Optoelectric Properties Of Small Molecules And Polymers With Push-pull Electronic Structures

Organic optoelectric materials have been of great interest in recent years and their applications in chemo/biosensors, in vitro or in vivo imaging, cell tracing, cell labeling and organic light-emitting diodes(OLEDs) have accomplished dramatic development as well. To meet the diverse range of requirements, the optoelectric properties of these materials should be tunable. In this paper, we concentrated on materials with push-pull electronic structures and researched the effect of polymer chains and physical changes on the optoelectric properties of chromophores.(1) We have designed and synthesized two pyran derivatives(Et Am Py and Et Ox Py), and introduced two PS chains to the periphery of initiators via ATRP. Et Am Py with strong charge transfer exhibited ACQ phenomenon. In contrast, Et Ox Py with weak charge transfer was AIE-active. After the introduction of PS chains, the end-functionalized polymers were turned to be AEE-active and the longer polymer chains could enhanced the emission of Et Am Py more effectively. After further modification, the Et Am Py end-functionalized polymer could be applied in cellular imaging.(2) We have designed and synthesized a 1,3,4-oxadiazole initiator, Vi OXD, possessing explicit charge transfer and solvatochromic behavior. However, the formation of H-aggregates of Vi OXD molecules could quench the emission in aggregate state, due to its approximately planar conformation. After introducing the PS or PVPCz chains, the aggregate emission of Vi OXD was recovered and the maximum emission wavelength could be tuned by the different electron-donating ability of polymer chains. After modified by BSA, Vi OXD-PS and Vi OXD-PVPCz had a potential application in TPEF imaging.(3) In order to achieve reversibly tunable optoelectric properties, we chose l,8-naphthalimide segment as acceptor and carbazole segment as donor to design and synthesize two small molecules with push-pull electronic structures. Both 2NOCz NI and Cz NINO exhibited solvatochromic behavior and AEE-active phenomenon. After their as-synthesized powder was ground, the ordered structures could be destroyed and their maximum emission wavelengths have red-shifted. Hence, both 2NOCz NI and Cz NINO displayed piezofluorochromic property.