Thiocyanate Linkage Isomerism in a Ruthenium Polypyridyl Complex

Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA.
Inorganic Chemistry (Impact Factor: 4.76). 11/2011; 50(23):11938-46. DOI: 10.1021/ic200950e
Source: PubMed


Ruthenium polypyridyl complexes have seen extensive use in solar energy applications. One of the most efficient dye-sensitized solar cells produced to date employs the dye-sensitizer N719, a ruthenium polypyridyl thiocyanate complex. Thiocyanate complexes are typically present as an inseparable mixture of N-bound and S-bound linkage isomers. Here we report the synthesis of a new complex, [Ru(terpy)(tbbpy)SCN][SbF(6)] (terpy = 2,2';6',2''-terpyridine, tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine), as a mixture of N-bound and S-bound thiocyanate linkage isomers that can be separated based on their relative solubility in ethanol. Both isomers have been characterized spectroscopically and by X-ray crystallography. At elevated temperatures the isomers equilibrate, the product being significantly enriched in the more thermodynamically stable N-bound form. Density functional theory analysis supports our experimental observation that the N-bound isomer is thermodynamically preferred, and provides insight into the isomerization mechanism.

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Available from: Wendu Ding, Apr 07, 2014
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    • "The study of the kinetic and thermodynamic aspects of electron transfer to generate phenoxyl radicals bearing bulky groups in the ortho-and para-positions may help to understand the different biological roles of phenols. The photochemistry and photophysics of transition metal complexes containing d 6 electronic configuration, particularly Ruthenium polypyridyl complexes ([Ru(NN) 3 ] 2+ ), have attracted the chemists in the design of light-driven water splitting photoanodes (Brimblecombe et al., 2010; Li et al., 2010; White et al., 2012; Young et al., 2012), molecular probes (Gill and Thomas, 2012; Liao et al., 2012; Tan et al., 2013; Tan et al., 2012), construction of solar cells (Adewale et al., 2012; Chitra et al., 2013; Sannino et al., 2013; Brewster et al., 2011; Tuikka et al., 2011), artificial photosynthesis (Kalyanasundaram and Graetzel, 2010) sensors (Cui et al., 2008; Schmittel and Lin, 2008), molecular machine devices (Balzani et al., 2009; Li et al., 2008) and organic light emitting diodes (Chi and Chou, 2010). This is due to the combination of excellent photophysical and electrochemical properties such as luminescence in solution at room temperature, moderate quantum yield and excited state lifetime, spectroscopically distinguishable metal redox states, tunable electronic properties, ability to undergo energy and electron transfer processes and chemical stability (Campagna et al., 2007; Kavan et al., 2008; Lee et al., 2003; Lo et al., 2008; Siebert et al., 2011; Sun et al., 2010). "
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