Reactions of 2-cyano-3-ethoxy-5,5-dimethyl-2-cyclohexen-1-one with 2-amino- and 2-hydrazionobenzimidazoles

The reactions of 2-cyano-3-ethoxy-5,5-dimethyl-2-cyclohexen-1-one with 2-amino- and 2-hydrazinobenzimidazoles gave 1-oxo-3,3-dimethyl-11-amino-1,2,3,4-tetrahydroquinazolino[3,2-a]benzimidazole and 2-(2-benzimidazolyl)-3-amino-4-oxo-6,6-dimethyl-4,5,6,7-tetrahydroindazole, respectively.Riga Technical University, Riga LV-1658. Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 235–240, Feburary, 1997.     

Resonance Raman intensity analysis of the excited state proton transfer dynamics of 2-nitrophenol in the charge-transfer band absorption

Resonance Raman spectra were obtained for 2-nitrophenol in cyclohexane solution with excitation wavelengths in resonance with the charge-transfer (CT) proton transfer band absorption. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion along more than 15 normal modes: the nominal CCH bend+CC stretch nu(12) (1326 cm(-1)), the nominal CCC bend nu(23) (564 cm(-1)), the nominal CO stretch+NO stretch+CC stretch nu(14) (1250 cm(-1)), the nominal CCH bend+CC stretch+COH bend nu(15) (1190 cm(-1)); the nominal CCH bend+CC stretch nu(17) (1134 cm(-1)), the nominal CCC bend+CC stretch nu(22) (669 cm(-1)), the nominal CCN bend nu(27) (290 cm(-1)), the nominal NO(2) bend+CC stretch nu(21) (820 cm(-1)), the nominal CCO bend+CNO bend nu(25) (428 cm(-1)), the nominal CC stretch nu(7) (1590 cm(-1)), the nominal NO stretch nu(8) (1538 cm(-1)), the nominal CCC bend+NO(2) bend nu(20) (870 cm(-1)), the nominal CC stretch nu(6) (1617 cm(-1)), the nominal COH bend+CC stretch nu(11) (1382 cm(-1)), nominal CCH bend+CC stretch nu(9) (1472 cm(-1)). A preliminary resonance Raman intensity analysis was done and the results for 2-nitrophenol were compared to previously reported results for nitrobenzene, p-nitroaniline, and 2-hydroxyacetophenone. The authors briefly discuss the differences and similarities in the CT-band absorption excitation of 2-nitrophenol relative to those of nitrobenzene, p-nitroaniline, and 2-hydroxyacetophenone.     

3-甲基-4-乙氧甲酰-2-环己烯酮合成方法的改进

甲基乙氧羰基环己烯酮;多聚甲醛;3-甲基-4-乙氧甲酰-2-环己烯酮合成方法的改进     

Femtosecond transient absorption, nanosecond time-resolved resonance Raman, and density functional theory study of fenofibric acid in acetonitrile and isopropyl alcohol solvents

Hydrogen abstraction reaction of fenofibric acid (FA) in acetonitrile and isopropyl alcohol solvents was studied by femtosecond transient absorption (fs-TA) and nanosecond time-resolved resonance Raman (ns-TR(3)) spectroscopy experiments. The singlet excite state ((1)FA) (nπ*) with a maximum transient absorption at 352 nm observed in the fs-TA experiments undergoes efficient intersystem crossing (ISC) to convert into a nπ* triplet state FA ((3)FA) that exhibits two transient absorption bands at 345 and 542 nm. The nπ* (3)FA species does not decay obviously within 3000 ps. In the ns-TR(3) experiments, the nπ* (3)FA is also observed and completely decays by 120 ns. Compared with the triplet states of benzophenone (BP) and ketoprofen (KP), the nπ* (3)FA species seems to have a much higher hydrogen abstraction reactivity so that (3)FA decays fast and generates a FA ketyl radical like species. In isopropyl alcohol solvent, the nπ* (3)FA exhibits similar reactivity and promptly abstracts a hydrogen from the strong hydrogen donor isopropyl alcohol solvent to generate a ketyl radical intermediate. With the decay of the FA ketyl radical, no light absorption transient (LAT) intermediate is observed in isopropyl alcohol solvent although such a LAT species was observed after similar experiments for BP and KP. Comparison of the ns-TR(3) spectra for the species of interest with results from density functional theory calculations were used to elucidate the identity, structure, properties, and major spectral features of the intermediates observed in the ns-TR(3) spectra. This comparison provides insight into the structure and hydrogen abstraction reactivity of the triplet states of BP derivatives.     

