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1.
Chemistry ; 24(43): 11177-11184, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-29782690

RESUMO

Self-assembled monolayers formed by chemisorption of thiolated molecules on gold surfaces are widely applied for biosensing. Moreover, and due to the low stability of thiol-gold chemistry, contributions to the functionalisation of gold substrates with linkers that provide a more stable platform for the immobilisation of electroactive or biological molecules are highly appreciated. Herein, it is demonstrated that a carboxylated organotin compound can be successfully grafted onto gold substrates to form a highly stable organic layer with reactivity for subsequent binding to an aminated molecule. A battery of techniques were used to characterise the surface chemistry. The grafted layer was used to anchor aminoferrocene and subjected to both thermostability tests and long-term stability studies over a period of one year, demonstrating thermostability up to 90 °C and storage stability for at least 12 months at 4 °C protected from light. The stable surface tethering of molecules on gold substrates can be exploited in a plethora of applications, including molecular techniques, such as solid-phase amplification and solid-phase melting curve analysis, that require elevated temperature stability, as well as biosensors, which require long-term storage stability.

2.
Molecules ; 23(5)2018 04 24.
Artigo em Inglês | MEDLINE | ID: mdl-29695059

RESUMO

Molecular tweezers are artificial receptors that have an open cavity generated by two recognition units pre-organized by a spacer. Switchable molecular tweezers, using a stimuli-responsive spacer, are particularly appealing as prototypes of the molecular machines that combine mechanical motion and allosteric recognition properties. In this present study, the synthesis of switchable molecular tweezers composed of a central terpyridine unit substituted in 4,4″ positions by two Pt(II)-salphen complexes is reported. The terpyridine ligand can be reversibly converted upon Zn(II) coordination from a free 'U'-shaped closed form to a coordinated 'W' open form. This new substitution pattern enables a reverse control of the mechanical motion compared to the previously reported 6,6″ substituted terpyridine-based tweezers. Guest binding studies with aromatic guests showed an intercalation of coronene in the cavity created by the Pt-salphen moieties in the closed conformation. The formation of 1:1 host-guest complex was investigated by a combination of NMR studies and DFT calculations.


Assuntos
Modelos Moleculares , Conformação Molecular , Fenilenodiaminas/química , Fenilenodiaminas/síntese química , Análise Espectral
3.
J Am Chem Soc ; 139(27): 9213-9220, 2017 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-28605200

RESUMO

A six level molecular switch based on terpyridine(Ni-salphen)2 tweezers and addressable by three orthogonal stimuli (metal coordination, redox reaction, and guest binding) is reported. By a metal coordination stimulus, the tweezers can be mechanically switched from an open "W"-shaped conformation to a closed "U"-shaped form. Theses two states can each be reversibly oxidized by the redox stimulus and bind to a pyrazine guest resulting in four additional states. All six states are stable and accessible by the right combination of stimuli and were studied by NMR, XRD, EPR spectroscopy, and DFT calculations. The combination of the supramolecular concepts of mechanical motion and guest binding with the redox noninnocent and valence tautomerism properties of Ni-salphen complexes added two new dimensions to a mechanical switch.

4.
Chemistry ; 23(44): 10597-10603, 2017 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-28544266

RESUMO

Redox-labeled nucleotides are of increasing interest for the fabrication of next generation molecular tools and should meet requirements of being thermally stable, sensitive, and compatible with polymerase-mediated incorporation while also being electrochemically discriminable. The synthesis and characterization of Keggin and Dawson polyoxometalate-deoxynucleotide (POM-dNTP) bioconjugates linked through 7-deaza-modified purines is described. The modified POM-dNTPs were used for polymerase-based amplification of a DNA sequence specific for Yersinia pestis and the amplified DNA detected using an electrochemical DNA sensor. This highlights the potential of polyoxometalates as thermally stable, sensitive and polymerase-compatible redox labels for exploitation in bioanalytical applications.


