Spectral-luminescence and lasing properties of several morpholine derivatives of naphathalimide in different solvents

The spectral-luminescence properties, lasing ability, and time-resolved gain spectra of three morpholine derivatives of naphthalimide (substituted in position 4) in polar (ethanol and dimethylformanide) and nonpolar (diethyl ester and toluene) solvents are investigated. It is found that rotation of the morpholine group about the single bond connecting the group with the rest molecule takes place, which results in a shift of the gain spectrum towards the longwave region and decrease of the fluorescence quantum yield. Deceased. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 603–606, September–October, 1997.     

Acetylene-Substituted Two-Photon Absorbing Molecules With Rigid Elongated Pi-Conjugation: Synthesis,Spectroscopic Properties and Two-Photon Fluorescence Cell Imaging Applications

Two asymmetrical molecules with substituted acetylene as central rigid elongated conjugation are reported as potential chromophores for two-photon microscopic imaging. These molecules consist of a typical D–π–A structure, have different donors (D), the same π-conjugated center (π) and the same acceptor (A). Structural characterization and spectroscopic properties, including single-photon (linear) absorption, quantum yields, single-photon fluorescence, and two-photon absorption spectra, were studied in solvents with different polarity. These acetylene-substituted molecules were found to have high two-photon absorption cross-sections (for example, 690 GM for molecule 1 in toluene), which were determined by a two-photon induced fluorescence method using a femtosecond Ti: sapphire laser as excitation source. Single- and two-photon cellular imaging experiments demonstrate that the substituted acetylene derivatives could be one kind of promising two-photon fluorescence probes for cellular imaging.     

Interaction of Electrons with Indole,Tryptophan, and their Derivatives in the Gas Phase

The electron energy loss spectra (EELS) of indole, 3-indolyl propionic acid, 3-indolealdehyde, 3-dimethylaminomethylindole, tryptophan, and N-acetyl-L-tryptophan in the gas phase upon excitation by monokinetic electrons with an energy of E₀ = 11–50 eV are obtained. The structure of EELS is determined in the main by the indole chromophore; the side groups, except for the C=O group of 3-indolealdehyde, exert an insignificant influence. The energy of the lower triplet level ³L_a is 3.3 eV for indole and its derivatives and 3.2 eV for tryptophan and N-acetyl-L-tryptophan. Four singlet transitions in the region of 4.4–7.2 eV have been identified. The molecules studied, except for tryptophan, fluoresce in the gas phase on excitation by electrons. At low values of E₀ (10–25 eV), the fluorescence spectra are similar and are due to the indole fluorophore. Just as in the case of optical excitation, fluorescence on excitation by electrons is associated with the ¹L_b-S₀ transitions. An increase in the energy E₀ up to 60–80 eV leads to dissociation of a portion of the indole molecules and to the appearance of additional bands in the fluorescence spectrum. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 468–472, July–August, 2005.     

Experimental determination and interpretation of fluorescence and fluorescence excitation spectra of 1,2-benzanthracene cooled in supersonic jet

We measured the fluorescence and fluorescence excitation spectra of supersonic jet-cooled 1,2-benzanthracene. Using the MO/M8ST method, we calculated the frequencies of in-plane vibrations in the ground and first excited singlet electronic states, and, in the Franck-Condon approximation, we calculated the intensities of transitions between them. Experimental spectra are interpreted based on these data. In the fluorescence excitation spectrum, the position of the line of the 0–0 transition (26535 ± 1 cm⁻¹), which is the most intense, is determined.     

