Azpy Ligands Research Articles

A self-sensitized Co (II)-MOF for efficient visible-light-driven hydrogen evolution without additional cocatalysts

Herein, a new metal-organic framework (MOF) {[Co(azpy) (bps) (H2O)]·DMF·2.3H2O}n, 1, (azpy ​= ​4,4′-azopyridine, H2bps ​= ​4, 4′- bibenzoic acid-2, 2′-sulfone (H2bps) has been synthesized by solvothermal method. Complex 1 was characterized in detail by X-ray single-crystal diffraction, elemental analysis, IR spectrum, PXRD and thermogravimetric analysis. X-ray single-crystal diffraction analysis for 1 indicates that two azpy ligands bearing unusual cis-configuration bridge two Co2+ cations, forming an interesting one-dimensional nanopore channel. And these nanopore channels finally form a three-dimensional framework by multiple π···π stacking interactions. Besides, visible-light-driven H2 production exhibited that complex 1 displayed a high-efficiently photocatalytic hydrogen generation (1.44 ​mmol ​g−1·h−1) without additional photosensitizers and cocatalysts. Moreover, the photocurrent response of 1, solid-state UV–Vis absorption spectra of 1 and free ligands were also explored.

Theoretical Determination of Influence of the Metallic State of Oxidation toward Cytotoxic Activity: Case of Ruthenium Complexes

Ruthenium complexes present two states of oxidation that are Ru(II) and Ru(III). Both are assumed to present cytotoxic activity at ground state. On the purpose of highlighting their differences, DFT, TD-DFT and NBO have been performed at both Wb97xd/Lanl2dz and B3lyp/Lanl2dz levels. NBO program shows that both groups of ruthenium complexes present almost the same charge of Ru atom. Moreover, they display nearly the same structure of valence orbitals of the ruthenium. However, when it comes to compare their frontier orbitals HOMO and LUMO, we notice that the chloride atom has a great influence on their energy. The lack of Chloride atoms reduces the energy of frontier orbitals regardless of the functional. And the more the number of chloride atoms, the higher the energy. Also, RuCl3Terpy and α-RuCl2(Azpy)2 have been discovered to display the best energy suitable for reaction as cytotoxic agents. Yet, both are from groups different. Thus, at ground state, there is practically no difference between both groups. However, regarding TDDFT prediction with the determination of vertical electronic affinity VEA and vertical ionization potential VIP both at ground state S and at exciting T1 state, we notice that Ru(II) complexes are not active either in the presence or absence of 3O2 molecule. Here, only Ru(III) complexes are able to react on Guanine through their radical cations or by generating the superoxide radical anion . Therefore, the Ru(III) complexes are assumed to be active both at a fundamental state and under the effect of light for photodynamic therapy. We come to conclude that Ru(II) complexes are not active by excitation as their valence electrons are paired thereby making these complexes more stable. Besides, , a Ru(II) molecule that is not active at ground state owing certainly to its C3 symmetry or Azpy ligand presents all the same a difficult activity on generating . For the coming paper, we intend to check whether Ru(II) complex can be active under the effect of light if it is in a triplet charge state.

Auxiliary ligand-induced structural diversities of octacyanometalate-based heterobimetallic coordination polymers towards diverse magnetic properties.

Three octacyanometalate-based bimetallic coordination polymers (CPs), {[μ4-MV(CN)8][Co(DMF)4]2(ClO4)}n (M = W CP-1, Mo CP-2) and {[μ4-WIV(CN)8]Co2(azpy)4}n CP-3, were synthesized in the absence (for CPs 1 and 2) or presence (for CP-3) of auxiliary ligand 4,4'-azopyridine (azpy), respectively. CPs 1 and 2 exhibit the same three-dimensional (3D) polymeric cation frameworks with [ClO4]- as the counterions, while CP-3 displays a porous 3D framework in an unusual 2-nodal (4,6)-connected 4,6T155 topology with point symbol as {42·64}{46·64·7·84}2. Notably is that octacyanometalate [WV(CN)8]3- has been reduced into [WIV(CN)8]4- during the synthetic process of CP-3. The magnetic investigations indicate that CP-1 exhibits the typical ferromagnetic property due to the ferromagnetic coupling between W(v) and Co(ii) spin centers, while CP-3 displays the weak ferromagnetic interaction at low temperature, which is consistent with the valence change of W center in CP-3.

