Tetrakis(4-pyridyl)porphyrin supramolecular complexes with cyclodextrins in aqueous solution

The formation of inclusion complexes of hydroxypropyl-beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin with 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TpyP) has been studied in aqueous buffer solution (phosphate buffer pH = 7 and I = 0.01 M) to give a structural and spectroscopic characterization of a new class of potential sensitizers for photodynamic therapy. The interaction was investigated by a combination of UV/Vis absorption, fluorescence anisotropy, time-resolved fluorescence and circular dichroism. The experimental results point to the presence of the pigment in water in a monomeric complexed form. The fluorescence anisotropy measurements suggest that TpyP forms 1:1 complexes with heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin, while 1:2 complexes are obtained with heptakis(2,6-di-O-methyl)-beta-cyclodextrin.     

Self-assembly of supramolecular complexes based on hydrogen bonding

Self-assembly of hydrogen-bonding recognition complexes—2.5-bis(alkylamino)-1,4-benzoquinones were studied, and thermotropic liquid crystalline behavior of 2.5-bis(dodecylamino)-1,4-benzoquinone was further investigated. The obtained results showed that a ribbon-like backbone in this system plays an important role in keeping the layered supramolecular structure.     

Three Mn(II) complexes with 1,3-bis(4-pyridyl)propane and their supramolecular nets

Three complexes, [Mn(bpp)₄(H₂O)₂](ClO₄)₂?·?1.5H₂O (1), [Mn(bpp)₃Br₂]?·?2H₂O (2), and [Mn(bpp)₂(H₂O)₂](ClO₄)?·?I?·?H₂O?·?bpp (3) (bpp?=?1,3-bis(4-pyridyl)propane), were synthesized and structurally characterized by single-crystal X-ray diffraction. Complex 1 is mononuclear where M(II) is coordinated to a monodentate TT-bpp, three monodentate TG-bpp, and two water molecules. Complex 2 possesses a single-stranded helical chain formed from MnN₄Br₂ octahedra by a single TT-bpp, with pendant monodentate TG-bpp ligands. Complex 3 consists of a ribbon-type double-stranded chain formed from MnN₄O₂ octahedra by double TG-bpp ligands. 2-D supramolecular architectures of 1–3 are formed by hydrogen bonds. The fluorescence of the three complexes comes from the π*–π transition of the ligand.     

Formation of supramolecular cavitands on copper electrode surfaces

The adsorption of 1,1'-dibenzyl-4,4'-bipyridinium molecules (dibenzyl-viologen or DBV(2+) for the sake of simplicity) on chloride precovered Cu(100) has been studied in an electrochemical environment by means of cyclic voltammetry and in situ scanning tunneling microscopy. DBV(2+) spontaneously forms a highly ordered phase on the chloride c(2 x 2) adlayer at potentials close to the onset of the copper dissolution reaction when the pure supporting electrolyte (10 mM HCl/5 mM KCl) is exchanged by one also containing DBV(2+). This ordered phase can be described by a ( radical 53 x radical 53)R15.9 degrees unit cell relating the organic adlayer to the chloride c(2 x 2) structure underneath or alternatively by a ( radical 106 x radical 106)R29.05 degrees unit cell relating the organic layer to the Cu(1 x 1) substrate structure. Thus, the negatively charged chloride layer acts as a template for the adsorption and phase formation of DBV(2+). Compared to the copper-chloride interaction, the DBV(2+)-chloride interaction appears to be weaker since the organic layer can be easily removed from the surface by the tunneling tip when drastic tunneling conditions (low bias voltage, high tunneling current) are applied. A key structural element of the DBV(2+) adlayer is an assembly of four individual DBV(2+) molecules forming square-shaped supramolecular units with pronounced cavities in their center. Characteristically, the supramolecular assemblies reveal a preferential rotational orientation resulting in the appearance of two chiral forms of these assemblies. Furthermore, these two chiral supramolecular assemblies occur in two mirrored domains of the ( radical 53 x radical 53)R15.9 degrees structure. It can be assumed that these viologen-based supramolecular architectures can be used as potential host cavitands for the inclusion of smaller organic molecules.     

