Triplet-triplet absorption spectra of phenanthrene and azaanalogues

Triplet-triplet (T-T) absorption spectra of phenanthrene and several azaanalogues were measured in the spectral range from 25000 to 17000 cm⁻¹ at 83 K. For the first time a vibrational structure of the main band systems in the T-T spectra could be detected. The vibrational modes producing these progressions are associated with the lower T₁ state. The assignment of the vibrational structure to the T₁ state has been confirmed by computation of the T-T spectra with the help of a lineshape function. Furthermore, in the spectra of the azaanalogues an additional absorption band appears which is assigned to a T-T transition from the T₂ state.     

Infrared absorption spectra of naphthalene and anthracene anion-radicals

The infrared spectra of naphthalene and anthracene anion-radicals and their completely deuterated analogs have been studied. The most intense bands have been assigned, and it has been shown that the frequencies of the bending and stretching vibrations of the ring and the C-H (D) bond are less than the corresponding frequencies for the hydrocarbons. The decrease in the frequencies has been attributed to the fact that the unpaired electron of the anionradical, present in an antibonding orbital, decreases the force constants of the bonds; this is analogous to an excited state of the hydrocarbon molecule. A product rule has been proposed for the anion-radicals and their original hydrocarbons.     

Theoretical characterization of the absorption spectra of phenanthrene and its radical cation

The vertical absorption spectra of phenanthrene and its radical cation have been studied theoretically by means of a multiconfigurational second-order perturbation approach. Singlet-singlet transition energies and oscillator strengths, and singlet-triplet excitation energies have been studied in the absorption spectrum of phenanthrene up to 6 eV. The absorption spectrum of the pehnanthrene radical cation has been computed up to 3.4 eV. The results obtained confirm previous assignments and also lead to new interpretations of the main features of the spectra of these systems.     

Optical T-T absorption of salicylidene-p-toluidine in solution

The observation of triplet-triplet absorption of salicylidene-p-toluidine, is complicated by the possible colored isomer formation during the optical pumping. The short-lived (singlet-singlet) and long-lived (triplet-triplet) absorption spectra were recorded phographically by microsecond flash and nanosecond laser flash photolysis techniques. Salicylidene-aniline complexes were purified by repeated recrystallisation until further recrystallisation produced no further changes for X-ray diffraction pattern and optical absorption, emission properties.     

Novel photochemical reaction of indole with naphthalene and phenanthrene in the solid state

Irradiation of mixed crystals of indole and naphthalene gave an addition product, 1-(1,4-dihydro-1-naphthyl)indole ( ), while irradiation in solution gave another product in addition to . Similar solid-state photoreaction of indole and phenanthrene gave .     

Electronic spectra of dithieno analogues of phenanthrene

The magnetic circular dichroism (MCD) spectra of some dithieno analogues of phenanthrene: benzo [2,1-b;3,4-b′] dithiophene (I) benzo [1,2-b;4,3-b′] dithiophene (II), benzo [1,2-c;3,4-c′] dithiophene (III) and benzo [1,2-b;3,4-b′] dithiophene (IV) are reported. For I–III the spectra corresponding to two different transition moment directions could be obtained from low-temperature linear dichroism spectra. The results compare well with theoretical energies, oscillator strengths, moment directions and MCD B-terms which were obtained from semi-empirical quantum mechanical calculations in the π-electron approximation.     

Theoretical IR spectra of ionized naphthalene

We report the results of a theoretical study of the effect of ionization on the IR spectrum of naphthalene, using ab initio molecular orbital theory. For that purpose we determined the structures, band frequencies, and intensities of neutral and positively ionized naphthalene. The calculated frequencies and intensities allowed an assignment of the most important bands appearing in the newly reported experimental spectrum of the positive ion. Agreement with the experimental spectrum is satisfactory enough to take into consideration the unexpected and important result that ionization significantly affects the intensities of most vibrations. A possible consequence on the interpretation of the IR interstellar emission, generally supposed to originate from polycyclic aromatic hydrocarbons (PAHs), is briefly presented.     

Excited singlet yield in T-T annihilation, a comparative study of naphthalene and anthracene in solution

A method based on the study of both triplet absorption and delayed fluorescence (DF) decays after flash excitation has been developed to determine DF yields. Values of the excited singlet yield in the T-T annihilation process have been obtained for naphthalene and anthracene in solution at room temperature by application of this method. Triplet extinction coefficients and annihilation rate constants for these compounds were also determined. Excited singlet generation is the predominant annihilation channel for naphthalene whereas it is only of minor importance for anthracene. The difference in DF yields is ascribed to differences between these aromatics with respect to the efficiencies of the annihilation channels leading respectively to excited singlet and triplet states. The higher rate of excited singlet formation for naphthalene is qualitatively accounted for by considering the possibility of radiationless transitions from the bimolecular states formed in T-T interaction towards an upper excimer singlet state.     