Theoretical calculation of influence of halogen at-oms (F, Cl, Br, I) on arylazopyridine (Azpy) ruthenium complexes behaving as photo sensitizers by DFT method

Photosensivity prediction of several azopyridine ruthenium complexes by DFT and TDDFT methods was performed. g-RuX2 (Azpy) 2 and d-RuX2(Azpy)2 where X stands for F, Cl, Br and I were studied todetermine their activities when halide atoms shift. So, frontier orbital, NBO, NLMO and MLCT transitions as well as an excited lifetime of those complexes was determined. The main difference between them stems from both the electronegativity of the halide atoms and the structure of each complex. Hence, the rank of halide's electronegativity that is as followscp(F)>cp (Cl)>cp (Br)>cp (I) has been discovered to influence all the reactivity of the complexes regardless their structure. Herein, the comparison with the gap energy shows that the most reactive complexes are those with fluorine atom. Especially, d-RuF2(Azpy)2 was admitted to be the most active isomer. Moreover, NBO calculation discloses that the complex becomes less ionic when the electronegativity decreases from F to I atoms. Furthermore, the calculation of NLMO orbitals shows that the bonding Ru-X are very strong. However, this strength decreases also from F to I and the nature of the bonding move from ionic to metallic. Moreover, the bonding from Npy and N2 with Ru are known to be the same confirming the bidentate state of Azpy ligand. Regarding the electronic prediction, the eight complexes are surely assumed to display MLCT transitions that originate the photosensitivity. However, the complex that requires the least energy remains d-RuF2(Azpy)2. This result was also determined by analyzing the excited lifetime that is the ability for a complex to longer linger in the cationic state. At last, we found out that with iodine atoms, the azopyridine ruthenium complex cannot behave as photosensitize dye insofar as I atom hides the main orbitals from Ru regardless the symmetry.

New pillared dioxomolybdenum(VI) complexes with ONS donor ligands and 4,4′-azopyridine spacer: 3D metal-organic supramolecular architectures and DFT calculations

Two new pillared binuclear dioxomolybdenum(VI) complexes [(MoO2L1)2(4,4′-azpy)] (1) and [(MoO2L2)2(4,4′-azpy)] (2) have been synthesized by the reaction of MoO2(acac)2 with Schiff base ligands (H2L1 and H2L2) derived from 2-hydroxyacetophenone and S-benzyl/S-methyl dithiocarbazates respectively and 4,4′-azopyridine as a spacer. Crystal and molecular structures of the investigated binuclear complexes 1 and 2 were determined by single crystal X-ray diffraction. The two complexes have similar centrosymmetric dimeric structures in which each molybdenum atom occupies distorted octahedral six-coordinate environments being bonded to a dianionic tridentate ONS donor ligand via phenolate oxygen, imine nitrogen and thioenolate structure as well as two terminal oxygen atoms and a nitrogen atom of the bridging 4,4′-azpy ligand. Complexes 1 and 2 give rise to 3D metal-organic supramolecular frameworks having rectangular cavities formed via hydrogen bonding and π-π stacking interactions. The complexes were further characterized by elemental analysis, spectroscopic methods (IR, 1H NMR and UV–vis), electrochemical study and thermogravimetric analysis. DFT calculations were used to study the electronic properties of the complexes.

