Issue 10, 2015

Zinc oxide nanocrystal quenching of emission from electron-rich ruthenium-bipyridine complexes

Abstract

A series of heteroleptic bipyridine ruthenium complexes were prepared using known synthetic methods. Each compound incorporated one electron withdrawing 4,4′-dicarboxylic acid-2,2′-bipyridine and two bipyridines each of which had electron donating dialkylamine substituents in the 4 and 4′ positions. The electronic absorption spectra exhibited absorptions that moved to lower energy as the donor ability of the amine substituent increased. Density functional calculations established that the HOMO was delocalized over the metal and two pyridine groups located trans to the pyridines of the dicarboxylic acid bipyridine. The LUMO was delocalized over the dicarboxylic acid bipyridine. Cyclic voltammetry of the deprotonated compounds exhibit one quasi-reversible oxidation and three reductions. Coupled with the emission data, the excited state reduction potentials were estimated to range from −0.93 to −1.03 V vs. NHE. Monodispersed 3.2 nm diameter nanocrystals (NCs) of zinc oxide were found to quench partially the excited state of the dyes via a static quenching electron transfer process involving the formation of a dyad of the complex and the NC. The magnitude of the partial quenching of complexed dyes was correlated to the distribution of band gaps for the NCs, which is an inverse function of diameter. Dyes attached to the NCs on the small end of the particle size distribution had electron transfer rates that were uncompetitive with radiative and nonradiative decay mechanisms.

Graphical abstract: Zinc oxide nanocrystal quenching of emission from electron-rich ruthenium-bipyridine complexes

Supplementary files

Article information

Article type
Paper
Submitted
23 Oct 2014
Accepted
28 Jan 2015
First published
06 Feb 2015

Dalton Trans., 2015,44, 4630-4639

Author version available

Zinc oxide nanocrystal quenching of emission from electron-rich ruthenium-bipyridine complexes

R. J. Hue, R. Vatassery, K. R. Mann and W. L. Gladfelter, Dalton Trans., 2015, 44, 4630 DOI: 10.1039/C4DT03272A

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