Syntheses and characterization of three lanthanide(III) complexes containing pyridine-3,5-dicarboxylic acid and oxalic acid ligands

Direct reaction of pyridine-3,5-dicarboxylic acid (H₂PDA) and oxalic acid (H₂ox) with Ln(ClO₄)₃ · nH₂O under hydrothermal conditions gave three 3-D coordination networks, [Ln(PDA)(ox)_0.5(H₂O)₂] · H₂O [Ln = La(1), Nd(2), and Eu(3)]. The complexes were characterized by elemental analysis (EA), X-ray single-crystal diffraction, infrared spectroscopy (IR), and thermogravimetric analysis (TGA). Single crystal X-ray diffractions shows that the compounds are isomorphous and have 3-D framework structures, in which pyridine-3,5-dicarboxylates (PDA^2?) link lanthanides to give 2-D layers, which are further fabricated into a 3-D network via bis-bidentate oxalate bridging. Luminescence of 3 is investigated.     

[1]Benzofuro[3,2-<Emphasis Type="Italic">c</Emphasis>]pyridine synthesis and coordination reactions

(E)-3-(1-Benzofuran-2-yl)propenoic acid (1) was prepared from 1-benzofuran-2-carbaldehyde under the Doebner’s conditions. The obtained acid was converted to the corresponding azide 2, which was cyclized by heating in diphenyl ether to [1]benzofuro[3,2-c]pyridine-1(2H)-one (3). This compound was aromatized with phosphorus oxychloride to chloroderivative 4 which was reduced with zinc and acetic acid to the title compound 5. [1]Benzofuro[3,2-c]pyridine-2-oxide (6) was synthesized by reaction of 5 with 3-chloroperoxybenzoic acid in dichloromethane. Treatment of 6 with benzoyl chloride and potassium cyanide (Reissert-Henze reaction) was shown to produce the corresponding [1]benzofuro[3,2-c]pyridine-1-carbonitrile (7). The title compound was used for preparation of complexes Cu₂(ac)₄(bfp)₂ (8) and CoCl₂(bfp)₂ (9), where ac=CH₃CO₂⁻ and bfp=[1]benzofuro[3,2-c]pyridine. Both oxygen atom of carboxylate ions is used in the coordination to Cu(II). Thermal properties of the complexes 8 and 9 have been studied by TG and DTA and both complexes exhibited high thermal stability while complex 9 are thermally more stable than complex 8.     

Syntheses and characterizations of four metal coordination polymers constructed by the pyridine-3,5-dicarboxylate ligand

A series of metal-organic frameworks, namely [Ni(PDB)(H₂O)]_n (1), [Pb(PDB)(H₂O)] · (H₂O) (2), [Co₂(PDB)₂(bpy)₂(H₂O)₄] · 4H₂O (3) and [Co₂(PDB)₂(phen)₂]_n (4) (H₂PDB = pyridine-3,5-dicarboxylic acid, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized based on pyridine-3,5-dicarboxylate acid and two neutral chelate ligands, with different metal ions such as Ni^II, Co^II and Pb^II, under hydrothermal conditions. The framework structures of these polymeric complexes have been determined by the X-ray single crystal diffraction technique. In the four complexes, the pyridine-3,5-dicarboxylate acid ligand exhibits diverse coordination modes, which play an important role in the construction of metal-organic frameworks. The thermal analyses of these four complexes have been measured and discussed. In addition, complex 2 shows strong phosphorescent emission at room temperature and the magnetic measurement of the polymer of 4 reveals a typical antiferromagnetic exchange.     

NMR and theoretical study on the coordination interactions between peroxovanadium(V) complex and bisubstituted pyridine ligands

To understand the substitution effects of pyridine ligands on coordination equilibrium, the coordination interactions between a series of bisubstituted pyridine ligands and peroxovanadium(V) [OV(O₂)₂(D₂O)]^?/[OV(O₂)₂(HOD)]^? in solution have been investigated by multinuclear (¹H, ¹³C, and ⁵¹V) magnetic resonance and HSQC. A series of new six-coordinate peroxovanadate complexes [OV(O₂)₂L] ^{n ?} (L?=?2, 3, 4, n?=?1 or 3) have been observed, and the coordination ability of the bisubstituted pyridines to peroxovanadium(V) is 3,4-dimethylpyridine (2)?>?3,5-dimethylpyridine (3)?>?pyridine-3,5-dicarboxylate (4)???2,3-dimethylpyridine (1). The coordination interactions among title system have been further studied by DFT (density functional theory) calculations, and the results indicate that solvent may play an important role in these coordination interactions.     

