Engineering with metallo-supramolecular polymers: linear coordination polymers and networks

Here we demonstrate the synthesis of telechelics with different spacer units and different numbers of metal-complexing units, like α-methoxy-ω-(2,2′:6′,2″-terpyrid-4′-yl)-poly(ethylenoxide)₇₈ ( 1 ), bis(2,2′:6′,2″-terpyrid-4′-yl) di(ethylene glycol) ( 2 ), bis(2,2′:6′,2″-terpyrid-4′-yl)-poly(ethylene oxide)₁₈₀ ( 3 ) and tris[(2,2′:6′,2″-terpyrid-4′-yl)-oligo (ethylenoxy-)_3.33]glycerin ( 4 ) utilizing 4-chloro-2,2′:6′,2″-terpyridine. The complexation behaviour of a variety of metal-salts towards the telechelics was studied and different supramolecular architectures were investigated, such as symmetric polymeric complexes and linear coordination polymers. Furthermore, attempts have been undertaken to prepare metallo-supramolecular cross-linked systems.     

DNA-binding and cleavage activity of polypyridyl ruthenium(II) complexes

Polypyridyl ruthenium(II) complexes [Ru^II(3-bptpy)(dmphen)Cl]ClO₄ (1), [Ru^II(3-cptpy)(dmphen)Cl]ClO₄ (2), [Ru^II(2-tptpy)(dmphen)Cl]ClO₄ (3), and [Ru^II(9-atpy)(dmphen)Cl]ClO₄ (4) {where 3-bptpy?=?4′-(3-bromophenyl)-2,2′:6′,2″-terpyridine, 3-cptpy?=?4′-(3-chlorophenyl)-2,2′:6′,2″-terpyridine, 2-tptpy?=?4′-(2-thiophenyl)-2,2′:6′,2″-terpyridine, 9-atpy?=?4′-(9-anthryl)-2,2′:6′,2″-terpyridine, dmphen?=?2,9-dimethyl-1,10-phenanthroline} have been synthesized and characterized. The DNA-binding properties of the complexes with Herring Sperm DNA have been investigated by absorption titration and viscosity measurements. The ability of complexes to break the pUC19 DNA has been checked by gel electrophoresis. The experimental results suggest that all the complexes bind DNA via partial intercalation. The results also show that the order of DNA-binding affinities of the complexes is 4?<?3?<?2?<?1, confirming that planarity of the ligand in a complex is very important for DNA-binding.     

The preparation and coordination chemistry of 2,2′:6′,2″-terpyridine macrocycles—1

A range of 6,6″-disubstituted derivatives of 2,2′: 6,2″-terpyridine have been prepared with the intention of forming macrocycles incorporating the 2,2′: 6′,2$\text{-}\text{?}$terpyridyl moiety. A high yield route to 6,6″-bis(methylhydrazino-4′-phenyl-2,2′:6′,2″-terpyridine is described, and a number of complexes of this novel pentadentate ligand have been prepared.     

Chromium(VI) oxide-mediated oxidation of polyalkyl-polypyridines to polypyridine-polycarboxylic acids with periodic acid

4,4′-Dicarboxy-2,2′-bipyridine was synthesized quantitatively by chromium(VI) oxide-mediated oxidation of 4,4′-dimethyl-2,2′-bipyridine or 4,4′-diethyl-2,2′-bipyridine with periodic acid as the terminal oxidant in sulfuric acid. 5,5′-Dicarboxy-2,2′-bipyridine and 6,6’-dicarboxy-2,2′-bipyridine were also synthesized by the method from the corresponding dimethyl bipyridines in excellent yields. 4,4′,4″-Tricarboxy-2,2′:6′,2″-terpyridine was obtained in 80% yield from 4,4′,4″-triethyl-2,2′:6′,2″-terpyridine, and 4,4′,4″,4′″-tetracarboxy-2,2′:6′,2″:6″,2′″-quaterpyridine was obtained in 72% yield from 4,4′,4″,4′″-tetraethyl-2,2′:6′,2″:6″,2′″-quaterpyridine by the same procedure.     

