Two polyaminophenolic fluorescent chemosensors for H<sup>+</sup>and Zn(<scp>ii</scp>). Spectroscopic behaviour of free ligands and of their dinuclear Zn(<scp>ii</scp>) complexes

Ambrosi, Gianluca; Battelli, Cristina; Formica, Mauro; Fusi, Vieri; Giorgi, Luca; Macedi, Eleonora; Micheloni, Mauro; Pontellini, Roberto; Prodi, Luca

doi:10.1039/b810228g

Cited by 21 publications

(32 citation statements)

References 47 publications

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“…The development of ‘conjugated’ chemosensors, e. g., molecules composed by a binding moiety, linked to a signalling unit by a spacer represents one of the most common approach to achieve effective molecular tools to detect metal cations. In particular, the structural features of the binding unit, the spacer and the typology of the fluorophore residue are key factors that can be finely tuned to obtain highly selective chemosensors towards specific metal cations …”

Section: Introductionmentioning

confidence: 99%

Switching on the Fluorescence Emission of Polypyridine Ligands by Simultaneous Zinc(II) Binding and Protonation

et al. 2020

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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-1,10phenanthroline (9-methyl-phen) moieties respectively, are reported. Their protonation and binding ability for Cu 2 + , Zn 2 + , Cd 2 + and Pb 2 + 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 Cu 2 + and Zn 2 + with respect to L2, the stability constants of the [ML1] 2 + complexes being 21.8 (Cu 2 + ) and 19.4 (Zn 2 + ) log units vs 20.34 and 16.8 log. units for the corresponding L2 species. Among all the metal ions tested, only the Zn 2 + complex with L2 features an enhanced fluorescence emission at neutral pH, thanks to the simultaneous binding of one Zn 2 + 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.[a] Dr.by the structural characteristics of the ligand and its Zn 2 + complexes, including the number and disposition of amine donors, the overall rigidity of the molecular backbone, and, in the case of macrocyclic ligands, the dimension of the cavity. In these complexes, the heteroaromatic nitrogens are unequivocally coordinated to the metal cations. However, the stiffening of the macrocyclic structure imposed by the heteroaromatic moieties may not allow the simultaneous coordination to the metal cations of all the nitrogen donors of the binding unit. Interestingly enough, the 'benzylic' amine groups, close to the heteroaromatic unit, are not coordinated, or weakly coordinated, to the metal cation. Therefore, their lone pairs are able to quench the fluorophore excited state thanks to a photoinduced electron transfer (PET) process. As a consequence, normally fluorescent Zn 2 + complexes result to be scarcely emissive. [8a,b,22-24] In this paper, we extend this study to two open-chain ligands, L1 and L2 in Scheme 1, containing a pentaamine aliphatic chain linked at its extremities to two equal 2,2'bipyridyl (bpy) or 9-methyl-1,10-phenanthroline (9-methylphen) moieties, respectively. Our purpose is the analysis of the effects on both metal binding and sensing of the presence of two fluorogenic units linked by a flexible chain.Therefore, complex stability and fluorescence emission in the presence of metal cations will be compared to those of the previously reported ligands L3 [24] and L4 [8a] (Scheme 1), which contain the same aliphatic pentaamine chain linking the 6,6' and 2,9 positions of a single...

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Section: Introductionmentioning

confidence: 99%

Switching on the Fluorescence Emission of Polypyridine Ligands by Simultaneous Zinc(II) Binding and Protonation

et al. 2020

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“…Macrocycles constitute an expanding class of natural and synthetic members with unlimited potentials (Gokel, 1992;Dietrich et al, 1993;Bö hmer, 1995;Ambrosi, Battelli et al, 2009;Ambrosi et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Synthesis, crystallization, X-ray structural characterization and solid-state assembly of a cyclic hexapeptoid with propargyl and methoxyethyl side chains

Tedesco

Macedi

Meli

et al. 2017

Acta Crystallogr Sect B

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The synthesis and the structural characterization of a cyclic hexapeptoid with four methoxyethyl and two propargyl side chains have disclosed the presence of a hydrate crystal form [form (I)] and an anhydrous crystal form [form (II)]. The relative amounts of form (I) and form (II) in the as-purified product were determined by Rietveld refinement and depend on the purification procedures. In crystal form (I), peptoid molecules assemble in a columnar arrangement by means of side-chain-to-backbone C=CH...OC hydrogen bonds. In the anhydrous crystal form (II), cyclopeptoid molecules form ribbons by means of backbone-to-backbone CH...OC hydrogen bonds, thus mimicking β-sheet secondary structures in proteins. In both crystal forms side chains act as joints among the columns or the ribbons and contribute to the stability of the whole solid-state assembly. Water molecules in the hydrate crystal form (I) bridge columns of cyclic peptoid molecules, providing a more efficient packing.