Assuntos
DNA Bacteriano/química , Técnicas Eletroquímicas , Nucleotídeos/química , Compostos de Tungstênio/química , Yersinia pestis/genética , DNA Bacteriano/metabolismo , Eletrodos , Eletroforese em Gel de Campo Pulsado , Ouro/química , Reação em Cadeia da Polimerase , Yersinia pestis/isolamento & purificação
5.
Chemistry ; 21(46): 16512-6, 2015 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-26406341

RESUMO

Can achiral organocatalysts linked to chiral polyanionic metal oxide clusters provide good selectivity in enantioselective C-C bond formations? The answer to this question is investigated by developing a new active hybrid polyoxometalate-based catalyst for asymmetric Diels-Alder reaction. Chirality transfer from the chiral anionic polyoxometalate to the covalently linked achiral imidazolidinone allows Diels-Alder cycloaddition products to be obtained with good yields and high enantioselectivities when using cyclopentadiene and acrylaldehydes as partners.

6.
Chemistry ; 21(7): 2948-53, 2015 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-25524503

RESUMO

Amphiphilic organo-polyoxometalates (POMs) used in the radical emulsion polymerization of styrene allowed the preparation in aqueous medium of stable 50-100 nm polystyrene-POM composite latexes. Thanks to the presence of a trithiocarbonate group in the POM amphiphile, POMs could be covalently linked to the polymer particle surface. The chemical and catalytic integrity of the POMs was confirmed, and the POM-mediated surface photoactivity of the latexes was demonstrated by the spatially controlled nucleation of silver nanoparticles at the periphery of the composites.

7.
Chemistry ; 21(22): 8271-80, 2015 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-25900250

RESUMO

Four hybrid polyoxometalate-porphyrin copolymer films were obtained by the electrooxidation of zinc octaethylporphyrin in the presence of four different Dawson-type polyoxometalates bearing two pyridyl groups (POM(py)2) with various spacers. The POM monomers were designed around 1,3,5-trisubstituted benzene rings. Two of the substituents of the benzene ring are linked to the pyridyl groups, and the third is connected to the POM subunit. The four monomers vary in the relative positions of the nitrogen atoms of the pyridine rings or in the distance from the carbonyl group. The monomers were fully characterized by (1)H, (31)P, and (13)C NMR spectroscopy, electrospray mass spectrometry, IR and UV/Vis spectroscopy, and electrochemistry. The copolymers were characterized by UV/Vis spectroscopy, X-ray photoelectron spectroscopy, electrochemistry, and AFM. Their photovoltaic performance under visible light irradiation was investigated by photocurrent transient measurements under visible illumination.


Assuntos
Metaloporfirinas/química , Polímeros/química , Porfirinas/química , Compostos de Tungstênio/química , Eletricidade , Técnicas Eletroquímicas , Luz , Espectroscopia de Ressonância Magnética , Metaloporfirinas/síntese química , Modelos Moleculares , Espectroscopia Fotoeletrônica , Porfirinas/síntese química , Espectrofotometria Ultravioleta , Compostos de Tungstênio/síntese química
8.
Chemistry ; 21(49): 17721-7, 2015 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-26490074

RESUMO

The bioconjugation of polyoxometalates (POMs), which are inorganic metal oxido clusters, to DNA strands to obtain functional labeled DNA primers and their potential use in electrochemical detection have been investigated. Activated monooxoacylated polyoxotungstates [SiW11 O39 {Sn(CH2 )2 CO}](8-) and [P2 W17 O61 {Sn(CH2 )2 CO}](6-) have been used to link to a 5'-NH2 terminated 21-mer DNA forward primer through amide coupling. The functionalized primer was characterized by using a battery of techniques, including electrophoresis, mass spectrometry, as well as IR and Raman spectroscopy. The functionality of the POM-labeled primers was demonstrated through hybridization with a surface-immobilized probe. Finally, the labeled primers were successfully used in the polymerase chain reaction (PCR) and the PCR products were characterized by using electrophoresis.