Synthesis,magnetic properties and theoretical calculations of novel nitronyl nitroxide and imino nitroxide diradicals grafted on terpyridine moiety

The synthetic route based on Stille coupling between tributyltinpyridyl derivatives and bromo substituted mono- and dipyridyl-carbaldehyde is used for the synthesis of 5,5″-diformyl-2,2′:6′,2″-terpyridine (8). A sequence of Ullman coupling with 2,3-bis(hydroxylamino)-2,3-dimethylbutane followed by oxidation under phase transfer conditions affords either 5,5″-Bis(1-oxyl-3-oxo-4,4,5,5-tetramethylimidazolidin-2-yl)2,2′:6′,2″-terpyridine (10) (diNN-Terpy) or the related 5,5″-Bis(1-oxyl-4,4,5,5-tetramethylimidazolidin-2-yl)2,2′:6′,2″-terpyridine (11) (diIN-Terpy), where both biradicals display clear intramolecular ferromagnetic interaction between the single spin units as evidenced by ESR spectroscopy. Quantum chemical calculations (ROHF/AM1) are performed showing the triplet ground-state for both 10 and 11 radicals.     

Ratiometric Fluorescent Determination of the Zinc Ion Using a Terpyridine Derivative

Zinc is essential for normal growth and development, and hence selective recognition and detection for zinc has been a significant area of research. Here 4′-(4-methoxyphenyl)-2,2′:6′,2″-terpyridine is described for the ratiometric fluorescence quantification of zinc ion with high selectivity. The fluorescence of 4′-(4-methoxyphenyl)-2,2′:6′,2″-terpyridine at 406?nm was quenched in the presence of zinc, and a new emission band appeared at 452?nm. The ratiometric method for the determination of zinc ion was based on the dual fluorescence measurements at 406 and 452?nm. This fluorescence response is caused by the formation of a 1:1 complex between 4′-(4-methoxyphenyl)-2,2′:6′,2″-terpyridine and the zinc(II) ion. The analytical figures of merit for the protocol were obtained. The linear dynamic range extended for zinc concentrations from 3.0 to 40.0?µmol/L with a limit of detection of 0.28?µmol/L. Zinc was determined in water with satisfactory results.     

Syntheses,characterizations of copper compounds containing a series of S-, N-containing aromatic heterocyclic 2,2′:6′,2″-terpyridine derivatives

A series of 2,2′:6′,2″-terpyridine (TPY) based aromatic heterocyclic compounds, extended by thiophene, 4-dibenzothiophene, and thiazole units at the para position of the central pyridine ring in TPY, are described in this paper. A new compound, 4′-(4′-dibenbenzothiophene-5-thiophene-2-yl)-2,2′:6′,2″-terpyridine (L_a), serves as a tridentate ligand to react with Cu(NO₃)₂·3H₂O and CuCl₂·2H₂O, respectively, to produce two different Cu(II) complexes [Cu(L_a)₂](NO₃)₂ and [CuL_aCl₂] with 1?:?2 and 1?:?1 metal/ligand ratios. Dibenzothiophene is first introduced to TPY via the thiophene bridge. The alterations in cis and trans configuration, dihedral angles between adjacent aromatic rings, and photophysical properties have been observed before and after Cu(II) complexation, which has been verified by their crystal structures, UV–vis and fluorescence spectra.     

New Approaches to the Synthesis of 2,2′: 6′,2″-Terpyridine and Some of Its Derivatives

A new two-step procedure has been developed for the synthesis of 2,2′: 6′,2″-terpyridine and 4′-methylsulfanyl-2,2′: 6′,2″-terpyridine in more than 70% yield on the basis of Potts’ condensation. Efficient methods have been proposed for purification of all condensation products.     

2Rotaxane based on terpyridyl bimetal ruthenium complexes and β-cyclodextrin as organic sensitizer for dye-sensitized solar cells

The conjugated carboxy-functionalized terpyridyl bimetal ruthenium complex [(tdctpy)Ru(dctpy-(ph)₄-dctpy)Ru(tdctpy)][PF₆]₄ and [2]rotaxane by self-assembly of [(tdctpy)Ru(dctpy-(ph)₄-dctpy)Ru(tdctpy)][PF₆]₄ with β-cyclodextrin are reported as sensitizer for dye-sensitized solar cells (DSSCs), where tdctpy?=?4′-p-tolyl-4,4″-dicarboxy-2,2′?:?6,2″-terpyridine, dctpy?=?4,4″-dicarboxy-2,2′?:?6,2″-terpyridine and dctpy-(ph)₄-dctpy represents a bridging ligand where two 4,4″-dicarboxy-2,2′?:?6′,2″-terpyridine units are connected through four phenyl spacers in the 4′-position. The DSSCs fabricated utilizing these materials give typical electric power conversion efficiency of 0.013–0.523% under air mass (AM) 1.5, 100?mW?cm^?2 irradiation at room temperature. The terpyridyl bimetal ruthenium complex [(tdctpy)Ru(dctpy-(ph)₄-dctpy)Ru(tdctpy)][PF₆]₄ with conjugated-bridge chains displayed much higher conversion efficiency compared with the carboxy-functionalized terpyridyl monometal ruthenium complex [tdctpy-Ru-(idctpy)][PF₆]₂, where idctpy?=?4′-p-iodophenyl-4,4″-dicarboxy-2,2′?:?6,2″-terpyridine. [2]Rotaxane displayed the highest electric power conversion efficiency of 0.523% when β-cyclodextrin was introduced into the conjugated terpyridyl bimetal ruthenium complex and formed [2]rotaxane.     