Resonance spectrum and dissociation dynamics of ozone in the 3B2 electronically excited state: experiment and theory

The rovibrational spectrum assigned to the low-lying (3)B(2) electronic state of ozone is measured with intracavity laser absorption spectroscopy. The experimental results are interpreted by means of quantum dynamical calculations on a global ab initio potential energy surface. The observed spectrum is shown to originate from the vibrational ground state in the local minimum of the (3)B(2) potential. The spectrum of short-lived resonance states in this local minimum is analyzed. Additionally, the global minimum of the surface is shown to lie in the dissociation channel in the van der Waals region. This region supports a short sequence of weakly bound vibrational states.     

Resonance Raman and theoretical investigation of the photodissociation dynamics of benzamide in S3 state

Resonance Raman spectra were obtained for benzamide in methanol and acetonitrile solutions with excitation wavelengths in resonance with the S(3) state. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with the motions mainly along the benzene ring C[Double Bond]C stretch nu(9), the Ph-CO-NH(2) and ring benzene stretch nu(14), the CCH in plane bend nu(17), the Ph-CO-NH(2) stretch and NH(2) rock nu(19), the ring trigonal bend nu(23), and the ring deformation and Ph-CO-NH(2) stretch nu(29). A preliminary resonance Raman intensity analysis was done, and the results were compared to those previously reported for acetophenone to examine the substituent effect. Solvent effect on the short-time photodissociation dynamics of benzamide was also examined. A conical intersection point S(2)S(3) between S(3) and S(2) potential energy surfaces of benzamide was determined by using a complete active space self-consistent field theory computations. The structural differences and similarities between S(3)S(2) point and S(0) were examined, and the results were used to correlate to the Franck-Condon photodissociation dynamics of benzamide in S(3) state.     

Resonance Raman spectroscopy and density functional theory calculation study of photodecay dynamics of tetra(4-carboxyphenyl) porphyrin

The 397.9 nm, 416.0 nm and 435.7 nm resonance Raman spectra were acquired for meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) in tetrahydrofuran solution, and the Raman effect of relaxation dynamics was analyzed according to Herzberg-Teller (vibronic coupling) contributions. Density functional calculations were done to help the elucidation of the Soret (B(x) and B(y)-band) electronic transitions and the corresponding photo relaxation dynamics of TCPP. The spectra indicate that the Franck-Condon region photo relaxation dynamics upon S(0) → S(4) electronic transition are predominantly along the totally symmetric C(m)-ph stretch and Porphin ring breath stretch, and simultaneously along the asymmetric ν(C(m)-Phenyl) + δ(N-H) and ν(C(α)-C(m)-C(α))(as) + def (pyr) vibrational relaxation processes. The excited state structural dynamics of TCPP determined from the resonance Raman spectra show that the internal conversion between the B(y) and B(x) electronic states occurs in tens of femtoseconds, and the electronic relaxation dynamics were firstly interpreted taking into account the time-dependent wave packet theory and Herzberg-Teller (vibronic coupling) contributions.     

Resonance Raman studies of excited state structural displacements of conjugated polymers in donor/acceptor charge transfer complexes

Resonance Raman spectra of poly(2-methoxy-5-(3'-7'-dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) and small molecule acceptor blend charge transfer (CT) complexes reveal long and detailed progressions of overtone and combination bands. These features are sensitive to the specific MDMO-PPV/acceptor interactions and enable quantitative calculations of vibrational mode specific displacements of the polymer CT complex.     

