Ground and excited state dynamics of new dinuclear ruthenium complexes: NMR, UV-Vis, IR, electrochemical, photophysical characterization, and theoretical study of Ru(bpy) 2(μ-dpp)Ru(CN-X) 4 n+ complexes

Margit Kovács, Gábor Szalontai, G. Lendvay, Günter Grampp, Attila Horváth

Research output: Contribution to journalArticle

Abstract

Two novel binuclear complexes of ruthenium(II) have been synthesized and characterized by various spectroscopic (NMR, IR, UV-Vis absorption and emission) and electrochemical methods. Extensive and detailed NMR studies of [(bpy) 2Ru(μ-dpp)Ru(CN) 4] 1 and [(bpy) 2Ru(μ-dpp) Ru(CNCH 3) 4] 4+ 2 complexes have revealed a dynamic equilibrium between the stereo isomers of the ground-state complexes. Small energy difference between the two isomers of 1 has been estimated using NMR data (2.7 kJ mol -1) and by quantum chemistry calculations (4.7 kJ mol -1). The relatively broad lowest energy absorption band appearing in the visible range is assigned as overlapping metal-to-ligand charge-transfer (MLCT) dπ(Ru) A → π*(μ-dpp) (MLCT 1A) and dπ(Ru) B → π*(μ-dpp) (MLCT 1B) transitions. The MLCT bands of complex 1 are solvatochromic (e.g. the lowest energy MLCT 1 band shifts from 506 to 540 nm upon changing the solvent from water to MeOH), while the same band of the complex 2 is not sensitive to the solvent nature. The luminescence properties of the excited 1 and 2 complexes are significantly different: (i) a rather small blue shift of the emission band (623 cm -1) is observed when the luminescence of complex 1 is detected at 77 K in rigid matrix instead of at ambient temperature in liquid phase. This blue shift is considerably larger (1923 cm -1) in the case of complex 2. (ii) Time resolved luminescence studies have revealed that the 3MLCT 1A and 3MLCT 1B excited states of complex 1 decay independently. On the other hand a dynamic equilibration occurs between two triplet excited states of complex 2. A slight interaction between the metal centers of complex 1 has been assumed by considering the electrochemical data, while a stronger coupling of the ruthenium atoms in complex 2 has been concluded by comparison of the oxidation potentials of the complex 2 with that of other binuclear ruthenium complexes of the metal centers possessing different chemical environment.

Original languageEnglish
Pages (from-to)261-270
Number of pages10
JournalInorganica Chimica Acta
Volume387
DOIs
Publication statusPublished - May 30 2012

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Ruthenium
Excited states
Ground state
ruthenium
Metals
Nuclear magnetic resonance
Charge transfer
nuclear magnetic resonance
ground state
Ligands
charge transfer
metals
excitation
ligands
Luminescence
Isomers
luminescence
blue shift
isomers
Quantum chemistry

Keywords

  • Binuclear complexes
  • Characterization
  • Isomers
  • Ruthenium(II)
  • Structure

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

Cite this

Ground and excited state dynamics of new dinuclear ruthenium complexes : NMR, UV-Vis, IR, electrochemical, photophysical characterization, and theoretical study of Ru(bpy) 2(μ-dpp)Ru(CN-X) 4 n+ complexes. / Kovács, Margit; Szalontai, Gábor; Lendvay, G.; Grampp, Günter; Horváth, Attila.

In: Inorganica Chimica Acta, Vol. 387, 30.05.2012, p. 261-270.

Research output: Contribution to journalArticle

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title = "Ground and excited state dynamics of new dinuclear ruthenium complexes: NMR, UV-Vis, IR, electrochemical, photophysical characterization, and theoretical study of Ru(bpy) 2(μ-dpp)Ru(CN-X) 4 n+ complexes",
abstract = "Two novel binuclear complexes of ruthenium(II) have been synthesized and characterized by various spectroscopic (NMR, IR, UV-Vis absorption and emission) and electrochemical methods. Extensive and detailed NMR studies of [(bpy) 2Ru(μ-dpp)Ru(CN) 4] 1 and [(bpy) 2Ru(μ-dpp) Ru(CNCH 3) 4] 4+ 2 complexes have revealed a dynamic equilibrium between the stereo isomers of the ground-state complexes. Small energy difference between the two isomers of 1 has been estimated using NMR data (2.7 kJ mol -1) and by quantum chemistry calculations (4.7 kJ mol -1). The relatively broad lowest energy absorption band appearing in the visible range is assigned as overlapping metal-to-ligand charge-transfer (MLCT) dπ(Ru) A → π*(μ-dpp) (MLCT 1A) and dπ(Ru) B → π*(μ-dpp) (MLCT 1B) transitions. The MLCT bands of complex 1 are solvatochromic (e.g. the lowest energy MLCT 1 band shifts from 506 to 540 nm upon changing the solvent from water to MeOH), while the same band of the complex 2 is not sensitive to the solvent nature. The luminescence properties of the excited 1 and 2 complexes are significantly different: (i) a rather small blue shift of the emission band (623 cm -1) is observed when the luminescence of complex 1 is detected at 77 K in rigid matrix instead of at ambient temperature in liquid phase. This blue shift is considerably larger (1923 cm -1) in the case of complex 2. (ii) Time resolved luminescence studies have revealed that the 3MLCT 1A and 3MLCT 1B excited states of complex 1 decay independently. On the other hand a dynamic equilibration occurs between two triplet excited states of complex 2. A slight interaction between the metal centers of complex 1 has been assumed by considering the electrochemical data, while a stronger coupling of the ruthenium atoms in complex 2 has been concluded by comparison of the oxidation potentials of the complex 2 with that of other binuclear ruthenium complexes of the metal centers possessing different chemical environment.",
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T1 - Ground and excited state dynamics of new dinuclear ruthenium complexes

