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1.
Chempluschem ; 85(4): 659-671, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32237220

RESUMO

The synthesis and characterization of the two new open-chain ligands 1,15-bis-[6-(2,2'-bipyridyl)]-2,5,8,11,14-pentaaza-octadecane (L1) and 1,15-bis-[2-(1,10-phenanthroline)-9-methyl]-2,5,8,11,14-pentaazaoctadecane (L2), both featuring a tetraethylenpentaamine chain linking via methylene bridges the 6 and 2 positions of two identical 2,2'-bipyridyl (bpy) and 9-methyl-1,10-phenanthroline (9-methyl-phen) moieties respectively, are reported. Their protonation and binding ability for Cu2+ , Zn2+ , Cd2+ and Pb2+ have been studied by coupling potentiometric titrations with UV-vis absorption and fluorescence emission measurements in water. L1 and L2 afford stable mono- and dinuclear complexes, in which the metal ion is bound by a single bpy or 9-methyl-phen unit and the amine groups on the aliphatic chain. However, L1 displays a greater binding ability for Cu2+ and Zn2+ with respect to L2, the stability constants of the [ML1]2+ complexes being 21.8 (Cu2+ ) and 19.4 (Zn2+ ) log units vs 20.34 and 16.8 log. units for the corresponding L2 species. Among all the metal ions tested, only the Zn2+ complex with L2 features an enhanced fluorescence emission at neutral pH, thanks to the simultaneous binding of one Zn2+ ion and H+ ion(s), that inhibits any possible photoinduced electron transfer (PET) process from the amine donors to the excited phen moiety. Binding of a second metal switches off the emission again.

2.
Curr Med Chem ; 26(21): 4065-4097, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-29493442

RESUMO

Pseudopeptides are privileged synthetic molecules built from the designed combination of peptide-like and abiotic artificial moieties. Consequently, they are benefited from the advantages of both families of chemical structures: modular synthesis, chemical and functional diversity, tailored three-dimensional structure, usually high stability in biological media and low non-specific toxicity. Accordingly, in the last years, these compounds have been used for different biomedical applications, ranging from bio-sensing, ion transport, the molecular recognition of biologically relevant species, drug delivery or gene transfection. This review highlights a selection of the most remarkable and recent advances in this field.


Assuntos
Pesquisa Biomédica , Peptídeos/química , Peptídeos/metabolismo , Técnicas Biossensoriais , Corantes Fluorescentes/química , Corantes Fluorescentes/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Transporte de Íons , Estrutura Molecular
3.
Chem Commun (Camb) ; 52(52): 8142-5, 2016 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-27271350

RESUMO

Here we report two new artificial pseudopeptidic cages that bind the EYE peptide epitope in pure water at physiological pH (as studied by fluorescence and NMR spectroscopies). The supramolecular complexation of the Tyr residues efficiently precludes their subsequent PTK-catalysed phosphorylation. Our results show a supramolecular modulation of the PTK activity by competitive substrate caging.


Assuntos
Peptídeos/metabolismo , Proteínas Tirosina Quinases/metabolismo , Tirosina/metabolismo , Biocatálise , Substâncias Macromoleculares/química , Substâncias Macromoleculares/metabolismo , Conformação Molecular , Peptídeos/química , Fosforilação , Proteínas Tirosina Quinases/química , Tirosina/química
4.
Org Biomol Chem ; 13(48): 11721-31, 2015 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-26481115

RESUMO

Pseudopeptidic molecular cages are appealing receptors since they can display different polar and non-polar interaction sites in a modular framework and a controlled disposition. Inspired by previous host-guest knowledge, two pseudopeptidic molecular cages based on serine and threonine (CySer and CyThr, respectively) were designed and synthesized as hosts for the binding of the four possible stereoisomers of the Ac-Glu-Tyr-OH dipeptide, a target sequence of tyrosine kinases. The careful NMR titration experiments in aqueous acetonitrile allowed the determination of the binding constants and reflected a difference in the stability of the corresponding diastereomeric host-guest complexes. The CySer cage proved to be slightly more efficient than the CyThr counterpart, although both showed similar stereoselectivity trends: LL > DD ≥ LD > DL. This stereoselective binding was retained in the gas phase, as shown by ESI-MS competition experiments using the enantiomer-labelled method (EL), as well as CID experiments. Thus, the MS-determined discriminations follow the same trends observed by NMR, suggesting that the stereoselectivity observed for these systems must be mainly dictated by the polar host-guest interactions. Despite the stereoselective binding of short peptide sequences in competitive media being a challenging issue in supramolecular chemistry, our results demonstrate the power of pseudopeptidic cages in molecular recognition with foreseen implications in chemical biology.