Resonance Raman spectra of β-carotene and its molecular structure in the excited electronic state

The resonance Raman spectra of β-carotene have been obtained at low temperature. The excitation profiles of ν₁ (1525 cm^?1) and 2ν₁ (3043 cm^?1) are analysed in terms of the Albrecht theory. The overlap integrals between the vibrational wavefunctions of the ground and the first excited electronic states are shown to be the most important factor in determining the resonance Raman intensities of this molecule. Information on the structure of the electronically excited state has been obtained.     

Real-time, local basis-set implementation of time-dependent density functional theory for excited state dynamics simulations

We present a method suitable for large-scale accurate simulations of excited state dynamics within the framework of time-dependent density functional theory (DFT). This is achieved by employing a local atomic basis-set representation and real-time propagation of excited state wave functions. We implement the method within SIESTA, a standard ground-state DFT package with local atomic basis, and demonstrate its potential for realistic and accurate excited state dynamics simulations using small and medium-sized molecules as examples (H(2), CO, O(3), and indolequinone). The method can be readily applied to problems involving nanostructures and large biomolecules.     

Novel heterocyclization of 3-(2-aminophenylamino)- 5,5-dimethyl-2-cyclohexen-1-one

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Time-resolved resonance Raman and density functional theory study of the deprotonation reaction of the triplet state of p-hydroxyacetophenone in water solution

[reaction; see text] Picosecond and nanosecond time-resolved resonance Raman (TR(3)) spectroscopy was employed to investigate the deprotonation/ionization reaction of p-hydroxyacetophenone (HA) after ultraviolet photolysis in water solution. The TR(3) spectra in conjunction with density functional theory (DFT) calculations were used to characterize the structure and dynamics of the excited-state HA deprotonation to form HA anions in near neutral water solvent. DFT calculations based on a solute-solvent intermolecular H-bonded complex model containing up to three water molecules were used to evaluate the H-bond interactions and their influence on the deprotonation reaction and the structures of the intermediates. The deprotonation reaction was found to occur on the triplet manifold with a planar H-bonded HA triplet complex as the precursor species. The HA triplet species is generated within several picoseconds and then decays with a approximately 10 ns time constant to produce the HA triplet anion species after 267 nm photolysis of HA in water solution. The triplet anion species was observed to decay with a time constant of about 90 ns into the ground-state anion species that was found to have a lifetime of about 200 ns. The DFT calculations on the H-bonded complexes of the anion triplet and ground-states species suggest that these anion species are H-bonded complexes with planar quinonoidal structures containing two water molecules H-bonded, respectively, with oxygen lone pairs of the carbonyl and deprotonated hydroxyl moieties. A deactivation scheme of the photoexcited HA in regard to the deprotonation reaction in neutral water solutions was proposed. With the above dynamic and structural information available, we briefly discuss the possible implications of the model HA photochemistry in water solutions for the photodeprotection reactions of related p-HP phototrigger compounds in aqueous solutions.     

Resonance Raman study of the A-band short-time photodissociation dynamics of 2-iodothiophene

Resonance Raman spectra were obtained for 2-iodothiophene in cyclohexane solution with excitation wavelengths in resonance with the A-band absorption spectrum. These resonance Raman spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mainly along the nominal symmetric C=C stretch of the thienyl ring and accompanied by a moderate amount of motion along the nominal symmetric CSC stretch, the nominal antisymmetric CSC stretch, and the nominal C-I stretch vibrational modes. A preliminary resonance Raman intensity analysis was done for the A-band resonance Raman spectra of 2-iodothiophene. These results were compared to previous results for related iodobenzene and iodoalkane molecules that also contain a C-I chromophore and the similarities and differences in the short-time photodissociation dynamics were discussed.     

