Luminescence quenching of tris(4,4′-dinonyl-2,2′-bipyridyl) ruthenium(II) cation with phenolate ions in DMSO

Daniel Sheeba; Allen Gnana Raj George

doi:10.1016/j.arabjc.2013.09.006

View/Download PDF

Buy Reprints

PDF

Translate this page into:

Original Article

10 (

2_suppl

); S2429-S2435

doi:

10.1016/j.arabjc.2013.09.006

Luminescence quenching of tris(4,4′-dinonyl-2,2′-bipyridyl) ruthenium(II) cation with phenolate ions in DMSO

Daniel Sheeba, Allen Gnana Raj George^⁎

Department of Chemistry and Research Centre, Scott Christian College (Autonomous), Nagercoil 629003, Tamil Nadu, India

⁎Corresponding author. Mobile: +91 9487311237. allengraj@gmail.com (Allen Gnana Raj George)

Received: 2013-3-11, Accepted: 2013-9-4, Published: 2013-05-01

Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Peer review under responsibility of King Saud University.

Abstract

The photoredox reactions of biologically important phenols (p-coumaric acid, ferulic acid, thymol, quercetin and gallic acid) with the excited state [Ru(nbpy)₃]²⁺ (nbpy = 4,4^′-dinonyl-2,2^′-bipyridine) complex proceed through photoinduced electron transfer reaction in DMSO and have been studied by luminescence quenching technique. The complex shows absorption and emission maximum at 457 and 628 nm and it shows a lifetime of 804 ns in DMSO. The excited state reduction potential of the complex $E_{{Ru}^{2 + * / +}}^{0}$ in DMSO is 0.72 V vs Ag/Ag⁺. The dynamic nature of quenching is confirmed from the ground state absorption studies. The reductive quenching of [Ru(nbpy)₃]²⁺ by phenolate ions has been confirmed from transient absorption spectra and from the linear variation of log k_q vs oxidation potential of the phenols. The quenching rate constant, (k_q) is highly sensitive to the availability of active phenolate ions, oxidation potential of the polyphenols, the free energy change (ΔG⁰) of the reaction and to the electron transfer distance between the complex and the quencher. Structural effects seem to play an important role in the photoinduced electron transfer reactions in DMSO.

Keywords

Luminescence quenching

Stern–Volmer equation

Photooxidation of phenols

Photoinduced electron transfer

Structural effects

Show Related Articles from PubMed

1 Introduction

Polyphenols constitute one of the most common and widespread groups of substances in flowering plants, occurring in all vegetative organs, as well as in flowers and fruits. They are considered as secondary metabolites involved in the chemical defense of plants against predators and in plant-plant interferences. Several thousand plant polyphenols are known, encompassing a wide variety of molecules that contain at least one aromatic ring with one or more hydroxyl groups in addition to other substituents. The biological properties of polyphenols include antioxidant, anticancer, and anti-inflammatory effects (Gianmaria et al., 2011). The antioxidant activity of phenolic compounds is due to their ability to scavenge free radicals, donate hydrogen atoms or electron, or chelate metal cations. Among the variety of phenolic compounds, phenolic acids have attracted considerable interest in the past few years due to their many potential health benefits. The conversion of phenol to phenoxyl radical is of interest to chemists because of its involvement in biologically important processes (Swarnalatha et al., 2011). The one electron oxidation of phenolates to the resulting phenoxyl radical is a key step in the oxidation of phenols. 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 d⁶ 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 ).

The synthesis of Ru(II) complexes with long chain hydrophobic ligands is of great interest in recent years because of their potential applications in thin film devices, sensors, heterogeneous catalysis (Dunn and Zink, 2007; Holder et al., 2005; Metera and Sleiman, 2007 ) and for the construction of dye sensitized solar cells (Chandrasekharam et al., 2011; Xu et al., 2012; Zhu et al., 2012 ). The dyes with longer hydrocarbon chains give higher efficiency when used as a sensitizer in dye sensitized solar cells (Mori et al., 2007). Castro and co-workers (Castro et al., 2005) have successfully designed a sensor for hydrocarbon, based on ruthenium(II)-complex, ([Ru(nbpy)₃]²⁺ (nbpy = 4,4^′-dinonyl-2,2^′-bipyridine)) which is able to detect reversibly and to quantify both aromatic and aliphatic hydrocarbons in aqueous samples.

The excited state properties like emission lifetime, quantum yield, wavelength of emission maximum and redox potentials of [Ru(bpy)₃]²⁺ (bpy = 2,2^′-bipyridine) are largely affected by the introduction of electron-donating and electron-withdrawing groups in the 4,4^′-position of 2,2^′-bipyridine (Rajendran et al., 2001; Rajendran et al., 1997; Swarnalatha et al., 2005 ). The excited state properties of ruthenium(II)-polypyridine complexes can also be finely tuned by changing the nature of the solvent or medium. The rate of electron transfer from a donor molecule to an acceptor in a solvent is controlled by several factors and the most important of them are the free energy change of the reaction (ΔG⁰), the reorganization energy (λ) and the electron transfer distance (d) between the donor and acceptor (Verma et al., 2012). Numerous works have been reported on the importance of the substituent, pH, steric and electronic effects on the photoinduced electron transfer reactions of ortho-, meta- and para-substituted phenolate ions to the excited state Ru(II)-polypyridine complexes in aprotic, protic, mixed solvents and in micelles (Miedlar and Das, 1982; Rajendran et al., 2001; Rajendran et al., 1997; Swarnalatha et al., 2011; Swarnalatha et al., 2005; Thanasekaran et al., 1998; Verma et al., 2012 ).

Luminescence quenching is an important technique used to obtain adequate information about structure and dynamics of luminescent molecules. It is a process, in which the luminescence intensity of the solute decreases by a variety of molecular interactions such as excited state reactions, molecular rearrangements, energy transfer, ground-state complex formation and collision-quenching (Huili et al., 2012; Matos et al., 2008). The present study concentrates on the quenching behavior of the [Ru(nbpy)₃]²⁺ complex with polyphenols and thymol (quenchers) in DMSO. The transient absorption spectra confirm the electron transfer nature of the reaction of the excited state [Ru(nbpy)₃]²⁺ with polyphenols in DMSO, where the quenching process proceeds through the formation of phenolate ions. Further, the nature of quenching (static or dynamic) is recorded by electronic absorption spectra as well as quenching rate constant.

