ABSTRACT Three new fluorescent ligands derived from 2-(9-anthrylmethylamino)ethyl-appended cyclen... more ABSTRACT Three new fluorescent ligands derived from 2-(9-anthrylmethylamino)ethyl-appended cyclen (cyclen=1,4,7,10-tetraazacyclododecane) intended for future use as metal ion activated molecular receptors have been synthesised and characterised. The new ligands, 1,4,7-tris[(2″S)-acetamido-2″-(methyl-3″-phenylpropionate)]-10-(2-N-(9-anthrylmethylamino)ethyl-1,4,7,10-tetraazacyclododecane, 1,4,7-tris[(2″S)-acetamido-2″-(methyl-3″-phenylpropionate)]-10-(2-N-(9-anthrylmethylamino)ethyl-N-[(2″S)-acetamido-2″-(methyl-3″-phenylpropionate])-1,4,7,10-tetraazacyclododecane and 1,4,7-tris[2-hydroxyethyl]-10-(2-N-(9-anthrylmethylamino)ethyl)-N-(2-hydroxyethyl))-1,4,7,10-tetraazacyclododecane, provide the opportunity to investigate the consequences of alkylating the 2-(9-anthrylmethylamino)ethyl fluorophore at the anthrylamine. It was discovered that by doing this the basicity of this amine is lowered and in consequence the pH range over which the PeT induced fluorescence quenching extends is increased by about 1 pH unit. Formation constants were determined in 20% aqueous methanol for the first two ligands with Cd(II) and Cu(II). This demonstrated that alkylation of the anthrylamine significantly increases the stability of the metal complexes.
Nanoassembled capsules (NACs) that incorporate a polymer aggregate inside a silica shell may be l... more Nanoassembled capsules (NACs) that incorporate a polymer aggregate inside a silica shell may be loaded with agents that are of particular interest for therapeutic or diagnostic applications. NACs formed using the MRI contrast agent GdDOTP 5− in the internal polymer aggregate are reported herein, the smaller of which show promise as potential MRI contrast agents. Unlike many other nanoencapsulated systems, water access to the inner core of these NACs does not appear to be limited and consequently the water relaxivity per Gd 3+ agent can reach as high as 24 mM −1 s −1 . Robust, spherical capsules were formed using polyallylamine or poly-L-lysine ranging from 0.2 to 5 µm in diameter. The greatest gains in relaxivity were observed for smaller NACs, for which water accessibility remained high but molecular rotation of the Gd 3+ chelate was effectively restricted. Larger NACs did not afford such large gains in relaxivity, the result of poorer water accessibility combined with less-effective rotational restriction. .
The synthesis and the photophysical evaluation of a novel pH dependent lanthanide luminescent sel... more The synthesis and the photophysical evaluation of a novel pH dependent lanthanide luminescent self-assembly in water between a cyclen based europium complex and a beta-diketonate is described and its use as a luminescent sensor in displacement assays for anions such as acetate, bicarbonate and lactate, where the Eu(III) emission was quenched upon anion recognition.
The synthesis and photophysical properties of a coordinatively unsaturated cationic dinuclear ter... more The synthesis and photophysical properties of a coordinatively unsaturated cationic dinuclear terbium complex, 2.Tb(2), that can detect the presence of mono- or bis(carboxylates) in buffered aqueous solution at physiological pH is described. Full ligand synthesis and structural characterization of 2.Na(2) are also described. Spectroscopic measurements determined that each Tb(III) metal center has two metal-bound water molecules (q = 2). The recognition or sensing of N,N-dimethylaminocarboxylic acid, 4, and the bis(carboxylate) terephthalic acid, 5, which can also function as sensitizing antennae, was found to occur through the binding of these carboxylates to the metal center via the displacement of the metal bound water molecules. This gave rise to the formation of luminescent ternary complexes in solution in 2:1 or 1:1 (ion:2.Tb(2)) stoichiometry, respectively. Aliphatic bis(carboxylates) also bind to 2.Tb(2) where the selectivity for the ion recognition and stoichiometry was dictated by the structure of the anion, being most selective for pimelic acid, 6. Binding of either l- or d-tartaric acid gave rise to the formation ternary complex formation, with 2:1 stoichiometry, where the ion recognition resulted in quenching of the lanthanide emission.
The design, synthesis, and characterization of a novel dinuclear Eu(III) bismacrocyclic conjugate... more The design, synthesis, and characterization of a novel dinuclear Eu(III) bismacrocyclic conjugate 1.Eu2 as a delayed luminescent lanthanide sensor for dicarboxylates is discussed. The sensor was shown to bind small dicarboxylic acids such as aspartic, malonic, succinic, or glutaric acid in pH 6.5 solutions. However, only malonic acid gave rise to selective Eu(III) luminescent enhancements, as the emission was reduced for all of the other acids.
