Di-maltol-polyamine ligands to form heterotrinuclear metal complexes: solid state, aqueous solution and magnetic characterization

The binding properties of the two ligands (L) N,N’-bis[(3-hydroxy-4-pyron-2-yl)methyl]-N,N’-dimethylethylendiamine (Malten) and 4,10-bis[(3-hydroxy-4-pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (Maltonis) towards M(II) transition metal ions (M(II) = Cu(II) for Malten and Co(II) for Maltonis, respectively), were investigated in aqueous solution. Each compound contains two 3-hydroxy- 2-methyl-4-pyrone units (Maltol) symmetrically spaced by a different polyamine fragment. The formation of only mononuclear complexes was detected and the main species present in a wide range of pH is the neutral [M(II)(H−2L)] complex. This is able to stabilize one hard M(III) metal ion such as Gd(III) and Y(III), giving rise to the formation of new hetero-trinuclear complexes of M(II)–M(III)–M(II) sequence. The trinuclear species having the formula {M(III)[M(II)(H−2L)]2}3+ (M(II) = Cu(II) and M(III) = Y(III) or Gd(III) for Malten and M(II) = Co(II) and M(III) = Gd(III) for Maltonis) are also formed in a wide range of pH, including pH = 7 and can be isolated in high yield as a perchlorate salt. The crystal structures of all the studied heterotrinuclear species highlight that such systems are formed thanks to the synergy between the different stereochemical requirement of the transition metal (Cu(II) or Co(II)) and the different donor atoms set of the ligands which preorganize the maltol units for the binding of the hard M(III) metal, otherwise difficult to bind in water, through L/M(II)/M(III) self-assembling. The magnetic properties of the heterotrinuclear spin systems were investigated; in the M(II)–Gd(III)–M(II) species, Gd(III) interacts with the two 3d ions of this class of compounds by similar coupling mechanism

PluS Nanoparticles as a tool to control the metal complex stoichiometry of a new thio-aza macrocyclic chemosensor for Ag(I) and Hg(II) in water

We report here the synthesis of a new thio-​aza macrocyclic chemosensor based on the 2,​5-​diphenyl[1,​3,​4]​oxadiazole in which two thioether groups were inserted in a macrocycle with the aim to make it suitable for the coordination of soft and heavy metal ions. In acetonitrile soln., the fluorescence of the chemosensor changes upon addn. of different metal ions, such as Cu(II)​, Zn(II)​, Cd(II)​, Pb(II)​, Hg(II) and Ag(I)​, that form a not fluorescent ML species and a fluorescent M2L species characterized also via NMR expts. The hosting of the chemosensor inside the PluS Nanoparticles leads to a high water soly., allowing to perform the metal detection without the use of addnl. solvents and also induced an higher selectivity towards Ag(I) and Hg(II)​. Moreover, it was demonstrated for the first time the possibility to control the stoichiometry of the formed complex upon changing the no. of ligands per nanoparticles. To our opinion, this possibility can give an addnl. tool for the tuning of the affinity and selectivity of the chemosensor that could be of great interest for the design of more and more efficient systems

Modulating the Sensor Response to Halide Using NBD-Based Azamacrocycles

Ligand L (2,6-bis{[7-(7-nitrobenzo[1,2,5]oxadiazole-4-yl)-3,10-dimethyl-1,4,7,10-tetraazacyclododeca-1-yl]methyl}phenol) is a fluorescent sensor that is useful for detecting Cu(II), Zn(II), and Cd(II). Some of the complexes formed are able to sense the presence of halides in solution. L passes through the cellular membrane, becoming fluorescent inside cells. The H−1L− species is able to form dinuclear complexes with [M2H−1L]3+ stoichiometry with Cu(II), Zn(II), and Cd(II) ions, experiencing a CHEF effect upon metal coordination in an acetonitrile/water 95:5 (v/v) solution. In all three of the complexes investigated, the metal cations are coordinatively unsaturated and can therefore bind secondary ligands as anionic species. The crystal structure of [Cd2(H−1L)Cl2](ClO4)•4H2O is discussed. The Zn(II) complex behaves as an OFF−ON sensor for fluoride and chloride anions

Modulating the Sensor Response to Halide Using NBD-Based Azamacrocycles

Ligand <b>L</b> (2,6-bis­{[7-(7-nitrobenzo­[1,2,5]­oxadiazole-4-yl)-3,10-dimethyl-1,4,7,10-tetraazacyclododeca-1-yl]­methyl}­phenol) is a fluorescent sensor that is useful for detecting Cu­(II), Zn­(II), and Cd­(II). Some of the complexes formed are able to sense the presence of halides in solution. <b>L</b> passes through the cellular membrane, becoming fluorescent inside cells. The H_<i>–</i>1<b>L</b>^<i>–</i> species is able to form dinuclear complexes with [M₂H_<i>–</i>1<b>L</b>]³⁺ stoichiometry with Cu­(II), Zn­(II), and Cd­(II) ions, experiencing a CHEF effect upon metal coordination in an acetonitrile/water 95:5 (v/v) solution. In all three of the complexes investigated, the metal cations are coordinatively unsaturated and can therefore bind secondary ligands as anionic species. The crystal structure of [Cd₂(H_<i>–</i>1<b>L</b>)­Cl₂]­(ClO₄)·4H₂O is discussed. The Zn­(II) complex behaves as an OFF–ON sensor for fluoride and chloride anions

Modulating the Sensor Response to Halide Using NBD-Based Azamacrocycles

Ligand <b>L</b> (2,6-bis­{[7-(7-nitrobenzo­[1,2,5]­oxadiazole-4-yl)-3,10-dimethyl-1,4,7,10-tetraazacyclododeca-1-yl]­methyl}­phenol) is a fluorescent sensor that is useful for detecting Cu­(II), Zn­(II), and Cd­(II). Some of the complexes formed are able to sense the presence of halides in solution. <b>L</b> passes through the cellular membrane, becoming fluorescent inside cells. The H_<i>–</i>1<b>L</b>^<i>–</i> species is able to form dinuclear complexes with [M₂H_<i>–</i>1<b>L</b>]³⁺ stoichiometry with Cu­(II), Zn­(II), and Cd­(II) ions, experiencing a CHEF effect upon metal coordination in an acetonitrile/water 95:5 (v/v) solution. In all three of the complexes investigated, the metal cations are coordinatively unsaturated and can therefore bind secondary ligands as anionic species. The crystal structure of [Cd₂(H_<i>–</i>1<b>L</b>)­Cl₂]­(ClO₄)·4H₂O is discussed. The Zn­(II) complex behaves as an OFF–ON sensor for fluoride and chloride anions