SARs Investigation of <i>α</i>-, <i>β</i>-, <i>γ</i>-, <i>δ</i>-, <i>ε</i>-RuCl<sub>2</sub>(Azpy)<sub>2</sub> Complexes as Antitumor Drugs

Structure Activity-Relationships (SARs) of the five possible isomers of RuCl2(Azpy)2 were predicted thanks to DFT method. Azpy stands for 2-phenylazopyridine and the structure of the isomers α-RuCl2(Azpy)2, β-RuCl2(Azpy)2, γ-RuCl2(Azpy)2, δ-RuCl2(Azpy)2 and ε-RuCl2(Azpy)2 call respectively α-Cl, β-Cl, γ-Cl, δ-Cl and ε-Cl are defined according to chlorine atoms orientations. Hence, they are divided into two groups. In the first group comprising α-Cl, β-Cl and ε-Cl, both chlorine atoms are in cis position and Azpy ligands are intervertical. Whereas the two others isomers (γ-Cl and δ-Cl), they form the second group. Here, both chlorine are in trans position and Azpy are planar. The five synthesized isomers were investigated as potential antitumor agents. Then, regarding the DNA, its bases are stacked by pair. Therefore, complexes are assumed to insert and to stack on them through intercalative mode. So the electronic and geometric structures become more important to describe their SARs. Consequently, group 2 regarding γ-Cl and δ-Cl presents the best structure to allow intercalation between DNA base-pairs. Besides, the energy order of the lower unoccupied molecular orbital (LUMO) of the isomers is ELUMO(β-Cl) > ELUMO(α-Cl) > ELUMO(ε-Cl) > ELUMO(γ-Cl) > ELUMO(δ-Cl). The energy gap between LUMO and HOMO was also sorted as Δ(L-H)(β-Cl) > Δ(L-H)(α-Cl) > Δ(L-H)(ε-Cl) > Δ(L-H)(γ-Cl) > Δ(L-H)(δ-Cl). In addition, the total dipole moment was classified as μ(ε-Cl) > μ(β-Cl) > μ(α-Cl) > μ(γ-Cl) > μ(δ-Cl). Finally, net charge of the ligand Azpy was also classified as QL(δ-Cl) > QL(γ-Cl) > QL(ε-Cl) > QL(α-Cl) > QL(β-Cl). All those parameters show that δ-Cl isomer displays the highest activity as antitumor drug when intercalating between the DNA basepairs Cytosine-Guanine/Cytosine-Guanine (CG/CG).

Metal-directed assembly of two one-dimensional coordination polymers: Structural, theoretical, fluorescent and non-linear optical studies

The reaction of Zn(II)/Cd(II) salts with azo-containing bipyridyl ligands afforded two coordination polymers (CPs), [Zn(μ2-4,4′-azpy)(NO2)2]n (1) and [Cd2(μ2-4,4′-azpy)3(NO2)4]n (2) (4,4′-azpy=4,4′-azopyridine). The identities of the CPs 1 and 2 have been unambiguously established by single-crystal X-ray diffraction, and further characterized by elemental analysis, powder X-ray diffraction, thermogravimetric analyses, electrospray ionization-mass spectrometry (ESI-MS), fluorescence analysis, Fourier-transform infrared and ultraviolet/visible spectroscopies. CP 1 exhibits one-dimensional (1-D) zigzag chains containing an octahedral [ZnO4N2] unit bridged by N-donor ligands in the crystal lattice. CP 2 presents a 1-D ladder chain constructed by T-shape units of [Cd(NO2)2(μ2-4,4′-azpy)3] and further forms a 1-D→three-dimensional (3-D) interpenetrated structure. In addition, density functional theory and time-dependent density functional theory calculations at the B3LYP/LanL2DZf+6-31G∗ level were performed on 4,4′-azpy and CP 1 to rationalize their experimental absorption spectra. The fluorescent properties of the free 4,4′-azpy ligand, 1 and 2 have been studied at room temperature. The results reveal that CPs 1 and 2 exhibit enhanced fluorescent emissions at about 410 and 427nm compared with the 4,4′-azpy ligand, respectively. Third-order non-linear optical (NLO) properties of 1 and 2 were also investigated.