Assuntos
Primers do DNA/química , DNA/química , Compostos de Tungstênio/química , DNA/metabolismo , Primers do DNA/metabolismo , Eletroquímica , Hibridização de Ácido Nucleico , Reação em Cadeia da Polimerase
9.
Chemistry ; 20(49): 16074-7, 2014 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-25345788

RESUMO

An α1 -Dawson polyanion bearing a lateral side chain with a 4-aminopyridine end group was synthesized. This organopolyoxometalate catalyzes the addition of indenyl allyl silanes to cinnamoyl fluorides. The polyanionic framework influences the organocatalyst activity and selectivity. A moderate but nonzero chirality transfer from the chiral inorganic framework to the organic substrate was observed.

10.
Chemistry ; 20(48): 15799-807, 2014 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-25286882

RESUMO

The design and synthesis of switchable molecular tweezers based on a luminescent terpy(Pt-salphen)2 (1; terpy=terpyridine) complex is reported. Upon metal coordination, the tweezers can switch from an open "W"-shaped conformation to a closed "U"-shaped form that is adapted for selective recognition of cations. Closing of the tweezers by metal coordination (M=Zn(2+), Cu(2+), Pb(2+), Fe(2+), Hg(2+)) was monitored by (1)H NMR and/or UV/Vis titrations. During the titration, exclusive formation of the 1:1 complex [M(1)] was observed, without appearance of an intermediate 1:2 complex [M(1)2]. The crystallographic structure of the 1:1 complex was obtained with Pb(2+) and showed a distorted helical structure. Selective intercalation of Hg(2+) cations by the closed "U" form was observed. The tweezers were reopened by selective metal decoordination of the terpyridine ligand by using tris(2-aminoethyl)amine (tren) as a competitive ligand without modification of the Pt-salphen complex. Detailed photophysical studies were performed on the open and closed tweezers. Structured emission was observed in the open form from the Pt-salphen moieties, with a high quantum yield and a long lifetime. The emission is slightly modified upon closing with 1 equivalent of Zn(2+) or Hg(2+), whereas a dramatic quenching was obtained upon intercalation of additional Hg(2+).

11.
Chemistry ; 20(35): 10915-20, 2014 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-25069825

RESUMO

Selectively functionalized cyclodextrins with a bodipy fluorescent tag or Gd(3+) complex were synthetized and threaded onto a polyammonium chain to form polyrotaxanes. This modular supramolecular assembly makes an ideal platform for bimodal (fluorescent and MRI) imaging applications.


Assuntos
Complexos de Coordenação/química , Ciclodextrinas/química , Corantes Fluorescentes/química , Corantes Fluorescentes/síntese química , Gadolínio/química , Rotaxanos/química , Espectroscopia de Ressonância Magnética , Modelos Moleculares
12.
Inorg Chem ; 53(19): 10039-41, 2014 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-25247489

RESUMO

A molecular triangle, based on the self-assembly of 4,7-phenanthroline by a neutral palladium complex, has been synthesized and characterized by a combination of techniques: (1)H NMR and UV-vis absorption spectroscopies, mass spectrometry, elemental analysis, and gel permeation chromatography. This new neutral metallocavitand has demonstrated the capacity to host both anionic and cationic guests, thus acting as an open-shaped heteroditopic receptor. Density functional theory calculations have shown that (i) there is no overtension in the assembly of the discrete triangle, which is more stable than open-chain oligomers, (ii) the adducts formed between the triangle and some salts (modeled in the gas phase) are thermodynamically stable, and (iii) two types of cavities coexist in the triangle, which host ions and ion pairs. This easily accessible triangular unit extends further the rational design of model nanoarchitectures in host-guest chemistry with applications in analytical chemistry and multifunctional molecular materials.

