京都大学 / 新制・課程博士 / 博士(理学) / 甲第23718号 / 理博第4808号 / 新制||理||1688(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 時任 宣博, 教授 依光 英樹, 教授 若宮 淳志 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Density functional theory (DFT) calculations (using Becke's exchange in conjunction with Lee-Yang-Parr's correlation functional (BLYP) and Becke's three-parameter hybrid DFT/HF method using Lee-Yang-Parr's correlation functional (B3LYP)) have been carried out to investigate the structure, dipole moment, and vibrational spectrum of azulene. Structural parameters obtained by both BLYP/6-31G* and B3LYP/6-31G* geometry optimization are in good agreement with available experimental data and show clearly the aromatic nature (bond equalization), a property the Hartree-Fock theory fails to describe correctly. The BLYP/6-31G* and B3LYP/6-31G* dipole moments are within experimental uncertainty and are in good agreement with results obtained from the much more expensive MP2 and MR-SDCI calculations. Most of the BLYP/6-31G* vibrational frequencies are in excellent agreement with available experimental assignments. On the basis of the calculated results, assignments of some missing frequencies in the experimental studies are proposed.

Nonalternant aromatic π-electron systems show promises for surface functionalization due to their unusual electronic structure. Based on our previous experiences for metal surfaces, we investigate the adsorption structures, adsorption dynamics and bonding characteristics of azulene and its alternant aromatic isomer naphthalene on the Si(001) surface. Using a combination of density functional theory, ab initio molecular dynamics, reaction path sampling and bonding analysis with the energy decomposition analysis for extended systems, we show that azulene shows direct adsorption paths into several, strongly bonded chemisorbed final structures with up to four covalent carbon–silicon bonds which can be described in a donor–acceptor and a shared-electron bonding picture nearly equivalently. Naphthalene also shows these tetra-σ-type bonding structures in accordance with an earlier study. But the adsorption path is pseudo-direct here with a precursor intermediate bonded via one aromatic ring and strong indications for a narrow adsorption funnel. The four surface-adsorbate bonds formed lead for both adsorbates to a strong corrugation and a loss of aromaticity.

No description available.

Este trabalho relata um estudo da fotólise de 4-clorometil-6,8-dimetil-azuleno (1), 4-bromometil-6,8-dimetil-azuleno (2) e 4-clorometil-1-metil-7-isopropilazuleno (3), em solventes polares e apoiares. Os fotoprodutos foram analisados e identificados ou por cromatografia a gás, comparando-se com padrões autênticos, ou por espectrometria de massas. Em solventes polares, foram obtidos somente produtos provenientes de clivagem heterolítica da ligação C-halogênio, enquanto, em solventes apoiares foi observada somente a presença de fotoprodutos de origem radicalar. O produto majoritário na fotólise de 1 em solventes apoiares, em todas as condições experimentais, foi identificado como 1-cloro-4,6,8-trimetil-azuleno, um isômero do reagente, cuja formação não é afetada pela presença de doadores de hidrogênio. Entretanto, este isômero não foi observado em solventes polares, em nenhuma condição experimental. Resultados similares foram obtidos nas fotólises de 2 e de 3. Com base nestas observações, foi possível formular um mecanismo geral para a fotólise dos derivados de azuleno estudados. Em solventes apoiares ocorre clivagem homolítica, levando exclusivamente a produtos provenientes de reações radicalares. Em solventes polares, ao contrário dos mecanismos propostos na maioria dos trabalhos de literatura, ocorre clivagem heterolítica direta, sem o envolvimento de um par radicalar inicial que levaria à formação do carbocátion via transferência de elétron. Foram feitos, ainda, estudos de fotólise por pulso de laser utilizando-se soluções do derivado 1 em solventes apoiares e polares. Entretanto, em nenhuma condição experimental foi possível detectar absorção transiente. / This work reports a study on the photolysis of 4-chloromethyl-6,8-dimethylazulene (1), 4-bromomethyl-6,8-dimethylazulene (2) and 4-chloromethyl-1-methyl-7-isopropylazulene (3) in polar and apolar solvents. The obtained photoproducts were analyzed and identified by gas chromatography, in comparison to authentic standards or by mass spectrometric analysis. In polar solvents, only products formed by the heterolytic cleavage of the C-X (X = Cl and Br) bond are obtained, whilst, in apolar solvents, only photoproducts originated from radical reactions are observed. The major product in apolar solvents in the photolysis of 1, in all experimental conditions, was identified as 1-chloro-4,6,8-trimethylazulene, an isomer of the reagent, whose formation is not affected by the presence of hydrogen donors. However, this isomer is not observed in polar solvents in any experimental conditions. Similar results are obtained in the photolysis of 2 and 3. These observations allowed us to formulate a general mechanism for the photolysis of the azulene derivatives studied. In apolar solvents, homolytic bond cleavage occurs leading exclusively to the formation of products originated from radical reactions. However, in polar solvents direct heterolytic bond cleavage occurs, without the involvement of an initial radical par which would lead to carbocation formation by electron transfer, in oposition to the mechanism proposed in most of the literature works. Flash photolysis studies with 1 in apolar and polar solvents were also performed. However, it was not possible to detect any transient absorption in all experimental conditions used.

