Pyridyl Moiety Research Articles

New metal organic frameworks incorporating the ditopic macrocyclic ligand dipyridyldibenzotetraaza[14]annulene

The synthesis and crystal structures of three new metal organic frameworks of type [Zn(L-2H)] n (1), {[ZnLCl2](CH3CN)0.5(DMF)0.5(H2O)0.5} n (2) and {[CdL(DMF)(NO3)2]·DMF} n (3), all based on the dipyridyl-derivatised macrocycle, dipyridyldibenzotetraaza[14]annulene (L), are reported along with the X-ray structure of the protonated metal-free ligand as its perchlorate salt, [(HL)(ClO4)] n (4). In [Zn(L-2H)] n , the zinc ion occupies the macrocyclic cavity, being bound to the N4-donor set of the macrocyclic ring in its doubly deprotonated form. Each zinc atom is also axially bound by a pyridyl moiety from an adjacent complex, resulting in formation of an infinite one-dimensional chain of the ‘herringbone’ type in which pairs of macrocyclic complexes interact via face-to-face π–π stacking interactions. In contrast, the zinc ion in {[ZnLCl2](CH3CN)0.5(DMF)0.5(H2O)0.5} n does not occupy the macrocyclic cavity but is bound to a pyridyl nitrogen from two ligands such that it acts as a bridge between macrocyclic units and results in the generation of a one-dimensional chain. Two chloro ligands also bind to each zinc centre to yield a distorted tetrahedral coordination geometry. Offset π–π stacking occurs between adjacent chains involving alternate macrocycles in each chain, giving rise to a zig-zag arrangement. Pairs of interacting chains pass through the above-mentioned chains to generate further π–π stacking to yield an overall three-dimensional structure that contains large ellipsoidal-shaped channels. In {[CdL(DMF)(NO3)2]·DMF} n the cadmium ion again does not occupy the macrocyclic cavity but acts as a bridge between macrocycles to once again afford a linear chain structure. Each cadmium is bound to two pyridyl groups (arising from different molecules of L), two nitrato ligands and one oxygen-bound dimethylformamide molecule to yield a distorted pentagonal bipyramidal coordination geometry. The protonated ligand, [(HL)(ClO4)] n , adopts a linear chain structure in which one pyridyl group is protonated and interacts intermolecularly via a hydrogen bond with the non-protonated pyridyl group of an adjacent macrocyclic unit to yield a hydrogen-bonded linear chain structure.

The Effects of Grafting of 2-Pyridyl to [Ru(bpy)2(Hpip)]2+ on Acid-Base and DNA-Binding Properties: Experimental and DFT Studies

A new Ru(II) complex of [Ru(bpy)2(Hppip)]2+ {bpy = 2,2′-bipyridine; Hppip = 2-(4-(pyridin- 2-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} has been synthesized by grafting of 2-pyridyl to parent complex [Ru(bpy)2(Hpip)]2+ {Hppip = 2-(4-phenyl)-1H-imidazo[4,5-f] [1,10]phenanthroline}. The acid-base properties of [Ru(bpy)2(Hppip)]2+ studied by UV-visible and luminescence spectrophotometric pH titrations, revealed off-on-off luminescence switching of [Ru(bpy)2(Hppip)]2+ that was driven by the protonation/deprotonation of the imidazolyl and the pyridyl moieties. The complex was demonstrated to be a DNA intercalator with an intrinsic DNA binding constant of (5.56 ± 0.2) × 105 M−1 in buffered 50 mM NaCl, as evidenced by UV-visible and luminescence titrations, reverse salt effect, DNA competitive binding with ethidium bromide, steady-state emission quenching by [Fe(CN)6]4-, DNA melting experiments and viscosity measurements. The density functional theory method was also used to calculate geometric/electronic structures of the complex in an effort to understand the DNA binding properties. All the studies indicated that the introduction of 2-pyridyl onto Hpip ligand is more favorable for extension of conjugate plane of the main ligand than that of phenyl, and for greatly enhanced ct-DNA binding affinity accordingly.