Assuntos
Dipeptídeos/química , Dipeptídeos/metabolismo , Glutamina/química , Modelos Biológicos , Tirosina/química , Amidas/química , Cicloexanos/química , Estrutura Molecular , Serina/química , Estereoisomerismo , Treonina/química
5.
Dalton Trans ; 44(28): 12700-10, 2015 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-26085383

RESUMO

Mono- and dinuclear Cu(ii) complexes were prepared with pseudopeptidic open chain and macrocyclic ligands, respectively. They were characterized by UV-vis spectroscopy, EPR, HRMS and X-ray diffraction. The Cu(ii) cation is coordinated by two amines and two deprotonated amides, in a slightly distorted square planar coordination geometry. The complexes interact with several substituted dicarboxylates, as shown by UV-vis titrations and EPR experiments. The interaction of both mono- and dinuclear complexes with very similar dicarboxylates of biological interest (malate and aspartate) resulted in strikingly different outcomes: in the first case a ternary complex [ligand...metal...dicarboxylate] was obtained almost quantitatively, while in the latter, the Cu(ii) displacement to form Cu(Asp)2 was predominant.


Assuntos
Ácido Aspártico/química , Complexos de Coordenação/química , Cobre/química , Malatos/química , Ligantes , Espectrofotometria Ultravioleta , Difração de Raios X
6.
J Org Chem ; 79(19): 9141-9, 2014 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-25184384

RESUMO

A family of simple receptors formed by two or three cationic imidazolium arms attached to a central aromatic linkage and displaying different conformational flexibility has been synthesized from the enantiopure (1S,2S)-2-(1-H-imidazol-1-yl)-cyclohexanol. The crystal structures of the corresponding bromides of two of the hosts showed remarkable differences. The tripodal receptor with a trimethylated central benzene ring (1a) showed a cone-type conformation defining an inner anion-binding site, while the bipodal molecule with the central meta-phenylene spacer (m-2a) displayed an extended conformation. The binding properties of the chiral imidazolium hosts toward citrate, isocitrate and the two enantiomers of malate have been studied by (1)H NMR titration experiments in 9:1 CD3CN:CD3OH at 298.15 K. Interestingly, 1a showed a stronger interaction with dianionic malate than with the trianionic citrate or isocitrate, suggesting that the smaller guest is better accommodated in the host cavity. Among this family, 1a proved to be the best receptor due to a combination of a larger number of electrostatic and H-bonding interactions and to a more efficient preorganization in the cone-type conformation. This preorganization effect is also present in solution as confirmed by (1)H NMR spectroscopy.


Assuntos
Citratos/química , Cicloexanóis/química , Malatos/química , Sítios de Ligação , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Conformação Molecular
7.
J Org Chem ; 79(10): 4590-601, 2014 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-24749998

RESUMO

The molecular recognition of short peptides is a challenge in supramolecular chemistry, and the use of peptide-like cage receptors represents a promising approach. Here we report the synthesis and characterization of a diverse family of pseudopeptidic macrobicycles, as well as their binding abilities toward N-protected dipeptides using a combination of different techniques (NMR, ESI-MS, and fluorescence spectroscopy). The cage hosts were assayed for dipeptide binding using competition ESI-MS experiments as high-throughput screening to obtain general trends for the recognition phenomena. Selected hosts were additionally studied by NMR spectroscopy ((1)H NMR titration and diffusion-ordered spectroscopy experiments) in different solvents. The results unambiguously demonstrated the formation of the [cage·dipeptide] supramolecular complexes and rendered quantitative information about the strength of the interaction (K(ass)). The structural variables within the pseudopeptidic cage framework that produced a stronger and more selective recognition were thus identified. The cages showed a remarkable selectivity for N-protected dipeptides with an aromatic amino acid at the carboxylic terminus, which prompted us to propose a mode of binding based on polar and nonpolar noncovalent interactions. Accordingly, we faced the molecular recognition of a target dipeptide (Ac-EY-OH) mimicking a biologically relevant sequence by NMR and fluorescence spectroscopy in highly competitive media.


