Study Of Electronic And Vibronic Contributions To Two-Photon Properties Of Benzylidene Cyclopentanone Dyes And Exploration Of Their Applications

Structure-property relationship was the focal point in the design and synthesis of high efficient two-photon polymerization (TPP) sensitizers. Electronic and vibronic contributions to two-photon absorption and photosensitizing efficiencies of novel benzylidene cyclopentanone dyes were studied in this thesis. Structure-property relationship was revealed by investigating the effects of the substituent position, substiturent group and branching structure of dyes on their properties. These results provide useful strategies for the design of novel two-photon initiators or sensitizers. Also, a high efficient sensitize-initiating system of TPP was designed and optimized. The application potentiality of these dyes in TPP was proved.1 Electronic and vibronic contributions to cooperative enhancement of two-photon absorption in multi-branched structures were studied, and electronic coupling was confirmed the crucial reason for the enhancement. A series of multi-branched benzylidene cyclopentanone dyes with a non-conjugated central moiety (T1-T3) were synthesized. Their properties were studied in comparison with corresponding triphenylamine derivatives (1-3). No electronic and vibronic coupling effects were observed in T2 and T3. It means that to increase the branch number only increases the number density of chromophores. On the contrary, cooperative enhancement of TPA was observed in 2 and 3 comparing to 1, which confirmed the electronic coupling was the crucial reason for the enhancement. Furthermore, the photosensitizing efficiencies of these compounds were investigated by one-photon polymerization (OPP) and the result indicated the electronic coupling effect was also beneficial to their photosensitizing efficiencies.2 Electronic contributions to two photon sensitizing or initiating efficiencies of coumarin/benzylidene cyclopentanone dyes were studied. Two novel benzylidene cyclopentanone dyes (T4 and T5) containing coumarin moiety were synthesized. Their bridging positions were the 4 and 3 positions of coumarin moiety, respectively. T5 was found to exhibit larger two-photon absorption cross-sections (TPACS) and higher two-photon sensitizing efficiencies. Also, their ground state configurations were optimized and excited states properties were calculated by quantum chemical calculations. It showed that their ground state configurations, charge distributions and charge densities were quite different. T5 shows better planar configuration and conjugated properties, exhibiting larger TPACS and higher two-photon sensitizing efficiencies. Contrarily, the configuration of T4 is twisted; it exhibits lower electron transfer free energy with initiator and higher sensitizing efficiencies in OPP.3 A novel bicoumarin/cyclopentanone dye (T6) was designed and synthesized based on the above-mentioned study. Its bridging point was 3 position of coumarin moiety. The novel dye showed higher photosensitizing efficiency and larger TPACS compared to T5 and common used photosensitizer BDMA (2,5-bis-[4-(dimethylamino)-benzylidene]-cyclopentanone). Combined with quantum chemical calculations, the main factor of its increased TPACS was confirmed to the introduction of coumarin moiety which increased the conjugated length while maintaining the rigid structure of T6. Furthermore, the cooperative effect between coumarin and cyclopentanone groups was found beneficial in the sensitizing efficiencies of dyes.4 A kind of TPP resin was designed by using benzylidene cyclopentanone dyes as one component initiator directly. All benzylidene cyclepentanone dyes containing coumarin moiety were proved that they could be used as photoinitiators directly in TPP and exhibited high initiating efficiencies to initiate acrylate monomers. Only small dosages of initiators were needed in these resins. Also, their threshold energies were very low. 2D and 3D nanopatterns with high resolution and low small molecule residues were successfully fabricated by TPP, which demonstrated extensive application prospects of these dyes and the corresponding resins in three-dimensional microfabrication and high-density optical data storage.