A disparate 3-D silver(I) coordination polymer of pyridine-3,5-dicarboxylate and pyrimidine with strong intermetallic interactions: X-ray crystallography,photoluminescence and antimicrobial activity

A polymeric silver(I) complex, [Ag₄(μ-pydc)₂(μ-pm)₂]_n (1) (pydc = pyridine-3,5-dicarboxylate and pm = pyrimidine), has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction. X-ray crystallographic data of 1 revealed that pydc exhibits two different coordinaton modes that play a key role in the construction of the 3-D crystal network including Ag–carboxylate clusters in which close Ag–Ag distances exist. The magnitudes of close Ag–Ag interactions in second-order energy (E²) have been revealed by natural bond orbital analysis performed with single point energy calculation using the experimental geometry of 1. Furthermore, the luminescent properties of 1 show strong fluorescence with two emission maxima in the visible region. Also, 1 has antifungal activity on Candida albicans (MIC value, 4 μg mL^?1) and good antibacterial activity on micro-organisms (MIC value, 64–256 μg mL^?1).     

Structure of tetra(3,5-dinitrobenzoate) bis(Piperidine) hexaaquanickel(II)—[Ni(OH2)6](PipH)2(3,5-DNB)4·2H2O dihydrate

It is found that M(AmH)₂(3,5-DNB)₄·8H₂O compounds (where M(II) = Co, Ni; AmH is piperidine PipH = (C₅H₁₀NH₂)⁺ or diethylamine DaH = (C₄H₁₀NH₂)⁺ cations; 3,5-DNB = (C₇H₃N₂O₆)⁻ is the dinitrobenzoic acid anion) are isotypic. The structure of the Ni(PipH)₂(3,5-DNB)₄·8H₂O single crystal is studied. The crystals have a monoclinic system, P2₁/n space group, Z = 2, a = 6.7694(3) ?, b = 16.0746(6) ?, c = 23.1250(9) ?, β = 97.794(1)°, V = 2493.1(2) ?³, T = 153 K. The final value R(F) = 0.0407 was obtained for 8191 independent reflections with I> 2σ(I). The structural units of the compound studied are as follows: [Ni(OH₂)₆]²⁺ complex hexaaquacation, two (PipH)⁺ cations, four (3,5-DNB)⁻ anions, and two molecules of water of crystallization with the structural formula [Ni(OH₂)₆](PipH)₂(3,5-DNB)₄·2H₂O. Similar compounds of Ni(II) and Co(II) are isostructural.     

Synthesis,Characterization and Molecular Structure of a new (?6-P-Cymene) Ruthenium(II) Amidine Complex, [(?6-P-Cymene)Ru{NH=C(Me)3,5-Dmpz}(3,5-Hdmpz)](BF4)2·H2O

A new arene ruthenium(II) complex [(η⁶-p-cymene)Ru(L)(3,5-Hdmpz)](BF₄)₂[sdot]H₂O (L = 1-methylcarbaldimino-3,5-dimethylpyrazole; 3,5-Hdmpz = 3,5-dimethylpyrazole) has been synthesized. The ligand L has been generated in situ through the condensation of 3,5-dimethylpyrazole and acetonitrile in the presence of [{(η⁶-p-cymene)RuCl₂}₂]. The complex [(η⁶-p-cymene)Ru{NH=C(Me)3,5-dmpz}(3,5-Hdmpz)](BF₄)₂[sdot]H₂O crystallizes in monoclinic space group P2₁/c, a = 10.943(2), b = 26.394(7), c = 11.502(1) Å, Β = 115.43(1)°, V = 3000.1(19) ų and Z = 4. The compound has been characterized by FTIR, ¹H NMR, 2D-COSY NMR spectroscopy and a single-crystal X-ray diffraction study.     