A twofold interwoven two-dimensional→two-dimensional (2-D→2-D) cluster–organic network based on the [Cu2I2] cluster and the 4,4′-(diazenediyl)dipyridine ligand: poly[[μ2-4,4′-(diazenediyl)dipyridine]-μ2-iodido-copper(I)

In the polymeric title compound, [CuI(C(10)H(8)N(4))](n), the Cu(I) atom is in a four-coordinated tetrahedral geometry, formed by two I atoms and two pyridine N atoms from two different 4,4'-(diazenediyl)dipyridine (4,4'-azpy) ligands. Two μ(2)-I atoms link two Cu(I) atoms to form a planar rhomboid [Cu(2)I(2)] cluster located on an inversion centre, where the distance between two Cu(I) atoms is 2.7781 (15) Å and the Cu-I bond lengths are 2.6290 (13) and 2.7495 (15) Å. The bridging 4,4'-azpy ligands connect the [Cu(2)I(2)] clusters into a two-dimensional (2-D) double-layered grid-like network [parallel to the (10-2) plane], with a (4,4)-connected topology. Two 2-D grid-like networks interweave each other by long 4,4'-azpy bridging ligands to form a dense 2-D double-layered network. To the best of our knowledge, this interwoven 2-D→2-D network is observed for the first time in [Cu(2)I(2)]-organic compounds.

Coordination Polymers Containing Manganese(II)-Azido Layers Connected by Dipyridyl-tetrazine and 4,4′-Azobis(pyridine) Linkers

Two new polynuclear manganese(II) complexes [Mn(dptz)(N(3))(2)](n) (1) and [Mn(azpy)(N(3))(2)](n) (2) (where dptz = dipyridyl-tetrazine and azpy = 4,4'-azobis(pyridine)) have been synthesized by self-assembly of the ligand azide, together with dptz and azpy as secondary spacers. The compounds are characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. The structural analyses reveal that in complex 1, which is the first reported Mn(II) complex with the ligand dptz, two μ(1,3) bridging azides connect neighboring manganese ions in a zigzag manner to generate a neutral two-dimensional (2D) sheet which is further connected by the dptz ligands to form a three-dimensional (3D) framework. By contrast, complex 2 contains dimeric [Mn(2)(μ(1,1)-N(3))(2)](2+) fragments linked to four identical motifs by means of four single μ(1,3)-N(3) bridges, that generates a neutral 2D Mn(II)-azide sheet which is further interconnected by azpy ligands to neighboring manganese ions forming an unprecedented 3D network. Variable-temperature (2-300 K) magnetic susceptibility measurements show the presence of predominantly antiferromagnetic coupling for both complexes that has been reproduced with a regular antiferromagnetic S = 5/2 chain (J) with interchain interactions (j) modeled with the molecular field approximation with J = -7.1 cm(-1) and j' = -0.8 cm(-1) for 1 and J = -4.2 cm(-1) and j' = 0.1 cm(-1) for 2.

Synthesis and characterization of four novel manganese(II) chains formed by 4,4′-azobis(pyridine) and benzoate or nitrobenzoates: Stabilization of unusual ladder structures

Four new manganese(II) coordination polymers: [Mn(4,4′-azpy)(C6H5COO)2](4,4′-azpy)0.5 (1), [Mn(4,4′-azpy)(p-(NO2)C6H4COO)2] (2), [Mn(4,4′-azpy)(m-(NO2)C6H4COO)2] (3) and [Mn(4,4′-azpy)(o-(NO2)C6H4COO)2(H2O)2] (4), where 4,4′-azpy=4,4′-azobis(pyridine), have been synthesized by self-assembly of MnX2 (X=benzoate, p-, m-, or o-nitrobenzoates) together with 4,4′-azpy. All four complexes were characterized by elemental analyses, IR spectroscopy, thermal analyses, single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. The structural analyses reveal that complexes 1, 2 and 3 feature a 1D molecular ladder formed by syn–syn (complex 1) or syn–anti (complexes 2 and 3) carboxylate-bridged dimeric Mn(II) units which are joined together by 4,4′-azpy ligands. In complex 1, these ladders assemble with the help of π–π and C–H⋯π interactions to form a nanoporous framework that incorporates non coordinated 4,4′-azpy molecules by exploiting host–guest C–H⋯π and hydrogen bonding interactions. Complex 2 presents a 3D supramolecular framework by π–π and CH⋯π interactions, whereas, complex 3 having a similar ladder structure to 1 and 2, forms a 2D grid through π–π interactions. On the other hand, complex 4 is a 4,4′-azpy bridged fish-bone chain of carboxylate-coordinated mononuclear manganese(II) units, which are linked together by strong hydrogen bonds to form a 2D structure. Variable-temperature (2–300K) magnetic susceptibility measurements show the presence of weak antiferromagnetic interactions within the discrete Mn–(OCO)2–Mn dimers for complexes 1, 2 and 3 that have been fitted with a S=5/2 dimer model (J=−0.8, −0.5 and −0.4cm−1 respectively). The magnetic data of complex 4 can be reproduced with a S=5/2 monomer model including a Zero Field Splitting (|D|=1.7cm−1).