Control of Singlet Oxygen Generation Photosensitized by meso‐Anthrylporphyrin through Interaction with DNA

To control the activity of photosensitized singlet oxygen ((1)O(2)) generation, the electron donor-connecting porphyrin, 5-(9'-anthryl)-10,15,20-tris(p-pyridyl)porphyrin (AnTPyP), was designed and synthesized. AnTPyP became water-soluble by the protonation of the pyridyl moieties in the presence of 5 mM trifluoroacetic acid (pH 2.3). The photoexcited state of the porphyrin ring in an AnTPyP molecule was effectively deactivated by intramolecular electron transfer from the anthracene moiety within 0.04 ns in an aqueous solution. The deactivation was suppressed by the interaction with a DNA strand, resulting in the elongation of the lifetime of the porphyrin excited state and the enhancement of the fluorescence intensity. Furthermore, it was confirmed that the interaction enabled the photoexcited AnTPyP to generate (1)O(2). Selective (1)O(2) generation by forming a complex with DNA should be the initial step to realize the target selective photodynamic therapy.

Lanthanide-Based Coordination Polymers Assembled from Derivatives of 3,5-Dihydroxy Benzoates: Syntheses, Crystal Structures, and Photophysical Properties

Two new aromatic carboxylic acids, namely, 3,5-bis(benzyloxy)benzoic acid (HL1) and 3,5-bis(pyridine-2-ylmethoxy)benzoic acid (HL2), have been prepared by replacing the hydroxyl hydrogens of 3,5-dihydroxy benzoic acid with benzyl and pyridyl moieties, respectively. The anions derived from HL1 and HL2 have been used for the support of a series of lanthanide coordination compounds [Eu(3+) = 1-2; Tb(3+) = 3-4; Gd(3+) = 5-6]. The new lanthanide complexes have been characterized on the basis of a variety of spectroscopic techniques in conjunction with an assessment of their photophysical properties. Lanthanide complexes 2, 4, and 6, which were synthesized from 3,5-bis(pyridine-2-ylmethoxy)benzoic acid, were structurally authenticated by single-crystal X-ray diffraction. All three complexes were found to exist as infinite one-dimensional (1-D) coordination polymers with the general formula {[Ln(L2)(3)(H(2)O)(2)]·xH(2)O}(n). Scrutiny of the packing diagrams for 2, 4, and 6 revealed the existence of interesting two-dimensional molecular arrays held together by intermolecular hydrogen-bonding interactions. Furthermore, the coordinated benzoate ligands serve as efficient light harvesting chromophores. In the cases of 1-4, the lowest energy maxima fall in the range 280-340 nm [molar absorption coefficient (ε) = (0.39-1.01) × 10(4) M(-1) cm(-1)]. Moreover, the Tb(3+) complexes 3 and 4 exhibit bright green luminescence efficiencies in the solid state (Φ(overall) = 60% for 3; 27% for 4) and possess longer excited state lifetimes than the other complexes (τ = 1.16 ms for 3; 1.38 ms for 4). In contrast to the foregoing, the Eu(3+) complexes 1 and 2 feature poor luminescence efficiencies.

Ion-Selective Electrodes Based on a Pyridyl-Containing Triazolophane: Altering Halide Selectivity by Combining Dipole-Promoted Cooperativity with Hydrogen Bonding

Triazolophanes are ionophores, with preorganized cyclic cavities that have tunable selectivities for halides. The interaction with halides is based on hydrogen bonding between the eight CH hydrogen atoms of the cavity and the halide anion. The rigidity of the cavity in tetraphenylene triazolophane along with the hydrogen bonding favors planar 1:1 complexation of "snugly" encapsulated chloride and bromide. Manipulating the triazolophane's structure by introducing two pyridyl moieties into the cavity alters the receptor's binding mode. This change adds a dipole-promoted driving force that combines with hydrogen bonding to favor the formation of 2:1 sandwich complexes around halides. The potentiometric response of electrodes based on this new ionophore was evaluated for optimal halide selectivity. The new triazolophane-based electrode showed an anti-Hofmeister selectivity toward iodide with a submicromolar detection limit. The stoichiometry of complexation and the stability constants with different halides were evaluated using a segmented sandwich membranes method. The pyridyl-triazolophane demonstrated a response consistent with a 2:1 sandwich-type complex with iodide, in polyvinyl chloride (PVC) membranes.