Photosensitization mechanisms of triplet excited state beta-lapachone. A density functional theory study

Beta-Lapachone is a natural product with multiple pharmacological activities and mechanistic studies indicated that reactive oxygen species (ROS) generated by beta-lapachone play significant roles in its pharmacological actions. As photosensitization is an important ROS-generating pathway, in the present work, the photosensitization mechanisms of beta-lapachone are explored on the basis of density functional theory estimated triplet excited state characters. Starting from triplet excited state beta-lapachone, the possible generating pathways of 1O2 and O2*- are elucidated and the solvent effects on the photosensitizing reactions are also discussed.     

Homogeneous electromediated reduction of the 2-cyclohexen-1-one by transition metals

The reduction of the 2-cyclohexen-1-one, mediated by some transition metal ions (Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺ and Fe²⁺) and complexes ([Ni^II(bipy)]Br₂ and [Fe^II(bipy)]Br₂, where bipy = 2,2′-bipyridine), was carried out by using a homogeneous electromediated system: sacrificial anode, nickel cathode, (0.2 M) NaI as supporting electrolyte and undivided cell. A constant current of <100 mA was applied with a maximum cell potential of 2.0 V. Cyclohexanone was the principal product in major cases yielding 98%. Cyclohexanol was also detected in some cases. The selectivity of the process can be controlled by choosing Ni as mediator and Zn or Ni as sacrificial anode. A more reactive system can be reached when Fe sacrificial anode is used, giving cyclohexanol as major product (87%).     

Time-dependent density functional theory excited state nonadiabatic dynamics combined with quantum mechanical/molecular mechanical approach: photodynamics of indole in water

We present a combination of time-dependent density functional theory with the quantum mechanical/molecular mechanical approach which can be applied to study nonadiabatic dynamical processes in molecular systems interacting with the environment. Our method is illustrated on the example of ultrafast excited state dynamics of indole in water. We compare the mechanisms of nonradiative relaxation and the electronic state lifetimes for isolated indole, indole in a sphere of classical water, and indole + 3H(2)O embedded in a classical water sphere. In the case of isolated indole, the initial excitation to the S(2) electronic state is followed by an ultrafast internal conversion to the S(1) state with a time constant of 17 fs. The S(1) state is long living (>30 ps) and deactivates to the ground state along the N-H stretching coordinate. This deactivation mechanism remains unchanged for indole in a classical water sphere. However, the lifetimes of the S(2) and S(1) electronic states are extended. The inclusion of three explicit water molecules opens a new relaxation channel which involves the electron transfer to the solvent, leading eventually to the formation of a solvated electron. The relaxation to the ground state takes place on a time scale of 60 fs and contributes to the lowering of the fluorescence quantum yield. Our simulations demonstrate the importance of including explicit water molecules in the theoretical treatment of solvated systems.     

Vibrational assignment, structure and intramolecular hydrogen bond study of 3-amino-1-phenyl-2-buten-1-one

Fourier transform infrared and Fourier transform Raman spectra of 3-amino-1-phenyl-2-buten-1-one and its deuterated analogue were recorded in the regions 400-4,000 and 150-4,000 cm(-1), respectively. Furthermore, the molecular structure and vibrational frequencies of title compound were investigated by a series of density functional theoretical, DFT, and ab initio calculations at the post-Hartree-Fock (MP2) level. Although, the calculated frequencies are generally in agreement with the observed spectra but the DFT results are in much better quantitative agreement with the observed spectra than the MP2 results. The observed wavenumbers were analyzed and assigned to different normal modes of vibration of the molecule. The calculated geometrical parameters show a strong intramolecular hydrogen bond with a N...O distance of 2.621-2.668 A. This bond length is shorter than that of its parent, 4-amino-3-penten-2-one (with two methyl groups in the beta-position), which is in agreement with spectroscopic results. The topological properties of the electron density contributions for intramolecular hydrogen bond in 3-amino-1-phenyl-2-buten-1-one and 4-amino-3-penten-2-one have been analyzed in term of the Bader theory of atoms in molecules (AIM). These results also support the stronger hydrogen bond in the title compound with respect to the parent molecule.