Self-assembly of hydrogen-bonded supramolecular structures of two copper(II) 2-bromobenzoate complexes with 4-pyridylmethanol and nicotinamide

The structures of [Cu(2-Brbz)₂(4PM)₂(H₂O)] (1) and [Cu(2-Brbz)₂(NIA)2] · 2H₂O 2 [where 2-Brbz is the 2-bromobenzoate anion, 4-PM is the 4-pyridylmethanol and NIA is nicotinamide] have been determined by X-ray and characterized by EPR spectroscopy. The Cu²⁺ cation in 1 is coordinated by a pair of oxygens from monodentate 2-bromobenzoate anions by a pair of pyridine nitrogens from monodentate 4-pyridylmethanol ligands and finally by a water forming a tetragonal-pyramidal coordination polyhedron. The Cu²⁺ cation in 2 is coordinated by two pairs of oxygens from the asymmetric bidentate 2-bromobenzoate anions and by a pair of pyridine nitrogen atoms from the monodentate nicotinamide in trans positions, forming an extremely elongated bipyramid. The molecules of both complexes are linked by O–H ··· O, C–H ··· O and for 2 by N–H ··· O hydrogen bonds, which create three-dimensional hydrogen-bonding networks. EPR spectra of 1 and 2 are in agreement with X-ray data. Nicotinamide as well as 4-pyridylmethanol are suitable ligands for construction of hydrogen bonding coordination polymers.     

Molecular structures and supramolecular association of chlorodiorganotin(IV) complexes with bis- and tris-dithiocarbamate ligand

Two series of di and trinuclear chlorodiorganotin(IV) complexes derived from bis- and tris-dithiocarbamate ligands have been prepared and structurally characterized. The dinuclear complexes 1-2 of the composition {(R₂SnCl)₂(bis-dtc)} (1, R = Me; 2, R = ⁿBu) have been obtained from R₂SnCl₂ (R = Me, ⁿBu) and the triethylammonium salt of N,N′-dibenzyl-1,2-ethylene-bis(dithiocarbamate). The trinuclear complexes 3-9 with the general formula {(R₂SnCl)₃(tris-dtc)} 3, R = Me, tris-dtc = tris-dtc-Me; 4, R = Me, tris-dtc = tris-dtc-ⁱPr; 5, R = Me, tris-dtc = tris-dtc-Bn; 6, R = ⁿBu, tris-dtc = tris-dtc-Me; 7, R = ⁿBu, tris-dtc = tris-dtc- ⁱPr; 8, R = ⁿBu, tris-dtc = tris-dtc-Bn; 9, R = ^tBu, tris-dtc = tris-dtc-Me) were prepared from R₂SnCl₂ (R = Me, ⁿBu, ^tBu) and the potassium dithiocarbamate salts of (tris[2-(methylamino)ethyl]amine) (tris-dtc-Me), (tris[2-(isopropylamino)ethyl]amine) (=tris-dtc-ⁱPr) and (tris[2-(benzylamino)ethyl]amine) (=tris-dtc-Bn). Compounds 1-9 have been analyzed as far as possible by elemental analysis, FAB⁺ mass spectrometry, IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy, and single-crystal X-ray diffraction analysis. The solid state and solution studies showed that the dtc ligands are coordinated to the tin atoms in the anisobidentate manner. In all cases the metal centers are five-coordinate. The coordination geometry is intermediate between square-pyramidal and trigonal-bipyramidal coordination polyhedra with τ-values in the range of 0.32-0.53. For the members of each series characterized in the solid state by X-ray diffraction analysis, different molecular conformations were found. The crystal structures show the presence of C-H?Cl, C-H?S, C-H?π, S?Cl, S?S, Cl?Sn and S?Sn contacts.     