Pillaring Role of 4,4′-Azobis(pyridine) in Substituted Malonate-Containing Manganese(II) Complexes: Syntheses, Crystal Structures, and Magnetic Properties

Six new manganese(II) complexes of formulas [Mn2(Rmal)2(H2O)2(azpy)]n (1–3), [Mn(Phmal)(H2O)(azpy)]n (4), [Mn2(Et2mal)2(H2O)4(azpy)2]n (5), and [Mn(Bzmal)(H2O)3(azpy)] (6) [azpy = 4,4′-azobispyridine (1–6), Rmal = methylmalonate (Memal) (1), dimethylmalonate (Me2mal) (2), and butylmalonate (Butmal) (3), Phmal = phenylmalonate (4), Et2mal = diethylmalonate (5), and Bzmal = benzylmalonate (6)] were synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1–3 are three-dimensional compounds whose structure consists of corrugated layers of manganese(II) linked through syn–anti carboxylate (Rmal) bridges, which are pillared through the bis-monodentate azpy molecule. Complex 4 has a layered structure of manganese(II) ions connected by carboxylate (Phmal) bridges in the syn–anti coordination mode as in 1–3, the azpy group acting here as a terminally bound monodentate ligand. The structure of 5 consists of Et2mal–Mn(II) neutral chains linked through the azpy ligand, giving rise to a complex three-dimensional network. Complex 6 is constituted by neutral [Mn(Bzmal)(H2O)3(azpy)] mononuclear units, which are interlinked through O–H···O, O–H···N, and π–π type intermolecular interactions to afford a three-dimensional supramolecular structure. The topological analysis of these crystallographic structures shows the occurrence of four different nets: a (3,4)-connected InS-type (1–3), a binodal layered hcb (4), a uninodal CdS-type (5), and a (4,5)-connected tcs topology (6). The magnetic properties of 1–5 were investigated in the 2.0–300 K temperature range. Overall antiferromagnetic behavior occurs in 1–4 with susceptibility maxima in the range 2.8–5.5 K, the exchange pathway being provided by the syn–anti carboxylate (substituted malonate) bridge [manganese–manganese separation in the range 5.4365(3)–5.5274(1) Å]. Very weak antiferromagnetic interactions are observed in 5 through the trans-bis-monodentate Et2mal ligand, the intrachain manganese–manganese separation being 7.328(3) Å. The much larger manganese–manganese separation through the bis-monodentate azpy ligand in 1–5 (values greater than 13.5 Å) accounts for the lack of any significant magnetic interaction though this extended bridge.

Synthesis, structural analysis, and thermal and spectroscopic studies of methylmalonate-containing zinc(II) complexes

