The Ruthenium Complex of Bis(1,10-Phenanthrolin- 2-yl)amine,
synthesis, structure and properties.
Chia-Jung Hsu, Hsien-Chang Kao, Abdel Ghany Shoair and Wen-Jwu Wang*
Department of Chemistry, Tamkang University, 151 Ying-chuan Road, Tamsui, Taipei
25137, Taiwan, Republic of China. E-mail: wjw@mail.tku.edu.tw
Abstract
Transition metal complexes of macrocycle provide a rigid geometry structure and
electronic environment can be fit desired chemical properties. Pseudo cyclic ligand,
HDPA (bis-(1,10-phenanthrolino-2-yl)-amine) was synthesized by condensation of
2-chloro-1,10-phenathroline in ammonia gas atmosphere. Structure of HDPA and
HDPA·HCl salt has been determined by x-ray diffractometry.
[Ru(HDPA)Cl2] (1) and
[Ru(HDPA)(PPh3)2](PF6)2 (2) complexes was obtained from reflux of HDPA with RuCl3
and [Ru(PPh3)Cl2] (PPh3 = triphenylphosphine). These complexes have been
characterized by EA. MS and H1-NMR. The structure of (2) is shown in Figure1. The
dihedral angle of two 1,10-phenanthroline moieties is lowered to 2.35 o. Luminescence
spectrum of (1) showed a phosphorescent at 822nm with vibronic fine splitting peaks
came from aromatic ring of 1,10-phenanthroline in room temperature.
Keywords: phenanthroline, macrocycle, Ru complex, luminescence spectrum,
electrochemistry.
Introduction
Azamacrocyclic system has interesting electron properties compare with porphyrin
and relative system has extensity for electron transfer system. The recent interesting
seems to be focused on transition metal complexes of cyclic like analogous ligands to
develop of reducing agent for biological study, for example, the ruthenium complex of
macrocycle use 1,10-phenanthroline can provided planer geometry structure to
decrease stereo effect effective to enhance binding ability with DNA and cleavage of
DNA.Transition metal complexes of macrocycle can provided rigid geometry structure
and electronic environment to fit and enhance desired chemical properties.[1,2]
Experiment Section
Electrochemical Cyclic Voltammetry prduced by EG&G Potentiostat / Galvanostat
Model 283, the reference electrode was Ag/AgCl, working electrode was glassy carbon
electrode, counter electrode was Pt rod. TEAP (tetraethylammonium perchlorate) was
used as electrolyte, prepared all the sample concentration about 10-5M and electrolyte
concentration was 0.01M fresh solution to measurement. The UV-Vis spectra produced
by Simadzu UV/1601 UV/Vis spectrometer, range was 1000 to 200 nm, band width was
1nm, scan rate was FAST. All the emission spectra produced by Aminco Bowman
SLM-AMINCO luminescence spectrometer, sample dissolved in mix solvent of
methanol and ethanol 1:4,than solvent degas of oxygen by frozen in liquid nitrogen and
under Argon environment repeated 3 times, used continuous wave, voltage 550V,
excitation band width was 8 wave number, emission band width was 8 wave number.
Result and discussion
Pseudo cyclic ligand HDPA (Bis-(1,10- phenanthrolino-2-yl)-amine) was synthesis
by condensation of CP (2-chloro-1,10-phenathroline) in ammonia gas environment
[3]
and it’s single crystal x-ray structure have been obtain. X-ray structure showed HDPA
(figure 1) have two tautomerism isomers inner and outer form, the ligand HDPA used
semi-empirical Hamiltonian PM3 parameter in MOPAC their geometry optimized
structure was obtain than investigated two geometry isomer of the energy state, HDPA
inner form HOMO was –6.935eV, HDPA outer form HOMO was –7.492eV, in addition
found the UV-Vis spectrum have remarkable different in 300-500nm by compare of this
two isomer that have a unlike in geometry structure.