13.
Dalton Trans ; 53(30): 12477-12485, 2024 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-38894665

RESUMO

A series of cyclometalated (N^C^N) Pt(II)-platinum complexes featuring a terpyridine ligand with a non-coordinating nitrogen atom and a Pt-C bond was synthesized. In the presence of Ag+, the bis(isonitrile)Pt(II) complex formed a remarkable self-assembled helicoidal dimer stabilized by coordination of Ag(I) and metallophilic Pt-Ag interactions. Its assembly was observed in the solid state and maintained in solution. All complexes show strong luminescence and multiple emitting states, which could be rationalized based on solid state X-ray structures and coordinating environment.

14.
Chemistry ; 18(41): 12962-5, 2012 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-22945503

RESUMO

Grafting of a gold complex to an organo-polyoxometalate delivers catalytically active bitopic hybrids. The gold end activates allenes, while the metal-oxide surface can capture protons (see scheme). The scope of the gold-catalyzed oxacyclization of allenols is expanded to highly sensitive tertiary benzylic alcohols.

15.
Chemistry ; 18(11): 3355-61, 2012 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-22302472

RESUMO

We report the synthesis of the first organo-POM with thermoresponsive properties. Our concept will provide chemists with a new tool to design POMs whose solubility is reversibly controllable through an external stimulus. POM-polymer TBA(7)[POM]-poly(N,N-diethylacrylamide) (POM-PDEAAm), was prepared by grafting PDEAAm-NH(2) (obtained by RAFT polymerization) onto the activated Dawson acyl-POM, α(2)-[P(2)W(17)O(61)SnCH(2)CH(2)C(=O)](6-). Extensive MS analysis was used to monitor the chain-functionalization steps and to confirm the formation of the hybrid. Aqueous solutions of the (NH(4))(7)[POM-PDEAAm] exhibited a LCST of 38 °C. Thus, the solubility/aggregation of the hybrid was reversibly controlled by changing the temperature. Above 38 °C, the solution became cloudy, and cleared again upon cooling. Dynamic light scattering (DLS) revealed the formation of small aggregates in the range 100 nm. We assumed that the charged POM head units prevented the formation of the larger-scattering aggregates that are usually observed for PDEAAm, and promoted the formation of micelle-like structures. The conjugate exhibited a temperature transition, which was different from that of the polymer and depended on the counterions associated with the POM. This result demonstrates the potential for merging organic (in this case, polymer) and inorganic structures to afford materials that exhibit new properties.

16.
Chem Sci ; 13(8): 2218-2225, 2022 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-35310501

RESUMO

The encapsulation of guests in a confined space enables unusual conformations and reactivities. In particular, the compression of akyl chains has been obtained by self-assembled molecular capsules but such an effect has not been reported in solution for pseudorotaxane architectures. By exploiting the tendency of cyclodextrin (CD) to form head to head [3]pseudorotaxanes and the hydrogen bonding abilities of phosphate groups, we have studied the effect of the CD dimer cavity on the conformation of threaded α,ω-alkyl-diphosphate axles. The formation of [2]pseudorotaxanes and [3]pseudorotaxanes was investigated by a combination of NMR, ITC and X-ray diffraction techniques. In the solid state, the [3]pseudorotaxane with a C8 axle presents a fully extended conformation with both terminal phosphate groups interacting with hydroxyl groups of the primary rim of CDs. Such hydrogen bonding interactions are also present with the C9 and C10 axles resulting in a compression of the alkyl chain with gauche conformations in the solid state. NMR studies have shown that this effect is maintained in solution resulting in a size-dependent progressive compression of the alkyl chain by the CD [3]pseudorotaxane architecture for C9, C10 and C11 axles.

