NDLI: Binding of H $^{+}$ and Zn( II) ions with a new fluorescent macrocyclic phenanthrolinophane

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Pina, Fernando Valtancoli, Barbara Mariani, Palma Bazzicalupi, Carla Bianchi, Antonio Faggi, Enrico Gratteri, Paola Biagini, Silvia
Description	Author Affiliation: Bazzicalupi C ( Department of Chemistry Ugo Schiff, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy.)
Abstract	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 $[ZnH_{2}L]^{4+}.$
ISSN	14779226
Issue Number	42
Volume Number	39
e-ISSN	13645447
Journal	Dalton Trans.
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2010-11-14
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Fluorescent Dyes Chemistry Macrocyclic Compounds Phenanthrolines Protons Zinc Diamines Hydrogen-Ion Concentration Ligands Models, Molecular Molecular Conformation Optical Phenomena Organometallic Compounds Journal Article
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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