2 Experimental

2.1

2.1 Materials

RuCl₃.3H₂O, ligand (4,4^′-dinonyl-2,2^′- bipyridine) and the quenchers (p-coumaric acid, ferulic acid, thymol, gallic acid, quercetin) were purchased from Sigma–Aldrich. HPLC grade solvents were used throughout the study for the synthesis of complex as well as for quenching studies. The complex, [Ru(nbpy)₃] Cl₂ was synthesized according to the procedure previously described (Castro et al., 2005). Then the complex was treated with sodium tetrafluoroborate to get the ${BF}_{4}^{-}$ salt [Ru(nbpy)₃](BF₄)₂.

2.2

2.2 Equipments

Samples of the complex, [Ru(nbpy)₃]²⁺ as well as the quenchers in DMSO were freshly prepared for each measurement. Absorption spectra were measured using SYSTRONICS 2203 double beam spectrophotometer. Emission spectra were recorded using JASCO FP-6300 spectrofluorometer. All the sample solutions used for emission and excited state lifetime measurements were deaerated for about 30 min by dry nitrogen gas purging keeping the solutions in cold water to ensure that there is no change in volume of the solution. All the spectral measurements were carried out at 298 K. Excited state lifetime and transient absorption measurements were made with laser flash photolysis technique using an Applied Photophysics SP-Quanta Ray GCR-2(10) Nd:YAG laser as the excitation source (Ramamurthy, 1993). The time dependence of the luminescence decay was observed using a Czerny–Turner monochromator with a stepper motor control and a Hamamatsu R-928 photomultiplier tube. The production of the excited state on exposure to 355 nm was measured by monitoring (pulsed Xenon lamp of 250 W) the absorbance change. Transient spectra were obtained by a point-to-point technique, monitoring the absorbance changes (ΔA) after the flash at intervals of 10 nm over the spectral range 300–700 nm, averaging at least 30 decays at each wavelength.

The redox potential of the complex, [Ru(nbpy)₃]²⁺ and the oxidation potentials of the polyphenols in DMSO medium were determined by cyclic voltammetric technique using CH1604C electrochemical analyzer. A glassy carbon (working electrode), Pt (counter electrode) and (Ag/Ag⁺) electrode (reference electrode) were used for the electrochemical measurements and tetrabutylammonium perchlorate was the supporting electrolyte.

2.3

2.3 Luminescent quenching studies

The structure of the ligand and the quenchers used in the present study are shown in Fig. 1. The complex and the quenchers taken in the present study are soluble in DMSO and the excited state life time of the [Ru(nbpy)₃]²⁺ is longer in aprotic solvents than protic one (Castro et al., 2005). DMSO has greater proton affinity than other aprotic solvent like acetonitrile (Astudillo et al., 2007). In DMSO, a hydrogen bonding interaction is established between the phenolic –OH groups of the phenols and the oxygen atom of DMSO (O–H … O), which polarize the O–H bond, making the proton transfer easier than in the case of acetonitrile (Astudillo et al., 2007). This proton transfer yields phenolate ion, which act as quenchers in these photoinduced ET reactions, hence we use DMSO as solvent in this study. The photochemical reduction of [Ru(nbpy)₃]²⁺ complex with these phenolate ions has been studied by the luminescence quenching technique. The sample solutions were purged carefully with dry nitrogen for 30 min. The luminescence measurements (Fig. 2) were performed at different quencher concentrations and the quenching rate constants, k_q, were determined from Stern–Volmer plots (Fig. 3) using the equation given below (Lakowicz, 2006).

(1)

I_{0} / I = 1 + k_{q} τ_{0} [Q]

Where I₀ and I are the emission intensities in the absence and presence of quencher respectively and τ₀ is the emission lifetime of [Ru(nbpy)₃]²⁺ in the absence of quencher.

The change in emission intensity of ∗[Ru(nbpy)3]2+ with different concentrations of gallic acid (2 × 10−4–1.4 × 10−3) in DMSO.

Stern–Volmer plot for the reductive quenching of ∗[Ru(nbpy)3]2+ with p-coumaric acid in DMSO.

3 Results and discussion

3.1

3.1 Electronic spectra and luminescent life time

The absorption spectrum of [Ru(nbpy)₃]²⁺ shows a high energy absorption at 286 nm corresponding to the ligand centered π–π^∗ transition and a low energy absorption at 457 nm assigned to the dπ–π^∗ metal to ligand charge transfer (MLCT) transition. The MLCT involves electronic excitation from the metal orbital [dπ (Ru)] to the ligand centered acceptor π^∗ orbitals (ligand). The [Ru(nbpy)₃]²⁺ complex shows an emission maximum at 625 nm and has an excited state lifetime at 804 ns in DMSO.

3.2

3.2 Redox potential

The ground state reduction potential of the Ru(II) complex in DMSO is −1.37 V vs Ag/Ag⁺ electrode. The redox potentials of excited state couples are calculated from the potential of the ground state couples and the zero–zero energy, E_0–0 (found to be 2.1 eV) (Swarnalatha et al., 2005). The excited state redox potential of the complex $(E_{Ru}^{2 + * / +})$ is 0.72 V vs Ag/Ag⁺. The free energy change (ΔG⁰) values are calculated from the excited state redox potential of [Ru(4,4′-dinonyl-2,2′-bipyridine)₃]²⁺ and oxidation potentials of polyphenols. The experimental bimolecular quenching rate constant (k_q) of ^∗[Ru(nbpy)₃]²⁺, oxidation potentials of quenchers vs Ag/Ag⁺, and ΔG⁰ in DMSO are shown in Table 1.

Table 1 Rate constants (k_q), oxidation potential of quenchers vs Ag/Ag⁺

(E_{oxd}^{0})

and free energy changes (ΔG⁰) for the reductive quenching of [Ru(nbpy)₃]²⁺ with the quenchers in DMSO.