Binding of Polyatomic Anions with Protonated Ureido-pyridyl Ligands

Two ureido-pyridyl ligands, 1-(4-nitro-phenyl)-3-pyridine-3-ylmethyl-urea (L1) and 1-pentafluorophenyl-3-pyridine-4-yl-urea (L2) were synthesized in good yields, and solid-state anion binding studies of (HL1)+ and (HL2)+ with polyatomic anions such as NO3−, AcO−, ClO4−, SO42−, and SiF62− were carried out in detail. Protonation of the pyridyl nitrogen center of L1 with HNO3, HClO4, and HF in different solvent media yielded crystals of complexes 1 (HL1·NO3), 2 (HL1·ClO4), and 3 (HL1·0.5SiF6) suitable for single crystal X-ray diffraction studies, respectively. Similarly, protonation of L2 with HNO3, CH3COOH, and H2SO4 yielded single crystals of complexes 4 [2(HL2·NO3)·DMF], 5 (HL2·AcO), and 6 [(HL2)2·SO4], respectively. X-ray crystallographic analysis of all these six complexes has been carried out and the details of anion binding with the urea functionality of ureido-pyridyl ligands were investigated. In all the complexes, the pyridyl moiety of the ligands is found to be protonated and the binding of anions...

Highly stable acyclic bifunctional chelator for 64Cu PET imaging

Abstract Ligand L1, based on a pyridine scaffold, functionalized by two bis(methane phosphonate)aminomethyl groups, was shown to display a very high affinity towards Cu(II) (log K CuL=22.7) and selectivity over Ni(II), Co(II), Zn(II) and Ga(III) (Δ log K ML>4) as shown by the values of the stability constants obtained from potentiometric measurements. Insights into the coordination mode of the ligand around Cu(II) cation were obtained by UV-Vis absorption and EPR spectroscopies as well as density functional theory (DFT) calculations (B3LYP model) performed in aqueous solution. The results point to a pentacoordination pattern of the metal ion in the fully deprotonated [CuL1]6− species. Considering the beneficial thermodynamic parameters of this ligand, kinetic experiments were run to follow the formation of the copper(II) complexes, indicating a very rapid formation of the complex, appropriat e for 64Cu complexation. As L1 represents a particularly interesting target within the frame of 64Cu PET imaging, a synthetic protocol was developed to introduce a labeling function on the pyridyl moiety of L1, thereby affording L2, a potential bifunctional chelator (BFC) for PET imaging.

Metal Coordinated Urea Based Fluorescent Receptors for Anion Recognition

Two bis urea based acyclic receptors (1 and 2) containing two pyridyl moieties with different spacers are synthesized. These receptors are further transformed to metallo-macrocyclic receptors (3 and 4) by coordinating with metal center through pyridine ring ‘N’. The binding-behavior as well as selectivity of the receptors towards anions upon metal coordinated cyclization is studied and the results are compared with parent acyclic receptors. Receptors 2 and 4 containing a naphthalene moiety as a spacer as well as a fluorophore behave as ‘on-off’ sensors towards anions. Keywords: Anion recognition, fluorescence sensing, urea and acyclic receptors, fluorophore, 3-Aminopyridine, DMF, acetonitrile, FT-IR, HRMS, FAB, UV-vis titration, Fluorescence emission titration, Stern-Volmer plot, Fluorescence Quenching, DMSO, 13C NMR, 1,1'-(4,4'-methylenebis(4,1-phenylene))bis(3-(pyridin-3-yl)urea), 1,1'-(naphthalene-1,8-diyl)bis(3-(pyridin-3-yl)urea), 1,1'-(4,4'-methylenebis(4,1-phenylene))bis(3-(pyridin-3-yl)urea) palladium dichloride, 1,1'-(naphthalene-1,8-diyl)bis(3-(pyridin-3-yl)urea) palladium dichloride

