pH Dependence of Absorption and Emission Spectra of Ru(phen)2(phenOH)2+(PF6)2 Complex

Aaron I. Baba, Simeon Atiga, Adejoh Ocheni


A ruthenium complex of the 4-hydroxy- 1,10-phenanthroline ligand was synthesized, and the variation of its absorption and emission intensity and litetime with pH characterized. Excited state lifetime, luminescence intensity, and emission properties were determined.  The complex exhibits a maximum at 460nm, and a small red shift at higher pH. The spectra show a well defined isobestic point. Luminescence intensity exhibited a sigmoidal relationship with pH, a behaviour that is similar to those of other ruthenium complexes carrying protonable functional groups. This characteristic is suggestive of the suitability of this complex for pH sensor design for medical practices as well as industrial processes. pH dependence is more evident in the emission than the absorption spectra, a behaviour characteristic of higher pH dependence on the excited than the ground state of the complex. Emission lifetimes of 165.4ns and 3.08ns for the protonated and deprotonated states respectively, were determined and the pK*a value calculated as 3.68.


Ruthenium; Phenanthroline; pH; Intensity; Sensor; Spectroscopic

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Ajay, J., Wenying, X.,Demas, J. N., & DeGraff, B. A. (1998). Binding of luminescent ruthenium (II) molecular probes to vesicles. Inorg. Chem., 37(8), 1876-1879.

Chan, C., Fung C., Wong K., & Lo W. (1998). Evaluation of a luminescent ruthenium complex immobilized inside nafion as optical pH sensor. Analyst, 123, 1843-1847.

Concepcion, J. J., House, R. L, Papanikolas J. M., & Meyer, T. J. (2012). Artificial photosynthesis of ruthenium complexes. PNAS, 109(39), 15560-15564.

Dollberg, C. L., & Turro, C. (2001). New quinone diimine complex of zinc with pH-dependent emission in the visible region. Inorg. Chem., 40, 2484-2485.

Ellerbrock, J. C., McLoughlin, S. M., & Baba, A. I. (2002). The effect of pH on the emission and absorption spectra of a ruthenium complex. Inorg. Chem. Comm., 5, 555-559.

Giarikos, D. G. (2013.) Artificial photosynthesis: Ruthenium complexes, in natural and artificial photosynthesis: Solar power as an energy source. In R. Razeghifard (Ed.). John Wiley & Sons Inc., Hoboken, NJ, USA. doi: 10.1002/9781118659892.ch5

Giordano, P. J., Bock, C. R., & Wrighton, M. S. (1978). Excited state proton transfer of ruthenium (II) complexes of 4,7-dihydroxy-1,10-phenanthroline. Increased acidity in the excited state. J. Am. Chem. Soc., 100, 6960-6965.

Guilbault, G. G. (1990). Practical fluorescence (2nd ed., pp.51-57). New York: Marcel Dekker, Inc.

Hartmut, R., Satoru, S., & Michael, F. R. (2002). Solid-state light-emitting devices based on the tris-chelated ruthenium (II) complex. 4. High-efficiency light-emitting devices based on derivatives of the tris (2,2‘-bipyridyl) ruthenium (II) complex. J. Am. Chem. Soc., 124(17), 4918-4921.

Heather, M. R., Wenying, X., Demas, J. N., & DeGraff, B. A. (2002). Metal ion sensors based on a luminescent ruthenium(II) complex: The role of polymer support in sensing properties. Applied Spectroscopy, 56, 167-173.

Helena, M. R., Gonc A., César, D., Mauleb, C., Pedro, A. S., & Jorgec, J. (2008). Fiber optic lifetime pH sensing based on ruthenium(II) complexes with dicarboxybipyridine. Analytica Chimica Act, 626, 62-70.

Henrique, E. T. (2003). Molecular materials and devices: Developing new functional systems based on the coordination chemistry approach. J. Braz. Chem. Soc., 14, 845-869.

Hicks, C., Ye, G., Levi, C., Gonzales, M., Rutenburg, I., Fan, J. W., … Gafney, H. D. (2001). Excited-state acid-base chemistry of coordination complexes. Coord. Chem. Rev., 211, 207-222.

Higgins, B., & DeGraff, B. A. (2005). Luminescent transition metal complexes as sensors: Structural effects on pH response. Inorg. Chem., 44, 6662-6669.

Hong, X., Chengbo, Z., Song, Q., Ping, L., Jingying, Z., & Yuguang, M. (2004). Highly efficient red phosphorescent light-emitting diodes based on ruthenium(II)-complex-doped semiconductive polymers. Appl. Phys. Lett., 84, 290-292.

Kalyanasundaram, K., Naeeruddin, M., Gatzel, M., Viscardi, G., Savarino, P., & Barni, E. (1992). Synthesis and photophysical characterization of highly luminescent complexes of ruthenium(II) Containing 4,4′-di (p-carboxyphenyl)-2,2′-bipyridine. Inorg. Chim. Acta., 198-200, 831-839.

Kim, H. J., Jeong, Y. C., Heo, J., Rhee, J., & Hwang, K. (2009). A wide-range luminescent pH sensor based on ruthenium (II) complex. Bull. Korean Chem. Soc., 30(3), 539.

Kohjiro, H., Hideki, S., Yasuhiro, T., Ashraful, I., Masatoshi, Y., Kazuhiro, S., & Hironori, A. (2001). Dye-sensitized nanocrystalline TiO2 solar cells based on ruthenium (II) phenanthroline complex photosensitizers. Langmuir, 17(19), 5992-5999.

