Journal article
Supramolecular Coordination Chemistry in Aqueous Solution: Lanthanide Ion-Induced Triple Helix Formation
Inorganic chemistry, Vol.39(15), pp.3114-3124
07/24/2000
Handle:
https://hdl.handle.net/2376/113844
PMID: 11196846
Abstract
The self-assembly of dinuclear triple helical lanthanide ion complexes (helicates), in aqueous solution, is investigated utilizing laser-induced, lanthanide luminescence spectroscopy. A series of dinuclear lanthanide(III) helicates (Ln(III)) based on 2,6-pyridinedicarboxylic acid (dipicolinic acid, dpa) coordinating units was synthesized by linking two dpa moieties using the organic diamines (1R,2R)-diaminocyclohexane (chxn-R,R) and 4,4‘-diaminodiphenylmethane (dpm). Luminescence excitation spectroscopy of the Eu3+ 7F0 → 5D0 transition shows the apparent cooperative formation of neutral triple helical complexes in aqueous solution, with a [Eu2L3] stoichiometry. Eu3+ excitation peak wavelengths and excited-state lifetimes correspond to those of the [Eu(dpa)3]3- model complex. CD studies of the Nd(III) helicate Nd2(dpa-chxn-R,R)3 reveal optical activity of the f−f transitions, indicating that the chiral linking group induces a stable chirality at the metal ion center. Molecular mechanics calculations using CHARMm suggest that the ΔΔ configuration at the Nd3+ ion centers is induced by the chxn-R,R linker. Stability constants were determined for both ligands with Eu3+, yielding identical results: log K = 31.6 ± 0.2 (K in units of M-4). Metal−metal distances calculated from Eu3+ → Nd3+ energy-transfer experiments show that the complexes have metal−metal distances close to those calculated by molecular modeling. The fine structure in the Tb3+ emission bands is consistent with the approximate D 3 symmetry as anticipated for helicates.
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Details
- Title
- Supramolecular Coordination Chemistry in Aqueous Solution: Lanthanide Ion-Induced Triple Helix Formation
- Creators
- Jeremy J LessmannWilliam DeW Horrocks
- Publication Details
- Inorganic chemistry, Vol.39(15), pp.3114-3124
- Publisher
- American Chemical Society
- Identifiers
- 99900547465401842
- Language
- English
- Resource Type
- Journal article