Quencher	k_q (M⁻¹ s⁻¹)	$E_{oxd}^{0}$ vs Ag/Ag⁺ (V)	ΔG⁰ (eV)
Phenol	1.4 × 10⁸	0.78	0.06
p-Coumaric acid	3.1 × 10⁸	0.67	−0.047
Ferulic acid	8.7 × 10⁸	0.51	−0.212
Thymol	1.24 × 10⁹	0.41	−0.307
Quercetin	2.48 × 10⁹	0.30	−0.422
Gallic acid	6.21 × 10⁹	0.082	−0.639

3.3

3.3 Luminescence quenching of ^∗[Ru(4,4′-dinonyl-2,2′- bipyridine)₃]²⁺ with phenolate ions

The Stern–Volmer plots for the emission intensity of the photoredox systems (Fig. 3) are found to be linear which indicates that, dynamic quenching is the dominant process and the contribution from static quenching is negligible. In order to check the ground-state complex formation, quenchers are added in increments to the [Ru(nbpy)₃]²⁺ complex in DMSO and the absorption spectra are recorded at different concentrations (Fig. 4). The absorption spectra of the reactants are equal to the sum of the component spectra. There is no significant change in MLCT absorption maxima of [Ru(nbpy)₃]²⁺ in the presence of the quenchers under the present experimental conditions which helps us to conclude that the contribution from the static quenching is negligible here (Swarnalatha et al., 2011).

Absorption spectra of [Ru(nbpy)3]2+ in the presence of different concentrations of ferulic acid in DMSO.

The k_q values for gallic acid, quercetin and thymol are 6.21 × 10⁹, 2.48 × 10⁹ and 1.24 × 10⁹ M⁻¹ s⁻¹, respectively, whereas ferulic acid and p-coumaric acid record 8.7 × 10⁸, 3.1 × 10⁸ M⁻¹ s⁻¹. For the sake of comparison of the quenching efficiencies, substituent effect and ΔG⁰ of the polyphenols with this complex, we have done this luminescent study with phenol also and the results are discussed here. Phenol shows the least k_q of 1.4 × 10⁸ M⁻¹ s⁻¹. Miedlar and Das reported this type of least k_q value for phenol in the photoredox reactions of [Ru(bpy)₃]²⁺. The availability of phenolate ions is more with respect to gallic acid (Angelique et al., 2010) due to the presence of three phenolic –OH groups, acts as an efficient quencher compared to the other polyphenols taken in the present study. Quercetin has two different pharmacophores, the catechol group (ring B) and the benzo-γ-pyrone derivative (ring A and C), of which the catechol moiety is the most reactive one where deprotonation occurs easily (Trouillas et al., 2006). Steric hindrance exerted by the benzo-γ-pyrone derivative at para-position of the ring B reduces its quenching efficiency when compared to gallic acid. This steric effect can be ascribed to the increase of electron transfer distance when the reaction occurs between two reactants carrying bulky groups (Swarnalatha et al., 2005). The quenching efficiency of thymol is somewhat lower than quercetin, due to the presence of one phenolic –OH and the isopropyl group at the ortho-position of phenol exerting a slight steric hindrance there by reducing the quenching rate constant. The hydroxyl derivatives of cinnamic acid (p-coumaric acid and ferulic acid) show the smallest k_q values. The –CH⚌CH–COOH chain at the para-position of phenol has electron acceptor properties and the stabilization of the resulting phenolate ion might be increased by electron delocalization. Hence the availability of phenolate ion is much less in p-coumaric acid and ferulic acid thus reduces the quenching rate constant. The k_q of ferulic acid is somewhat higher than p-coumaric acidformer due to the presence of an electron-releasing methoxy group in the ortho-position of the phenol. Here the nature of the substituent in the ortho- and para-positions of phenols affects the k_q.

The BDE for the phenolic –OH group in gallic acid (75.5 kcal/mol) (Harris et al., 2007), is less than that of the other phenols taken in the present study. Due to this low BDE, gallic acid undergoes ionization easily and acts as the most efficient quencher than quercetin, thymol, ferulic acid, p-coumaric acid and phenol. Though quercetin consists of four phenolic –OH groups, the BDE of the catechol group (ring B) is less compared to the phenolic –OH groups in ring A; therefore the catechol group undergoes oxidation easily (Trouillas et al., 2006). The quenching rate constant depends on the number of phenolic –OH groups present in the quencher. As the number of phenolic –OH group increases the quenching rate constant also increases. Here in this study the quenching rate constant for gallic acid is higher than the other phenols, owing to the presence of three phenolic –OH groups.

Phenolate ions containing alkyl groups in the ortho-position play an important role in the antioxidant activity of phenols (Lakowicz, 2006). The compounds with two or more electron donating groups have lower oxidation potentials than monosubstituted phenols, although –OH groups have stronger effects than –OCH₃ groups (Aleksandra et al., 2007). Here the oxidation potentials of the polyphenols containing electron releasing groups in the ortho-position are very low, i.e., ΔG⁰ becomes more negative. The ΔG⁰ values (Table 1) indicate that all reactions are exergonic except with phenol. The oxidation potential (0.78 V) and ΔG⁰ (0.06 eV) of phenol also support the lowest k_q for [Ru(nbpy)₃]²⁺ in DMSO. This is in good agreement with the reported k_q value for luminescent quenching of [Ru(bpy)₃]²⁺ by phenolate ions in aqueous medium at pH 12.5 (Swarnalatha et al., 2005). Gallic acid has a very low oxidation potential (0.082 V) and the ΔG⁰ value is more negative (−0.639 eV), hence it undergoes oxidation easily and acts as an efficient quencher compared to the other polyphenols taken in the present study. p-coumaric acid shows a high oxidation potential value of 0.67 V and the free energy change is −0.047 eV, recording a very low quenching rate constant. The oxidation potential of ferulic acid (0.51 V) is less than that of p-coumaric acid indicating that the former undergoes oxidation easily, and shows somewhat higher k_q than the latter. The oxidation potentials of quercetin and thymol are 0.3, and 0.41 V, respectively and the corresponding ΔG⁰ values are −0.422 and −0.307 eV. Thus the k_q values are highly sensitive to the oxidation potential of the quenchers and the ΔG⁰ of the reactions.