A 3-D pillar-layered coordination polymer {[EuCu(C2O4)(na)2] · 2H2O} n : synthesis,structure and photoluminescent properties

A 3d–4f heterometallic coordination polymer, {[EuCu(C₂O₄)(na)₂] ·?2H₂O} _n (1) [Hna=nicotinic acid], has been synthesized by hydrothermal reaction of lanthanide oxides, Cu(I), and pyridine-2,3-dicarboxylic acid. 1 features a 3-D pillar-layered coordination framework constructed from two-dimensional lanthanide-carboxylate layers and Cu(na) pillars. Interestingly, the na ligand was obtained by the in situ decarboxylation of pyridine-2,3-dicarboxylic acid.     

Coordination of reduced Schiff base anion to Pd(II): Synthesis,characterization, DFT calculation and catecholase activity

The article reports the synthesis and characterization of a new palladium(II) complex of type [(L_NNN¹⁻)PdCl] (1) where L_NNN¹⁻ is a mono anionic Schiff's base having a imine bond in reduced state. The L_NNN¹⁻ is generated from a tridentate NNN donor ligand (L_NNN) through in-situ reduction using sodium borohydride, where L_NNN is [(E)-N-(phenyl(pyridine-2-yl)methylene)quinoline-8-amine)]. 1 is characterized by the single crystal X-ray diffraction study, IR, mass and UV–Vis spectroscopy. The X-ray bond parameter authenticates the imine bond of the coordinated Schiff's base anion is in reduced state. 1 exhibits catalytic activity towards the oxidation of 3,5-ditertiarybutyl catechol(3,5-DTBC) with turnover number (K_cat) ​= ​135.6 h^-1. The catalytic oxidation of 3,5-DTBC is authenticated by the UV–Vis, mass and EPR spectroscopy. An isotropic EPR signal with g ​= ​2.011 of a solution containing 1 and 3,5-DTBC authenticating the generation of organic radical during the oxidation process. Cyclic voltammogram of 1 displays an irreversible anodic wave at +0.22 ​V may be due to the oxidation of N⁻ to N^•−. The atomic spin density of 1⁺ obtained from DFT calculation is also supporting the N-centre oxidation process.     

Tuning a Single Ligand System to Stabilize Multiple Spin States of Manganese: A First Example of a Hydrazone‐Based Manganese(III) Spin‐Crossover Complex

A series of bis‐chelate pseudo‐octahedral mononuclear coordination complexes of manganese with the chromophore [MnN₄O₂]ⁿ⁺ (n=0, 1) have been generated in all three principal oxidation states of this transition‐metal center under ambient conditions by utilizing a readily tunable, versatile phenolic pyridylhydrazone ligand system (i.e., H₂(3,5‐R¹,R²)‐L; L=ligand). Strategic combinations of the nature and position of a variety of substituent groups afforded selective, spontaneous stabilization of multiple spin states of the manganese center, which, upon close crystallographic scrutiny, appears to be in part due to the occurrence or absence of hydrogen‐bonding interactions that involve the phenolate/phenolic oxygen atom. The divalent complexes are isolable in two forms, namely, molecular [Mn^II{H(3,5‐R¹,R²)‐L}₂] and ionic [Mn^II{H₂(3,5‐R¹,R²)‐L}{H(3,5‐R¹,R²)‐L}]ClO₄, with the latter complex converting easily into the former complex on deprotonation. Accessibility of the higher‐valent states is achievable only when the phenolate oxygen atom is sterically hindered from participation in hydrogen bonding. The [Mn^III{H(3,5‐tBu₂)‐L}₂]ClO₄ complex is the first example of a hydrazone‐based Mn^III complex to exhibit spin crossover. Formation of the tetravalent complexes [Mn^IV{(3,5‐R¹,R²)‐L}₂] (R¹=tBu, R²=H; R¹=R²=tBu) necessitates base‐assisted abstraction of the hydrazinic proton.     