Assuntos
Aminoácidos/química , Dipeptídeos/síntese química , Iminas/química , Compostos Macrocíclicos/química , Dipeptídeos/química , Espectroscopia de Ressonância Magnética , Espectrometria de Fluorescência , Espectrometria de Massas por Ionização por Electrospray , Difração de Raios X
8.
J Org Chem ; 78(16): 8169-75, 2013 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-23859634

RESUMO

Direct dehydrogenative coupling between the linear ter- and quaternaphthalenes and substituted benzenes was achieved under the Kita conditions using the hypervalent PIFA/BF3 reagent. Products resulting from either the double arylation of the naphthalenic substrate or the formal dimerizative arylation have been prepared. For example, in the latter mode, ternaphthalene was converted into a series of linear octiarenes (counting the capping Ar). The process represents an alternative to the cross-coupling methodologies employed in related syntheses and proceeds via a selective functionalization of six relatively inert aromatic CH bonds.


Assuntos
Boranos/química , Iodobenzenos/química , Naftalenos/química , Naftalenos/síntese química , Ácido Trifluoracético/química , Benzeno/química , Estrutura Molecular
9.
J Am Chem Soc ; 132(51): 17980-2, 2010 Dec 29.
Artigo em Inglês | MEDLINE | ID: mdl-21128625

RESUMO

Direct oxidative Kita-type coupling between naphthalene and substituted benzenes was found to proceed via four-component coupling, leading to a linear tetraarene with a binaphthalene core. The methodology was extendable to the coupling of unfunctionalized 1,1'-binaphthalene with mesitylene to give a linear hexaarene product in a remarkably chemoselective manner in 87% yield. The method represents an attractive alternative to the traditional syntheses of related oligonaphthalene products via a sequence of metal-catalyzed cross-coupling steps.

10.
Dalton Trans ; 39(42): 10128-36, 2010 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-20922246

RESUMO

The new macrocyclic ligand 1,9(4,7)-diphenanthroline-3,7,11,15-tetraazacyclohexadecaphane (L) was synthesized by a 2 : 2 reaction of 1,10-phenanthroline-4,7-dialdehyde with 1,3-diaminopropane, followed by reduction with NaBH(4). L contains two phenanthroline groups linked together by two 1,3-diaminopropane chains in such a way that the heteroaromatic nitrogen atoms point outside the ligand cavity. The ligand structure defines two pairs of identical compartments displaying a specific ability in the binding of protons (1,3-diaminopropane) and metal ions (phenanthroline). Protonation and Zn(II) coordination were studied by means of potentiometric and spectroscopic ((1)H NMR, UV-vis, fluorescence) techniques. Both protonation and Zn(II) coordination consistently affect the fluorescence emission properties of L, giving rise to enhancement or quenching of the emission, depending on the species involved. L becomes emissive upon protonation, but the formation of the highly protonated species, in particular the fully protonated [H(6)L](6+), quenches the emission. The mono- and dinuclear Zn(II) complexes of the unprotonated ligand are non-emissive, like free L, while Zn(II) binding to [HL](+) activates the emission. The most interesting aspect, however, is the chelation enhancement of quenching (CHEQ) observed upon Zn(II) binding to [H(2)L](2+) and [H(4)L](4+), being among the few examples of CHEQ effect observed for Zn(II) complexes. Hydrogen bonding between a metal coordinated water molecule and a phenanthroline group seems to be responsible for the CHEQ observed for [ZnH(2)L](4+).


Assuntos
Corantes Fluorescentes/química , Compostos Macrocíclicos/química , Fenantrolinas/química , Prótons , Zinco/química , Diaminas/química , Concentração de Íons de Hidrogênio , Ligantes , Modelos Moleculares , Conformação Molecular , Fenômenos Ópticos , Compostos Organometálicos/química
11.
Dalton Trans ; 39(30): 7080-90, 2010 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-20532303