?-Conjugated systems have been the focus of study in recent years in order to understand their charge transport and optical properties for use in organic electronic devices, fluorescence bioimaging, sensors, and 3D optical data storage (ODS), among others. As a result, several molecular building blocks have been designed, allowing new frontiers to be realized. While various successful building blocks have been fine-tuned at both the electronic and molecular structure level to provide advanced photophysical and optoelectronic characteristics, the azulene framework has been under-appreciated despite its unique electronic and optical properties. Among several attributes, azulenes are vibrant blue naturally occurring hydrocarbons that exhibit large dipolar character, coupled with stimuli-responsive behavior in acidic environments. Additionally, the non-toxic nature and the accompanying eco-friendly feature of some azulenes, namely guaiazulene, may set the stage to further explore a more "green" route towards photonic and conductive materials. The first part of this dissertation focuses on exploiting guaiazulene as a natural building block for the synthesis of chromophores with varying stimuli-responsiveness. Results described in Chapter 1 show that extending the conjugation of guaiazulene through its seven-membered ring methyl group with aromatic substituents dramatically impacts the optical properties of the guaiazulenium carbocation. Study of these ?–stabilized tropilium ions enabled establishing photophysical structure-property trends for guaiazulene-terminated ?-conjugated analogs under acidic conditions, including absorption, emission, quantum yield, and optical band gap patterns. These results were exploited in the design of a photosensitive polymeric system with potential application in the field of three dimensional (3D) optical data storage (ODS). Chapter 2 describes the use of guaiazulene reactive sites (C-3 and C-4 methyl group) to generate a series of cyclopenta[ef]heptalenes that exhibit strong stimuli-responsive behavior. The approach presents a versatile route that allows for various substrates to be incorporated into the resulting cyclopenta[ef]heptalenes, especially after optimization that led to devising a one-pot reaction toward such tricyclic systems. Examining the UV-vis absorption profiles in neutral and acidic media showed that the extension of conjugation at C(4) of the cyclopenta[ef]heptalene skeleton results in longer absorption maxima and smaller optical energy gaps. Additionally, it was concluded that these systems act as sensitizers of a UV-activated (< 300 nm) photoacid generator (PAG), via intermolecular photoinduced electron transfer (PeT), upon which the PAG undergoes photodecomposition resulting in the generation of acid. In a related study, the guaiazulene methyl group at C-4 was employed to study the linear and nonlinear optical properties of 4-styrylguaiazulenes, having the same ?–donor with varying ?-spacer. It was realized that the conjugation length correlates with the extent of bathochromic shift of the protonated species. On the other hand, a trend of decreasing quantum yield was established for this set of 4-styrylguaiazulenes, which can be explained by the increasingly higher degree of flexibility. The second part of this dissertation presents a comprehensive investigation of the linear photophysical, photochemical, and nonlinear optical properties of diketopyrrolopyrrole (DPP)-based derivatives, including two-photon absorption (2PA), femtosecond transient absorption, stimulated emission spectroscopy, and superfluorescence phenomena. The synthetic feasibility, ease of modification, outstanding robustness, and attractive spectroscopic properties of DPPs have motivated their study for fluorescence microscopy applications, concluding that the prepared DPP's are potentially suitable chromophores for high resolution stimulated emission depletion (STED) microscopy.

Open-shell non-alternant polycyclic hydrocarbons (PHs) are attracting increasing attention due to their promising applications in organic spintronics and quantum computing. Herein we report the synthesis of three cyclohepta[def]fluorene-based diradicaloids (1–3), by fusion of benzo rings on its periphery for the thermodynamic stabilization, as evidenced by multiple characterization techniques. Remarkably, all of them display a very narrow optical energy gap (Egopt=0.52–0.69 eV) and persistent stability under ambient conditions (t1/2=11.7–33.3 h). More importantly, this new type of diradicaloids possess a low-lying triplet state with an extremely small singlet–triplet energy gap, as low as 0.002 kcal mol−1, with a clear dependence on the molecular size. This family of compounds thus offers a new route to create non-alternant open-shell PHs with high-spin ground states, and opens up novel possibilities and insights into understanding the structure–property relationships.