Stereoselectivity in Reactions of Metal Complexes. Part XV. Structure and stability of chiral cobalt(III) complexes with pentadentate ligands

The syntheses and characterization of four new linear pentadentate ligands and their Co^III complexes are described: N,N′-[(pyridine-2,6-diy)bis(methylene)]bis[sarcosine] (sarmp), N,N′-[(pyridine-2,6-diyl)bis(methylene)]bis[(R)- or (S)-proline] ((R,R)- or (S,S)-promp), N,N′-[(pyridine-2,6-diyl)bis(methylene)]bis[N-(methyl)-(R)- or (S)-alanine] ((R,R)- or (S,S)-malmp); 2,2′-[pyridine-2,6-diyl]bis[(S)- or rac-N-(acetic acid)pyrrolidine] ((S,S)- or rac-bapap). The complexes were characterized and, with but one exception, complex formation is stereospecific: Δ-exo-(R,R) (or Λ-exo-(S,S)) for promp and Λ-(R,R) (or Δ-(S,S)) for bapap. The exception is [Co((R,R)- or (S,S)-malmp)H₂O]ClO₄ for which two forms are obtained, to which Λ-endo-(R,R) (or Δ-endo-(S,S)) and, tentatively, Δ-unsymmetric-(R,R)- (or Λ-unsymmetric-(S,S)-) configurations are assigned. X-Ray crystal structures are presented for the complexes [Co(sarmp)H₂O]ClO₄, [Co((S,S)-promp)H₂O]ClO₄, [Co(rac-bapap)H₂O]ClO₄ and endo-[Co(rac-malmp)H₂O]ClO₄. Ligand acid dissociation and Co^II and Fe^II complex-formation constants are reported.     

Synthesis and carboxylate anion binding studies on cyclic sugar-amino acid hybrids

Abstract

Here in, the condensation of boc-glycine with 2,6-anhydro-3,4,5-tri-O-benzyl-D-gluco-heptitol followed by its boc-deprotection to form 2,6-anhydro-3,4,5-tri-O-benzyl-D-gluco-heptitolyl bis-glycinate, which in turn on condensation with succinic acid/pyridine-2,6-dicarboxylic acid led to the formation of sugar-amino acid hybrid macrocyclic compounds 4, 6 and debenzylated marocyclic compound 5, having amide bonds that function as efficient host for polar, hydrogen bond acceptors and carboxylate ions. The anion inclusion capability of synthesized macrocylic hosts has been evaluated by the study of their binding with boc-GlyCOOˉ anion as guest through 1H NMR titration studies in CDCl₃. The binding constant (K_a) of boc-GlyCOOˉ guest with macrocyclic hosts 4 and 6 involving succinate and pyridine-2,6-dicarboxylate linkers was found to be 9.201?×?10³ and 1.437?×?10⁴ M^?1, respectively. The higher binding constant was observed in the complex of boc-GlyCOOˉ with pyridine-dicarboxylate containing host may be due to the extra rigidity & suitable conformation attained by the presence of rigid-aromatic dicarboxylate linker.     

Synthesis,crystal structure,and magnetism of a dinuclear nickel(II) complex [Ni2(MOBPT)2(N3)4] · 2H2O

A dinuclear nickel(II) complex, [Ni₂(MOBPT)₂(N₃)₄] · 2H₂O (MOBPT = 4-(p-methoxyphenyl)-3,5-bis(pyridine-2-yl)-1,2,4-triazole), has been synthesized and characterized by elemental analysis, UV, IR, ESI-MS, and single crystal X-ray crystallography. The complex crystallizes in triclinic system, space group P 1 with a = 9.877(2) Å, b = 10.396(2) Å, c = 11.975(3) Å, α = 71.638(3)°, β = 74.968(3)°, γ = 64.747(3)°, V = 1044.2(4) ų, Z = 1, R = 0.0371 for 5774 observed reflections. The crystal structure determination shows that the dinuclear Ni₂N₈ unit is almost planar with each Ni²⁺ coordinated by four nitrogens from two MOBPT ligands and two axial azides in a distorted octahedral geometry. Magnetic measurements reveal weak antiferromagnetic exchange in the complex.     