Foreword

Abstract

The crystal structure of the dinucleating 2,2′:6′,2″-terpyridine ligand 6′,6″-bis(2-pyridyl)-2,2′:4′,4″:2″,2?-quaterpyridine (btpy) has been determined and the two metal-binding tpy domains shown to be essentially planar and co-planar (P 1, a = 6.304(2), b = 8.208(2), c = 11.535(3) Å, α = 97.42(2), β = 104.25(2), γ = 96.23(2)°, Z = 1, d _c = 1.36 g cm^?3, 2214 unique observed reflections with I > 1.5[sgrave] (I), R = 0.0583); a methodology involving sequential reaction with non-labile and labile metal centres allows the specific assembly of heterometallic supramolecular oligomers such as [(Xtpy)Ru(btpy)M(btpy)Ru(Ytpy)]ⁿ⁺ (M = cobalt(II), cobalt(III) or iron).     

Synthesis and supramolecular networks of mono- and dinuclear manganese chloride complexes with 2-(2,2′ : 6′,2″-terpyridin-4′-yl)phenol

2-(2,2′?:?6′,2″-Terpyridin-4′-yl)phenol has been prepared with an improved one-pot method. The reaction between the ligand and MnCl₂ in ethanol at ambient or hydrothermal conditions afforded dichlorido[2-(2,2′?:?6′,2″-terpyridin-4′-yl)phenol-κ³ N,N′,N″]manganese(II) and dichloridobis[µ-2-(2,2′?:?6′,2″-terpyridin-4′-yl)phenolate-κ³ N,N′,N″-κO]dimanganese(II), respectively. Face-to-face π–π stacking interactions between the pyridine rings play a crucial role in supramolecular networks of both complexes. Both complexes display weaker photoluminescence than the free ligand and the dinuclear complex luminescence was stronger than the mononuclear one.     

DFT study of the electronic and charge transfer properties of perfluoroarene–thiophene oligomers

The ground state structures of 5,5″-diperfluorophenyl-2,2′:5′,2″:5″,2‴-quaterthiophene (1), 5,5′-bis{1-[4-(thien-2-yl)perfluorophenyl]}-2,2′-dithiophene (2), 4,4′-bis[5-(2,2′-dithiophenyl)]-perfluorobiphenyl (3), 5,5″-diperfluorophenyl-2,2′:5′,2″-tertthiophene (4), 5,5′-diperfluorophenyl-2,2′-dihiophene (5), and 5,5-diperfluorophenylthiophene (6) have been optimized at the B3LYP/6-31G(d), B3LYP/6-31G(d,p), PBE0/6-31G(d), and PBE0/6-31G(d,p) level of theories. The B3LYP/6-31+G(d) and PBE0/6-31+G(d) level of theories have been applied to investigate the absorption spectra. The PBE0 functional is good to predict the C–S bond lengths while the C–F bond lengths are good envisaged with B3LYP functional. The increment of thiophene rings between two perfluoroarene rings leads to red shift in absorption spectra. The electron affinities are energetically destabilized while energetic stabilization of the radical-cation increases by decreasing the thiophene rings from four to one. The perfluoroarene rings leads to enhance the electron injection.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> magnetic nanoparticles for bulk scale synthesis of 4′-chloro-2,2′:6′,2″-terpyridine

