex 2 is an active precatalyst for the intramolecular hydroamination/cyclization of representative aminoalkenes with turnover frequencies as high as 205 h⁻¹ at room temperature.     

The relationship between the structures of periphery ligands and the DNA binding mode of [Ru(II)(1,10-phenanthroline)(L1L2)dipyrido[3,2-a:2',3'-c]phenazine](n+) (L1=Cl or pyridine and L2=pyridine, n=1,2)

The binding modes of the [Ru(II)(1,10-phenanthroline)(L₁L₂) dipyrido[3,2-a:2′,3′-c]phenazine]²⁺ {[Ru(phen)(py) Cl dppz]⁺ (L₁ = Cl, L₂ = pyridine) and ([Ru(phen)(py)₂dppz]²⁺ (L₁ = L₂ = pyridine)} to native DNA is compared to that of the [Ru(II)(1,10-phenanthroline)₂dipyrido[3,2-a:2′,3′-c]phenazine]²⁺ complex ([Ru(phen)₂dppz]²⁺) by various spectroscopic and hydrodynamic methods including electric absorption, linear dichroism (LD), fluorescence spectroscopy, and viscometric titration. All measured properties, including red-shift and hypochromism in the dppz absorption band, nearly perpendicular molecular plane of the dppz ligand with respect to the local DNA helix axis, prohibition of the ethidium binding, the light switch effect and binding stoichiometry, increase in the viscosity upon binding to DNA, increase in the melting temperature are in agreement with classical intercalation of dppz ligand of the [Ru(phen)₂dppz]²⁺ complex, in which both phenanthroline ligand anchored to the DNA phosphate groups by electrostatic interaction. [Ru(phen)(py)₂ dppz]²⁺ and [Ru(phen)(py) Cl dppz]⁺ complexes had one of the phenanthroline ligand replaced by either two pyridine ligands or one pyridine plus a chlorine ion. They exhibited similar protection from water molecules, interaction with DNA bases, and occupying site that is common with ethidium. The dppz ligand of these two Ru(II) complex were greatly tilted relative to the DNA helix axis, suggesting that the dppz ligand resides inside the DNA and is not perpendicular relative to the DNA helix axis. These observation suggest that anchoring the [Ru(phen)₂dppz]²⁺complex by both phenanthroline is essential for the dppz ligand to be classically intercalated between DNA base-pairs.     

[Hg(9-methyl-1-deazapurine)2](NO3)2 · H2O: a complex with a distorted hexagonal bipyramidal metal ion coordination sphere

Reaction of 9-methyl-1-deazapurine (9-MeDP) with Hg(CF₃COO)₂ in the presence of NaNO₃ yields the title compound [Hg(9-MeDP)₂](NO₃)₂ · H₂O with the two 9-MeDP ligands bound to the metal ion via their N7 positions. The X-ray structure is reported: monoclinic, P2₁/c (no. 14), a = 5.4015(11), b = 20.467(4), c = 17.775(4) Å, β = 97.00(3)°, V = 1950.4(7) ų, Z = 4. Hg is eight-coordinate with two trans-oriented Hg-N bonds (2.073(3) and 2.075(3) Å) and three nearly coplanar, bidentate nitrate moieties (Hg-O: 2.716(3)-2.985(4) Å), leading to a distorted hexagonal bipyramidal environment of the metal ion. Within this structure, the nitrate ions form a honeycomb-like chain structure with Hg^II being positioned inside the combs. This work represents the first report of such geometry for a transition metal ion surrounded by symmetrically bidentate nitrate ions. The corresponding nucleoside, 1-deazapurine 2′-deoxyribonucleoside, also forms a stable 2:1 complex with Hg^II, as was shown by ¹H NMR spectroscopy, making it a potential candidate for incorporation into nucleic acids based on metal-mediated base pairs.     

Synthesis and characterization of tris(heteroleptic) diimine complexes of chromium(III)

A preparative procedure of potentially wide applicability is described for the synthesis of previously unreported tris(heteroleptic) [Cr(diimine)₃]³⁺ complexes. The synthetic scheme involves the sequential addition of three different diimine ligands, and employs CrCl₃ · 6H₂O as the initial Cr(III) reagent. The synthesis and characterization of the complexes [Cr(TMP)(phen)(diimine′)]³⁺ are reported (where TMP = 3,4,7,8-tetramethyl-1,10-phenanthroline, phen = 1,10-phenanthroline; and diimine′ is either bpy = 2,2′-bipyridine, Me₂bpy = 4,4′-dimethyl-2,2′-bipyridine, 5-Clphen = 5-chloro-1,10-phenanthroline, or DPPZ = dipyridophenazine). Chiral capillary electrophoresis and electrospray mass spectrometry were essential aids in determining the presence or absence of diimine ligand scrambling. Utilizing emission and electrochemical data obtained on these compounds, the oxidizing power of the lowest lying excited state (²E_g(O_h)) was calculated, and was found to vary in a systematic fashion with diimine ligand type.     