Fluorescence spectra of blood plasma treated with ultraviolet irradiation <Emphasis Type="Italic">in vivo</Emphasis>

We have studied the fluorescence spectra of blood plasma from patients with acute coronary syndrome, and also the effect of therapeutic doses of in vivo ultraviolet blood irradiation (UBI) on the spectra. We have established that the maxima in the fluorescence spectra of the original plasma samples, obtained from unirradiated blood, are located in the wavelength interval 330–340 nm, characteristic for the fluorescence of tryptophan residues. In extracorporeal UBI (λ = 254 nm), we observed changes in the shape and also both a blue and a red shift in the maxima of the fluorescence spectra, differing in magnitude for blood plasma samples from different patients in the test group. We show that UBI-initiated changes in the fluorescence spectra of the plasma depend on the original pathological disturbances of metabolite levels, and also on the change in the oxygen-transport function of the blood and the acid–base balance, affecting the oxidative stability of the plasma. We have concluded that UV irradiation, activating buffer systems in the blood, has an effect on the universal and specific interactions of the tryptophan residue with the amino acid residues and water surrounding it.     

Absorption,fluorescence, and fluorescence excitation spectra of free molecules of indole and its derivatives

We have obtained and analyzed the absorption, fluorescence, and fluorescence excitation spectra of indole vapor, N-acetyl-L-tryptophan vapor, and 3-indole aldehyde vapor. From analysis of the dependence of the fluorescence spectrum of the free indole molecules on the wavelength of the exciting radiation λ_ex, it follows that emission of fluorescence occurs when the molecules undergo a transition from the one electronically excited state ¹L_b. The fluorescence spectra of the studied compounds are insignificantly different, suggesting a major role for the indole chromophore in formation of the compounds. The absorption spectrum of N-acetyl-L-tryptophan, in which the group of atoms is added to the indole ring through a-C-C bond, is similar to the spectrum of indole, while the spectrum of 3-indole aldehyde is significantly different from the indole spectrum due to the effect of the C=O group conjugated with the indole ring. The fluorescence excitation spectra are considerably different from the absorption spectra. This is associated with the strong dependence of the quantum yield for the free molecules on λ_ex. Qualitatively, they are mirror-symmetric to the fluorescence spectra of the stodied compounds. Analysis of the data obtained provides a basis for assuming that in the case of free molecules of indole and its derivatives, the ¹L_a absorption in the extreme long-wavelength region of the spectrum does not overlap ¹L_b absorption. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 218–222, March–April, 2007.     

Spectral-luminescent properties and photoinduced transformations of bisanthene and bisanthenequinone

Based on the study of photochemical transformations of bisanthene in oxygen-containing solutions, it was established that the final product of this reaction is bisanthenequinone. It is shown that in the course of this oxidation reaction the intermediate compounds endomonoperoxide and bisanthene endobiperoxide are formed. Quantum-chemical calculation of the geometrical structure and electronic spectra of the endoperoxides has shown that they have a nonplanar structure, and their absorption spectra experience a large hypsochromic shift. The absorption and fluorescence spectra of solutions of bisanthene in different solvents at 300 and 77 K were investigated. The large Stokes shift of the fluorescence spectra of the solutions of bisanthene in benzene and in its methyl derivatives is explained by the action of intermolecular interactions. The quasi-line fluorescence spectra of solutions of bisanthene in the matrices of saturated hydrocarbons were recorded. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 176–182, March–April, 2000.     

Formation of fluorescence bands of polyatomic organic molecules in the gaseous phase upon excitation by electrons

Information on paths in absorption and deactivation of energy gained by molecules in their excitation by electron impact to low-lying singlet states has been obtained from an analysis of changes in the fluorescence spectra of these molecules. It is shown that there is a significant difference in the formation of fluorescence spectra when free molecules are excited by optical radiation and by electrons. It contrast to optical excitation, the interaction of an electron with a molecule is nonselective in character. All electronic states have a chance to be excited, which results in ensembles of emitting molecules with a different store of vibrational energy, and these ensembles each contribute to the fluorescence spectrum. Deceased. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 216–223, March–April, 1998.     