HDPA
can
coordinate
as
tetra-dentate
ligand
reflux
with
RuCl3
or
[Ru(PPh3)Cl2](PPh3 = triphenylphosphine) in ethanol to give ruthenium complexes of
[Ru(HDPA)Cl2] (1) and [Ru(HDPA)(PPh3)2](PF6)2 (2) this complexes had characterized
by elemental analysis, mass and H1-NMR.
The X-ray structure of 2 has also obtained (figure 2). Two triphenylphosphine can
coordinate at trans site to metal, the large stereo effect of triphenylphosphine to
decrease of dihedral angle of 1,10-phenanthroline moieties to 2.35o. In UV-vis pH
titration experiment of 1 (figure 3) can find one pKa value at 7.6 when a proton leave
from bridge amine group of ligand. In UV-vis redox titration found a new peak growth at
550nm by oxidization of 1 from RuIII to RuII it show the oxidation state of complex will be
reversible. The cyclic voltammetry of complex 1 (figure 4) can find quasi-reversible
peaks by RuIII/RuII at 1.00V and irreversible peak of RuII reduction to RuI at -0.38V, after
reduction 1 at –0.10V will change axial ligand from Cl- to AN (AN= acetonitrile) and
show at [RuII(HDPA)(Cl)(AN)] oxidize to [RuI(HDPA)(Cl)(AN)] this redox peaks will be
reversible. Finally In luminescence spectrum of 1 it’s have fine triplet state splitting
peak came from 1,10-phenanthroline aromatic ring vibration mode in room temperature
at 822nm, compare with [Ru(bpy)3]2+ need quench to 80K can found fine triplet state
splitting peak, this advantage will be provide more useful information for biological
system examine[4,5].
Conclusion
In this report have two single crystal x-ray structure of ligand HDPA and
[RuII(HDPA)(PPh3)2](PF6)2.In pH titration experiment can found the dissociation
constant pKa of [Ru(HDPA)Cl2]+ was 7.6. The CV spectra of [Ru(HDPA)Cl2]+ show
RuIII-RuII redox potential at 1.0V and RuII-RuI at -0.1V and found the axial ligand can be
changed by solvnet acetonitrile. Finally the luminescence spectrum of [Ru(HDPA)Cl2]+
show at 788nm, 822nm have vibronic coupling emission this is unusual behavior of
this kinds of polypyridine Ruthenium systems.
Reference
[1] Wang, W. J., Chuang, K. S., Luo, C. F., Liu, H. Y., Tetrahedron Lett. 41, 8565
(2000).
[2] Wang, W. J., Liu, H. Y., Chuang, K. S., Luo, Chi. F., Molecules 5, [1] M133 (2000).
[3] Wang, W. J., Sengul, A., Luo,C. F., Kao, H. C., Cheng, Y. H., Tetrahedron Lett. 44,
7099 (2003).
[4] Hirai, M., Shinozuka, K., Ogawa, S., Sawai, H., Chem. Lett. 1113 (1996).
[5] Hirai, M., Shinozuka, K., Sawai, H., Ogawa, S., Chem. Lett. 2023 (1992).
Figure 1. ORTEP diagram of [HDPA], hydrogen atoms have been omitted for clarity.
Bridging nitrogen-phenanthroline distances was C(10)-N(3) 1.407Å and C(13)-N(3)
1.396Å, Bridge C(10)-N(3)-C(13) angle was 131.86º, Dihedral angle of two
phenanthroline was 178.09º.
Figure 2. ORTEP diagram of [Ru(HDPA)(PPh3)2], counter ions (PF6-) and hydrogen
atoms have been omitted for clarity. Ru-N bond length was 2.049 Å, Ru-P bond length
was 2.435 Å. Bridging nitrogen-phenanthroline distances was C(10)-N(5) 1.441 Å and
C(22)-N(5) 1.419 Å, Bridge C(10)-N(5)-C(22)angle 137.74 Å. Dihedral angle of two
phenanthroline was 2.35º.
Figure 3. Change pH value in the UV/Vis spectra of [Ru(HDPA)Cl2]+ in EtOH 7.34x10-7
M. Add TEAOH control pH value from 6.68 to 8.65.
Figure 4. CV spectra of [Ru(HDPA)Cl2]+ in acetonitrile.