Ultrafast dynamics in various porphyrioids from triphyrin to decaphyrin

다국어 초록 (Multilingual Abstract)

There have been continuous attempts to develop functional π-electronic systems considered as being one of the most important research of core technology such as renewable energy, nano scale molecular device and low-cost photovoltaic technologies. Porphyrinoids, one of the most famous functional π-electronic systems, have attracted the interest of scientists due to their facile tunability of the molecular structures and the number of π-electrons which can determine the photophysical properties (e.g. ground-state electronic feature, excited-state dynamics, and nonlinear optical properties). In this reagard, much research has been conducted to control the chemical properties of porphyrinoids, which is important as not only the basic research, but also application in industry due to their potential applications in photovoltaic devices, photodynamic therapy, and photosensitizers.
To control the chemical features of porphyrinoids, there are strenuous efforts by the modification of porphyrins such as subtracting and adding pyrrole subunit in porphyrins, substituting the pyrrole to pyrrole-related ring, and metal insertion. Although there are numerous study to synthesize various porphyrinoids, the photophysical and theoretical study on porphyrinoids have not yet been fully conducted.
In this regard, I have prepared porphyrinoids (trihyrins, vacataporphyrins, etheneporphyrin, rhodium hexaphyrins, larger expanded porphyrins to explain the chemical and physical features of porphyrinoids and reveal the photophysical properties depending on the number of π-electrons, the molecular structures, π-conjugation and aromaticity.
First of all, I have investigated the photophysical properties of two type of triphyrins with a focus on the fused-moiety effects by performing various spectroscopic measurements and theoretical calculations. Secondly, I have investigated the photophysical properties of vacataporphyrins possessing systematically controlled butadiene linkers on their π-electron pathways by conducting various spectroscopic analysis along with quantum mechanical calculations. Thirdly, I have revealed the the electronic structure and photophysical properties of (C=C)TTP2+ by using quantum mechanical calculations and transient absorption spectroscopic measurements. Fourthly, by investigating the photophysical properties of a series of thiaaceneporphyrinoids in a various condition such as high viscosity and low temperature, I could confirm that a series of thiaaceneporphyrinoids show structural diversity giving rise to conformers with either aromatic or nonaromatic π-conjugation depending on their structures. Fifthly, I have demonstrated the reversal of Huckel (anti)aromaticity in the lowest triplet states, suggested by Baird in 1972, by revealing the difference between the ground and excited state properties of two closely-related bis-rhodium hexaphyrins containing [26]- and [28] π-electron peripheries. Finally, through the spectroscopic measurements of larger expanded porphyrins, I have revealed that the protonation effect which can retrieve the aromaticity in either planar Huckel or distorted Mobius structures of larger expanded porphyrins with all meso-carbon bridged pyrroles is achieved up to [42] Nonaphyrins.
I expected that the researches in this thesis would provide fruitful insight into the relationship between the molecular structures and photophysical properties, and as a consequence, development of innovative nano-materials.