Organic/Metal-Organic Materials Chemistry

Our research focuses on the synthesis and characterization of photofunctional organic/metallo-organic materials for optical limiting and/or photodynamic therapy applications.

Optical limiting materials are nonlinear optical materials that can transmit most of the light at low intensities, but absorb, reflect, refract, or scatter light at high incident intensities for the protection of human eyes and optical sensors. Nonlinear absorption, particular reverse saturable absorption and two-photon absorption, has long been recognized as useful for optical limiting, however, it is not currently possible to a-prior design molecules that exhibit large nonlinear absorption. To remedy this deficiency, the relationship between nonlinear absorption and molecular structure must be explored. Organic/metallo-organic complexes are ideal candidates for this application because of their large, fast, and broadband optical nonlinearity. In addition, the chemical structures of these complexes can be easily modified. The complexes currently under study include nanoparticle-expanded metalloporphyrin composites, transition-metal terpyridyl acetylide complexes (Figure 1), polyads, and dendrimers, and stilbazolium derivatives. This project involves organic synthesis, spectroscopic studies (UV-Visible absorption, transient absorption, fluorescence and phosphorescence), and nonlinear optical characterization (using degenerate four wave mixing, Z-scan and nonlinear absorption techniques).

Figure 1. Transition-metal terpyridyl acetylide complexes

Photodynamic therapy (PDT) is an emerging cancer treatment method based on the interaction of light, a photosensitizer, and oxygen. It has specific selectivity comparing to other cancer treatment modalities. Unfortunately, limitations of current photosensitizers, such as toxicity, inability to treat deeply situated cancers, cutaneous photosensitivity, and water insolubility prevent the widespread use of PDT to date. In order to overcome these limitations, a series of water-soluble pentaazadentate porphyrin-like rare-earth complexes (Figure 2) and core-modified Texaphyrins that can absorb near-infrared light are being synthesized and investigated in my group. A variety of spectroscopic and structural methods including UV-VIS, IR, MS, NMR, X-ray crystallography, fluorescence and phosphorescence spectroscopy, transient absorption, and spin-trapping electron paramagnetic resonance (EPR) spectroscopy are being used to characterize the structures and to investigate the photophysics and photosensitization mechanisms of the complexes.

Figure 2. Pentaazadentate porphyrin-like rare-earth complexes

Selected Publications

W. Sun,* G. Wang, Y. Li, M.J.F. Calvete, D. Danilo, M. Hanack,  “Axial halide ligand effect on photophysics and optical limiting of some indium naphthalocyanines”,  Submitted to J. Phys. Chem. A  (2007)

W. Sun,* H.-J. Zhu, P.M. Barron,  “Binuclear cyclometalated platinum(II) 4,6-diphenyl-2,2’-bipyridine complexes: Interesting photoluminescent and optical limiting materials”,  Chem. Mater. 18 (10), 2602 (2006).

F. Guo, W. Sun,*  “Photophysics and optical limiting of platinum (II) 4’-arylterpyridyl phenylacetylide complexes”,  J. Phys. Chem. B  110(30), 15029 (2006).

G. Wang, W. Sun,*  “Optical limiting of gold nanoparticle aggregates induced by electrolytes”,  J. Phys. Chem. B  110(42), 20901 (2006).

W. Sun,* P.M. Barron,  “pH sensitive photophysical and photochemical properties of a pentaazadentate porphyrin-like gadolinium complex”,  Frontiers in Bioscience.  11, 2795 (2006).

W. Jia, F. Guo, E.P. Douglas, W. Sun,*  “Third-order nonlinear optical responses of semiconductor nanoparticles to picosecond laser pulses”,  Submitted to J. Phy. Chem. C (2006)

P. Shao, W. Sun,*  “A trinuclear platinum(II) 4,6-diphenyl-2,2’-bipyridine complex with bis(diphenylphosphinomethyl)phenylphosphine auxiliary ligand: synthesis, structural characterization and photophysics”,  submitted to Inorg. Chem.  (2006)

Qiu Dai, Jianhua Zou, James G. Worden, Wenfang Sun, Qun Huo,*  “Monofunctional gold nanoparticles and nanoparticles/polymer hybrid materials”,  Polymer Preprint 47(2), 891 (2006).