The k_q also depends on the electron transfer distance between the complex and the quenchers. From MM2 molecular model the radius of gallic acid, quercetin and thymol, are 4.1, 5.93 and 3.9 Å whereas p-coumaric acid and ferulic acid show the same radius (4.8 Å). The radius of thymol is less than that of gallic acid, hence the electron transfer distance is less in thymol than gallic acid but the k_q value of gallic acid is superior to thymol due to its lower oxidation potential (0.08 V) and ΔG⁰ value (−0.64 eV). Quercetin excerts greater electron transfer distance due to its high radius and it reduces the k_q. The radius of ferulic acid and p-coumaric acid seem to be the same but the nature of the substituent (–OCH₃) in the former increases the k_q to some extent than the latter. This result concludes that the k_q value depends not only on the ET distance but also on ΔG⁰ value.

The reductive quenching of ^∗[Ru(nbpy)₃]²⁺ by the phenolate ions has been confirmed from the transient absorption spectra (Fig. 5) and from the linear variation of log k_q vs oxidation potential of the phenols (Fig. 6). The band at 510 nm in the transient absorption spectra of the complex with quercetin confirms the reductive nature ([Ru(nbpy)₃]⁺) of the complex. The behavior of these redox systems can be discussed by a common mechanism depicted in Scheme 1 (Swarnalatha et al., 2005). The reactants diffuse together to form the encounter complex at the closest distance of approach. The electron transfer occurs in this association complex [^∗Ru(NN)₃²⁺ … ArO⁻] resulting in the formation of a caged pair of radicals or radical ions. These radical ions either escape from the solvent cage to give the redox products or undergo back electron transfer to form original reactants.

Transient absorption spectra of [Ru(nbpy)3]2+ at 100 ns after 355 nm laser flash photolysis in the absence and presence of 0.0008 M quercetin in DMSO.

Plot of log kq vs oxidation potential of quenchers.

Mechanism for the electron transfer quenching of ∗[Ru(NN)3]2+ with ArO−.

4 Conclusion

The present study clearly establishes the luminescence quenching mechanism of photoredox reactions of the ^∗[Ru(nbpy)₃]²⁺ with the polyphenols in DMSO. The k_q depends on the availability of phenolate ions, oxidation potentials of the polyphenols, ΔG⁰ values and the electron transfer distance between the ^∗[Ru(nbpy)₃]²⁺ and the quencher. The nature of the substituent in the ortho- and para-positions affects the quenching rate constant. Gallic acid behaves as an efficient quencher compared to other polyphenols due to the availability of more number of phenolate ions. The oxidation potential and the corresponding free energy change values also confirm the higher rate of quenching for gallic acid than other polyphenols taken in the present study. This study confirms the structural effect on the electron transfer reactions of biologically important phenolate ions with the excited state ^∗[Ru(nbpy)₃]²⁺.

Acknowledgments

One of the authors Sheeba Daniel thanks the Council of Scientific and Industrial Research (CSIR), New Delhi for the award of Senior Research Fellowship and Prof. P. Ramamurthy, Director, National Centre for Ultrafast Processes, University of Madras, Chennai for permitting to do lifetime measurements.

