1. Spectroscopic Analysis of Therapeutic Drugs
Laura Perdisatt, Christine O’Connor, Samar Moqadasi, Luke O’Neill
DT203/4 Forensic and Environmental Analysis
School of Chemical and Pharmaceutical Sciences, DIT
1. Introduction
The aim of this project was to investigate the photochemistry of three new Ruthenium (II) complexes as possible therapeutics and their associated ligands. The objectives were to use the following spectroscopic techniques: Absorption, Emission and Raman spectroscopy. Luminescent lifetime measurements were obtained by laser studies (Nd:YAG laser and Time coupled single photon counting (TCSPC) ).
3. Laser Studies
The luminescent lifetimes were determined for each of the complexes under two conditions aerated and degassed. The aerated lifetimes were found to be significantly shorter than the degassed solutions and this is shown in table 3.
Complex Name
(τ) Lifetime ns (Nd:YAG)
(τ)Lifetime ns (TCSPC)
Ru(bpy)2fmp
160 (204)
155
Ru(bpy)2mfmp
183 (286)
182
Ru(bpy)2NO2-mp
102 (164) 96
Complexes
Ligands
Ru(bpy)2fmp
fmp
Ru(bpy)2mfmp
mfmp
Ru(bpy)2NO2-mp
NO2-mp
Table 1: All The complexes and ligands investigated in this project.
Figure 1: The ruthenium complex structure where R1& R2= (H, CHO), (CHO, H), (H, NO2) for fmp, mfmp and NO2-mp respectively
Table 3 Comparison of aerated and degassed(in brackets) luminescent lifetimes from both laser techniques
4. Raman Spectroscopy
Raman Spectroscopy was completed on one of the complexes Ru(bpy)2NO2-mp as a powder at a laser line of 785 nm. This laser line proved to have one of the weakest fluorescence signals in comparison to the others as an emission study was completed by exciting the complexes at various wavelengths (488 nm, 514 nm, 540 nm, 633 nm, 660 nm & 785 nm.). The highest fluorescence signal was observed at 488 nm which was expected as its very close to their absorption (λmax).
2. Experimental Details & Absorption/Emission Spectroscopy Results
A concentration range of 0.1 mM to mM were made of each complex and ligand. The complexes were thermally stable and soluble in MeCN and the ligands soluble in DMSO. The extinction coefficients were determined along with the quantum yields for the complexes relative to a standard Ru(bpy)3Cl2 and the results are shown in Table 2. The emission spectra of each of the complexes can be seen below in figure 2.
(a)
(b)
Figure 2: Emission Spectra of all the complexes and standard at 0.1 mM in MeCN excited at their λmax
Compound Name
Abs
λmax (nm)
Extinction coefficient
Emission λmax (nm)
Quantum Yield (Φf)
Ru(bpy)2fmp
457
10,600
597
0.29
Ru(bpy)2mfmp
12,480
0.21
Ru(bpy)2NO2-mp
456
22,480
600
0.08
Std: Ru(bpy)3Cl2
451
12,108
602
0.20
fmp
284
14,280
424.5
n/a
mfmp
25,320
425
NO2-mp
294
20,080
592
Figure 3: (a)Ru(bpy)2NO2-mp emission intensity at excitation wavelengths of 488 nm (green), 514 nm (blue) and 540 nm (red). (b) The Raman Spectrum at 785 nm laser line.
5. Conclusion
Absorption and Emission studies were completed on each of the Ru (II) complexes and ligands and from this the extinction coefficients and quantum yields were calculated. The luminescent lifetimes were determined for each of the ruthenium (II) complexes by two laser techniques ( Nd:YAG and TCSPC). Preliminary Raman studies was completed on the complex, Ru(bpy)2NO2-mp.
6. Acknowledgments
A huge thank you to Christine O’Connor, Samar Moqadasi and Luke O'Neill for all their help
Table 2: Absorption and Emission λmax with corresponding extinction coefficients and quantum yields of the Ru(II) complexes and ligands