Abstract The synthesis, crystal structure, thermal analysis and spectroscopic studies of five zinc(II) complexes of formulae [Zn(Memal)(H2O)]n (1) and [Zn2(L)(Memal)2(H2O)2]n (2-5) [H2Memal = methylmalonic acid, and L = 4,4′-bipyridine (4,4′-bpy) (2), 1,2-bis(4-pyridyl)ethylene (bpe) (3), 1,2-bis(4-pyridyl)ethane (bpa) (4) and 4,4′-azobispyridine (azpy) (5)] are presented here. The crystal structure of 1 is a three-dimensional arrangement of zinc(II) cations interconnected by methylmalonate groups adopting the μ3-κ2O:κO’:κO”:κO”’ coordination mode to afford a rare (10,3)-d utp-network. The structures of the compounds 2-5 are also three-dimensional and they consist of corrugated square layers of methylmalonate-bridged zinc(II) ions which are pillared by bis-monodentate 4,4′-bpy (2), bpe (3), bpa (4) and azpy (5) ligands. The Memal ligand in 2-5 adopts the μ3-κO:κO′:κO′′:κO′′′ coordination mode. Each zinc(II) ion in 1-5 is six-coordinated with five (1)/four (2-5) methylmalonate-oxygen atoms, a water molecule (1-5) and a nitrogen atom from a L ligand (2-5) building distorted octahedral environments. The rod-like L co-ligands in 2-5 appear as useful tools to control the interlayer metal-metal separation, which covers the range 8.4311(5) A (2) – 9.644(3) A (5). The influence of the co-ligand on the fluorescence properties of this series of compounds has been analyzed and discussed by steady-state and time resolved spectroscopy on all five compounds in the solid state.

Two Zn(II) and Co(II) compounds with dicarboxylates and curved 4,4′-azopyridine ligands: Syntheses, crystal structures and gas sorption properties

Two new compounds Zn(PDA)(AZPY)·4H2O (1) and [Co(NDC)(AZPY)]2·2H2O·DMF (2) (H2PDA=pyridine-2,6-dicarboxylic acid, AZPY=4,4′-azopyridine, H2NDC=2,6-naphthalenedicarboxylic acid) were prepared through solvothermal reactions and characterized. Single crystal X-ray diffraction analysis indicates that compound 1 exhibits a one-dimensional chain structure, while compound 2 features a three-dimensional framework. Notably the bridged AZPY ligands involved in both compounds exhibit rare bent configurations. The thermal stability and gas sorption properties of compound 2 have also been studied. A normal amount (2.8mmolg−1) of hydrogen uptake at 1atm and −196°C for compound 2 were observed, which can be attributed to the presence of micropores.

Layer-pillared zinc(II) metal–organic framework built from 4,4′-azo(bis)pyridine and 1,4-BDC

Novel layer-pillared metal–organic framework {[Zn 2(OH)(AZPY)(BDC) 1.5]·H 2O} n (AZPY = 4,4′-azo(bis)pyridine; BDC = 1,4-benzenedicarboxylate) was prepared and characterized. The compound is formed by binuclear secondary building units of the composition [Zn 2(OH)(BDC) 0.5] 2+, that are interconnected by AZPY and other BDC ligand giving neural (4,4)-grid-like polymeric sheets. Two adjacent sheets are pillared by 1,4-BDC 2− anions forming bilayers, that are further interpenetrated. Wide-angle X-ray scattering experiments demonstrated that the framework structure of the coordination polymer is stable upon the removal of the water molecule by heating and the compound remains crystalline. The packing of the crystal is characteristic by the presence of voids and small structure channels that are propagated along [0 1 1] crystallographic direction. The adsorption studies reveal that prepared compound can adsorb nitrogen and carbon dioxide. The adsorption capacity for CO 2 at 273 K, determined as amount of carbon dioxide adsorbed at p/ p 0 = 0.9, was 1.04 mmol/g.

Thermal and Light-Induced Spin Crossover Phenomena in New 3D Hofmann-Like Microporous Metalorganic Frameworks Produced As Bulk Materials and Nanopatterned Thin Films