Effect of the extent of reduction of naphthalene↭d phenanthrene-cyclopentadienyl iron complexes on their electronic absorption spectra

Conclusions The unequivocal correspondence of the extent of reduction of naphthalene-cyclopentadienyl and phenanthrene-cyclopentadienyl iron complexes with changes in the region for the d-d transitions in their electronic absorption spectra was established experimentally, indicating localization of the outer electrons on the Fe atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimieheskaya, No. 2, pp. 482–485, February, 1985.     

Cyclization of β-ketosulfoxide—III: Synthesis of naphthalene and phenanthrene derivatives

On heating with trichloroacetic acid or trifluoroacetic acid, 2,4-dimethoxyphenethyl methylsulfinylmethyl ketone (1) cyclized to 2,3-dimethoxy-5-methylthio-6-oxo-5, 6, 7, 8-tetrahydronaphthalene (2) through an intramolecular nucleophilic substitution of a sulfonium ion intermediate (20b), while a β -ketosulfoxide having naphthalene nucleus (3) cyclized to a tetrahydrophenanthrene 4via a Pummerer rearrangement product 23. Treatment of 1 with p-toluenesulfonic acid gave a mixture of 2,3,6-trisubstituted naphthalenes (7–10), whose composition was dependent on the reaction conditions. The aromatization proceeded via2.     

Ice growth from supercooled aqueous solutions of benzene, naphthalene, and phenanthrene

Classical molecular dynamics (MD) were performed to investigate the growth of ice from supercooled aqueous solutions of benzene, naphthalene, or phenanthrene. The main objective of this study is to explore the fate of those aromatic molecules after freezing of the supercooled aqueous solutions, i.e., if these molecules become trapped inside the ice lattice or if they are displaced to the QLL or to the interface with air. Ice growth from supercooled aqueous solutions of benzene, naphthalene, or phenanthrene result in the formation of quasi-liquid layers (QLLs) at the air/ice interface that are thicker than those observed when pure supercooled water freezes. Naphthalene and phenanthrene molecules in the supercooled aqueous solutions are displaced to the air/ice interface during the freezing process at both 270 and 260 K; no incorporation of these aromatics into the ice lattice is observed throughout the freezing process. Similar trends were observed during freezing of supercooled aqueous solutions of benzene at 270 K. In contrast, a fraction of the benzene molecules become trapped inside the ice lattice during the freezing process at 260 K, with the rest of the benzene molecules being displaced to the air/ice interface. These results suggest that the size of the aromatic molecule in the supercooled aqueous solution is an important parameter in determining whether these molecules become trapped inside the ice crystals. Finally, we also report potential of mean force (PMF) calculations aimed at studying the adsorption of gas-phase benzene and phenanthrene on atmospheric air/ice interfaces. Our PMF calculations indicate the presence of deep free energy minima for both benzene and phenanthrene at the air/ice interface, with these molecules adopting a flat orientation at the air/ice interface.     

Substitution effects on the triplet-triplet absorption spectrum of naphthalene

The polarization of the triplet-triplet (T-T) absorption spectrum of α-, β-hydroxynaphathalene and 2,3-dihydroxynaphthalene from 4000 to 6000 Å was measured. The obtained data were compared with theoretical calculations on T-T absorption spectra and polarization data on the lowest-energy singlet-singlet absorption bands of these compounds.     

Inelastic electron tunnelling spectra of some derivatives of naphthalene

Inelastic electron tunnelling spectra of 1- and 2-naphthylacetic acid, 1- and 2-naphthoic acid, 1- and 2-naphthylacetate and 1-naphthylacetamide were measured at 4.2 K in the range 100–4000 cm⁻¹. The molecules were transferred onto the alumina surface by the vacuum deposition method. The spectra showed intensive and sharp peaks originating from aromatic rings. However, the spectra from naphthylacetates were of poorer quality than those from the other compounds and hence their adsorption orientation was concluded to be more parallel with respect to the surface of alumina. The adsorption of the naphthylacetates was possibly followed by dissociation of the molecules. The I, U characteristics were also measured, and it was observed that the naphthoic acids yielded the most nonlinear curves.     

Far-infrared spectra of alkali naphthalene ion pairs in solution

The far-infrared spectrum of an ethereal solution of the naphthalene radical anion prepared by reduction with an alkali metal shows an absorption band which is considered to be due to a vibration of an ion pair. The corresponding force constant was calculated for each ion pair from the observed frequency. The obtained values are of reasonable magnitude.     

A simple, two-step, site-specific preparation of fluorinated naphthalene and phenanthrene derivatives from fluorobromo-substituted alkenes

A facile two-step procedure for the site-specific preparation of fluorinated naphthalene and phenanthrene derivatives is described. The Sonogashira reaction of bromofluoro-substituted alkenes with terminal alkynes, followed by base-catalyzed cyclization in refluxing N-methyl-2-pyrrolidinone (NMP), affords the corresponding fluorinated naphthalene and phenanthrene derivatives in good yields.