RESUMO

Proton and Cu(II), Zn(II), Cd(II) and Pb(II) binding by ligand H(2)L, containing two bis(aminoethyl)amine (dien) units connected by a 2',7'-dichlorofluorescein (DCF) unit has been analyzed by means of potentiometric, UV-vis and fluorescence emission measurements. Considering proton binding, the ligand in its fully deprotonated form, L(2-), binds up to four acidic protons in the alkaline pH region. These protonation steps occur on the amine groups, whereas protonation of DCF takes place only below pH 4. In metal complexation, the ligand displays a marked selectivity for Zn(II) over Cd(II) and Pb(II), due to the better accommodation of the smaller and harder Zn(II) ion within the binding pocket generated by a dien unit and the adjacent deprotonated oxygen. The fluorescence emission study points out that Zn(II) binding is accompanied by a marked increase of the DCF emission from neutral to slightly alkaline pH values, where protonated forms of the complex are present in solution. The system is weakly emissive at slightly acidic pH values, where Zn(II) is essentially not bound to the receptor and above pH 9.5, probably due to the formation of the not protonated [ZnL] complex. Cd(II) binding gives rise to a much less intense increase of the emission only above pH 8.5, whereas Cu(II) and Pb(II) complexation leads to fluorescence quenching. Furthermore, the interaction of H(2)L with cells was investigated to explore its application as a new sensor for the evaluation of cellular Zn(II) content and distribution.


Assuntos
Compostos Organometálicos/química , Zinco/química , Aminas/química , Cádmio/química , Células Cultivadas , Cobre/química , Eletrodos , Fluoresceínas/química , Células HL-60 , Humanos , Concentração de Íons de Hidrogênio , Chumbo/química , Ligantes , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/síntese química , Compostos Organometálicos/farmacocinética , Potenciometria , Distribuição Tecidual
12.
J Org Chem ; 74(19): 7349-63, 2009 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-19743804

RESUMO

The synthesis of receptor 2,6,10,14,18-pentaaza[20]-21,34-phenanthrolinophane (L1), containing a pentaamine chain linking the 2,9 positions of a phenanthroline unit, is reported. The protonation features of L1 and of receptor 2,6,10,14,18,22-hexaaza[23]-24,37-phenanthrolinophane (L2) have been studied by means of potentiometric, (1)H NMR, and spectrofluorimetric measurements; this study points out that the fluorescent emission of both receptors depends on the protonation state of the polyamine chain. In fact, the receptors are emissive only at neutral or acidic pH values, where all the aliphatic amine groups are protonated. Potentiometric titrations show that L2 is able to bind selectively ATP over TTP, CTP, and GTP. This selectivity is lost in the case of L1. (1)H and (31)P NMR measurements and molecular mechanics calculations show that the phosphate chains of nucleotides give strong electrostatic and hydrogen-bonding interactions with the ammonium groups of the protonated receptors, while the nucleobases interact either via pi-stacking with phenanthroline or via hydrogen bonding with the ammonium groups. Of note, MM calculations suggest that all nucleotides interact in an inclusive fashion. In fact, in all adducts the phosphate chain is enclosed within the receptor cavities. This structural feature is confirmed by the crystal structure of the [(H(6)L2)(2)(TTP)(2)(H(2)O)(2)](4+) adduct. Fluorescence emission measurements at different pH values show that L2 is also able to ratiometrically sense ATP in a narrow pH range, thanks to emission quenching due to a photoinduced electron transfer (PET) process from an amine group of the receptor to the excited phenanthroline.


Assuntos
Corantes Fluorescentes/química , Nucleotídeos/química , Fenantrolinas/química , Compostos de Amônio Quaternário/química , Ânions/química , Sítios de Ligação , Ligação de Hidrogênio , Fenantrolinas/síntese química , Compostos de Amônio Quaternário/síntese química , Eletricidade Estática
13.
Chemistry ; 15(32): 8049-8063, 2009 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-19504514