J. Brenna, Q. Huo, W. Sun, K. Zhong,  “Total chemical synthesis, Property and Modeling Studies of Nanoparticle/Polymer Hybrid Materials”,  Proceeding of 2006 NSF Design, Service, and Manufacturing Grantees and Research Conference (2006).

F. Guo, W. Sun,* Y. Liu, K. Schanze  “Synthesis, photophysics and optical limiting of platinum (II) 4’-tolylterpyridyl arylacetylide complexes”,  Inorg. Chem. 44, 4055 (2005).

M.M. McKerns*, W. Sun, C.M. Lawson, G.M. Gray,  “Higher-order triplet-triplet interaction in energy-level modeling of excited state absorption for an expanded porphyrin cadmium complex”,  J. Opt. Soc. Am. B 22 (4), 852-861 (2005).

W. Sun,* Q. Dai, J. Worden, Q. Huo,  “Optical limiting of a covalently bonded gold nanoparticle/polylysine hybrid material”,  J. Phys. Chem. B. 109 (44), 20854 (2005).

W. Sun,* F. Guo,  “Excited state absorption and optical limiting of platinum(II) 4’-arylterpyridyl acetylide complexes”,  Chin. Opt. Lett. S3, S34 (2005).

C.C. Byeon, M.M. McKerns, W. Sun, T.M. Nordlund, C.M. Lawson*, G.M. Gray,  “Excited state lifetime and intersystem crossing rate of asymmetric pentaazadentate porphyrin-like metal complexes”,  Appl. Phys. Lett.  84 (25), 5174 (2004).

W. Jia, E.P. Douglas, F. Guo, W. Sun,*  “Optical limiting of semiconductor nanoparticles for nanosecond laser pulses”,  Appl. Phys. Lett.  85 (26), 6326 (2004).

W. Sun,* Z.-X. Wu, Q.-Z. Yang, L.-Z. Wu, C.-H. Tung,  “Reverse saturable absorption of platinum ter/bipyridyl polyphenylacetylide complexes”,  Appl. Phys. Lett. 82 (6), 850 (2003).

W. Sun,* T. Carvalho, M.M. Bader,  “Third-order optical nonlinearities of a,w-Dithienylpolyenes and oligo(thienylvinylene)”,  Opt. Commun. 215, 185 (2003).

W. Sun,* P.H. Patton, L. K. Stultz, J.-P. Claude,  “Resonant third-order nonlinearities of tetrakis(2,2’-dipyridyl)diruthenium complexes”, Opt. Commun. 218, 189 (2003).

W. Sun,* F. Guo, D. Martyshkin, S. Mirov, C.-L. Zhan, D. Wang,  “Wavelength dispersion of two-photon absorption and two-photon induced fluorescence of stilbazolium derivatives”,  Proc. SPIE Vol. 5211, 75 (2003).

W. Sun,* D. Martyshkin, S. Mirov, X.-J. Tang, L.-Z. Wu, C.-H. Tung,  “Excited state absorption and two-photon induced fluorescence of novel organic dyes”,  Proc. SPIE Vol. 4797, 204 (2002).

W. Sun, C.M. Lawson, G.M. Gray, C. Zhan, D. Wang,  “Degenerate four wave mixing and Z-scan measurements of stilbazolium derivatives”,  Appl. Phys. Lett. 78(13), 1817 (2001).

F. Guo, W. Sun, D. Wang, L. Zhao, Z. Lu, Y. Nie,  “Optical limiting of pentaazadentate metal complexes for picosecond pulses in solution”,  Appl. Opt. 40(9), 1386 (2001).

F. Guo, W. Sun, D. Wang, Y. Song,  “Optical limiting of pentaazadentate complexes in solution for ns pulses”,  Opt. Engineering 40(1), 138 (2001).

W. Sun, C.M. Lawson, G.M. Gray, C. Zhan, D. Wang,  “Nonlinear absorption of stilbazolium derivatives”,  Proc. SPIE Vol. 4462, 17 (2001).