T2 - NMR, UV-Vis, IR, electrochemical, photophysical characterization, and theoretical study of Ru(bpy) 2(μ-dpp)Ru(CN-X) 4 n+ complexes

AU - Kovács, Margit

AU - Szalontai, Gábor

AU - Lendvay, G.

AU - Grampp, Günter

AU - Horváth, Attila

PY - 2012/5/30

Y1 - 2012/5/30

N2 - Two novel binuclear complexes of ruthenium(II) have been synthesized and characterized by various spectroscopic (NMR, IR, UV-Vis absorption and emission) and electrochemical methods. Extensive and detailed NMR studies of [(bpy) 2Ru(μ-dpp)Ru(CN) 4] 1 and [(bpy) 2Ru(μ-dpp) Ru(CNCH 3) 4] 4+ 2 complexes have revealed a dynamic equilibrium between the stereo isomers of the ground-state complexes. Small energy difference between the two isomers of 1 has been estimated using NMR data (2.7 kJ mol -1) and by quantum chemistry calculations (4.7 kJ mol -1). The relatively broad lowest energy absorption band appearing in the visible range is assigned as overlapping metal-to-ligand charge-transfer (MLCT) dπ(Ru) A → π*(μ-dpp) (MLCT 1A) and dπ(Ru) B → π*(μ-dpp) (MLCT 1B) transitions. The MLCT bands of complex 1 are solvatochromic (e.g. the lowest energy MLCT 1 band shifts from 506 to 540 nm upon changing the solvent from water to MeOH), while the same band of the complex 2 is not sensitive to the solvent nature. The luminescence properties of the excited 1 and 2 complexes are significantly different: (i) a rather small blue shift of the emission band (623 cm -1) is observed when the luminescence of complex 1 is detected at 77 K in rigid matrix instead of at ambient temperature in liquid phase. This blue shift is considerably larger (1923 cm -1) in the case of complex 2. (ii) Time resolved luminescence studies have revealed that the 3MLCT 1A and 3MLCT 1B excited states of complex 1 decay independently. On the other hand a dynamic equilibration occurs between two triplet excited states of complex 2. A slight interaction between the metal centers of complex 1 has been assumed by considering the electrochemical data, while a stronger coupling of the ruthenium atoms in complex 2 has been concluded by comparison of the oxidation potentials of the complex 2 with that of other binuclear ruthenium complexes of the metal centers possessing different chemical environment.

AB - Two novel binuclear complexes of ruthenium(II) have been synthesized and characterized by various spectroscopic (NMR, IR, UV-Vis absorption and emission) and electrochemical methods. Extensive and detailed NMR studies of [(bpy) 2Ru(μ-dpp)Ru(CN) 4] 1 and [(bpy) 2Ru(μ-dpp) Ru(CNCH 3) 4] 4+ 2 complexes have revealed a dynamic equilibrium between the stereo isomers of the ground-state complexes. Small energy difference between the two isomers of 1 has been estimated using NMR data (2.7 kJ mol -1) and by quantum chemistry calculations (4.7 kJ mol -1). The relatively broad lowest energy absorption band appearing in the visible range is assigned as overlapping metal-to-ligand charge-transfer (MLCT) dπ(Ru) A → π*(μ-dpp) (MLCT 1A) and dπ(Ru) B → π*(μ-dpp) (MLCT 1B) transitions. The MLCT bands of complex 1 are solvatochromic (e.g. the lowest energy MLCT 1 band shifts from 506 to 540 nm upon changing the solvent from water to MeOH), while the same band of the complex 2 is not sensitive to the solvent nature. The luminescence properties of the excited 1 and 2 complexes are significantly different: (i) a rather small blue shift of the emission band (623 cm -1) is observed when the luminescence of complex 1 is detected at 77 K in rigid matrix instead of at ambient temperature in liquid phase. This blue shift is considerably larger (1923 cm -1) in the case of complex 2. (ii) Time resolved luminescence studies have revealed that the 3MLCT 1A and 3MLCT 1B excited states of complex 1 decay independently. On the other hand a dynamic equilibration occurs between two triplet excited states of complex 2. A slight interaction between the metal centers of complex 1 has been assumed by considering the electrochemical data, while a stronger coupling of the ruthenium atoms in complex 2 has been concluded by comparison of the oxidation potentials of the complex 2 with that of other binuclear ruthenium complexes of the metal centers possessing different chemical environment.

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