References

Adewale O., Adeloye A.O., Olomola T.O., Adebayo A.I., Ajibade P.A., . A high molar extinction coefficient bisterpyridyl homoleptic Ru(II) complex with trans-2-methyl-2-butenoic acid functionality: potential dye for dye-sensitized solar cells. Int. J. Mol. Sci.. 2012;13:3511-3526.
[Google Scholar]
Aleksandra S., Dragan M., Dejan S., Marija T., . Electrochemical behavior and antioxidant and prooxidant activity of natural phenolics. Molecules. 2007;12:2327-2340.
[Google Scholar]
Angelique C.E., Wanvimol P., Brett A.W., Garry R.B., . Free radicals produced by the oxidation of gallic acid: an electron paramagnetic resonance study. Chem. Cent. J. 2010
[CrossRef] [Google Scholar]
Astudillo P.D., Tiburcio J., González F.J., . The role of acids and bases on the electrochemical oxidation of hydroquinone: hydrogen bonding interactions in acetonitrile. J. Electroanal. Chem.. 2007;604:57-64.
[Google Scholar]
Balzani V., Credi A., Venturi M., . Light powered molecular machines. Chem. Soc. Rev.. 2009;38:1542-1550.
[Google Scholar]
Brewster T.P., Ding W., Schley N.D., Hazari N., Batista V.S., Crabtree R.H., . Thiocyanate linkage isomerism in a ruthenium polypyridyl complex. Inorg. Chem.. 2011;50:11938-11946.
[Google Scholar]
Brimblecombe R., Koo A., Dismukes G.C., Swiegers G.F., Spiccia L., . Solar driven water oxidation by a bioinspired manganese molecular catalyst. J. Am. Chem. Soc.. 2010;132:2892-2894.
[Google Scholar]
Campagna S., Puntoriero F., Nastasi F., Bergamini G., Balzani V., . Photochemistry and photophysics of coordination compounds: ruthenium. Top. Curr. Chem.. 2007;280:117-214.
[Google Scholar]
Castro A.M., Delgado J., Orellana G., . Hydrocarbon in water sensing with PTFE membranes doped with a luminescent Ru(II) poly(pyridyl) complex. J. Mater. Chem.. 2005;15:2952-2958.
[Google Scholar]
Chandrasekharam M., Rajkumar G., Rao C.H.S., Suresh T., Reddy P.Y., Soujanya Y., . Ruthenium(II)- bipyridyl with extended π-system: improved thermo-stable sensitizer for efficient and long-term durable dye sensitized solar cells. J. Chem. Sci.. 2011;123:555-565.
[Google Scholar]
Chi Y., Chou P.T., . Transition-metal phosphors with cyclometalating ligands: fundamentals and applications. Chem. Soc. Rev.. 2010;39:638-655.
[Google Scholar]
Chitra S., Somasundaram N., Easwaramoorthy D., . Ruthenium dyes with donor and acceptor moieties for TiO₂ solar cells. Arch. Appl. Sci. Res.. 2013;5:112-119.
[Google Scholar]
Cui Y., Niu Y.L., Cao M.L., Wang K., Mo H.J., Zhong Y.R., Ye B.H., . Ruthenium(II) 2,2^′-bibenzimidazole complex as a second-sphere receptor for anions interaction and colorimeter. Inorg. Chem.. 2008;47:5616-5624.
[Google Scholar]
Dunn B., Zink J.I., . Molecules in glass: probes, ordered assemblies and functional materials. Acc. Chem. Res.. 2007;40:747-755.
[Google Scholar]
Gianmaria F.F., Ivana A., Aniello I., Armando Z., Gabriele P., Antonino P., . Plant polyphenols and their anti-cariogenic properties: a review. Molecules. 2011;16:1486-1507.
[Google Scholar]
Gill M.R., Thomas J.A., . Ruthenium(II) polypyridyl complexes and DNA-from structural probes to cellular imaging and therapeutics. Chem. Soc. Rev.. 2012;41:3179-3192.
[Google Scholar]
Harris C.S., Mo F., Migahed L., Chepelev L., Haddad P.S., Wright J.S., Willmore W.G., Arnason J.T., Bennett S.A.L., . Plant phenolics regulate neoplastic cell growth and survival: a quantitative structure–activity and biochemical analysis. Can. J. Physiol. Pharmacol.. 2007;85:1124-1138.
[Google Scholar]
Holder E., Langeveld B.M.W., Schubert U.S., . New trends in the use of transition metal-ligand complexes for applications in electroluminescent devices. Adv. Mater.. 2005;17:1109-1121.
[Google Scholar]
Huili W., Jingwen M., Ailian D., Baoguang C., Wenwei W., Meiping M., Xuedong W., . Fuorescence quenching of 4-tert-octylphenol by room temperature ionic liquids and its application. J. Fluoresc. 2012 10.1007/s10895-012-1150-1
[Google Scholar]
Kalyanasundaram K., Graetzel M., . Artificial photosynthesis: biomimetic approaches to solar energy conversion and storage. Curr. Opin. Biotechnol.. 2010;21:298-310.
[Google Scholar]
Kavan L., Exnar I., Zakeeruddin S.M., Grätzel M., . Molecular wiring of olivine LiFePO₄ by ruthenium(II)-bipyridine complexes and by their assemblies with single-walled carbon nanotube. J. Phys. Chem. C. 2008;112:8708-8714.
[Google Scholar]
Lakowicz J.R., . Principles of Fluorescence Spectroscopy (third ed.). New York: Springer Press; 2006.
Lee K.W., Slinker J.D., Gorodetsky A.A., Torres S.F., Abruna H.D., Houston P.L., Malliaras G.G., . Photophysical properties of tris(bipyridyl)ruthenium(II) thin films and devices. Phys. Chem. Chem. Phys.. 2003;5:2706-2709.
[Google Scholar]
Li M.J., Chen Z., Yam V.W., Zu Y., . Multifunctional ruthenium(II) polypyridine complex-based core-shell magnetic silica nanocomposites: magnetism, luminescence, and electrochemiluminescence. ACS Nano.. 2008;2:905-912.
[Google Scholar]
Li L., Duan L.L., Xu Y.H., Gorlov M., Hagfeldt A., Sun L.C., . A photoelectrochemical device for visible light driven water splitting by a molecular ruthenium catalyst assembled on dye-sensitized nanostructured TiO₂. Chem. Commun.. 2010;46:7307-7309.
[Google Scholar]
Liao G.L., Chen X., Ji L.N., Chao H., . Visual specific luminescent probing of hybrid G-quadruplex DNA by a ruthenium polypyridyl complex. Chem. Commun.. 2012;48:10781-10783.
[Google Scholar]
Lo K.K., Lee T.K., Lau J.S., Poon W.L., Cheng S.H., . Luminescent biological probes derived from ruthenium(II) estradiol polypyridine complexes. Inorg. Chem.. 2008;47:200-208.
[Google Scholar]
Matos M.S., Holfkens J., Gehlen M.H., . Static and dynamic biomolecular fluorescence quenching of porphyrin dendrimers in solution. J. Fluoresc.. 2008;18:821-826.
[Google Scholar]
Metera K.L., Sleiman H.A., . Luminescent vesicles, tubules, bowls and star micelles from ruthenium bipyridine block copolymers. Macromolecules. 2007;40:3733-3738.
[Google Scholar]
Miedlar K., Das P.K., . (Tris(2,2^′-bipyridine)ruthenium(II)-sensitized photooxidation of phenols. environmental effects on electron transfer yields and kinetics. J. Am. Chem. Soc.. 1982;104:7462-7469.
[Google Scholar]
Mori S.N., Kubo W., Kanzaki T., Masaki N., Wada Y., Yanagida S., . Investigation of the effect of alkyl chain length on charge transfer at TiO₂/dye/electrolyte interface. J. Phys. Chem. C. 2007;111:3522-3527.
[Google Scholar]
Rajendran T., Rajagopal S., Srinivasan C., Ramamurthy P., . Micellar effect on the photoinduced electron-transfer reactions of ruthenium(II)-polypyridyl complexes with pnenolate ions. Effect of cetylammonium chloride. J. Chem. Soc. Faraday Trans.. 1997;93:3155-3160.
[Google Scholar]
Rajendran T., Thanasekaran P., Rajagopal S., AllenGnanaraj G., Srinivasan C., Ramamurthy P., Venkatachalapathy B., Manimaran B., Lu L., . Steric effects in the photoinduced electron transfer reactions of ruthenium(II)-polypyridine complexes with 2,6-disubstituted phenolate ions. Phys. Chem. Chem. Phys.. 2001;3:2063-2069.
[Google Scholar]
Ramamurthy P., . Build your data station for fast kinetic equipments. Chem. Educ.. 1993;9:56-60.
[Google Scholar]
Sannino D., Vaiano V., Ciambelli P., Zama I., Gorni G., . Evaluation of N719 amount in TiO₂ films for DSSC by thermogravimetric analysis. J. Therm. Anal. Calorim.. 2013;111:453-458.
[Google Scholar]
Schmittel M., Lin H., . Electropolymerisable ruthenium(II) phenanthroline carrying azacrown ether receptors: metal ion recognition in thin film redox sensors. J. Mater. Chem.. 2008;18:333-343.
[Google Scholar]
Siebert R., Winter A., Schubert U.S., Dietzek B., Popp J., . Molecular mechanism of dual emission in terpyridine transition metal complexes – ultrafast investigations of photoinduced dynamics. Phys. Chem. Chem. Phys.. 2011;13:1606-1617.
[Google Scholar]
Sun Y., Sibrina N.C., Lauren E.J., Turro C., . Unusual Photophysical properties of a ruthenium(II) complex related to [Ru(bpy)2(dppz)]²⁺. Inorg. Chem.. 2010;49:4257-4262.
[Google Scholar]
Swarnalatha K., Rajkumar E., Rajagopal S., Ramaraj R., Lu Y.L., Lu K.L., Ramamurthy P., . Photoinduced electron transfer reactions of ruthenium(II) complexes containing 2,2^′-bipyridine-4,4^′-dicarboxylic acid with phenols Steric and charge effects. J. Photochem. Photobiol. A Chem.. 2005;171:83-90.
[Google Scholar]
Swarnalatha K., Rajkumar E., Rajagopal S., Ramaraj R., Banu I.SP., Ramamurthy P., . Proton coupled electron transfer reaction of phenols with excited state ruthenium(II) – polypyridyl complexes. J. Phys. Org. Chem.. 2011;24:14-21.
[Google Scholar]
Tan L.F., Liu J., Shen J.L., Liu X.H., Zeng L.L., Jin L.H., . First ruthenium(II)-polypyridyl complex as a true molecular “Light Switch” for triplex RNA structure: [Ru(phen)(₂)(mdpz)]⁽²⁺⁾ enhances the stability of Poly(U)center dot Poly(A)(^∗)Poly(U) Inorg. Chem.. 2012;51:4417-4419.
[Google Scholar]
Tan L.F., Xie L.J., Sun X.N., . Binding properties of Ru(II) polypyridyl complexes with poly(U) poly(A)^∗poly(U) triplex: the ancillary ligand effect on third-strand stabilization. J. Biol. Inorg. Chem.. 2013;18:71-80.
[Google Scholar]
Thanasekaran P., Rajagopal S., Chockalingam S., . Photoredox reactions of tris(2,2^′-bipyrazine)-, tris(2,2^′-bipyrimidine)- and tris(2,3-bis[2-pyridyl] pyrazine)ruthenium(II) cations with phenolate ions in aqueous acetonitrile. J. Chem. Soc. Faraday Trans.. 1998;94:3339-3344.
[Google Scholar]
Trouillas P., Marsal P., Siri D., Lazzaroni R., Duroux J.L., . A DFT study of the reactivity of OH groups in quercetin and taxifolin antioxidants: The specificity of the 3-OH site. Food Chem.. 2006;97:679-688.
[Google Scholar]
Tuikka M., Hirva P., Rissanen K., Tommola J.K., Haukka M., . Halogen bonding – a key step in charge recombination of the dye-sensitized solar cell. Chem. Commun.. 2011;47:4499-4501.
[Google Scholar]
Verma S., Tripathi P.N., Rajesh P.S., . Marcus inverted region in the photoinduced electron transfer reactions of ruthenium(II)-polypyridine complexes with phenolate ions. Int. Multidiscip. Res. J.. 2012;2:45-50.
[Google Scholar]
White T.A., Knoll J.D., Arachchige S.M., Brewer K.J., . A series of supramolecular complexes for solar energy conversion via water reduction to produce hydrogen: an excited state kinetic analysis of Ru(II), Rh(III), Ru(II) photoinitiated electron collectors. Materials. 2012;5:27-46.
[Google Scholar]
Xu J., Wu H., Jia X., Zou D., . A dendron modified ruthenium complex: enhanced open circuit voltage in dye-sensitized solar cells. Chem. Commun.. 2012;48:7793-7795.
[Google Scholar]
Young K.J., Martini L.A., Milot R.L., Snoeberger R.C., Batista V.S., Schmuttenmaer C.A., Crabtree R.H., Brudvig G.W., . Light-driven water oxidation for solar fuels. Coord. Chem. Rev.. 2012;256:2503-2520.
[Google Scholar]
Zhu K., Jang S.R., Arthur J., . Frank effects of water intrusion on the charge-carrier dynamics, performance, and stability of dye-sensitized solar cells. Energy Environ. Sci.. 2012;5:9492-9495.
[Google Scholar]