Thermosolutal Self-Organization of Supramolecular Polymers into Nanocraters

The ability of two complementary molecular modules bearing H-bonding uracilic and 2,6-(diacetylamino)pyridyl moieties to self-assemble and self-organize into submicrometer morphologies has been investigated by means of spectroscopic, thermogravimetric, and microscopic methods. Using uracilic (3)N-BOC-protected modules, it has been possible to thermally trigger the self-assembly/self-organization process of the two molecular modules, inducing the formation of objects on a mica surface that exhibit crater-like morphology and a very homogeneous size distribution. Confirmation of the presence of the hydrogen-bonding-driven self-assembly/self-organization process in solution was obtained by variable-temperature (VT) steady-state UV-vis absorption and emission measurements. The variation of the geometric and spatial features of the morphologies was monitored at different T by means of atomic force microscopy (AFM) and was interpreted by a nonequilibrium diffusion model for two chemical species in solution. The formation of nanostructures turned out to be affected by the solid substrate (molecular interactions at a solid-liquid interface), by the matter-momentum transport in solution (solute diffusivity D(0) and solvent kinematic viscosity ν), and the thermally dependent cleavage reaction of the BOC functions (T-dependent differential weight loss, θ = θ(Τ)) in a T interval extrapolated to ∼60 K. A scaling function, f = f (νD(0), ν/D(0), θ), relying on the onset condition of a concentration-driven thermosolutal instability has been established to simulate the T-dependent behavior of the structural dimension (i.e., height and radius) of the self-organized nanostructures as ⟨h⟩ ≈ f (T) and ⟨r⟩ ≈ 1/f (T).

Pyridyldithiafulvene as N-ligand towards molybdenum carbonyl complexes and evidence of protonation through hydrolysis of lead perchlorate

The ability of pyridyldithiafulvenes to react as monodentate ligand with Mo(CO) 6 and Pb(ClO 4) 2 has been investigated. The corresponding molybdenum carbonyl complexes have been isolated while no coordination to lead has been observed. As evidenced by X-ray crystal structure analysis, protonation of the pyridyl moiety has occurred due to the propensity of lead perchlorate trihydrate to hydrolyze in acetonitrile. The spectroscopic and redox properties of the molybdenum complexes as well as the pyridinium dithiafulvenes have been compared with their precursors and discussed.

Homopolymerization of ethylene, 1-hexene, styrene and copolymerization of styrene with 1,3-cyclohexadiene using (η⁵-tetramethylcyclopentadienyl)dimethylsilyl(N-Ar')amido-TiCl₂/MAO (Ar'=6-(2-(diethylboryl)phenyl)pyrid-2-yl, biphen-3-yl).

The propensity of a half-sandwich (η5-tetramethylcyclopentadienyl)dimethylsilylamido TiIV-based catalyst bearing an auxiliary diethylboryl-protected pyridyl moiety (Ti-8), activated by methylaluminoxane (MAO) to homopolymerize α-olefins such as ethylene, 1-hexene and styrene as well as to copolymerize styrene with 1,3-cyclo-hexadiene is described. The reactivity of Ti-8 was investigated in comparison to a 6-(2-(diethylboryl)phenyl)pyrid-2-yl-free analogue (Ti-3).

Isocyanide insertion and cyclization reactions to form indolines using pincer-type complexes of scandium

The addition of 2,6-dimethylphenyl isocyanide (CN[DMeP], two equivalents) to previously reported (PNP)Sc(III) pyridyl complexes resulted in the formation of novel indoline complexes of scandium. By varying the nature of the pyridyl moiety one can intercept an intermediate prior to methyl migration. In addition to structural studies of two indolene complexes, we also propose a mechanism for the insertion and indolene ring closure.

Syntheses, crystal structures and magnetic properties of two dicopper(II) complexes and a zigzag 1-D Cu(II) complex of a bidentate pyridyl-pyrazole ligand

Two new dinuclear copper compounds, [Cu2(pypz)2(N3)2(NO3)2] (1) and [Cu2(pypz)2(OH)2(NO3)2] (2), and one 1-D polymeric Cu(II) complex, [Cu(pypz)(dca)3]n (3) [‘pypz’=(3,5dimethyl-1-(2′-pyridyl)pyrazole) and dca=(dicyanamide)], have been synthesized and characterized crystallographically and spectroscopically. Complex 1 is pseudo-octahedral, adjacent Cu atoms are connected by a pair of μ(1,1) azido groups and the structure is stabilized by π–π interactions between two pyridyl moieties from two different neighboring complex molecules. Complexes 2 and 3 are square pyramidal. The hydroxo bridged complex 2 is further stabilized through H-bonding. The 1-D polymeric chain of 3 is bridged by an end-to-end dicyanamide bridge and it propagates along the crystallographic b axis, whilst the polymer chains are stacked one upon another along the crystallographic c axis. Low temperature magnetic measurement shows that complexes 1 and 2 are ferromagnetic (J values are 30.81 and 14.79cm−1, respectively), whereas due to larger Cu–Cu distances, complex 3 shows weak ferromagnetism.