Three novel three-dimensional coordination polymers, {FeII(azpy)[(MII(CN)4)]}·nH2O (azpy = 4,4′-azopyridine; M = Ni, Pd, and Pt), have been synthesized as polycrystalline bulk materials and as continuous as well as nanopatterned thin films on gold substrates. Single crystals of the Pt derivative have also been isolated and the corresponding X-ray diffraction analysis at 140 K indicates that it crystallizes in the tetragonal P4/mmm space group with a = b = 7.1670(5) Å, c = 13.0330(13) Å, V = 669.40(9) Å3 and Z = 1. Four square-planar [Pt(CN)4]2− anions occupy the equatorial positions of [FeIIN6] octahedron and four Fe(II) atoms are coordinated to each [Pt(CN)4]2− anion, thereby defining an infinite set of 2D planar layers pillared by the azpy ligands which bridge through the axial positions consecutive Fe(II) atoms. Magnetic susceptibility, calorimetric, and Mössbauer measurements reveal the occurrence of a thermal spin crossover phenomenon in the powder samples, which depends strongly on the water-content of the lattice in the case of Pd and Pt derivatives. The spin crossover is less cooperative with Tc = 245 K in the case of Ni, but the Pd (Pt) analogues display almost complete spin transitions with a hysteresis loop centered around 292 (280) and 191 (183) K, in the hydrated and dehydrated forms, respectively. Thin films of the three compounds were grown via a sequential assembly method using coordination reactions. Raman spectroscopic study proves that thermal spin crossover, similar to the bulk forms, occurs in the films. With the exception of the bulk Ni complex, a virtually complete light-induced spin conversion (LIESST effect) is detected by Raman spectroscopy in the thin films as well as in the powders below ca. 130 K.

The synthesis, chemical and biological properties of dichlorido(azpy)gold(III) chloride (azpy = 2-(phenylazo)pyridine) and the gold-induced conversion of the azpy ligand to the chloride of the novel tricyclic pyrido[2,1-c][1,2,4]benzotriazin-11-ium cation

A new Au(III) coordination compound with the ligand 2-(phenylazo)pyridine has been synthesized and fully characterized by means of elemental analysis, IR, UV–visible, conductivity measurements, NMR, electrospray ionization (ESI-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The chemical stability of the cation in this compound, [Au(azpy)Cl2]+ (abbreviated: Au-azpy), was analyzed by means of several physicochemical methods. While stable in the solid state, stability studies performed with the gold compound in solution showed an unexpected and unprecedented reactivity. A cationic organic derivative of 2-(phenylazo)pyridine, (abbreviated: pyrium), was produced from the solution and has been isolated as its chloride salt and characterized by crystal structure determination, elemental analysis, NMR, ESI-MS and conductivity studies in solution. This cyclization reaction is reported for the first time in the case of gold coordination compounds.The Au adduct and the pyrium cation were investigated as potential cytotoxic and anticancer agents, and both show moderate to high cytotoxic properties in cisplatin-sensitive and cisplatin-resistant ovarian carcinoma cell lines, A2780; and cisplatin-sensitive and cisplatin-resistant murine lymphocytic leukemia cell lines, L1210. Significant anticancer activity against the cisplatin resistant cell lines was found for the pyrium salt, ruling out the occurrence of cross resistance phenomena.

Crystal Structure of the [Ru(azpy)2(bpy)](PF6)2 Complex (azpy = 2-(phenylazo)pyridine, bpy = 2,2'-bipyridine)

The complex [Ru(azpy)2(bpy)](PF6)2 (azpy=2-(phenylazo)pyridine, bpy=2,2′-bipyridine) was synthesized and characterized by X-ray diffraction analysis. The coordination geometry around ruthenium(II) was distorted octahedral with coordinating from two N-donor centers of bpy and four N-donor centers of two azpy units. The Ru-N (pyridine of azpy) distance was (average, 2.048(4)A), shorter than the Ru-N (bpy) distance (average, 2.088(4)A). The average N = N distance in the title compound was 1.278(5)A, slightly longer than that of the free azpy ligand, 1.248(4)A. These results confirm that azpy is a stronger π-acceptor than bpy.