Introduction

Experimental

Materials
Equipments
Luminescent quenching studies

Results and discussion

Electronic spectra and luminescent life time
Redox potential
Luminescence quenching of ∗[Ru(4,4′-dinonyl-2,2′- bipyridine)3]2+ with phenolate ions

Conclusion

Fulltext Views
1,058

PDF downloads
638

View/Download PDF
Download Citations

BibTeX
RIS

Show Sections

[1] Adewale O., Adeloye A.O., Olomola T.O., Adebayo A.I., Ajibade P.A., . A high molar extinction coefficient bisterpyridyl homoleptic Ru(II) complex with trans-2-methyl-2-butenoic acid functionality: potential dye for dye-sensitized solar cells. Int. J. Mol. Sci.. 2012;13:3511-3526.
[Google Scholar]

[2] Aleksandra S., Dragan M., Dejan S., Marija T., . Electrochemical behavior and antioxidant and prooxidant activity of natural phenolics. Molecules. 2007;12:2327-2340.
[Google Scholar]

[3] Angelique C.E., Wanvimol P., Brett A.W., Garry R.B., . Free radicals produced by the oxidation of gallic acid: an electron paramagnetic resonance study. Chem. Cent. J. 2010
[CrossRef] [Google Scholar]

[4] Astudillo P.D., Tiburcio J., González F.J., . The role of acids and bases on the electrochemical oxidation of hydroquinone: hydrogen bonding interactions in acetonitrile. J. Electroanal. Chem.. 2007;604:57-64.
[Google Scholar]

[5] Balzani V., Credi A., Venturi M., . Light powered molecular machines. Chem. Soc. Rev.. 2009;38:1542-1550.
[Google Scholar]

[6] Brewster T.P., Ding W., Schley N.D., Hazari N., Batista V.S., Crabtree R.H., . Thiocyanate linkage isomerism in a ruthenium polypyridyl complex. Inorg. Chem.. 2011;50:11938-11946.
[Google Scholar]

[7] Brimblecombe R., Koo A., Dismukes G.C., Swiegers G.F., Spiccia L., . Solar driven water oxidation by a bioinspired manganese molecular catalyst. J. Am. Chem. Soc.. 2010;132:2892-2894.
[Google Scholar]