ChemInform Abstract: One‐Pot Synthesis of Polyfunctionalized 4H‐Pyran Derivatives Bearing Fluorochloro Pyridyl Moiety.

AbstractThe three‐component reaction offers a direct synthesis of the structurally important pyran system.

Synthesis of a 2-benzocymantrenylpyridine and further mechanistic insights

The synthesis of a new benzocymantrene derivative containing an appended pyridyl moiety was attempted by reacting a lithioindenylpyridine with (CO) 5MnBr. The reaction led to the formation of small amounts of the targeted benzocymantrene, which was subsequently characterized by structural X-ray diffraction analysis. Alternative treatment of the same ligand with (η 1-benzyl)pentacarbonylmanganese led to the formation of a five-membered manganacycle resulting from the C–H bond activation at the five-membered ring of the indenyl group. To rationalize the origin of the poor yield in the benzocymantrene derivative a complete study of the reaction profile was carried out by means of a state-of-the-art DFT-D2 method. The theory indicated that the main difficulty in producing the targeted benzocymantrene stems from the relatively high activation energy barrier necessary to convert a (η 1-indenyl)Mn(CO) 5 intermediate into a (η 3-indenyl)Mn(CO) 4 transient species.

Bridging Azines in the Coordination Sphere of Low-Valent Vanadocene Derivatives

Complexes of vanadocene(II) and -(III) derivatives with aromatic N-heterocyclic ligands are scarcely known. Here we present the first syntheses of several mono-, di-, and trinuclear complexes of this type and their detailed characterization. Reactions of vanadocene(II) derivatives are limited to N-heterocycles with distinct π-acceptor ability such as 4,4′-azobis(pyridine), which reacts as a bridging ligand to form [(Cp2V)2(μ2-Py2N2)] (13). In contrast Cp2VII reacts with, for example, 1,2-bis(4-pyridiyl)acetylene (C2Py2) solely to give the corresponding metallacyclopropene [Cp2V(η2-C2Py2)] (12) without affecting the pyridyl moieties. On the other hand, the reactivity of vanadocene(III) cations with this class of ligands is unrestricted and dominated by the acid−base properties of the reactants. The application of permethylated cyclopentadienyl ligands (Cp*) significantly enhances the solubility of those complexes, which leads to a better crystallizability. Due to the cationic properties of vanadocenium(III...

Binding of a 2-pyridyl moiety to a B/Sn bidentate Lewis acid

Reaction of the bidentate Lewis acid 1,2-Fc(SnMe 2Cl)(B(Me)Cl) ( 1, Fc = 1,2-ferrocenylene) with 2-trimethylstannylpyridine gave a complex ( 2), in which the 2-pyridyl group forms a bridge between the Lewis acidic tin and boron centers. The structure of 2 was confirmed by multinuclear and two-dimensional NMR, single crystal X-ray diffraction, and elemental analysis. The crystal structure shows that the pyridyl moiety is positioned endo relative to the substituted Cp ring and UV–Vis spectroscopy revealed an enhancement of the ferrocene-centered dd transition in comparison to related complexes with pyridine as a terminal ligand.

ChemInform Abstract: Chirality Organization of Peptide Conjugated Molecules in Bioorganometallic Chemistry

AbstractReview: 40 refs.

One-pot synthesis of polyfunctionalized 4 H-pyran derivatives bearing fluorochloro pyridyl moiety

Polyfunctionalized 4 H-pyran derivatives bearing fluorochloro pyridyl moiety were readily prepared in high yields via one-pot multicomponent reaction catalyzed by piperidine. This present protocol provides an efficient synthetic route to the target compounds with the characteristics of short reaction time, high yield, and easy separation of the products.

Towards the synthesis of substituted porphyrins by a pyridyl group bearing a reactive functionality

Pyridyl-substituted porphyrins bearing a reactive functionality were prepared via Suzuki cross-coupling reactions and resulted in very good yields. These compounds are precursors of new porphyrin architectures able to coordinate two metals: one in the porphyrin core and the second around the pyridyl moiety. During the coupling reactions, a higher reactivity of a chloro picolyl group was evidenced compared to a bromo function on the same reacting molecule.