An aza-analogue of N-phyridinium cyclopentadienide

Boyd, G. V.

doi:10.1016/s0040-4039(01)82795-7

Cited by 22 publications

(14 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[13] The dark-gray regions correspond to those increased electron density in the excited state, while the light-gray regions correspond to depleted regions from the ground state. Both from the MOs and the charge difference map, it is found that the benzene ring derived from DDE acts as an electrondonating group and the five-membered imide and the benzene rings derived from PMDA act as electron withdrawing groups [14], and that the first excited state is characterized by a strong intramolecular CT. [12] For the M(A-D-A) model, I ~e ADA/ of the first excited Mate (387nm light absorption) was also calculated, and it is expressed as The CI coefficients show that the predominant elctronic transition is HOMO -a LUMO and that its contribution in the first excited state is estimated to be 49%. Based on the calculation of the MOs and the difference electron density between the ground and the first excited states (Figures 4(a), 4(b), and 4(c)) , the first excited state is found to be caused by an intramolecular CT similarly to the M(D-A-D) model.…”

Section: Measurementsmentioning

confidence: 99%

The Origin of Coloration in Aromatic Polyimides. An Approach from Quantum Chemistry.

Matsumoto

1999

J. Photopol. Sci. Technol.

View full text Add to dashboard Cite

The origin of coloration in aromatic polyimides was elucidated from a viewpoint of quantum chemistry. The MOs and the difference electron density between the ground and the first excited states of the model compounds were calculated using semiempirical AM1 (MOPAC97) and INDO/S (MOS-F) methods. Two model compounds of PI(PMDA-DDE) were adopted for the MO calculations. The calculated X max's were around 390nm, which were in good agreement with the cut-off wavelength of the PI(PMDA-DDE) film. From the CI coefficients, the predominant electronic transition was found to be HOMO --~ LUMO in each model, and its contribution to the first excited state was estimated to be approximately 50%. The calculations of the MOs and the difference electron density clearly indicate that the benzene ring derived from DDE acts as an electron-donating group and the five-membered imide and the benzene rings derived from PMDA act as electron-withdrawing groups. Therefore, it is evident that a strong intramolecular CT characterizes the first excited state, and this nature of the first excited state based on the predominant HOMO --LUMO transition contributes to the coloration of aromatic polyimides.

show abstract

Section: Measurementsmentioning

confidence: 99%

The Origin of Coloration in Aromatic Polyimides. An Approach from Quantum Chemistry.

Matsumoto

1999

J. Photopol. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…where | HOMO-13→LUMO is the monoexcited configuration state function. In this state an electron is excited from the HOMO-13, which denotes the thirteenth orbital below the highest occupied MO (HOMO), to the lowest unoccupied MO (LUMO) [33]. The CI coefficients of the first excited state indicate that HOMO-13 → LUMO is the major electronic transition, and the calculated contribution of the transition to the first excited state is 48% for the M(PMDA-BBH).…”

Section: Optical Properties and Quantum Chemical Considerationmentioning

confidence: 99%

“…The dark gray regions correspond to regions of increased electron density in the excited state, while the light gray regions correspond to depleted regions from the ground state. From both the MOs and the charge difference map, it is found that the imide carbonyl oxygen and nitrogen atoms act as electron donors, and that the imide carbonyl carbon and the benzene ring carbon atoms act as electron-withdrawing parts [33]. Hence, the first excited state is characterized by light-induced , it is evident that the benzene ring derived from DDE acts as an electron-donating group, that the five-membered imide and the benzene rings derived from PMDA act as electron-withdrawing groups, and that the first excited state is characterized by a strong intramolecular CT [31].…”

Section: Optical Properties and Quantum Chemical Considerationmentioning

confidence: 99%

Semiaromatic Polyimides based on Bis(Aminomethyl)Bicyclo[2.2.1]Heptane

Matsumoto

1999

High Performance Polymers

View full text Add to dashboard Cite

Semiaromatic polyimides with a polyalicyclic structure were prepared by the polycondensation of bis(aminomethyl)bicyclo[2.2.1]heptane (BBH) with aromatic dianhydrides. The corresponding poly(amic acid)s possessed an inherent viscosity range of 0.60-1.00 dl g −1 . The polyimides were soluble in organic polar solvents and most of them formed flexible, free-standing films. The polyimides had good thermal stability with no significant weight loss up to approximately 400 • C and possessed a 5% weight loss temperature range of 428-465 • C. These polyimide films showed a tensile modulus range of 1.4-3.0 GPa, a tensile strength range of 62-115 MPa, and an elongation at break range of 5.4-6.1%. The semiaromatic polyimide films exhibit a cut-off wavelength around 322-362 nm and are entirely colourless, while the cut-off wavelengths of PI(PMDA-DDE) and PI(BPDA-DDE) films were 426 and 376 nm respectively. The origin of coloration in the aromatic polyimides and the lack of colour in the semiaromatic polyimides were elucidated from the standpoint of molecular orbital (MO) calculations of the model compounds using semiempirical AM1 and INDO/S methods. The calculated λ max of the M(PMDA-BBH) was 371 nm, and the first excited state is mainly characterized by an n-π * transition. Based on both the MOs and the difference in electron density between the ground and the first excited states, the first excited state is attributable to light-induced polarization in the five-membered imide ring. The λ max of the M(PMDA-DDE) model for a representative aromatic polyimide was calculated to be 392 nm. From the charge difference map, it is theoretically evident that the coloration in the aromatic polyimides caused intramolecular charge transfer between the diamine and dianhydride moieties.

show abstract

“…The enzyme bound model 3b was prepared by literature methods [18]. Reaction of 2-chlorobenzimidazole with pyridine yielded 4, isolated as the perchlorate (MP, 230-232°C; literature MP, 232-233°C [19]>. The ylide 5, prepared from 4 [19], gave an MP of 256-257°C dec. (reported MP, about 260°C dec).…”

Section: ; I M-mentioning

confidence: 99%

“…Reaction of 2-chlorobenzimidazole with pyridine yielded 4, isolated as the perchlorate (MP, 230-232°C; literature MP, 232-233°C [19]>. The ylide 5, prepared from 4 [19], gave an MP of 256-257°C dec. (reported MP, about 260°C dec). Radical species 6 resulted from the decomposition of timoprazole in 0.1 M HCl at room temperature [6].…”

Section: ; I M-mentioning

confidence: 99%

Electrochemistry of omeprazole, active metabolites and a bound enzyme model. Possible involvement of electron transfer in anti-ulcer action

Ames

Kovacic

1992

Bioelectrochemistry and Bioenergetics

View full text Add to dashboard Cite

Electrochemical studies were performed with omeprazole, active metabolites and a bound enzyme model. The active metabolites, cyclic sulfenamide and sulfur radical entities, exhibited reduction potentials of-0.3 V and-0.2 V respectively. The value for the bound enzyme model was-0.7 V and that for omeprazole was >-1.4 V. The results lend credence to the hypothesis that electron transfer comprises part of the mode of action in addition to (H+/K+ J ATPase inhibition.

show abstract

An aza-analogue of N-phyridinium cyclopentadienide

Cited by 22 publications

References 3 publications

The Origin of Coloration in Aromatic Polyimides. An Approach from Quantum Chemistry.

The Origin of Coloration in Aromatic Polyimides. An Approach from Quantum Chemistry.

Semiaromatic Polyimides based on Bis(Aminomethyl)Bicyclo[2.2.1]Heptane

Electrochemistry of omeprazole, active metabolites and a bound enzyme model. Possible involvement of electron transfer in anti-ulcer action

Contact Info

Product

Resources

About