RESUMO

The synthesis of the macrocyclic receptor L1, which contains a tetraamine chain linking the 6,6'-positions of a 2,2'-dipyridine moiety, is reported. Its basicity properties and complexation features toward Cu(II), Zn(II), Cd(II) and Pb(II) have been studied in aqueous solutions by means of potentiometric, UV/Vis spectroscopy and fluorescence emission measurements and compared with those of ligand L2, in which a 1,10-phenanthroline moiety replaces the dipyridine unit of L1. In metal coordination, L1 shows a marked selectivity toward Cd(II) over Zn(II) and Pb(II). The crystal structures of its metal complexes shows that L1 possesses a preferential tetradentate binding site for metal cations, composed of the dipyridine unit and the two adjacent benzylic amine groups. This binding site has the proper dimension and conformation to selectively coordinate the Cd(II) ion, as confirmed by DFT calculations carried out on the complexes. This coordinative zone is lost in L2. The rigidity of phenanthroline does not allow the simultaneous binding of both the benzylic amine groups to Zn(II) and Cd(II) and, in fact, one benzylic amine is not coordinated to these metal cations. The fluorescence emission properties of the L1 and L2 complexes are strongly pH dependent. Only the Zn(II) and Cd(II) complexes with L1 display fluorescence emission at neutral pH. This feature is related to the formation in solution at pH 7 of emissive protonated complexes of the type [M(H(x)L)]((2+x)+) (x=1-3), in which all the nitrogen donors are involved in metal or proton binding. The emissive characteristics of these protonated complexes are confirmed by the fluorescence emission spectra collected on the [Zn(HL1)Br][ClO(4)](2) and [Cd(HL1)Br][ClO(4)](2) solid compounds dissolved in CH(3)CN. Conversely, the Zn(II) and Cd(II) complexes with L2 are not emissive; in fact, they contain a benzylic amine group not involved in metal or proton binding that can quench the fluorescence emission of the fluorophore, thanks to a photoinduced electron-transfer process.


Assuntos
Cádmio/química , Cobre/química , Corantes Fluorescentes/síntese química , Chumbo/química , Fenantrolinas/química , Poliaminas/química , Zinco/química , 2,2'-Dipiridil/análogos & derivados , 2,2'-Dipiridil/química , Fluorescência , Corantes Fluorescentes/química , Estrutura Molecular
14.
Dalton Trans ; (7): 1223-30, 2009 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-19322495

RESUMO

The synthesis and characterisation of a new macrocyclic compound (L), composed of a pentamine chain linking the 2,7 positions of an acridine moiety, is reported. Cu(ii) complexation was studied by means of potentiometric, UV-vis and EPR measurements in aqueous solutions. This study reveals that the ligand forms a stable tetranuclear complex with an overall [Cu(4)L(2)(OH)(4)](4+) stoichiometry in aqueous solution. The crystal structure of the [Cu(8)L(4)(micro-OH)(8)(micro-NO(3))(3)](NO(3))(5).32H(2)O complex, isolated from neutral aqueous solution, shows that it is formed by tetranuclear clusters [Cu(4)L(2)(micro-OH)(4)(micro-NO(3))(x)]((4-x)+) (x= 1 or 2), composed of two [Cu(2)L](4+) macrocyclic units linked together by four bridging hydroxide and nitrate anions to give an overall metallomacrocyclic structure. Magnetic measurements shows that the hydroxide-bridged Cu(ii) ions are ferromagnatically coupled. Inspection of the crystal packing shows that couples of metallomacrocycles are paired by pi-stacking interactions between acridine moieties, giving rise to an internal hydrophilic cavity were hexameric or pentameric water clusters are enclosed. The coupled metallomacrocycles assume a columnar disposition growing along the a axis, giving rise to channels passing through the cavities of the metallomacrocycles; these channels are filled by chains of 5- or 6-membered water clusters linked together by [NO(3).H(2)O](2) units.

15.
Chemistry ; 15(7): 1627-36, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19123216

RESUMO

Total synthesis of naturally occurring casuarine (1) and the first total synthesis of casuarine 6-O-alpha-glucoside (2) were achieved through complete stereoselective nitrone cycloaddition, Tamao-Fleming oxidation and selective alpha-glucosylation as key steps. Biological assays of the two compounds proved their strong and selective inhibitory properties towards glucoamylase NtMGAM and trehalase Tre37A, respectively, which place them among the most powerful inhibitors of these enzymes. The structural determination of the complexes of NtMGAM with 1 and of Tre37A with 2 revealed interesting similarities in the catalytic sites of these two enzymes which belong to different families and clans.