[8] Campagna S., Puntoriero F., Nastasi F., Bergamini G., Balzani V., . Photochemistry and photophysics of coordination compounds: ruthenium. Top. Curr. Chem.. 2007;280:117-214.
[Google Scholar]

[9] Castro A.M., Delgado J., Orellana G., . Hydrocarbon in water sensing with PTFE membranes doped with a luminescent Ru(II) poly(pyridyl) complex. J. Mater. Chem.. 2005;15:2952-2958.
[Google Scholar]

[10] Chandrasekharam M., Rajkumar G., Rao C.H.S., Suresh T., Reddy P.Y., Soujanya Y., . Ruthenium(II)- bipyridyl with extended π-system: improved thermo-stable sensitizer for efficient and long-term durable dye sensitized solar cells. J. Chem. Sci.. 2011;123:555-565.
[Google Scholar]

[11] Chi Y., Chou P.T., . Transition-metal phosphors with cyclometalating ligands: fundamentals and applications. Chem. Soc. Rev.. 2010;39:638-655.
[Google Scholar]

[12] Chitra S., Somasundaram N., Easwaramoorthy D., . Ruthenium dyes with donor and acceptor moieties for TiO₂ solar cells. Arch. Appl. Sci. Res.. 2013;5:112-119.
[Google Scholar]

[13] Cui Y., Niu Y.L., Cao M.L., Wang K., Mo H.J., Zhong Y.R., Ye B.H., . Ruthenium(II) 2,2^′-bibenzimidazole complex as a second-sphere receptor for anions interaction and colorimeter. Inorg. Chem.. 2008;47:5616-5624.
[Google Scholar]

[14] Dunn B., Zink J.I., . Molecules in glass: probes, ordered assemblies and functional materials. Acc. Chem. Res.. 2007;40:747-755.
[Google Scholar]

[15] Gianmaria F.F., Ivana A., Aniello I., Armando Z., Gabriele P., Antonino P., . Plant polyphenols and their anti-cariogenic properties: a review. Molecules. 2011;16:1486-1507.
[Google Scholar]

[16] Gill M.R., Thomas J.A., . Ruthenium(II) polypyridyl complexes and DNA-from structural probes to cellular imaging and therapeutics. Chem. Soc. Rev.. 2012;41:3179-3192.
[Google Scholar]

[17] Harris C.S., Mo F., Migahed L., Chepelev L., Haddad P.S., Wright J.S., Willmore W.G., Arnason J.T., Bennett S.A.L., . Plant phenolics regulate neoplastic cell growth and survival: a quantitative structure–activity and biochemical analysis. Can. J. Physiol. Pharmacol.. 2007;85:1124-1138.
[Google Scholar]

[18] Holder E., Langeveld B.M.W., Schubert U.S., . New trends in the use of transition metal-ligand complexes for applications in electroluminescent devices. Adv. Mater.. 2005;17:1109-1121.
[Google Scholar]

[19] Huili W., Jingwen M., Ailian D., Baoguang C., Wenwei W., Meiping M., Xuedong W., . Fuorescence quenching of 4-tert-octylphenol by room temperature ionic liquids and its application. J. Fluoresc. 2012 10.1007/s10895-012-1150-1
[Google Scholar]

[20] Kalyanasundaram K., Graetzel M., . Artificial photosynthesis: biomimetic approaches to solar energy conversion and storage. Curr. Opin. Biotechnol.. 2010;21:298-310.
[Google Scholar]

[21] Kavan L., Exnar I., Zakeeruddin S.M., Grätzel M., . Molecular wiring of olivine LiFePO₄ by ruthenium(II)-bipyridine complexes and by their assemblies with single-walled carbon nanotube. J. Phys. Chem. C. 2008;112:8708-8714.
[Google Scholar]

[22] Lakowicz J.R., . Principles of Fluorescence Spectroscopy (third ed.). New York: Springer Press; 2006.

[23] Lee K.W., Slinker J.D., Gorodetsky A.A., Torres S.F., Abruna H.D., Houston P.L., Malliaras G.G., . Photophysical properties of tris(bipyridyl)ruthenium(II) thin films and devices. Phys. Chem. Chem. Phys.. 2003;5:2706-2709.
[Google Scholar]

[24] Li M.J., Chen Z., Yam V.W., Zu Y., . Multifunctional ruthenium(II) polypyridine complex-based core-shell magnetic silica nanocomposites: magnetism, luminescence, and electrochemiluminescence. ACS Nano.. 2008;2:905-912.
[Google Scholar]

[25] Li L., Duan L.L., Xu Y.H., Gorlov M., Hagfeldt A., Sun L.C., . A photoelectrochemical device for visible light driven water splitting by a molecular ruthenium catalyst assembled on dye-sensitized nanostructured TiO₂. Chem. Commun.. 2010;46:7307-7309.
[Google Scholar]

[26] Liao G.L., Chen X., Ji L.N., Chao H., . Visual specific luminescent probing of hybrid G-quadruplex DNA by a ruthenium polypyridyl complex. Chem. Commun.. 2012;48:10781-10783.
[Google Scholar]

[27] Lo K.K., Lee T.K., Lau J.S., Poon W.L., Cheng S.H., . Luminescent biological probes derived from ruthenium(II) estradiol polypyridine complexes. Inorg. Chem.. 2008;47:200-208.
[Google Scholar]

[28] Matos M.S., Holfkens J., Gehlen M.H., . Static and dynamic biomolecular fluorescence quenching of porphyrin dendrimers in solution. J. Fluoresc.. 2008;18:821-826.
[Google Scholar]

[29] Metera K.L., Sleiman H.A., . Luminescent vesicles, tubules, bowls and star micelles from ruthenium bipyridine block copolymers. Macromolecules. 2007;40:3733-3738.
[Google Scholar]

[30] Miedlar K., Das P.K., . (Tris(2,2^′-bipyridine)ruthenium(II)-sensitized photooxidation of phenols. environmental effects on electron transfer yields and kinetics. J. Am. Chem. Soc.. 1982;104:7462-7469.
[Google Scholar]