The synthesis of the novel Eu(III) cyclen complex, Eu1, is described. In buffered pH 7.4 water, t... more The synthesis of the novel Eu(III) cyclen complex, Eu1, is described. In buffered pH 7.4 water, the Eu(III) emission was "switched on" upon excitation of the Terpy antenna. In the presence of various transition-metal ions (e.g., Fe(II) and Ni(II)), both the singlet-excited state and the Eu(III) emission were quenched ("switched off"), whereas in the ground state, an MLCT band was formed, signifying the formation of stable mixed linear trimetallic f−d supramolecular self-assemblies.
Interest in the design and development of water soluble polyaza macrocycles with possible applica... more Interest in the design and development of water soluble polyaza macrocycles with possible applications as enzyme mimics and MRI agents has attracted much attention over recent years. The objective of our studies is to develop a series of water soluble polyaza macrocyclic ligands bearing donor pendant arms derived from amino acids.
The delayed lanthanide luminescence of the terbium [Tb(III)] diaryl-urea complex 1xTb is signific... more The delayed lanthanide luminescence of the terbium [Tb(III)] diaryl-urea complex 1xTb is significantly enhanced upon sensing of dihydrogenphosphate (H2PO4(-)) in CH3CN, which occurs through multiple anion binding through hydrogen bonding interactions and potential metal ion coordination to Tb(III).
In this Letter, we describe selective one step mono N-alkylations of cyclen (1,4,7,10-tetraazacyc... more In this Letter, we describe selective one step mono N-alkylations of cyclen (1,4,7,10-tetraazacyclododecane) using a range of functionalized alkyl halides. This 'easy to use' synthesis gives rise to mono-derivatives of cyclen from various alkyl halides or, when using alkyl dihalides, bis-cyclen derivatives, where the alkyl group links two cyclen macrocycles together. While the reaction conditions require the use of 1:4 stoichiometry (alkyl halide:cyclen), any unreacted cyclen can be recovered with an aqueous extraction and successfully reused. This procedure was found to be quite versatile, being particularly well-suited for cyclen targets bearing protected thiol groups, as well as a-chloroamide-derived chromophores; such cyclen pendant chromophores are employed as antennae for lanthanide luminescence probes and sensors.
The synthesis, complexation, and photophysical properties of the Eu(III)-based quinoline cyclen c... more The synthesis, complexation, and photophysical properties of the Eu(III)-based quinoline cyclen conjugate complex Eu1 and its permanent, noncovalent incorporation into hydrogels as sensitive, interference-free pH sensing materials for biological media are described. The ...
ABSTRACT Three new fluorescent ligands derived from 2-(9-anthrylmethylamino)ethyl-appended cyclen... more ABSTRACT Three new fluorescent ligands derived from 2-(9-anthrylmethylamino)ethyl-appended cyclen (cyclen=1,4,7,10-tetraazacyclododecane) intended for future use as metal ion activated molecular receptors have been synthesised and characterised. The new ligands, 1,4,7-tris[(2″S)-acetamido-2″-(methyl-3″-phenylpropionate)]-10-(2-N-(9-anthrylmethylamino)ethyl-1,4,7,10-tetraazacyclododecane, 1,4,7-tris[(2″S)-acetamido-2″-(methyl-3″-phenylpropionate)]-10-(2-N-(9-anthrylmethylamino)ethyl-N-[(2″S)-acetamido-2″-(methyl-3″-phenylpropionate])-1,4,7,10-tetraazacyclododecane and 1,4,7-tris[2-hydroxyethyl]-10-(2-N-(9-anthrylmethylamino)ethyl)-N-(2-hydroxyethyl))-1,4,7,10-tetraazacyclododecane, provide the opportunity to investigate the consequences of alkylating the 2-(9-anthrylmethylamino)ethyl fluorophore at the anthrylamine. It was discovered that by doing this the basicity of this amine is lowered and in consequence the pH range over which the PeT induced fluorescence quenching extends is increased by about 1 pH unit. Formation constants were determined in 20% aqueous methanol for the first two ligands with Cd(II) and Cu(II). This demonstrated that alkylation of the anthrylamine significantly increases the stability of the metal complexes.
Nanoassembled capsules (NACs) that incorporate a polymer aggregate inside a silica shell may be l... more Nanoassembled capsules (NACs) that incorporate a polymer aggregate inside a silica shell may be loaded with agents that are of particular interest for therapeutic or diagnostic applications. NACs formed using the MRI contrast agent GdDOTP 5− in the internal polymer aggregate are reported herein, the smaller of which show promise as potential MRI contrast agents. Unlike many other nanoencapsulated systems, water access to the inner core of these NACs does not appear to be limited and consequently the water relaxivity per Gd 3+ agent can reach as high as 24 mM −1 s −1 . Robust, spherical capsules were formed using polyallylamine or poly-L-lysine ranging from 0.2 to 5 µm in diameter. The greatest gains in relaxivity were observed for smaller NACs, for which water accessibility remained high but molecular rotation of the Gd 3+ chelate was effectively restricted. Larger NACs did not afford such large gains in relaxivity, the result of poorer water accessibility combined with less-effective rotational restriction. .