Assuntos
Alcaloides/síntese química , Alcaloides/metabolismo , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/metabolismo , Glucosídeos/síntese química , Glucosídeos/metabolismo , Glicosídeo Hidrolases/metabolismo , Pirróis/síntese química , Pirróis/metabolismo , Domínio Catalítico , Glucana 1,4-alfa-Glucosidase/metabolismo , Ligação de Hidrogênio , Cinética , Trealase/metabolismo
17.
Chem Commun (Camb) ; (12): 1230-2, 2007 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-17356765

RESUMO

A dizinc complex with a polyamine macrocycle is able to selectively bind and sense uridine (U) as well as the uridine-containing ribodinucleotides U(3'-5')pU and U(3'-5')pA, thanks to an exciplex emission arising from a pi-stacked complex involving the dipyridine unit and Zn(II)-bound uridine moieties.


Assuntos
Fluorescência , Nucleotídeos/química , Uridina/química , Zinco/química , Concentração de Íons de Hidrogênio
18.
19.
Dalton Trans ; (11): 1409-18, 2006 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-16518510

RESUMO

The synthesis and characterisation of a new bis([9]aneN3) ligand (L4) containing two [9]aneN3 macrocyclic moieties separated by a 2,6-dimethylenepyridine unit is reported. A potentiometric and 1H NMR study in aqueous solution reveals that ligand protonation occurs on the secondary amine groups and does not involve the pyridine nitrogen. The coordination properties toward Cu(II), Zn(II), Cd(II) and Pb(II) were studied by means of potentiometric and UV spectrophotometric measurements. The ligand can form mono- and binuclear complexes in aqueous solution. In the 1 : 1 complexes, the metal is sandwiched between the two [9]aneN3 moieties and the pyridine N-donor is coordinated to the metal, as actually shown by the crystal structure of the compound [ZnL4](NO3)2.CH3NO2. L4 shows a higher binding ability for Cd(II) with respect to Zn(II), probably due to a better fitting of Cd(II) ion inside the cavity generated by the two facing [9]aneN3 units. The formation of binuclear complexes is accompanied by the assembly of OH-bridged M2(OH)x (x = 1-3) clusters inside the cavity defined by the two facing [9]aneN3 units, and pyridine is not involved in metal coordination. A potentiometric and (1)H NMR study on the coordination of halogenide anions by L4 and its structural analogous L3 in which the two [9]aneN3 units are separated by a shorter quinoxaline linkage, shows that bromide is selectively recognised by L4, while chloride is selectively bound by L3. Such a behaviour is discussed in terms of dimensional matching between the spherical anions and the cavities generated by the two [9]aneN3 units of the receptors.

20.
Dalton Trans ; (18): 2994-3004, 2005 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-16127493

RESUMO

The coordination chemistry of the N-aminopropyl pendant arm derivatives (L1c-4c) of the mixed donor macrocyclic ligands [12]aneNS2O, [12]aneNS3, [12]aneN2SO, and [15]aneNS2O2(L1a-4a) towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) in aqueous solution has been investigated. The protonation and stability constants with the aforementioned metal ions were determined potentiometrically and compared, where possible, with those of the unfunctionalised macrocycles. The measured values show that Hg(II) and Cu(II) in water have the highest affinity for all ligands considered, with the N-aminopropyl pendant arm weakly coordinating the metal centres. Crystals suitable for X-ray diffraction analysis were grown for the perchlorate salt (H2L1c)(ClO4)2.dmf, and for the 1 : 1 complexes [Cd(L3a)(NO3)2](1), [Cu(L4a)dmf](ClO4)2(2), [Zn(L1c)(ClO4)]ClO4(3), [Cd(L1c)(NO3)]NO3(4), and [Hg(L2c)](ClO4)2(5). Their structures show the macrocyclic ligands adopting a folded conformation, which for the 12-membered systems can be either [2424] or [3333] depending on the nature of the metal ion. L1c-4c were also functionalised at the primary amino pendant group with different fluorogenic subunits. In particular the N-dansylamidopropyl (Lnd, n= 1-4), and the N-(9-anthracenylmethyl)aminopropyl (Lne, n= 1, 2, 4, ) pendant arm derivatives of L1a-4a were synthesised and their optical responses to the above mentioned metal ions were investigated in MeCN/H2O (4 : 1 v/v) solutions.


Assuntos
Corantes Fluorescentes/química , Compostos Macrocíclicos/química , Metais Pesados/química , Compostos Organometálicos/química , Cristalografia por Raios X , Concentração de Íons de Hidrogênio , Modelos Moleculares , Estrutura Molecular
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