Electronic spectra of ?,?-unsaturated ketones ? Indole derivatives (original) (raw)
Related papers
The Journal of Physical Chemistry A, 2009
The electronic structures of a homologous series of indole and benzofuran derivatives, in which the nitrogen or oxygen atom is replaced by group 15 and group 16 heavier heteroatoms, have been investigated by means of various spectroscopic techniques coupled with density functional calculations. It was found that the excitation energies of the group 16 benzoheteroles systematically shift to the red in the order of benzofuran , benzothiophene , benzoselenophene (8), and benzotellurophene . In contrast, the electronic absorption spectra of the group 15 benzoheteroles, 1-phenyl derivatives of indole (1b), phosphindole (2b), arsindole (3b), stibindole (4b), and bismuindole (5b), did not exhibit this type of spectral shift. X-ray analysis and density functional theory (DFT) studies revealed that 2b-5b adopt a bent conformation both in the crystalline and in the solution phases. In contrast, planar structures were calculated for the group 16 heterocycles. Using the observed spectroscopic properties and time-dependent density functional theory (TDDFT) calculations, the electronic absorption spectra of the present heterocycles were assigned. A molecular orbital analysis was performed to rationalize the effect of replacement of the heteroatom on the electronic structures. The observed magnetic circular dichroism (MCD) sign patterns of these heterocycles are interpreted according to Michl's perimeter model.
Electronic structure, UV spectra and reactivity of non-benzenoid systems by the INDO/S-CI method
Journal of Molecular Structure: THEOCHEM, 1981
The electronic spectra, frontier molecular orbitals, charge distribution and dipole moments of nine compounds containing the cyclopropenyl ring have been studied by the all-valenceelectrons INDO/S-CI method. The theoretical results agree fairly well with the experimental indications, where available. The o-contribution to the net charge density on the ring as well as the p0 and sp polarization contributions to the dipole moments are higher than in the fulvene derivatives, indicating greater participation of the smaller-ring system. The UV spectra of compounds containing two coupled rings correlate with those of the component frameworks, in agreement with previous semi-empirical calculations.
Research Journal of Pharmaceutical, Biological and Chemical Sciences
Molecular geometry, vibrational frequencies, energy gaps, net charges, dipole moments and heats of indole formation at the ground state have been calculated by using the Molecular Mechanics, PM3, ab initio/HF and DFT/B3LYP methods. The optimized geometrical parameters are in good agreement with experimental values. Comparison of the obtained fundamental vibrational frequencies of Indole result by DFT/B3LYP (6-311G++(d,p)) method, are in a close agreement with the experimental data. Ab initio/HF with 6-31G basis set was used to investigate the effects of a variety of substituents (methyl, cyanide and dimethylamino) on the electronic properties of Indole derivatives.
Substituent Effects and Vibrational Coupling in Indole-2,3-diones: An IR , NMR and Theoretical Study
Heterocyclic Communications, 2001
The IR C=0 stretching vibrational wave numbers, 'H, IJ C and l5 N NMR chemical shifts are reported for 5-and 6-substituted indole-2,3-diones and correlated with Hammett substituent constants and semiempirical AMI data. As an alternative to the previous assignment of the C=0 stretching vibrational wave numbers the two v(C=0) absorption bands can also be interpreted as the symmetric and asymmetric stretching vibrational modes in the mechanically coupled cyclic α-dicarbonyl system. The use of 2D NMR techniques enabled to make correct assignments of the l3 C NMR chemical shifts, which are substantially different from those reported earlier.
RESOLUTION OF OVERLAPPING BANDS IN THE NEAR-UV ABSORPTION SPECTRUM OF INDOLE DERIVATIVES
Photochemistry and Photobiology, 1985
Ahstract-The second derivative spectra of tryptophan in water and in ethylene glycol at 22°C have been integrated in order to obtain the corresponding primitive functions. The integration was carried out by making use of Tchebychev polynomials. The results show that the integrated primitive functions do not correspond to the original absorption spectra of tryptophan in various solvents, but they reflect only the contributions of the 'L,, bands of the indolic chromophore. The identification of the electronic component. which generates the second derivative spectrum, was based on the solvent insensitivity of the dcrivative peaks. The comparison between the absorption spectra reported in this paper and those calculated for the 'L,, +-'A electronic transition of indole confirmed the assumption that the derivation process eliminates the broad, although more intense, contributions coming from the 'L. + 'A electronic transition.
