0000000000617641
AUTHOR
J. A. Gareth Williams
Poly(amine) biphenyl derivatives as fluorescent sensors for anions and cations
Four new ligands, derived from tetramethylbenzidine and containing additional amino groups, are described. The influence of pH on the fluorescent properties of these ligands has been studied, and the effect of the dihedral angle between the aromatic rings on the fluorescent response has been established. The behaviour of the new ligands, and that of others previously described in both the complexation and sensing of different anions and cations, are also described.
Conformationally regulated fluorescent sensors. Study of the selectivity in Zn 2+ versus Cd 2+ sensing
Abstract The Zn 2+ and Cd 2+ complexing properties of four ligands containing a 4,4′-substituted biphenyl moiety are described. Ligands 1 and 3 , containing only one 1-aza-18-crown-6 cavity, lead to selective complexation of Cd 2+ versus Zn 2+ . Ligand 4 , with two crown cavities linked to a tetramethylbenzidine unit, is able to form 1:1 complexes with Zn 2+ and Cd 2+ , showing a higher complexing constant with Zn 2+ than with Cd 2+ , probably due to enthalpic factors. Several complementary experiments suggest that the 1:1 complexes formed by ligand 4 involve both crown cavities acting together to give rise to clamp structures. The formation of this type of zinc complex gives rise to red sh…
Monoamide Derivatives of EDTA Incorporating Pendent Carboxylates or Pyridyls: Synthesis, Metal Binding, and Crystal Structure of a Dinuclear Ca2+ Complex Featuring Bridging Na+ Ions
EDTA is a powerful, cheap and widely-used chelating unit for a large range of metal ions. To link it covalently to other molecules, the formation of an amide bond using one of the carboxylates is an attractive and simple approach, even though it may compromise metal ion binding as one of the four carboxylate donors is lost. Here we undertake a quantitative study of the metal ion binding of two new mono-amide derivatives of EDTA, namely AmGly1 and AmPy1, featuring an additional coordinating carboxylate or pyridyl group in the amide, respectively. The compounds are conveniently synthesised through alkylation of the tris-t-butyl ester of ethylenediamine-triacetic acid with the appropriate α-ch…
Polyazapodands Derived from Biphenyl. Study of their Behaviour as Conformationally Regulated Fluorescent Sensors
Eight new polyazapodands containing a 4,4′-substituted biphenyl moiety have been synthesised. Four (7, 8, 9 and 11) are functionalised on positions 4 and 4′ with a nitro group and four (1, 2, 3 and 10) with a dimethylamino substituent. Comparison of the emission behaviour of 1, 2, 3 with that of the reference compounds 10 and tetramthylbenzidine, clearly suggests that a modification in the dihedral angle between the biphenyl rings is an important factor in determining the fluorescent response of the molecule. The fluorescence is pH dependent, due to the formation of intramolecular hydrogen bonds between protonated aliphatic nitrogens and a carbonyl oxygen, which influences the aforementione…
On the Antibacterial Activity of Azacarboxylate Ligands: Lowered Metal Ion Affinities for Bis-amide Derivatives of EDTA do not mean Reduced Activity.
EDTA is widely used as an inhibitor of bacterial growth, affecting the uptake and control of metal ions by microorganisms. We describe the synthesis and characterisation of two symmetrical bis-amide derivatives of EDTA, featuring glycyl or pyridyl substituents: AmGly2 and AmPy2 . Metal ion affinities (logK) have been evaluated for a range of metals (Mg2+ , Ca2+ , Fe3+ , Mn2+ , Zn2+ ), revealing less avid binding compared to EDTA. The solid-state structures of AmGly2 and of its Mg2+ complex have been determined crystallographically. The latter shows an unusual 7-coordinate, capped octahedral Mg2+ centre. The antibacterial activities of the two ligands and of EDTA have been evaluated against …
CCDC 1814350: Experimental Crystal Structure Determination
Related Article: Raminder S. Mulla, Marikka S. Beecroft, Robert Pal, Juan A. Aguilar, Javier Pitarch‐Jarque, Enrique García‐España, Elena Lurie‐Luke, Gary J. Sharples, J. A. Gareth Williams|2018|Chem.-Eur.J.|24|7137|doi:10.1002/chem.201800026
CCDC 1814351: Experimental Crystal Structure Determination
Related Article: Raminder S. Mulla, Marikka S. Beecroft, Robert Pal, Juan A. Aguilar, Javier Pitarch‐Jarque, Enrique García‐España, Elena Lurie‐Luke, Gary J. Sharples, J. A. Gareth Williams|2018|Chem.-Eur.J.|24|7137|doi:10.1002/chem.201800026
CCDC 1508045: Experimental Crystal Structure Determination
Related Article: Raminder S. Mulla, Javier Pitarch-Jarque, Enrique García-España, Tanya Desa, Elena Lurie-Luke, J. A. Gareth Williams|2017|Chem. Sel.|2|5045|doi:10.1002/slct.201700995
CCDC 1508044: Experimental Crystal Structure Determination
Related Article: Raminder S. Mulla, Javier Pitarch-Jarque, Enrique García-España, Tanya Desa, Elena Lurie-Luke, J. A. Gareth Williams|2017|Chem. Sel.|2|5045|doi:10.1002/slct.201700995
CCDC 1814349: Experimental Crystal Structure Determination
Related Article: Raminder S. Mulla, Marikka S. Beecroft, Robert Pal, Juan A. Aguilar, Javier Pitarch‐Jarque, Enrique García‐España, Elena Lurie‐Luke, Gary J. Sharples, J. A. Gareth Williams|2018|Chem.-Eur.J.|24|7137|doi:10.1002/chem.201800026