Terpyridines are unique class of functional compounds that is extensively spotlighted in diverse fields like synthesis of supramolecular chemistry, nanomaterials, medicinal chemistry intermediates, drugs and active pharmaceutical ingredients and so on. The key challenges for the production of terpyridine lie in the bulk scale synthesis of intermediates. The expansively used synthon for terpyridine synthesis is 4′-chloro-2,2′:6′,2″-terpyridine and their bulk scale synthesis under the ambient conditions using a Fe₃O₄@SiO₂ magnetic nanomaterial catalyst is investigated in the present work. In the protocol stabilized, ethyl-2-pinacolate and acetone were reacted in the presence of NaH to obtain 1,5-bis(2-pyridinyl) pentane-1,3,5-trione. The enolate of acetone is difficult to generate even with NaH and we used Fe₃O₄@SiO₂ to increase the rate of H₂ gas evolution. The triketone is cyclized with CH₃COONH₄ to obtain 2,6-bis(2-pyridinyl)-4-pyridine. This reaction proceeds quantitatively and the off-white solid was easy to isolate from the reaction medium. The subsequent aromatization was observed with PCl₅/POCl₃ and acidic silica gel promoted the product yield to reach ~78%. The crux of the present protocol is that it does not involve any column purification and significant yield of 4′-chloro-2,2′:6′,2″-terpyridine can be conveniently attained. The Fe₃O₄@SiO₂ aids in the stabilization of carbonyl on the solid support and abstraction of hydrogen from methyl group of acetone. The 40 nm sized Fe₃O₄@SiO₂ favored the maximum yield attributed to the density of active sites to promote the reactions. Due to high value nature of 4′-chloro-2,2′:6′,2″-terpyridine, the nominal 30% yield improvement achieved at the bulk scale gauges significant at the industrial scale.     

Synthesis,characterization, electrochemical and theoretical study of substituted phenyl-terpyridine and pyridine-quinoline based mixed chelate ruthenium complexes

In the present work, we report two methoxy-substituted phenyl-terpyridine ruthenium complexes with pyridine carboxyquinoline and NCS as ancillary ligands, [Ru(OMePhtpy)(pcqH)(NCS)](PF₆) (1) and [Ru(triOMePhtpy)(pcqH)(NCS)](PF₆) (2) (where OMePhtpy = (4′-(4-methoxy)phenyl-2,2′:6′,2″-terpyridine, triOMePhtpy = (4′-(3,4,5-trimethoxy)phenyl-2,2′:6′,2″-terpyridine and pcqH = pyridine-carboxyquinoline). Both complexes have been characterized by spectroscopic techniques e.g., mass, ¹H-NMR and FTIR. UV–vis spectrophotometric and electrochemical studies for both complexes have been performed. The substitution pattern of the –OMe groups have been successfully utilized to tune the redox potential of the metal complexes. On the anodic side of cyclic voltammogram, 1 and 2 show an irreversible wave corresponding to Ru^II/III couple at 0.95 and 0.85 V, respectively. The lower Ru^II/III oxidation potential for 2 may be attributed to increased electron density on ruthenium due to three (+R) methoxy–groups appended to the phenyl moiety of triOMePhtpy. DFT optimization of structure and energy calculation reveals that in both complexes, HOMO is metal- and thiocyanate-based, whereas the LUMO is based on pcqH. Correlation of TDDFT results with experimental electronic spectrum indicates that bands at 502 nm (1) and 528 nm (2) are of MLLCT character from ruthenium-thiocyanate to pcqH.     

Synthesis and characterization of new copolymers of thiophene and vinylene: Poly(thienylenevinylene)s and poly(terthienylenevinylene)s with thioether side chains

Poly[3,4-bis(3-methylbutylthio)thienylenevinylene], poly[3,4-bis-(S)-(2-methylbutylthio)thienylenevinylene], poly[3′,4′-bis(3-methylbutylthio)-2,2′:5′,2″-terthienylene-5,5″-vinylene], and poly{3′,4′-bis-(S)-[2-methylbutylthio]-2,2′:5′,2″-terthienylene-5,5″-vinylene} have been synthesized. The synthesis starts from the thiophene monomers and trimers, which are formylated to give the corresponding dialdehydes. The dialdehydes are reductively polymerized using a McMurry coupling. The polymers are characterized by GPC, optical spectroscopy (FT-IR, UV-vis, circular dichroism spectroscopy and photoluminescence) and by proton and carbon NMR spectroscopy. The polymers are soluble in common organic solvents, such as THF, chloroform, toluene, benzene and 1,2-dichlorobenzene. The solvatochromism and thermochromism of the polymers in solution are investigated, while the optical activity of the polymers is used to investigate the supramolecular aggregation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4629–4639, 1999     

An Efficient and Easy Synthesis of Tetrasubstituted 2,2′:6′,2″-Terpyridines

An efficient synthesis of 4,4″-dinitro-5,5″-dimethyl-2,2′:6′,2″-terpyridine was accomplished. The crystal structures of three different 2,2':6’,2″-terpyridines were determined by x-ray analysis.     