The Photophysical Properties of Quaternary Lanthanide (Eu3+, Tb3+, Sm3+, Dy3+) Functional Molecular Complexes

Summary. In this paper, according to the molecular fragment principle, a series of twelve quaternary luminescent lanthanide complex molecular systems were assembled. Both elemental analysis and infrared spectroscopy allowed to determine the complexes formula: Ln(Nic)₃(L)·H₂O, where Ln=Sm, Eu, Tb, Dy; HNic=pyridine-3-carboxylic acid; L=N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), pyrrolidone (pyro). The photophysical properties of these functional molecular systems were studied by recording both ultraviolet-visible absorption, phosphorescence, fluorescence excitation, and emission spectra. It was found that the conjugated pyridine-3-carboxylic acid acts as the main energy donor and luminescence sensitizer due to the suitable energy match and effective energy transfer to the luminescent Ln ³⁺ ions. Amide molecules (DMF, DMA, pyro) were only used as assistant structural ligands to enhance the luminescence. Especially the europium complexes show the strongest luminescence due to the optimum energy transfer between the HNic triplet state energy level and Eu³⁺.     

Copper (II) complexes of sterically hindered o-diphenol derivatives: synthesis, characterization and microbiological studies

Cu (II) complexes with the sterically hindered diphenol derivatives 3,5-di(tert-butyl)-1,2-benzenediol (I), 4,6-di(tert-butyl)-1,2,3-benzenetriol (II) and the sulfur-containing 4,6-di(tert-butyl)-3-(2-hydroxyethylsulfanyl)-1,2-benzenediol (III) and 2-[4,6-di(tert-butyl)-2,3-dihydroxyphenylsulfanyl]acetic acid (IV) have been synthesized and characterized by elemental analysis, TG/DTA, FT-IR, ESR, XPS, XPD and conductivity measurements. Compounds I–III can coordinate in their singly deprotonated forms and act as bidentate ligands. These compounds yield Cu (II) complexes of the stoichiometry Cu(L)₂, which have square planar geometry (g_| > g_⊥ > g_e). Unlike them, compound IV behaves as a terdentate ligand, and its complex Cu(L^IV)₂ has distorted octahedral geometry. According to ESR data, only the Cu(L^II)₂ complex contains a very small amount of phenoxyl radicals. Antimicrobial activities of these ligands and their respective Cu (II) complexes have been determined with respect to Gram-positive and Gram-negative bacteria, as well as on yeasts. Their phytotoxic properties against Chlorella vulgaris 157 were also examined.     

1,6- and 1,7-naphthyridines. II. Synthesis from acyclic precursors

A number of 8-hydroxy-6-methyl-1,6-naphthyridin-5(6H)-one-7-carboxylic acid alkyl esters 3 and the isomeric 5-hydroxy-7-methyl-1,7-naphthyridin-8(7H)-one-6-carboxylic acid alkyl esters 4 were synthesized from acyclic precursors obtained starting from quinolinic anhydride 5. Thus, methanolysis of 5 afforded the hemiester 6 which treated with oxalyl chloride and sarcosine ethyl ester gave 3-(N-ethoxycarbonylmethyl-N-methylcarbamoyl)pyridine-2-carboxylic acid methyl ester 8. Compound 8 was cyclized to naphthyridines 3a-e with sodium alkoxides. The isomeric naphthyridines 4a-c were obtained by cyclization of the open intermediary 2-(N-ethoxycarbonylmethyl-N-methylcarbamoyl)pyridine-3-carboxylic acid methyl ester 9 obtained by a route that involves treatment of 5 with sarcosine ethyl ester and esterification with diazomethane. Spectroscopic properties (¹H nmr, uv, ir) of compounds 3 and 4 are discussed and confirmed the proposed structures.     