Self-assembly of interlocked supramolecular dendrimers

Interlocked supramolecular dendrimers were spontaneously self-assembled from molecular components, metallocycles, and dumbbells bearing benzyl ether repeating units. Here, the metallocycles were in situ self-assembled from L-shaped ligands with dendritic branches, 2,3-dimethyl-2-butene and osmium tetraoxide. The supramolecular dendrimers were stabilized by hydrogen-bonding interactions between the pyridine-2,6-dicarboxamide unit in the metallocycle and the adipamide unit in the dumbbell.     

Advances on supramolecular assembly of cyclometalated platinum(Ⅱ) complexes

Organoplatinum(Ⅱ) compounds have received enormous attention over the past decades due to their square-planar geometry as well as intriguing photo-physical properties.Self-assembly has emerged as an excellent approach to create well-ordered supramolecular architectures with tunable properties,which underpin the role of solvent-directed approach for the design of functional materials.In this minireview,the recent advances on supramolecular self-assembly of cyclometalated platinum(Ⅱ) complexes have been discussed.During the self-assembly process,non-covalent Pt-Pt and π-π interactions play crucial roles in controlling the structures and functions of the resulting assemblies.     

Self-assembly of heterogeneous supramolecular structures with uniaxial anisotropy

Uniaxial anisotropy in two-dimensional self-assembled supramolecular structures is achieved by the coadsorption of two different linear molecules with complementary amine and imide functionalization. The two-dimensional monolayer is defined by a one-dimensional stack of binary chains, which can be forced to line up along steps in vicinal surfaces. The competing driving forces in the self-organization process are discussed in light of the structures observed during single molecule adsorption and coadsorption on flat and vicinal surfaces and the corresponding theoretical calculations.     

Synthesis and characterization of supramolecular complexes of a tetranuclear metallocycle with platinum(II) bis-ethynylphenylethynylpyridine organometallic complexes

A novel Pt(II) organometallic complex with 4-(4-ethynyl-phenylethynyl)-pyridine (DEBPy-H), namely [Pt(dppp)(DEBPy)₂] (dppp = 1,3-bis-(diphenylphosphino)-propane), has been prepared by two synthetic routes. The DEBPy-H ligand was prepared by a shorter synthetic pathway and in higher yield than the method of previous reports. New Pt(II) organometallic complexes with DEBPy-H and four bidentate ligands [Pt(L–L)(DEBPy)₂] (L–L = 1,2-bis-(diphenylphosphino)-benzene, bis-(dicyclohexyl)-ethane, 4,4′-dimethyl-2,2′-bipyridine, or 5,5′-dimethyl-2,2′-bipyridine) have also been prepared. These five Pt(II) complexes have two pyridyl units as an available coordination site that can operate as a metalloligand in nanoscale tectonics. A supramolecular complex of a tetranuclear metallocycle, [Pt(dppp)(DEBPy)₂]₂[Pt(dppp)]₂(OTf)₄, was synthesized from [Pt(dppp)(DEBPy)₂] and [Pt(dppp)(OTf)₂] as a corner connection through coordination-driven self-assembly. This supramolecular Pt(II) complex exists as a tetranuclear structure of the square type according to the interpretation of the ESI-mass and NMR spectra in solution. Five Pt(II) organometallics demonstrated the formation of similar tetranuclear metallocycles with [Pt(dppp)(OTf)₂], as indicated by their ESI-mass and UV–vis spectra in solution.     

Self-assembly of nanoscale supramolecular truncated tetrahedra

Two nanoscale truncated tetrahedra were synthesized via Pt(II)-mediated self-assembly. The first resulted from the reaction of 3 equiv of cis-Pt(PMe3)2(OTf)2 and 2 equiv of 1,3,5-tris(4-pyridylethynyl)benzene, giving a truncated tetrahedron with a diameter of approximately 25 A. The second, analogous structure was obtained by the self-assembly of cis-Pt(PMe3)2(OTf)2 and 1,3,5-tris(4-pyridyl-trans-ethenyl)benzene. These two truncated tetrahedra were crystallized after partially exchanging the counterion to cobalticarborane for the X-ray structural analysis.     