Electrochemical coupling of mono and dihalopyridines catalyzed by nickel complex in undivided cell

One step nickel-catalyzed electroreductive homocoupling among 2-bromopicolines and 2-bromopyridine has been investigated by our group in an undivided cell and using zinc or iron as sacrificial anode. In this work, it was developed mono and dihalopyridines coupling to obtain possible products from heterocoupling. A series of reactions were carried out in order to develop a synthetic method for the preparation of unsymmetrical 2,2′-bipyridines and 2,2′:6′,2″-terpyridines. Statistical yields (50%) were observed for 2-bromopyridines/2-bromo-6-methylpyridine heterocoupling. In a preliminary study devoted to terpyridines preparation, good results were obtained for 2,6-dihalopyridines homocoupling, affording 2,6-dichloro-2,2′-bipyridine (46%) and 2,6-dibromo-2,2′-bipyridine (56%), at controlled reaction time. At major reaction time, it was observed that the direct electroreduction of the 2,6′-dihalo-2,2′-bipyridines intermediates and 2,6″-dihalo-2,2′:6′,2″-terpyridines products on the cathode surface. A reasonable isolated product yield of 6,6″-dimethyl-2,2′:6′,2″-terpyridine (10%) was only observed in the reaction between 2,6-dichloropyridine and 2-bromo-6-methylpyridine (1:2).     

New Monoterpene-Substituted Dihydrochalcones from Piper aduncum

Five New unusual monoterpene-substituted dihydrochalcones, the adunctins A–E (1″S)-1-{2′-hydroxy-4′-methoxy-6′-[4″-methyl-1″-(1?-methylethyl)cyclohex-3″ -en-1″ -yloxy]phenyl}-3-phenylpropan-1-one ( 1 ), (5aR*,8R*,9aR*)-3-phenyl-1-[5′,8′,9′,9′a-tetrahydro-3′-hydroxy-1′-methoxy-8′-(1″-methylethyl)-5′-a-methyldibenzo-[b,d]furan-4′-yl]propan-1-one ( 2 ), (2′R*,4″S*)-1-{6′-hydroxy-4′-methoxy-4″-(1?-methylethyl)spiro[benzo[b]-furan-2′(3′H),1″ -cyclohex-2″ -en]-7′-yl}-3-phenylpropan-1-one ( 3 ), (2′R*,4″R*)-1-{6′-hydroxy-4′-methylethyl-4″-(1?-methylethyl)spiro[benzo[b]furan-2′(3′H),1″-cyclohex-2″-en]-7′-yl}-3-phenypropan-1-one ( 4 ), and (5′aR*,6′S*, 9′R*,9′aS*)-1-[5′a,6′,7′,8′,9′a-hexahydro-3′,6′-methoxy-6′-methyl-9′-(1″-methylethyl)dibenzo[b,d]-furan-4′-yl]-3-phenylpropan-1-one ( 5 ) were isolated from the leaves of Piper aduncum (Piperaceae) by preparative liquid chromatography. In addition, (?)-methyllindaretin ( 6 ), trans-phytol, and α-tocopherol ( = vitamin E) were also isolated and identified. The structures were elucidated by spectroscopic methods, including 1D- and 2D-NMR spectroscopy as well as single-crystal X-ray diffraction analysis. The antibacterial and cytotoxic potentials of the isolates were also investigated.     

Synthesis,crystal structure,and density functional theory study of a zinc(II) complex containing terpyridine and pyridine-2,6-dicarboxylic acid ligands: Analysis of the interactions with amoxicillin

An octahedral zinc(II) complex of 2,2′:6′,2″-terpyridine (Tpy) and pyridine-2,6-dicarboxylate (Pydc), [Zn(II)(Tpy)(Pydc)·4H₂O] was synthesized and its structure was determined by a single-crystal X-ray diffraction. The ligand pyridine-2,6-dicarboxylate coordinated to the zinc(II) ion via two pairs of carboxylate oxygens and one nitrogen atom, whereas 2,2′:6′,2″-terpyridine also contributed three coordination bonds through its nitrogen atoms. [Zn(II)(Tpy)(Pydc)·4H₂O] showed luminescence properties between 412 and 435 nm in DMSO. The solid-state octahedral geometry of [Zn(II)(Tpy)(Pydc)·4H₂O] was also preserved in solution as confirmed by the observed UV λ_ex = 346. Experimental and theoretical studies indicated that [Zn(II)(Tpy)(Pydc)·4H₂O] interacted with amoxicillin. Density functional theory calculations at B3LYP/LanL2dz level of theory suggested that [Zn(II)(Tpy)(pydc)·4H₂O] dimer interacts with (2S,5R,6R)-6-{[(2R)-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid (amoxicillin) via highest occupied molecular orbital and lowest unoccupied molecular orbital, π–π interaction, hydrogen bond interaction, and van der Waals forces, thus influencing [Zn(II)(Tpy)(Pydc)·4H₂O] properties.