Biological activities of pyridine-2-carbaldehyde Schiff bases derived from S-methyl- and S-benzyldithiocarbazate and their zinc(II) and manganese(II) complexes. Crystal Structure of the Manganese(II) complex of pyridine-2-carbaldehyde S-benzyldithiocarbazate

Transition metal complexes [Zn(L¹)₂] (I) and [Mn(L²)₂] (II), where HL¹ = pyridine-2-carboxaldehyde S-methyldithiocarbazate, HL² = pyridine-2-carboxaldehyde S-benzyldithiocarbazate, have been synthesized. Complex II was characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction studies. The manganese(II) atom in complex II adopts a distorted octahedral geometry with the Schiff base coordinated to it as a uninegatively charged tridentate chelating agent via the pyridine and azomethine nitrogen atoms and the thiolate sulfur atom. Biological studies carried out in vitro against selected bacteria, fungi, and K562 leukemia cell line, respectively, have shown that the free ligands and their metal complexes exhibited distinctive differences in the biological properties. Ligand HL¹ and complex I have the marked and broad antimicrobial activities compared to HL² and complex II while only HL¹ and complex II show significant antitumor activity against K562 leukemia cell line, since they exhibit IC₅₀ values in the μM range.     

Metal-cinnamic acids interactions. Part IV. Synthesis,study and antimicrobial activity of copper(II) complexes of 3,4-dimethoxyhydrocinnamic acid

Summary Compounds [Cu(DPP)₂] (1), [Cu(DPP)₂H₂O]MeOH (2) (DPPH=3,4-dimethoxyhydrocinnamic acid), were synthesized and investigated by means of electronic, i.r. and room and low temperature e.s.r. spectroscopy. Compound (2) shows an e.s.r. spectrum characteristic of axially symmetric carboxylate dimers with S=1, whereas the anhydrous compound (1) shows e.s.r. features that can be interpreted if the triplet state, depending on the temperature, is able to migrate through the crystal lattice. The results for the copper(II) compounds obtained with DPPH are compared with those obtained with 3,4- and 3,5-DMCH (3,4-, and 3,5-DMCH=3,4- and 3,5-dimethoxycinnamic acid). The ligands and their complexes have been tested for antimicrobial activity.     

Synthesis, crystal structure and magnetic property of the novel dinuclear nickel(II) complex with 4-(p-methoxyphenyl)-3,5-bis(pyridine-2-yl)-1,2,4-triazole

A novel dinuclear nickel(II) complex, [Ni₂(MOBPT)₂Cl₂(H₂O)₂]Cl₂ · 7H₂O (MOBPT = 4-(p-methoxyphenyl) −3,5-bis(pyridine-2-yl)-1,2,4-triazole), has been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction methods. The crystal structure determination shows that the dinuclear Ni₂N₈ unit is almost planer in which each Ni^II ion is coordinated by four nitrogen atoms from MOBPT equatorially and a water molecule and a chloride ion axially in a distorted octahedral geometry. Magnetic measurements reveal a relatively weak antiferromagnetic exchange in the complex.     

In situ synthesis of mononuclear copper(II) complexes of the new tridentate ligand bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methyl]amine

Two mononuclear copper complexes, {bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl‐κN²)methyl]amine‐κN}(3,5‐dimethyl‐1H‐pyrazole‐κN²)(perchlorato‐κO)copper(II) perchlorate, [Cu(ClO₄)(C₅H₈N₂)(C₁₂H₁₉N₅)]ClO₄, (I), and {bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl‐κN²)methyl]amine‐κN}bis(3,5‐dimethyl‐1H‐pyrazole‐κN²)copper(II) bis(hexafluoridophosphate), [Cu(C₅H₈N₂)₂(C₁₂H₁₉N₅)](PF₆)₂, (II), have been synthesized by the reactions of different copper salts with the tripodal ligand tris[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methyl]amine (TDPA) in acetone–water solutions at room temperature. Single‐crystal X‐ray diffraction analysis revealed that they contain the new tridentate ligand bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methyl]amine (BDPA), which cannot be obtained by normal organic reactions and has thus been captured in the solid state by in situ synthesis. The coordination of the Cu^II ion is distorted square pyramidal in (I) and distorted trigonal bipyramidal in (II). The new in situ generated tridentate BDPA ligand can act as a meridional or facial ligand during the process of coordination. The crystal structures of these two compounds are stabilized by classical hydrogen bonding as well as intricate nonclassical hydrogen‐bond interactions.