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Density-functional study of luminescence in polypyridine ruthenium complexes

Paper ID Volume ID Publish Year Pages File Format Full-Text
26687 43971 2014 8 PDF Available
Title
Density-functional study of luminescence in polypyridine ruthenium complexes
Abstract

•Modeling TD-DFT reproduction of X-ray strusctures and absorption spectra.•Formulating computationally cheap supporting design of photochemical molecular devices.•PDOS prediction of luminescence and non-luminescence in complexes.

A density-functional theory (DFT) study of five ruthenium complexes has been carried out with the goal of gaining deeper insight into factors governing luminescence lifetimes. The five compounds are [Ru(bpy)3]2+ (1), [Ru(L1)2]2+ (2), [Ru(tpy)2]2+ (3), [Ru(L1)(tpy)]2+ (4), and [Ru(L2)2]2+ (5), where bpy = 2,2′-bipyridine, tpy = 2,2′;6′,2″-terpyridine, L1 = 1,1′-[2,6-pyridinediylbis(methylene)]bis[3-methylimidazolium] hexafluorophosphate and L2 = 1,1′-[2,6-pyridinediylbis(methylene)]bis[3-methylbenziimidazolium]. Experimental work, including the synthesis and photophysical properties of 5 is also reported in the context of this study. Gas phase geometries optimized using X-ray crystallography geometries as start geometries were found to be close to the start geometries. Gas phase absorption spectra calculated using time-dependent DFT were found to be in good agreement with spectra measured in solution. A partial density of states (PDOS) analysis of the molecular orbitals shows that it is possible to recover a ligand field theory (LFT)-like picture. On the basis of this PDOS-derived LFT-like picture we propose two orbital-based luminescence indices, both motivated by the idea that luminescence quenching results from a low 3MLCT → 3MC barrier. The first luminescence index is ΔE  , the difference between the eg* and lowest energy π* PDOS bands. The second luminescence index is d × π, the product of the amount of π character in the t2g band with the amount of ruthenium d character in the 1π* band. These luminescence measures are intended as qualitative rather than quantitative predictors. Low values of ΔE and high values of d × π are shown to correlate with lack of luminescence for the five compounds studied in this paper, while high values of ΔE and low values of d × π correlate well with luminescence.

Keywords
Polypyridine ruthenium complexes; Luminescence; DFT; TD-DFT
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Density-functional study of luminescence in polypyridine ruthenium complexes
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 276, 15 February 2014, Pages 8–15
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
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