Project Number: MQP-REC-0046 Synthesis and Photophysical Properties of (2E,5E)-2-benzylidene-5-(4- dimethylaminobenzylidene)-cyclopentanone A Major Qualifying Project Submitted to the faculty of WORCESTER POLYTECHNIC INSTITUTE In partial fulfillment of the requirements for the Degree of Bachelor of Science in Chemistry By: Laura E. Murray on April 25, 2013 Approved by: _____________________________ Professor Robert E. Connors, PhD Project Advisor Abstract This project continues research of photophysical properties of asymetrically substituted 2,5-diarylidene cyclopentanone dyes. A new conjugated cyclopentanone dye (2E,5E)-2- benzylidene-5-(4-dimethylaminobenzylidene)-cyclopentanone was synthesized and its photophysical properties studied. Absorbance and fluorescence spectra taken in several solvents of varying polarity illustrated that the maxima undergo a red shift with increasing solvent polarity. Quantum yields were calculated from fluorescence curves and radiative and nonradiative decay constants were calculated from lifetime measurements in dichloromethane, ethanol, and toluene. Geometry optimization and TD-DFT calculations were also performed for this new compound. 2 Acknowledgements I would like to acknowledge and extend my utmost thanks to Professor Robert E. Connors for the use of his equipment and materials as well as his help and guidance as I underwent this project. I would also like to recognize Christopher Zoto for his continuous help and support throughout the year, and to Cara DiIorio, another MQP student with whom I spent several hours in lab where we could help each other out. 3 Contents Abstract ......................................................................................................................................................... 2 Acknowledgements ....................................................................................................................................... 3 List of Tables ................................................................................................................................................. 5 List of Figures ................................................................................................................................................ 6 Introduction .................................................................................................................................................. 7 Experimental ................................................................................................................................................. 9 Synthesis of (E)-2-benzylidene-cyclopentanone (1pdbun) ....................................................................... 9 Synthesis of (2E,5E)-2-benzylidene-5-(4-dimethylaminobenzylidene)-cyclopentanone (bdmab) ......... 11 Spectroscopic and Photophysical Measurements ...................................................................................... 12 Absorbance and Fluorescence Spectra ................................................................................................... 12 Fluorescence Quantum Yield Measurements ......................................................................................... 12 Fluorescence Lifetime Measurements .................................................................................................... 13 Synthetic Analysis Spectra ...................................................................................................................... 14 Results and Discussion ................................................................................................................................ 19 Absorbance and Fluorescence Spectra ................................................................................................... 20 TD-DFT Results ........................................................................................................................................ 21 Spectroscopic Analysis Spectra ............................................................................................................... 22 Conclusions ................................................................................................................................................. 27 Appendix A: Procedures .............................................................................................................................. 29 Creating a Stock Solution with Serial Dilutions of known concentration ........................................... 29 Two Phase Extraction .......................................................................................................................... 29 Preparing a column for column chromatography............................................................................... 30 Preparing a TLC sample ....................................................................................................................... 30 Preparing an NMR sample .................................................................................................................. 30 Obtaining an absorption spectrum ..................................................................................................... 31 Obtaining a Fluorescence spectrum ................................................................................................... 31 Appendix B: Additional Tables ................................................................................................................... 32 Appendix C: Sample Fluorescence Quantum Yield Calculation .................................................................. 34 Appendix D: Sample Fluorescence Lifetime Calculation ............................................................................. 39 References .................................................................................................................................................. 41 4 List of Tables Table 1: Spectroscopic and photophysical properties for bdmab in various solvents................................. 19 Table 2: Mole table for 1pdbun .................................................................................................................. 32 Table 3: Synthetic Analysis of 1pdbun ....................................................................................................... 32 Table 4: Synthetic Analysis of bdmab ........................................................................................................ 32 Table 5: 1H NMR, 13C NMR, and IR data for bdmab ............................................................................... 33 Table 6: Solvents for absorbance and fluorescence spectra ........................................................................ 33 Table 7: Solvents for fluorescence quantum yield calculations and fluorescence lifetimes* ..................... 33 5 List of Figures Figure 1: Example of a Jablonski Diagram ................................................................................................... 7 Figure 2: General Structure of a 2,5-diarylidene cyclopentanone dye (left) and the structure of bdmab (right) ............................................................................................................................................................ 8 Figure 3: Synthesis mechanism of bdmab .................................................................................................... 9 Figure 4: Infared Spectrum for bdmab ........................................................................................................ 14 Figure 5: Complete 1H NMR spectrum for bdmab region 2.0-8.0 ppm .................................................. 15 Figure 6: 1H NMR for bdmab region 2.9-3.06 ppm ................................................................................ 15 Figure 7: 1H NMR spectrum for bdmab region 6.5-7.7 ppm .................................................................. 16 Figure 8: 13C NMR spectrum for bdmab 10-210 ppm ............................................................................ 16 Figure 9: 13C NMR spectrum for bdmab DEPT-90 100-140 ppm.......................................................... 17 Figure 10: 13C NMR spectrum for bdmab DEPT-135 region 20-140 ppm ........................................... 17 Figure 11: 13C NMR spectrum for bdmab DEPT-135 region 25-40 ppm .............................................. 18 Figure 12: 13C NMR spectrum for bdmab DEPT-135 100-140 ppm...................................................... 18 Figure 13: Compound molecular orbitals of bdmab in the gas phase ......................................................... 21 Figure 14: Absorbance (red) and fluorescence (blue) for the seven solvents ............................................. 22 Figure 15: Plot of the fluorescence quantum yield against the corrected fluorescence spectral maxima for bdmab in protic solvents (unfilled) and aprotic solvents (filled) outlined in Table 7. ................................ 23 Figure 16: Plot of the fluorescence quantum yield for bdmab against ET(30) in protic solvents (unfilled) and aprotic solvents (filled) outlined in Table 7. ........................................................................................ 24 Figure 17: Plot of the absorbance (red) and fluorescence (blue) spectral maxima for bdmab in protic solvents (unfilled) and aprotic solvents (filled) against the ET(30) scale. .................................................. 25 Figure 18: Lippert-Mataga plot for bdmab