The interesting DNA-binding properties of three novel dinuclear Ru(II) complexes with varied lengths of flexible bridges

Three binuclear Ru(II) complexes with two [Ru(bpy)₂(pip)]²⁺-based subunits {where bpy = 2,2′-bipyridine and pip = 2-phenylimidazo[4,5-f][1,10]phenanthroline} being linked by varied lengths of flexible bridges, were synthesized and characterized by ¹H NMR, elemental analysis, UV-visible (UV-vis) and photoluminescence spectroscopy. The structures of the three complexes were optimized by density functional theory calculations. The interaction of the complexes with calf thymus DNA was investigated by UV-vis and luminescence titrations, steady-state emission quenching by [Fe(CN)₆]⁴⁻, DNA competitive binding with ethidium bromide, DNA melting experiments, and viscosity measurements. The experimental results indicated that the three complexes bound to the DNA most probably in a threading intercalation binding mode with high DNA binding constant values three orders of magnitude greater than the DNA binding constant value reported for proven DNA intercalator, mononuclear counterpart [Ru(bpy)₂(p-mopip)]²⁺ {p-mopip = 2-(4-methoxylphenyl)imidazo[4,5-f][1,10]phenanthroline}.     

Synthesis, crystal structure and solid state photoluminescence of [Pt(trpy)(CCPh)]SbF6 (trpy=2,2′:6′,2″-terpyridine)

The synthesis and characterisation of an orange polymorph of [Pt(trpy)(CCPh)]SbF₆ is described where trpy = 2,2′:6′,2″-terpyridine. An X-ray crystal structure determination at 293 K reveals that the cations are planar and stacked head-to-tail with alternating Pt?Pt distances of 3.604(1) and 4.412(1) Å. The perpendicular distances between successive cation planes are constant along the stack at a value of 3.33 Å. Crystal structure determinations at 240 and 200 K show that reducing the temperature to 200 K has no significant effect on the cation arrangement. However, below 200 K there is a phase change that we have not been able to characterise, but which has an effect on the solid state photoluminescence exhibited by [Pt(trpy)(CCPh)]SbF₆. Thus, whereas at temperatures of ?200 K, a broad peak with two components at ca. 566 and 597 nm is observed, below 200 K a longer wavelength peak develops that red-shifts as the temperature is lowered [λ(em)_max = 637 nm at 80 K]. We assign the ?200 K emission as ³MLLCT in origin, since the X-ray data show that ligand-ligand (LL) and not metal-metal (MM) interactions are important at T ? 200 K. On the other hand, the long wavelength emission observed below 200 K is typical of ³MMLCT emission, suggesting that the phase change leads to d_z²(Pt)-d_z²(Pt) orbital interactions. Of particular interest is that the cation exhibits ³MLCT emission in dichloromethane that maximizes at 619 nm, i.e., the high temperature solid state emission occurs at a shorter wavelength, an unexpected result since intermolecular interactions in the solid usually cause the emission to occur at longer wavelengths. A possible explanation for this unexpected result is given.     

Two cadmium-thiocyanate coordination polymers with organic cations: Synthesis, crystal structures and luminescent properties

Two new inorganic-organic hybrid polymers [ClBzQl]₂[Cd(SCN)_3.5Br_0.5]·0.25H₂O (1) and [ClBzMePy][Cd(SCN)₃] (2) (ClBzQl = 1-(4′-Cl-benzyl)quinolinium cation and ClBzMePy = 1-(4′-Cl-benzyl)-2-methylpyridinium cation) have been synthesized and characterized by IR, UV, elemental analysis and X-ray crystallography. Crystal structure analyses show that two polymers belong to the monoclinic space group P2/n (1) and P2₁/c (2) with a = 18.548(2) Å, b = 9.526(1) Å, c = 20.689(2) Å, β = 94.008(1)°, V = 3646.6(5) Å³ for 1, and a = 11.195(2) Å, b = 16.415(3) Å, c = 10.751(2) Å, β = 102.930(3)°, V = 1925.7(7) Å³ for 2. The Cd atom exhibits a distorted octahedral coordination geometry for 1 and 2. For 1, a pair of 1,1-μ-SCN⁻ anions and a pair of 1,3-μ-SCN⁻ anions are alternately bridge adjacent Cd centers to form infinite polymeric chains. For 2, adjacent Cd atoms are linked by three 1,3-μ-SCN⁻ anions to form infinite [Cd(SCN)₃⁻]_∞ polymeric chains. The luminescent properties of the two polymers in the solid state at room temperature were investigated.     

