Related Experiment Video
Updated: Jul 14, 2026
05:32
In Vitro Chemical Mapping of G-Quadruplex DNA Structures by Bis-3-Chloropiperidines
Published on: May 12, 2023
Marked differences in light-switch behavior of Ru(II) complexes possessing a tridentate DNA intercalating ligand
Yao Liu1, Richard Hammitt, Daniel A Lutterman
1Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
Inorganic Chemistry
|June 15, 2007
Summary
Ruthenium complexes with the pydppz ligand show varied DNA interactions. The heteroleptic complex [Ru(tpy)(pydppz)](2+) exhibits longer excited-state lifetimes, DNA luminescence enhancement, and photocleavage, unlike the homoleptic [Ru(pydppz)(2)](2+).
Area of Science:
- Coordination Chemistry
- Photophysics
- Biophysical Chemistry
Background:
- Ruthenium(II) complexes are widely studied for their photophysical properties and potential applications in medicine and materials science.
- The tridentate ligand 3-(pyrid-2'-yl)dipyrido[3,2-a:2',3'-c]phenazine (pydppz) offers unique structural features for designing novel metal complexes.
- Understanding the influence of ligand environment on the photophysical and DNA-binding properties of ruthenium complexes is crucial for developing targeted therapeutics.
Purpose of the Study:
- To synthesize and characterize homoleptic [Ru(pydppz)(2)](2+) and heteroleptic [Ru(tpy)(pydppz)](2+) complexes.
- To investigate the photophysical properties, including excited-state lifetimes and DNA interactions, of these novel ruthenium complexes.
- To elucidate the structure-activity relationships governing DNA intercalation, luminescence enhancement, and photocleavage capabilities.
Main Methods:
- Synthesis of the pydppz ligand and its subsequent complexation with ruthenium(II).
- Characterization using 1H NMR spectroscopy, absorption, and emission spectroscopy.
- Femtosecond transient absorption spectroscopy to determine excited-state lifetimes.
- DNA binding studies, including luminescence enhancement and photocleavage assays.
- Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations.
Main Results:
- Both homoleptic and heteroleptic ruthenium complexes were successfully synthesized and characterized.
- The (3)MLCT excited-state lifetimes of [Ru(tpy)(pydppz)](2+) (5 ns) and [Ru(pydppz)(2)](2+) (2.4 ns) are significantly longer than that of [Ru(tpy)(2)](2+) (120 ps), attributed to lower-energy MLCT states.
- [Ru(tpy)(pydppz)](2+) shows luminescence enhancement upon DNA binding and induces DNA photocleavage in air, while [Ru(pydppz)(2)](2+) does not exhibit these properties.
- DFT calculations support the observed photophysical differences and DNA interaction mechanisms.
Conclusions:
- The pydppz ligand significantly influences the photophysical properties and DNA interaction modes of ruthenium complexes.
- The heteroleptic complex [Ru(tpy)(pydppz)](2+) demonstrates promising photophysical characteristics for potential DNA-targeting applications due to its longer-lived excited state and ability to induce photocleavage.
- The differential photophysical behavior in the presence of DNA is linked to the intercalation efficiency of the pydppz ligands.
Related Concept Videos
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:52Stereoisomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
02:34Structural Isomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...