Synthesis and Crystallographic Characterization of Low-Dimensional and Porous Coordination Compounds Capable of Supramolecular Aromatic Interaction Using the 4,4‘-Azobis(pyridine) Ligand

Coordination compounds with a 4,4'-azobis(pyridine) (azpy) ligand, {[M2(azpy)6(H2O)5] x 4PF6 x azpy x H2O}n (M = Ni(II) (1) or Co(II) (2)) (0-dimensional (0-D) dimer), {[Zn(azpy)3(H2O)2] x 2PF6 x 2azpy x 4H2O}n (3) (1-dimensional (1-D) fishbone-type chain), {[Ag(azpy)] x PF6}n (4) (1-D linear chain), {[Mn(NCS)2(azpy)2] x azpy}n (5) (2-dimensional (2-D) grid sheet), and {[Ni(NCS)2(azpy)2] x 3toluene}n (6) (2-D grid sheet), were synthesized and structurally characterized. Compounds 1 and 2 have a 0-D dimer motif, in which one M(II) (M(II) = Ni(II) or Co(II)) coordination site is shared by unidentate azpy and H2O ligands, each with half-occupancy, i.e., exhibiting static disorder. Compounds 3 and 4 afford 1-D fishbone-type and 1-D linear chain motifs, respectively. Azpy mediates pi-pi and pi-p interactions between these low-dimensional structures. Compounds 5 and 6 possess a 2-D grid sheet motif. These sheets assemble to form microporous frameworks that incorporate aromatic guests, such as coordination-free azpy (5) and toluene (6). There exist not only pi-pi and pi-p interactions but also CH-pi interactions between the framework azpy ligands and guests. It should be noted that the azpy ligand is a good candidate for the construction of new assembling systems of coordination compounds through its aromatic interactions.

Iron(II) Molecular Framework Materials with 4,4'-Azopyridine

Three new iron(ii) molecular-framework materials incorporating the bridging ligand 4,4′-azopyridine (azpy) have been synthesized and structurally characterized: Fe2(azpy)4(NCS)4·(azpy) (A), Fe(azpy)(NCSe)2(EtOH)2·(azpy) (B), and Fe(azpy)2(NCSe)2·2(MeCN) (C). A and C consist of non-interpenetrating (4,4) grids of iron(ii) centres bridged by azpy ligands with non-coordinating azpy ligands or acetonitrile molecules occupying the spaces within and between the layers. For B, hydrogen-bonding interactions between coordinated ethanol molecules and non-coordinated azpy ligands link linear Fe–azpy chains to give a two-dimensional framework.

Dichlorobis(2-phenylazopyridine)ruthenium(II) complexes: characterisation, spectroscopic and structural properties of four isomers.

The didentate ligand 2-phenylazopyridine (azpy) can--in theory--give rise to five different isomeric complexes of the type [Ru(azpy)2Cl2], of which three have been known since 1980. The molecular structures of the cis-dichlorobis(2-phenylazopyridine) ruthenium(II) complexes alpha-[Ru(azpy)2Cl2] and beta-[Ru(azpy)2Cl2](in which the coordinating pyridine nitrogen atoms are in mutually trans and cis positions, respectively, whilst the azo nitrogen atoms are in mutually cis positions) were unambiguously determined in the early 1980s. The third isomer, gamma-[Ru(azpy)2Cl2], has for two decades, erroneously, been assumed to be the all-trans isomer. In a recent communication we have proven that for this gamma isomer the chloride ions are indeed in a trans geometry, but the pyridine nitrogen and azo nitrogen atoms of the two azpy ligands are in mutually cis geometries. In this paper the isolation of a fourth isomer is presented, the hitherto unknown delta-[Ru(azpy)2Cl2]. The isomeric structure of delta-[Ru(azpy)2Cl2] has been determined by 1H-NMR spectroscopy and single-crystal X-ray diffraction analysis, and is the all-trans isomer. The bis(azpy)-ruthenium(II) isomers are of interest because of the pronounced cytotoxicity they exhibit against tumour cell lines and could be very useful in the search for structure-activity relationships of antitumour-active ruthenium complexes, as among the isomers there is a significant difference in activity. It is of paramount importance to have a good understanding of the structural and spectroscopic properties of these complexes, which in this paper are compared and discussed, with a particular emphasis on 1D and 2D 1H NMR spectroscopies.