Photophysics of ruthenium(II) complexes carrying amino acids in the ligand 2,2′-bipyridine and intramolecular electron transfer from methionine to photogenerated Ru(III)

New ruthenium(II) complexes carrying methionine and phenylalanine in the bipyridine ligand, [Ru(bpy)₂(4-Me-4′-(CONH-l-methionine methyl ester)-2,2′-bipyridine)](PF₆)₂ (IV) and [Ru(bpy)₂(4-Me-4′-(CONH-l-phenylalanine ethyl ester)-2,2′-bpy)](PF₆)₂(V) have been synthesized and characterized and their photophysical properties studied. Flash photolysis measurements of complex IV, in the presence of an electron acceptor, methyl viologen (MV²⁺) show that an intermolecular electron transfer from the excited state of Ru(II) in complex IV, to MV²⁺ takes place, forming Ru(III) and the methyl viologen cation radical, MV⁺. The formation of MV⁺ in this system is confirmed using time-resolved transient absorption spectroscopy. This intermolecular electron transfer is followed by intramolecular electron transfer from the thioether moiety (methionine) to the photogenerated Ru(III), regenerating Ru(II).     

Carboxy-derived (tpy)2Ru complexes as sub-units in supramolecular architectures: The solubilized ligand 4′-(4-carboxyphenyl)-4,4″-di-(tert-butyl)tpy and its homoleptic Ru(II) complex

We herein describe the synthesis and characterization of a series of homoleptic, Ru(II) complexes bearing peripheral carboxylic acid functionality based upon the novel ligand 4′-(4-carboxyphenyl)-4,4″-di-(tert-butyl)tpy (L₁), as well as 4′-(4-carboxyphenyl)tpy (L₂) and 4′-(carboxy)tpy (L₃) (where tpy = 2,2′: 6′,2″-terpyridine). Inspection of the metal-based oxidations (E_1/2 = 1.22-1.42 V) indicates an anodic shift (∼0.2 V) for (L₃)₂Ru²⁺ (3b) (E_1/2 = 1.40 V) relative to (L₂)₂Ru²⁺ (2b) (E_1/2 = 1.22 V). The metal-based oxidation (E_1/2 = 1.22 V) and ligand-based reductions (E_1/2 = −1.25 to −1.52 V) of (L₁)₂Ru²⁺ (1) are essentially invariant relative to those of the structural analogue 2b (PF₆)₂, which suggests no significant electronic effect caused by the tert-butyl groups. This is supported by invariance in the metal-to-ligand charge transfer bands in both the electronic absorption (494-489 nm) and emission spectra (654-652 nm). However, contrary to 2b, complex 1 is both very soluble and exhibits a highly porous solid-state structure with internal cavity dimensions of 15 Å × 14 Å due to the preclusion of inter-annular interactions by the bulky tert-butyl substituents.     

One-dimensional copper(II) coordination polymers bridged both by mu-trans-oxamidates and phenyldicarboxylates: Synthesis, crystal structure and DNA binding studies

Two new one-dimensional copper(II) polymers with formulae of [Cu₂(H₂O)₂(dmapox)(ipa)₂]_n (1) and [Cu₂(H₂O)₂(dmapox)(tpa)₂]_n (2), where dmapox, ipa and tpa stand for the dianion of N,N′-bis[3-(dimethylamino)propyl]oxamide, isophthalic acid and terephthalic acid respectively, have been synthesized and characterized by elemental analysis, conductivity measurement, IR and electronic spectral studies. The crystal structures of the two complexes have been determined by X-ray single-crystal diffraction. The structures of 1 and 2 consist of one-dimensional copper(II) coordination polymeric chain constructed both by the bis-tridentate trans-dmapox and bis-monodentate phenyldicarboxylate bridging ligands. In the two complexes, the environment around the copper(II) atoms can be described as distorted square-pyramid and the Cu···Cu separations through μ-trans-dmapox and phenyldicarboxylato bridging ligands are 5.245(5) Å and 8.212(3) Å for 1, 5.237(8) Å and 11.171(1) Å for 2, respectively. The binding properties of the two copper(II) polymers with herring sperm DNA (HS-DNA) have been investigated by using absorption and emission spectral and electrochemical techniques and viscometry. The results show that the two copper(II) complexes interact with the HS-DNA in the mode of intercalation with the intrinsic binding constants of 1.22(±0.2) × 10⁴ M⁻¹ and 1.45(±0.3) × 10⁴ M⁻¹ for 1 and 2, respectively.