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“…These form mono and dinuclear complexes in which phenol or biphenol fragments play a fundamental role in both the stabilization of the metal ion and the photochemical response. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Phenol and polyphenols have well known optical properties which mainly depend on their protonation degree. [28][29][30][31] In this study, we want to extend our knowledge of the spectroscopic properties of a ligand containing two 2,2'-biphenol moieties (BPH) that are linked to the ethylenediamine scaffold (L in Chart 1).…”

Section: Introductionmentioning

confidence: 99%

A Biphenol-Based Chemosensor for Zn^II and Cd^II Metal Ions: Synthesis, Potentiometric Studies, and Crystal Structures

et al. 2016

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We synthesized and characterized the ligand N,N'-bis[(2,2'-dihydroxybiphen-3-yl)methyl]-N,N'-dimethylethylenediamine (L), which contains two biphenol moieties linked as side arms to an N,N'-dimethylethylenediamine scaffold. The ligand is highly soluble in a 50/50 (v/v) water/ethanol mixture and, in its deprotonated form H-2L(2-), is able to coordinate transition-metal ions such as Ni(II), Zn(II), Cu(II), Cd(II), and Pd(II). The crystal structures of [Ni(H-2L)·2n-BuOH], [Ni(H-2L)·2MeOH], [Cd(H-2L)·2DMF], [Cu(H-2L)(DMF)], and [Pd(H-2L)(DMF)] were also determined and described. Potentiometric titrations were carried out in a mixed solvent with Zn(II), Cu(II), and Ni(II) metal ions to determine the acid-base and stability constants. L was highly fluorescent in the visible range (400 nm). Moreover, its emission intensity increased upon the addition of Zn(II) or Cd(II) ions in an ethanol/water solution and behaved as a chemosensor for the presence of these ions in the solution.

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Two polyaminophenolic fluorescent chemosensors for H⁺and Zn(ii). Spectroscopic behaviour of free ligands and of their dinuclear Zn(ii) complexes

Cited by 21 publications

References 47 publications

Switching on the Fluorescence Emission of Polypyridine Ligands by Simultaneous Zinc(II) Binding and Protonation

Switching on the Fluorescence Emission of Polypyridine Ligands by Simultaneous Zinc(II) Binding and Protonation

Synthesis, crystallization, X-ray structural characterization and solid-state assembly of a cyclic hexapeptoid with propargyl and methoxyethyl side chains

A Biphenol-Based Chemosensor for Zn^II and Cd^II Metal Ions: Synthesis, Potentiometric Studies, and Crystal Structures

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Two polyaminophenolic fluorescent chemosensors for H+and Zn(ii). Spectroscopic behaviour of free ligands and of their dinuclear Zn(ii) complexes

Cited by 21 publications

References 47 publications

Switching on the Fluorescence Emission of Polypyridine Ligands by Simultaneous Zinc(II) Binding and Protonation

Switching on the Fluorescence Emission of Polypyridine Ligands by Simultaneous Zinc(II) Binding and Protonation

Synthesis, crystallization, X-ray structural characterization and solid-state assembly of a cyclic hexapeptoid with propargyl and methoxyethyl side chains

A Biphenol-Based Chemosensor for ZnII and CdII Metal Ions: Synthesis, Potentiometric Studies, and Crystal Structures

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Two polyaminophenolic fluorescent chemosensors for H⁺and Zn(ii). Spectroscopic behaviour of free ligands and of their dinuclear Zn(ii) complexes

A Biphenol-Based Chemosensor for Zn^II and Cd^II Metal Ions: Synthesis, Potentiometric Studies, and Crystal Structures