The synthesis and the photophysical evaluation of a novel pH dependent lanthanide luminescent sel... more The synthesis and the photophysical evaluation of a novel pH dependent lanthanide luminescent self-assembly in water between a cyclen based europium complex and a beta-diketonate is described and its use as a luminescent sensor in displacement assays for anions such as acetate, bicarbonate and lactate, where the Eu(III) emission was quenched upon anion recognition.
The synthesis and photophysical properties of a coordinatively unsaturated cationic dinuclear ter... more The synthesis and photophysical properties of a coordinatively unsaturated cationic dinuclear terbium complex, 2.Tb(2), that can detect the presence of mono- or bis(carboxylates) in buffered aqueous solution at physiological pH is described. Full ligand synthesis and structural characterization of 2.Na(2) are also described. Spectroscopic measurements determined that each Tb(III) metal center has two metal-bound water molecules (q = 2). The recognition or sensing of N,N-dimethylaminocarboxylic acid, 4, and the bis(carboxylate) terephthalic acid, 5, which can also function as sensitizing antennae, was found to occur through the binding of these carboxylates to the metal center via the displacement of the metal bound water molecules. This gave rise to the formation of luminescent ternary complexes in solution in 2:1 or 1:1 (ion:2.Tb(2)) stoichiometry, respectively. Aliphatic bis(carboxylates) also bind to 2.Tb(2) where the selectivity for the ion recognition and stoichiometry was dictated by the structure of the anion, being most selective for pimelic acid, 6. Binding of either l- or d-tartaric acid gave rise to the formation ternary complex formation, with 2:1 stoichiometry, where the ion recognition resulted in quenching of the lanthanide emission.
The design, synthesis, and characterization of a novel dinuclear Eu(III) bismacrocyclic conjugate... more The design, synthesis, and characterization of a novel dinuclear Eu(III) bismacrocyclic conjugate 1.Eu2 as a delayed luminescent lanthanide sensor for dicarboxylates is discussed. The sensor was shown to bind small dicarboxylic acids such as aspartic, malonic, succinic, or glutaric acid in pH 6.5 solutions. However, only malonic acid gave rise to selective Eu(III) luminescent enhancements, as the emission was reduced for all of the other acids.
The synthesis of the novel Eu(III) cyclen complex, Eu1, is described. In buffered pH 7.4 water, t... more The synthesis of the novel Eu(III) cyclen complex, Eu1, is described. In buffered pH 7.4 water, the Eu(III) emission was "switched on" upon excitation of the Terpy antenna. In the presence of various transition-metal ions (e.g., Fe(II) and Ni(II)), both the singlet-excited state and the Eu(III) emission were quenched ("switched off"), whereas in the ground state, an MLCT band was formed, signifying the formation of stable mixed linear trimetallic f−d supramolecular self-assemblies.
Interest in the design and development of water soluble polyaza macrocycles with possible applica... more Interest in the design and development of water soluble polyaza macrocycles with possible applications as enzyme mimics and MRI agents has attracted much attention over recent years. The objective of our studies is to develop a series of water soluble polyaza macrocyclic ligands bearing donor pendant arms derived from amino acids.
The delayed lanthanide luminescence of the terbium [Tb(III)] diaryl-urea complex 1xTb is signific... more The delayed lanthanide luminescence of the terbium [Tb(III)] diaryl-urea complex 1xTb is significantly enhanced upon sensing of dihydrogenphosphate (H2PO4(-)) in CH3CN, which occurs through multiple anion binding through hydrogen bonding interactions and potential metal ion coordination to Tb(III).
In this Letter, we describe selective one step mono N-alkylations of cyclen (1,4,7,10-tetraazacyc... more In this Letter, we describe selective one step mono N-alkylations of cyclen (1,4,7,10-tetraazacyclododecane) using a range of functionalized alkyl halides. This 'easy to use' synthesis gives rise to mono-derivatives of cyclen from various alkyl halides or, when using alkyl dihalides, bis-cyclen derivatives, where the alkyl group links two cyclen macrocycles together. While the reaction conditions require the use of 1:4 stoichiometry (alkyl halide:cyclen), any unreacted cyclen can be recovered with an aqueous extraction and successfully reused. This procedure was found to be quite versatile, being particularly well-suited for cyclen targets bearing protected thiol groups, as well as a-chloroamide-derived chromophores; such cyclen pendant chromophores are employed as antennae for lanthanide luminescence probes and sensors.
The synthesis, complexation, and photophysical properties of the Eu(III)-based quinoline cyclen c... more The synthesis, complexation, and photophysical properties of the Eu(III)-based quinoline cyclen conjugate complex Eu1 and its permanent, noncovalent incorporation into hydrogels as sensitive, interference-free pH sensing materials for biological media are described. The ...
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