Abstract
Two EDTA-based bichromophoric isomers form Zn(II) complexes that exhibit distinct fluorescent behaviors; the ligands are abbreviated as (edta1nap)H 2 and (edta2nap)H2, each of which consists of an EDTA chain linked to two 1-naphthyl or 2-naphthyl groups. The coordination chemistry of these complexes was studied by UV-Vis, fluorescence and 1H NMR. The formation constants and the inherent emission intensities were determined by the pH dependence of the emission spectra; the species of the most intense emission is ML(OH) for L = (edta1nap)2-, and ML for (edta2nap) 2-. The 1H NMR of Zn-(edta1nap)2- exhibits two sets of signals due to a slow exchange between two equivalent coordination geometries, whereas Zn-(edta2nap)2- undergoes a fast exchange to show a single set of NMR signals. The spin-lattice relaxation time T1 determined for the isostructural Mn(II) complexes shows that the naphthyl proton closest to the metal ion is H(8) in the (edta1nap)2- complex, and H(3) in the (edta2nap)2- complex. The two ligands differ only in the substitution position of the naphthyl group, but this apparently small difference leads to the notable difference in structural, dynamic, and consequent emission-spectral properties of their metal complexes as a result of the steric and size effects of the aromatic rings.
Original language | English |
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Pages (from-to) | 690-696 |
Number of pages | 7 |
Journal | Polyhedron |
Volume | 30 |
Issue number | 5 |
DOIs | |
State | Published - 24 Mar 2011 |
Bibliographical note
Funding Information:This work was supported in part by the Consejo Nacional de Ciencia y Tecnología de México (CONACYT, Project No. 79272 ). The NMR spectrometer is operated under the support of the Secretaría de Educación Publica, México (SES-SEP, programs No. P/PIFI 2008-26 and No. P/FPCU2008-07 ).
Keywords
- Bichromophores
- EDTA
- Fluorescence
- NMR
- Naphthalene
- Zn complexes