[31] Mori S.N., Kubo W., Kanzaki T., Masaki N., Wada Y., Yanagida S., . Investigation of the effect of alkyl chain length on charge transfer at TiO₂/dye/electrolyte interface. J. Phys. Chem. C. 2007;111:3522-3527.
[Google Scholar]

[32] Rajendran T., Rajagopal S., Srinivasan C., Ramamurthy P., . Micellar effect on the photoinduced electron-transfer reactions of ruthenium(II)-polypyridyl complexes with pnenolate ions. Effect of cetylammonium chloride. J. Chem. Soc. Faraday Trans.. 1997;93:3155-3160.
[Google Scholar]

[33] Rajendran T., Thanasekaran P., Rajagopal S., AllenGnanaraj G., Srinivasan C., Ramamurthy P., Venkatachalapathy B., Manimaran B., Lu L., . Steric effects in the photoinduced electron transfer reactions of ruthenium(II)-polypyridine complexes with 2,6-disubstituted phenolate ions. Phys. Chem. Chem. Phys.. 2001;3:2063-2069.
[Google Scholar]

[34] Ramamurthy P., . Build your data station for fast kinetic equipments. Chem. Educ.. 1993;9:56-60.
[Google Scholar]

[35] Sannino D., Vaiano V., Ciambelli P., Zama I., Gorni G., . Evaluation of N719 amount in TiO₂ films for DSSC by thermogravimetric analysis. J. Therm. Anal. Calorim.. 2013;111:453-458.
[Google Scholar]

[36] Schmittel M., Lin H., . Electropolymerisable ruthenium(II) phenanthroline carrying azacrown ether receptors: metal ion recognition in thin film redox sensors. J. Mater. Chem.. 2008;18:333-343.
[Google Scholar]

[37] Siebert R., Winter A., Schubert U.S., Dietzek B., Popp J., . Molecular mechanism of dual emission in terpyridine transition metal complexes – ultrafast investigations of photoinduced dynamics. Phys. Chem. Chem. Phys.. 2011;13:1606-1617.
[Google Scholar]

[38] Sun Y., Sibrina N.C., Lauren E.J., Turro C., . Unusual Photophysical properties of a ruthenium(II) complex related to [Ru(bpy)2(dppz)]²⁺. Inorg. Chem.. 2010;49:4257-4262.
[Google Scholar]

[39] Swarnalatha K., Rajkumar E., Rajagopal S., Ramaraj R., Lu Y.L., Lu K.L., Ramamurthy P., . Photoinduced electron transfer reactions of ruthenium(II) complexes containing 2,2^′-bipyridine-4,4^′-dicarboxylic acid with phenols Steric and charge effects. J. Photochem. Photobiol. A Chem.. 2005;171:83-90.
[Google Scholar]

[40] Swarnalatha K., Rajkumar E., Rajagopal S., Ramaraj R., Banu I.SP., Ramamurthy P., . Proton coupled electron transfer reaction of phenols with excited state ruthenium(II) – polypyridyl complexes. J. Phys. Org. Chem.. 2011;24:14-21.
[Google Scholar]

[41] Tan L.F., Liu J., Shen J.L., Liu X.H., Zeng L.L., Jin L.H., . First ruthenium(II)-polypyridyl complex as a true molecular “Light Switch” for triplex RNA structure: [Ru(phen)(₂)(mdpz)]⁽²⁺⁾ enhances the stability of Poly(U)center dot Poly(A)(^∗)Poly(U) Inorg. Chem.. 2012;51:4417-4419.
[Google Scholar]

[42] Tan L.F., Xie L.J., Sun X.N., . Binding properties of Ru(II) polypyridyl complexes with poly(U) poly(A)^∗poly(U) triplex: the ancillary ligand effect on third-strand stabilization. J. Biol. Inorg. Chem.. 2013;18:71-80.
[Google Scholar]

[43] Thanasekaran P., Rajagopal S., Chockalingam S., . Photoredox reactions of tris(2,2^′-bipyrazine)-, tris(2,2^′-bipyrimidine)- and tris(2,3-bis[2-pyridyl] pyrazine)ruthenium(II) cations with phenolate ions in aqueous acetonitrile. J. Chem. Soc. Faraday Trans.. 1998;94:3339-3344.
[Google Scholar]

[44] Trouillas P., Marsal P., Siri D., Lazzaroni R., Duroux J.L., . A DFT study of the reactivity of OH groups in quercetin and taxifolin antioxidants: The specificity of the 3-OH site. Food Chem.. 2006;97:679-688.
[Google Scholar]

[45] Tuikka M., Hirva P., Rissanen K., Tommola J.K., Haukka M., . Halogen bonding – a key step in charge recombination of the dye-sensitized solar cell. Chem. Commun.. 2011;47:4499-4501.
[Google Scholar]

[46] Verma S., Tripathi P.N., Rajesh P.S., . Marcus inverted region in the photoinduced electron transfer reactions of ruthenium(II)-polypyridine complexes with phenolate ions. Int. Multidiscip. Res. J.. 2012;2:45-50.
[Google Scholar]

[47] White T.A., Knoll J.D., Arachchige S.M., Brewer K.J., . A series of supramolecular complexes for solar energy conversion via water reduction to produce hydrogen: an excited state kinetic analysis of Ru(II), Rh(III), Ru(II) photoinitiated electron collectors. Materials. 2012;5:27-46.
[Google Scholar]

[48] Xu J., Wu H., Jia X., Zou D., . A dendron modified ruthenium complex: enhanced open circuit voltage in dye-sensitized solar cells. Chem. Commun.. 2012;48:7793-7795.
[Google Scholar]

[49] Young K.J., Martini L.A., Milot R.L., Snoeberger R.C., Batista V.S., Schmuttenmaer C.A., Crabtree R.H., Brudvig G.W., . Light-driven water oxidation for solar fuels. Coord. Chem. Rev.. 2012;256:2503-2520.
[Google Scholar]

[50] Zhu K., Jang S.R., Arthur J., . Frank effects of water intrusion on the charge-carrier dynamics, performance, and stability of dye-sensitized solar cells. Energy Environ. Sci.. 2012;5:9492-9495.
[Google Scholar]

Luminescence quenching of tris(4,4′-dinonyl-2,2′-bipyridyl) ruthenium(II) cation with phenolate ions in DMSO