Journal of Molecular Structure, 1991
The asymmetric transfer hydrogenation (ATH) of imines catalyzed by the Noyori-Ikariya [RuCl(η 6-arene)(N-arylsulfonyl-DPEN)] (DPEN = 1,2-diphenylethylene-1,2-diamine) half-sandwich complexes is a research topic that is still being intensively developed. This article focuses on selected aspects of this catalytic system. First, a great deal of attention is devoted to the N-arylsulfonyl moiety of the catalysts in terms of its interaction with protonated imines (substrates) and amines (components of the hydrogen-donor mixture). The second part is oriented toward the role of the η 6-coordinated arene. The final part concerns the imine substrate structural modifications and their importance in connection with ATH. Throughout the text, the summary of known findings is complemented with newly-presented ones, which have been approached both experimentally and computationally.
The Journal of Physical Chemistry A, 2003
Steady state electronic absorption, fluorescence emission, polarized spectra of some disubstituted indoles, 2,3-dimethylindole (23DMI), 2,5-dimethylindole (25DMI), and 1,2-dimethylindole (12DMI), were studied in solvents of different polarity coupled with time resolved measurements. The electrochemical measurements demonstrate that DMIs should act as electron donors in photoinduced electron transfer (PET) reactions with 9Cyanoanthracene (9CNA) which serves as the electron acceptor. The photoexcited 9CNA undergoes fluorescence quenching in the presence of DMI both in nonpolar n-heptane (NH) and highly polar acetonitrile (ACN) solvents though no ground state complex formation was apparent between the reactants. In NH, the observation of the reduction of fluorescence emission intensity of 9CNA accompanied by the formation of emissive exciplex was made only for the N-methyl substituted indole 12DMI. Transient absorption spectra recorded by the laser flash photolysis technique show that photoinduced charge separation reaction proceeds both in the excited singlet and triplet states of 9CNA. Moreover, it is also established that production of the monomeric triplet of 9CNA occurs through the ion recombination mechanism. In NH, the possibility of the formation of a contact neutral radical, through the H-atom transfer reaction, as an additional route for rapid nonradiative decay of the exciplex is hinted at in the case of N-H indoles 23DMI and 25DMI. Nevertheless, it is inferred that in the case of 12DMI the observed emissive exciplex in nonpolar medium is due to its inability to form a contact neutral radical. In ACN, the major nonradiative pathway appears to be due to photoinduced ET rather than formation of exciplex.
Open Chemistry, 2017
(5-Methoxy-1H-indol-1-yl)(5-methoxy-1H-indol-2-yl)methanone (MIMIM) is a bis-indolic derivative that can be used as a precursor to a variety of melatonin receptor ligands. In this work, the energetic and spectroscopic profiles of MIMIM were studied by a combined DFT and experimental approach. The IR, Raman, UV-Vis, 1 H NMR and 13 C NMR spectra were calculated by PBEPBE and B3LYP methods, and compared with experimental ones. Results showed good agreement between theoretical and experimental values. Mulliken population and natural bond orbital analysis were also performed by time-dependent DFT approach to evaluate the electronic properties of the title molecule.
Quantum-chemical study of spectral-luminescent properties of indole
Atmospheric and Oceanic Optics
The quantum-chemical study of spectral and photophysical properties of indole by the Intermediate Neglect of Differential Overlap (INDO) method is carried out. The rate constants of radiative degradation kr, internal transition kint, and intercombination conversion kST are calculated. Various models of the indole molecule in neutral and aqueous solutions at low temperature are considered. The obtained results agree well with experimental data. In aqueous solutions, the indole absorption and fluorescence bands are shifted toward longer waves relative to neutral solutions.
Spectral and non-linear optical properties of cyanine bases' derivatives of benzo[c,d]indole
Dyes and Pigments, 2007
The complex investigation of the cyanine bases, containing benzo[c,d]indole as residue group was carried out by linear and non-linear optical spectroscopic and quantum-chemical modelling methods. It was found that non-linear optical properties were more sensitive to the nature of the varied donor terminal group than the absorption spectra; the increase of the donor strength in indolenine, benzothiazole, quinoline, and pyridine causes an increase of the second and third hyperpolarizibilities by a factor of 3.5, which is qualitatively in good agreement with the experimental data.