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31.
32.
Ahn TK Yoon ZS Hwang IW Lim JK Rhee H Joo T Sim E Kim SK Aratani N Osuka A Kim D 《The journal of physical chemistry. B》2005,109(22):11223-11230
We have investigated the overall excitation energy relaxation dynamics in linear porphyrin arrays as well as the energy transport phenomena by attaching an energy acceptor to one end of a linear porphyrin array by using steady state and time-resolved spectroscopic measurements. We have revealed that the solvation dynamics as well as the conformational dynamics contributes significantly to the energy relaxation processes of linear porphyrin arrays. Consequently, long porphyrin arrays no longer serve as good energy transmission elements in donor-acceptor linked systems due to conformational heterogeneities which provide the non-radiative deactivation channels as energy quenchers. 相似文献
33.
Tanaka Y Hoshino W Shimizu S Youfu K Aratani N Maruyama N Fujita S Osuka A 《Journal of the American Chemical Society》2004,126(10):3046-3047
When heated, bis-Cu(II) octaphyrin(1.1.1.1.1.1.1.1) is quantitatively split into two Cu(II) porphyrins both in solution and film states, which is accompanied by large absorption spectral changes. 相似文献
34.
Machida S Mineta S Fujimori A Nakahara H 《Journal of colloid and interface science》2003,260(1):135-141
From AFM observation of transferred films on mica, it has been found that mixed monolayers of hexadecanol with poly(vinyl stearate) give a film with a less-defective and flat surface by spreading from bulk solids of those mixtures onto a water surface without using any organic solvent. As a result, those mixed monolayers have a considerably larger effect on retardation of water evaporation in comparison with those spread from the solution of the mixtures. After the saturated surface pressure of the mixed monolayer spread from the bulk solids, an enhanced effect on retardation of water evaporation was found, accompanied by the preferential spreading of hexadecanol and the gradual reduction of defects in the mixed monolayer. 相似文献
35.
Shanmugam Easwaramoorthi Dr. Jae‐Yoon Shin Sung Cho Dr. Pyosang Kim Yasuhide Inokuma Eiji Tsurumaki Atsuhiro Osuka Prof. Dr. Dongho Kim Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(44):12005-12017
Donor–acceptor systems based on subporphyrins with nitro and amino substituents at meta and para positions of the meso‐phenyl groups were synthesized and their photophysical properties have been systematically investigated. These molecules show two types of charge‐transfer interactions, that is, from center to periphery and periphery to center depending on the peripheral substitution, in which the subporphyrin moiety plays a dual role as both donor and acceptor. Based on the solvent‐polarity‐dependent photophysical properties, we have shown that the fluorescence emission of para isomers originates from the solvatochromic, dipolar, symmetry‐broken, and relaxed excited states, whereas the non‐solvatochromic fluorescence of meta isomers is of the octupolar type with false symmetry breaking. The restricted meso‐(4‐aminophenyl) rotation at low temperature prevents the intramolecular charge‐transfer (ICT)‐forming process. The two‐photon absorption (TPA) cross‐section values were determined by photoexcitation at 800 nm in nonpolar toluene and polar acetonitrile solvents to see the effect of ICT on the TPA processes. The large enhancement in the TPA cross‐section value of approximately 3200 GM (1 GM=10?50 cm4 s photon?1) with donor–acceptor substitution has been attributed to the octupolar effect and ICT interactions. A correlation was found between the electron‐donating/‐withdrawing abilities of the peripheral groups and the TPA cross‐section values, that is, p‐aminophenyl>m‐aminophenyl>nitrophenyl. The increased stability of octupolar ICT interactions in highly polar solvents enhances the TPA cross‐section value by a factor of approximately 2 and 4, respectively, for p‐amino‐ and m‐nitrophenyl‐substituted subporphyrins. On the other hand, the stabilization of the symmetry‐broken, dipolar ICT state gives rise to a negligible impact on the TPA processes. 相似文献
36.