Lin, J., Brown, & C. W. (2000). Recent development and applications of optical and fiber-optic pH sensor. Trends Anal. Chem., 19(9), 541.

Maman, N., Dhami, S., Phillips, D., & Brault, D. (1999). Kinetic and equilibrium studies of incorporation of di-sulfonated aluminum phthalocyanine into unilamellar vesicles. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1420(1-2), 168-178.

Nazeeruddin, M. K., Pe’chy, P., Renouard, T., Zakeeruddin, S. M., Humphry-Baker, R., Comte, … Gra1tzel, M. (2001). Engineering of efficient panchromatic sensitizers for nanocrystalline TiO2-based solar cells. J. Am. Chem. Soc., 123, 1613-1624.

Robin, B., Annette, K., Dismukes, G. C., Gerhard, F. S., & Leone, S. (2010). Solar driven water oxidation by a bioinspired manganese molecular catalyst. J. Am. Chem. Soc., 132(9) 2892-2894.

Ronald, G., Jeremy, M. H., Shaun, K. J., & Amilaprasadh, N. (1994). Luminescent pH sensors based on p-tert-butylcalix[4]arene-linked ruthenium(II) trisbipyridyl complexes. J. Chem. Soc., Chem. Commun., 185-187.

Sarah, J. P., Gina, L. F., Cassandra, L. F., & Demas, J. N. (2010). Luminescence oxygen sensor based on a ruthenium(II) star polymer complex. Anal. Chem., 82(3), 917-921.

Santos, G., Andrade, A. M., Patrocínio, A. O. T., Mizoguchi, S. M., Murakami, I. N. Y., Peres M., ... Pereira, L. (2008). Development and characterization of Light-Emitting Diodes (LEDs) based on ruthenium complex single layer for transparent displays. Physica Status Solidi (a), 205(8), 2057-2060.

Schulman, S. G. (1988). Molecular luminescence spectroscopy, methods and applications, Part 2. USA: John Wiley & Sons Inc.

Sheeba, D., & George, A. G. R. (2013). Luminescence quenching of tris(4,4’-dinonyl-2,2’- bipyridyl) ruthenium(II) cation with phenolate ions in DMSO. Arabian Journal of Chemistry. Retrieved from

Sun L., Åkermark, B., Styring, S., & Hammarström, L. (2001). Chemical approaches to artificial photosynthesis. Chem. Soc. Rev., 38, 36; E. A. Medlycott, G. S. Hanan. (2006). Coord. Chem. Rev., 1763-1782.

Sylvestre, B., & Jean, P. C. (2008). Ruthenium-based light-driven molecular machine prototypes: Synthesis and properties. Chem. Soc. Rev., (37), 1207-1217.

Szmacinski, H., Terpetschnig, E., & Lakowicz, J. R. (1996). Synthesis and evaluation of ru-complexes as anisotropy probes for protein hydrodynamics and immunoassays of high-molecular-weight antigens. Biophys. Chem., 62(1-3), 109-20.

Wacholtz, W. F., Auerbach, R. A., & Schmehl, R. H. (1986). Independent control of charge-transfer and metal-centered excited states in mixed-ligand polypyridine ruthenium(II) complexes via specific ligand design inorg. Chem., 25(2), 227-234.

Wolfbeis, O. S. (2005). Materials for fluorescence-based optical chemical sensors. J. Mater. Chem., 15, 2657-2669.

Wolfbeis, O. S., Klimant, I., Werner, T., Huber, C., Kosch, U., Krause, G., … Dürkop, A. (1998). Set of luminescence decay time based chemical sensors for clinical applications. Sensors and Actuators, B., 51, 17-24.

Wong, C., Chung, L., Lin, S., Chan, D. S., Leung, C., & Ma, D. (2014). A ruthenium(II) complex supported by trithiacyclononane and aromatic diimine ligand as luminescent switch-on probe for biomolecule detection and protein staining. Scientific Reports, 4. Article number: 7136. doi:10.1038/srep07136

Wu, A., Yoo, D., Lee, J. K., & Rubner, M. F. (1999). Solid-state light-emitting devices based on the tris-chelated ruthenium(II) complex: 3. High efficiency devices via a layer-by-layer molecular-level blending approach. J. Am. Chem. Soc., 121(20), 4883-4891.

Xie, P., Hou, Y., Zhang, B., Cao, Y., Wu, F., Tian, W., & Shen, J. (1999). Spectroscopic and electrochemical properties of ruthenium(II) polypyridyl complexes. J. Chem. Soc., Dalton Trans., 4217-4221.

Yu, Q., Huang, J., Shen, Y., Xiao, L., Liu, J., Kuang, D., & Su, C., (2013). Novel phenanthroline-based ruthenium complexes for dye-sensitized solar cells: Enhancement in performance through fluoro-substitution. RSC Adv., (3), 19311-19318.

Yuancheng, Q., & Qiang, P. (2012). Ruthenium sensitizers and their applications in dye-sensitized solar cells. International Journal of Photoenergy, 21. Article ID 291579. doi:10.1155/2012/291579

Zhang, Y., Liu, Z., Yang, K., Zhang, Y., Xu, Y., Li, H.,... Sun, S. (2015). A ruthenium(II) complex as turn-on cu(II) luminescent sensor based on oxidative cyclization mechanism and its application in vivo. Scientific Reports, 5, Article Number: 8172.

Zheng, G. Y., Wang, Y., & Rillema, D. P. (1996). Acid-base properties of the ground and excited states of ruthenium(II) Bis(2,2’-bipyridine) 3-carboxyl-2,2’-bipyridine. Inorg Chem., 35(24), 7118-7123.




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