Protonation-state-dependent luminescence and excited-state electron-transfer reactions of 2- and 4-Pyridine (-ium)-substituted metallo-1,2-enedithiolates

Show full item record

Title: Protonation-state-dependent luminescence and excited-state electron-transfer reactions of 2- and 4-Pyridine (-ium)-substituted metallo-1,2-enedithiolates
Author: Kaiwar, Sharada; Vodacek, Anthony; Blough, Neil; Pilato, Robert
Abstract: Luminescence and excited-state electron-transfer reactions of (dppe)Pt{S2C2(2-pyridine)(H)} and (dppe)Pt{S2C2(4-pyridine)(H)} (dppe = diphenyldiphosphinoethane) are enabled by protonation of the appended pyridine, thus serving as a novel means of electronic switching. The neutral complexes have low-lying d-to-d transitions that lead to rapid decay of excited states by nonradiative processes. However, upon protonation, a 1,2-enedithiolate-to-heterocycle (pi)* intraligand charge-transfer transition (ILCT) becomes lower in energy than the d-to-d transition, thus giving rise to emissive 1ILCT* and 3ILCT* excited states for [(dppe)Pt{S2C2(2-pyridinium)(H)}][BF4] and [(dppe)Pt{S2C2(4-pyridinium)(H)}][BF4]. The assignment of these excited states was based on their energies and lifetimes (t) which range from t = 3 to 4 ns for the singlet and from t = 2000 to 7500 ns for the triplet, respectively. Emission quantum yields () increase with solvent polarity and range from = 0.0006 to 0.003 for the singlet and from = 0.001 to 0.03 for the triplet. The electron acceptors p-dinitrobenzene and tetracyanoquinodimethane quench the 3ILCT* with kq values of 4 × 109 and 9 × 109 M^-1 s^-1, respectively. The kq values are nearly identical for the 2- and 4-pyridinium complexes, reflecting the similarity in the thermodynamic driving forces for electron transfer from these complexes. The ability to employ a simple and reversible ground-state reaction (ligand protonation) to control access to reactive excited states should prove useful in numerous applications (Refer to PDF file for exact formulas).
Description: RIT community members may access full-text via RIT Libraries licensed databases: http://library.rit.edu/databases/
Record URI: http://hdl.handle.net/1850/4361
Publishers URL: http://dx.doi.org/10.1021/ja970834q
Date: 1997-10-01

Files in this item

Files Size Format View

An open access version of this file is not available. Check "Publisher URL" field for access

This item appears in the following Collection(s)

Show full item record

Search RIT DML


Advanced Search

Browse