Spectroscopic and biological properties of platinum complexes derived from 2-pyridyl Schiff bases

The reactions of a range of aromatic primary amines with pyridine-2-carboxaldehyde were reported, highlighting the effect of the substituents of the amine on the outcomes of the Schiff base reactions. The variant products of the Schiff base reactions were reacted with cis-[PtCl₂(DMSO)₂], generating platinum(II) complexes with PtCl₂(N^N) general formula. The ligands and platinum(II) complexes were identified and characterized by IR and NMR spectroscopic methods. Single crystal XRD offered structural confirmation for three of the organic compounds and two platinum complexes. The spectral, antimicrobial, DNA-binding and molecular docking of the platinum complexes were studied, highlighting the effect of the different functional group in the Schiff base ligands on their properties. In general, introducing the electron-withdrawing group nitro or acetyl in the 2-pyridyl Schiff base ligands, results in a red-shift in the absorption maxima of the platinum complex. In addition, the enhancement in the antimicrobial activities and the increase in the ct-DNA-binding affinity were also observed when the nitro or acetyl functional group is introduced to the Schiff base ligand in the platinum(II) complex.     

New bis-, tris- and tetrakis(pyrazolyl)borate ligands with 3-pyridyl and 4-pyridyl substituents: synthesis and coordination chemistry

The new ligands dihydrobis[3-(4-pyridyl)pyrazol-1-yl]borate [Bp(4py)]-, hydrotris[3-(4-pyridyl)pyrazol-1-yl]borate [Tp(4py)]-, tetrakis[3-(4-pyridyl)pyrazol-1-yl]borate [Tkp(4py)]-, dihydrobis[3-(3-pyridyl)pyrazol-1-yl]borate [Bp(3py)]-, hydrotris[3-(3-pyridyl)pyrazol-1-yl]borate [Tp(3py)]- and tetrakis[3-(3-pyridyl)pyrazol-1-yl]borate [Tkp(4py)]- are derivatives of the well known bis-, tris- and tetrakis-(pyrazolyl)borate cores, bearing 4-pyridyl or 3-pyridyl substituents attached to the pyrazolyl C3 positions. These pyridyl groups cannot chelate to the metal ions in the poly(pyrazolyl) cavity but are externally directed. Structural studies on a range of metal complexes show how, in many cases, coordination of these pendant pyridyl groups to the M(pyrazolyl)n core of an adjacent metal complex fragment results in formation of coordination oligomers or polymeric networks. [Tl(Bp(3py))], [Tl(Bp(4py))] and [Tl(Tp(4py))] form one-dimensional polymeric chains via coordination of one of their pendant pyridyl units to the Tl(I) centre of an adjacent complex fragment; in contrast, in [Tl(Tp(3py))] coordination of all three pendant pyridyl units to separate Tl(I) neighbours results in formation of a two-dimensional polymeric sheet. In [Tl(Tkp(3py))] and [Tl(Tkp(4py))] the Tl(I) is coordinated by two or three of the four pyrazolyl arms, respectively; bridging interactions of pendant 4-pyridyl groups with adjacent Tl(I) centres result in a two-dimensional sheet forming in each case. In Ag(Tkp(4py)) each Ag(I) ion is coordinated by two pyrazolyl rings, and two bridging pyridyl ligands from other complex units, resulting in a one-dimensional chain consisting of pairs of cross-linked zigzag chains. In contrast to these polymeric coordination networks, the structures of [Cu(Tp(4py))] and [(Tp(3py))Cd(CH3CO2)] are dimers, with a pendant pyridyl residue from the first metal centre attaching to a vacant coordination site on the second, and vice versa; these dimers are stabilised by pi-stacking interactions between sections of the two ligands. [Ni(Tp(3py))2] is monomeric, with an octahedral coordination geometry arising from two tris(pyrazolyl)borate chelates; the array of pendant 3-pyridyl groups is involved only in intramolecular hydrogen-bonding. [(Tp(4py))Re(CO)3] is also monomeric, with a facial arrangement of three pyrazolyl ligands and three carbonyls, with the pendant 4-pyridyl groups not further coordinated. [(Tp(2py))Re(CO)3], based on the related ligand hydrotris[3-(2-pyridyl)pyrazol-1-yl]borate, has a similar fac-(CO)3(pyrazolyl)3 coordination geometry.     

