Browsing by Author "Chatterjee, Shreyam"

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[2.2.2.2](2,7)-1-Bromonaphthalenophane from a Desymmetrized Building Block Bearing Electrophilic and Masked Nucleophilic Functionalities
(2019-03-01)
Cai, Guangke
;
Chatterjee, Shreyam
;
Hisaki, Ichiro
;
Tobe, Yoshito
;
應用化學系
In search of 2,7-ethylene-bridged naphthalenophanes with desymmetrized naphthalene cores as inherently chiral cyclophanes, nucleophilic substitution of 1-bromo-7-(bromomethyl)-2-[(trimethylsilyl)methyl]naphthalene, a desymmetrized building block bearing an electrophilic group (CH2Br) and a masked nucleophilic functionality (CH2TMS) which can be activated by fluoride anion, was examined. As a result, in contrast to the case of parent naphthalenophanes wherein the smallest [2.2]naphthalenophane was obtained as the major product, only [2.2.2.2](2,7)-1-bromonaphthalenophane was obtained albeit in low yields, whereas the corresponding [2.2]- or [2.2.2]naphthalenophanes were not obtained. Though the [2.2.2.2]-1-bromonaphthalenophane can adopt four idealized geometries of different symmetry, among which three are inherently chiral, theoretical calculations predict that three conformers have almost equal energy and may equilibrate in solution. The X-ray crystallographic study shows that it adopts a C-2 conformation with anti,anti,anti orientation of the C-Br bonds at least as a major component in crystal.
9,10-Dihydro-as-indacenodithiophenes: Isomers with an asIndacene Core
(2019-04-05)
Miyoshi, Hirokazu
;
Nabe, Akino
;
Chatterjee, Shreyam
;
Tobe, Yoshito
;
應用化學系
Two isomers of 9,10-dihydro-as-indacenodithiophenes (DIDTs) and the corresponding diketones having an as-indacene core were synthesized. Their thermal, photophysical, and electrochemical properties were investigated, revealing that they depend on the direction of the fusion of the thiophene rings. For the DIDTs, the effect of the mode of ring fusion on the physical properties is discussed by comparison with the previously reported derivatives of DIDT isomers with an s-indacene core. The observed difference between the highest occupied molecular orbital (HOMO)/ lowest unoccupied molecular orbital (LUMO) levels of the DIDT isomers is ascribed to the efficiency of 7z-conjugation, which depends on a- or f3-linkage between the terminal thiophenes with the central benzene ring. In addition, the effect of the peripheral aromatic ring (thiophene or benzene) is elucidated by comparison with indeno[2,1-a]fluorene (DIF) bearing an as-indacene core. The HOMO levels of DIDTs are significantly raised compared to that of structurally related DIF because of electron-donating character of the thiophene rings. For the DIDT diketones, structural effect due to the proximate carbonyl groups is discussed by comparison with the isomers with remote carbonyl groups. In diketones bearing proximate carbonyl groups, the LUMO levels are destabilized owing to antibonding interaction between the carbonyl oxygen atoms, resulting in approach of the LUMO and LUMO+1 energy levels.