Probing the Rotational Dynamics of meso‐(2‐Substituted)aryl Substituents in A2B‐Type Subporphyrins 下载免费PDF全文
Kota Yoshida Graeme Copley Hirotaka Mori Prof. Dr. Atsuhiro Osuka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(32):10065-10072
A2B‐type B‐methoxy subporphyrins 3 a – g and B‐phenyl subporphyrins 7 a – c , e , g bearing meso‐(2‐substituted)aryl substituents are synthesized, and their rotational dynamics are examined through variable‐temperature (VT) 1H NMR spectroscopy. In these subporphyrins, the rotation of meso‐aryl substituents is hindered by a rationally installed 2‐substituent. The rotational barriers determined are considerably smaller than those reported previously for porphyrins. Comparison of the rotation activation parameters reveals a variable contribution of ΔH≠ and ΔS≠ in ΔG≠. 2‐Methyl and 2‐ethyl groups of the meso‐aryl substituents in subporphyrins 3 e , 3 f , and 7 e induce larger rotational barriers than 2‐alkoxyl substituents. The rotational barriers of 3 g and 7 g are reduced by the presence of the 4‐dibenzylamino group owing to its ability to stabilize the coplanar rotation transition state electronically. The smaller rotational barriers found for B‐phenyl subporphyrins than for B‐methoxy subporphyrins indicate a negligible contribution of SN1‐type heterolysis in the rotation of meso‐aryl substituents. 相似文献
37.
Daiki Shimizu Yuki Ide Takahisa Ikeue Atsuhiro Osuka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(15):5077-5081
A bis(NiII‐porphyrinyl)aminyl radical with meso‐C6F5 groups was prepared as a spin‐delocalized stable aminyl radical with a doublet spin state. Upon addition of pyridine, both NiII centers became hexacoordinated by accepting two axial pyridines, which triggered a spin‐state change of the NiII centers from diamagnetic (S=0) to paramagnetic (S=1). The resulting high‐spin NiII centers interact with the aminyl radical ferromagnetically to give rise to an overall sextet state (S=5/2). Importantly, this coordination‐induced spin‐state switching can be conducted in a reversible manner, in that washing of the high‐spin radical with aqueous hydrochloric acid regenerates the original doublet radical in good yield. 相似文献
38.
PdII Complexes of [44]‐ and [46]Decaphyrins: The Largest Hückel Aromatic and Antiaromatic,and Möbius Aromatic Macrocycles 下载免费PDF全文
Tomoki Yoneda Young Mo Sung Dr. Jong Min Lim Prof. Dr. Dongho Kim Prof. Dr. Atsuhiro Osuka 《Angewandte Chemie (International ed. in English)》2014,53(48):13169-13173
Reductive metalation of [44]decaphyrin with [Pd2(dba)3] provided a Hückel aromatic [46]decaphyrin PdII complex, which was readily oxidized upon treatment with DDQ to produce a Hückel antiaromatic [44]decaphyrin PdII complex. In CH2Cl2 solution the latter complex underwent slow tautomerization to a Möbius aromatic [44]decaphyrin PdII complex which exists as a mixture of conformers in dynamic equilibrium. To the best of our knowledge, these three PdII complexes represent the largest Hückel aromatic, Hückel antiaromatic, and Möbius aromatic complexes to date. 相似文献
39.
Shota Ooi B. Adinarayana Daiki Shimizu Takayuki Tanaka Atsuhiro Osuka 《Angewandte Chemie (International ed. in English)》2020,59(24):9423-9427
While oxidation of 5,5′,15,15′‐tetramesityl‐10‐10′‐linked 3NH‐corrole dimer with DDQ gave the corresponding triply linked 2NH‐corrole tape, the use of an equimolar amount of p‐chloranil as a milder oxidant resulted in the formation of a 10‐10′‐linked neutral 2NH‐corrole radical dimer as a stable product. The stability of this peculiar product is ascribed largely to strong antiferromagnetic interaction of the two spins. Further oxidation of this diradical produced corrole tape, suggesting its involvement as a reaction intermediate to the corrole tape. Oxidation of 10‐10′‐linked bis‐pyridine‐coordinated CoIII corrole dimer with DDQ produced a cobalt corrole radical dimer and a doubly linked corrole dimer both as stable compounds bearing pyridine and cyanide axial ligands. This type of oxidative transformation involving neutral diradical intermediates is a unique reaction mechanism specific for corrole dimers. 相似文献
40.