17.
Chemistry ; 17(50): 14129-38, 2011 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-22076707

RESUMO

The [ε-PMo(V)(8)Mo(VI)(4)O(36)(OH)(4){Ln(III)(H(2)O)}(4)](5+) (Ln=La, Ce, Nd, Sm) polyoxocations, called εLn(4), have been synthesized at room temperature as chloride salts soluble in water, MeOH, EtOH, and DMF. Rare-earth metals can be exchanged, and (31)P NMR spectroscopic studies have allowed a comparison of the affinity of the reduced {ε-PMo(12)} core, thus showing that the La(III) ions have the highest affinity and that rare earths heavier than Eu(III) do not react with the ε-Keggin polyoxometalate. DFT calculations provide a deeper insight into the geometries of the systems studied, thereby giving more accurate information on those compounds that suffer from disorder in crystalline form. It has also been confirmed by the hypothetical La→Gd substitution reaction energy that Ln ions beyond Eu cannot compete with La in coordinating the surface of the ε-Keggin molybdate. Two of these clusters (Ln=La, Ce) have been tested to evidence that such systems are representative of a new efficient Lewis acid catalyst family. This is the first time that the catalytic activity of polyoxocations has been evaluated.

18.
Inorg Chem ; 50(14): 6737-45, 2011 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-21661721

RESUMO

The rational design and synthesis of organic-inorganic hybrids as functional molecular materials relies on both the careful conception of building-blocks and the strategy for their assembly. Three families of trialkoxo polyoxometalates (Lindqvist 2, Anderson 3, Dawson 4) grafted with remote terpyridine coordination sites have been synthesized to extend the available building-blocks. These new units can be combined with metal complexes that play a role as (i) chromophores toward charge-separated systems in light-harvesting devices and (ii) coordination motifs for metal-directed self-assembly toward multifunctional molecular hybrid materials. The X-ray crystal structures of polyoxometalate-terpyridine hybrids indicate distances of 21 Å and 19 Å between the two terpyridyl coordination sites in 2 and 3, respectively, with angles between the coordination vectors of 180° and 177.4°, respectively. Lindqvist 2 displays a reduction at -0.52 V vs SCE while Anderson 3 exhibits one reversible oxidation attributed to Mn(III)/Mn(IV) (+0.75 V vs SCE) and a broad wave at -1.28 V vs SCE assigned to the Mn(III)/Mn(II) reduction. Dawson 4 displays several processes on a wide range of potentials (+0.5 to -2.0 V vs SCE) centered on V(V), W(VI) and the organic ligand in order of decreasing potentials. The grafted terpyridine ligands in Anderson 3 and Dawson 4 were successfully coordinated to {PdCl}(+) and {RuCl(3)} moieties, respectively. The polyoxometalates and transition metal complexes retain their intrinsic properties in the final assemblies.

19.
Org Lett ; 23(20): 7938-7942, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34582212

RESUMO

A family of cyclodextrins functionalized with zero, one, two, or six amines was shown to control the rate of their threading and dethreading on a molecular axle depending on the pH and their substitution pattern. The originality of this system lies in the rate control of the switch by operating the stimulus directly on the macrocycle.

20.
Chemistry ; 16(24): 7256-64, 2010 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-20455223

RESUMO

The preparation of new organosoluble Lewis acidic polyoxometalates (POMs) is reported. These complexes were prepared by the incorporation of Zr, Sc, and Y atoms into the corresponding monolacunary Dawson [P(2)W(17)O(61)](10-) and Keggin [PW(11)O(39)](7-) polyoxotungstates. The catalytic activity of these compounds was evaluated for C-C bond formation in the Diels-Alder, Mannich, and Mukaiyama-type reactions. Comparisons with previously described Lewis acidic POMs are reported. Competitive reactions between imines and aldehydes or between various imines demonstrated that fine tuning of the reactivity could be reached by varying the metal atom incorporated into the polyanionic framework. A series of experiments that employed pyridine derivatives allowed us to distinguish between the Lewis and induced Brønsted acidity of the POMs. These catalysts activate imines in a Lewis acidic way, whereas aldehydes are activated by indirect Brønsted catalysis.

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