Self-assembly of two zinc complexes with flexible building block of 4-pyridylthioethylphosphonate

A new organophosphonate ligand containing sulfide group, 4-pyridylthioethylphosphonic acid hydrobromide (H₂pytep·HBr), is synthesized through a facile route. Two zinc complexes of Zn₂(pytepH₂)₂Br₄ (1) and [Zn(pytep)]·H₂O (2) are obtained by reacting H₂pytep·HBr with zinc nitrate in solution and under hydrothermal condition, respectively. X-ray crystallographic studies reveal that 1 has a dinuclear structure in which the equivalent Zn atoms are doubly bridged by phosphonate groups. Compound 2 has a layer structure where ladder-like chains made up of corner-sharing {ZnNO₃} and {CPO₃} tetrahedra are linked by the organic groups of pytep. Photoluminescent properties are investigated. Different from complex 1 which shows no photoluminescence, complex 2 exhibits photoluminescence at 468 nm (λ_ex = 353 nm) in the solid state at room temperature.     

Self-assembly of supramolecular chiral insulated molecular wire

Supramolecular chiral insulated molecular wire was constructed by self-assembly of a neutral one-dimensional schizophyllan host and a water-soluble polythiophene guest. The work presented here will not only open a door to a new application of polysaccharides but also provide an important clue to prepare stable supramolecular insulated molecular wires with one-handed helical structure.     

Structure of a 4:1:4 supramolecular assembly of neutral TiiiiPO cavitands and tetrakis(N-methylpyridinium)porphyrin iodide

Four tetraphosphorylated TiiiiPO cavitands 1 encapsulate the pyridinium heads of a tetrakis(N-methylpyridinium)porphyrin iodide to form a 4:1:4 (host)4/guest4+/4I- complex. The single-crystal X-ray diffraction analysis shows the arrangement of the four cavities bound to the CH3N+ groups of the porphyrin moiety and the four iodide anions nested between the phenethyl substituents of the hosts. 1H NMR investigations show that the structure is preserved in chloroform solution and underscore the effect of the counteranions.     

Self-assembly of supramolecular complexes of cyanine dyes containing terminal ammonium groups with bis(18-crown-6)stilbene

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Bridged cyanine dyes. Part 3 . Zwitterionic bis-4-pyridyl and cationic bis-dimethylanilino derivatives

The preparation is described of two novel classes of bridged cyanines: zwitterionic bis-4-pyridyl and cationic bis-dimethylanilino and bis-methylcarbazolyl derivatives 5 and 11 . In these compounds an uneven number of carbon atoms of the methine chain forms part of a five- or six-membered ring. The visible absorption is discussed.     

镧系乙酰丙酮-5,10,15,20-四(4-吡啶基 )卟啉配合物

制备了乙酰丙酮-5,10,15,20-四(4-吡啶基)卟啉稀土配合物Ln(TPyP)acac[In:Dy,Ho,Yb,Lu;H~2TPyP:5,10,15,20-四(4-吡啶基)卟啉;Hacac:乙酰丙酮].配合物由一 个中心稀土离子,一个乙酰丙酮和一个四(4-吡啶基)卟啉组成,乙酰丙酮以氧双卤配位,卟啉以氮四卤配位,因此配合物有六配位的结构.