Subnanosecond spectrofluorimetry of new indolocarbazole derivatives in solutions and protein complexes and their dipole moments

The spectral and temporal characteristics of new 6,12-dimethoxyindolo[3,2-b]carbazole, 5,11-dimethyl-6,12-dimethoxyindolo[3,2-b]carbazole, and 5,11-dihexyl-6,12-di(hexyloxy)indolo[3,2-b]carbazole fluorescence probes in organic solvents and protein complexes are studied. The dipole moments of indolocarbazoles in 1,4-dioxane were measured by electrooptical absorption method. The measured dipole moments have values within the range of (3.1–3.6) × 10⁻³⁰ C m in the equilibrium ground state and increase to (4.8–5.6) × 10⁻³⁰ C m after excitation. The excited state lifetime of indolocarbazole derivatives increases with increasing polarity and viscosity of the environment. The binding of indolocarbazoles with trypsinogen and human serum albumin increases the fluorescence intensity, changes the intensity ratio of fluorescence bands, and increases the average excited state lifetime of indolocarbazoles. The analysis of the instantaneous fluorescence spectra and fluorescence decay parameters at different wavelengths revealed the existence of several types of probe binding sites in proteins. It is found that the fluorescence characteristics of indolocarbazole derivatives depend on the conformation rearrangements of trypsinogen due to its thermal denaturation.     

Conformational Flexibility of Cytokine-Like C-Module of Tyrosyl-tRNA Synthetase Monitored by Trp144 Intrinsic Fluorescence

The non-catalytic COOH-terminal module formed after proteolytic cleavage of full-length mammalian tyrosyl-tRNA synthetase displays dual function: tRNA binding ability and cytokine activity. With the aim to explore the intramolecular dynamics of C-module in solution we used fluorescence spectroscopy to study conformational changes of isolated protein. We used information from fluorescence spectra and computational model for characterization of a microenvironment of a single tryptophan residue (Trp144). Its fluorescence parameters and protection from quenching by Cs⁺ ions indicate the internal localization—buried into protein globule. The fluorescence quenching of Trp144 by acrylamide suggests rapid conformation dynamics of the C-module in nanosecond time scale. The temperature-induced conformational changes in the C-module were monitored by the fluorescence measurements of Trp144 emission and by red-edge excitation shift. An emission maximum shift up to ∼349 nm and significant decrease of the red-edge shift effect at 37–52 °C indicated a major conformational transition of Trp144 from buried native state into highly relaxing polar solvent environment.     

Intramolecular charge transfer and formation of luminescence centers of 4-nitro-4-dimethylaminobutadiene in binary solvents

Absorption and luminescence spectra of a 4-nitro-4-dimethylaminobutadiene molecule in binary solvents have been experimentally obtained and investigated. Formation of the absorption spectra is associated with a chromophore grouping of the molecule in a bent state, while the bathochromic shift of the band in the absorption spectrum is consistent with the theory of dipole-dipole interaction of a bipolar molecule with solvent molecules. The fluorescence spectrum and its form and bathochromic shift depend not only on the solvent polarity but also on the proportion and kind of binary mixture of solvents. For a certain proportion of the binary solvent, radiation has been generated at λ=610 nm in pumping by a nitrogen laser. Reported at the International Conference on Luminescence, November, 22–24, 1994, Moscow. Belarusian State University, 4, F. Skorina Ave., Minsk, 220080, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 119–121, January–February, 1997.     

Sub-Structures Formed in the Excited State are Responsible for Tryptophan Residues Fluorescence in β-Lactoglobulin

Origin of tryptophan residues fluorescence in β-lactoglobulin is analyzed. Fluorescence lifetimes and spectra of β-lactoglobulin solution are measured at pH going from 2 to 12 and in 6 M guanidine. Tryptophan residues emit with three lifetimes at all conditions. Two lifetimes (0.4–0.5 ns and 2–4 ns) are in the same range of those measured for tryptophan free in solution. Lifetimes in the denatured states are lower than those measured in the native state. Pre-exponential values are modified with the protein structure. Data are identical to those already obtained for other proteins. Fluorescence lifetimes characterize internal states of the tryptophan residues (Tryptophan sub-structures) independently of the tryptophan environments, the third lifetime results from the interaction that is occurring between the Trp residues and its environment. Pre-exponential values characterize substructures populations. In conclusion, tryptophan mission occurs from substates generated in the excited state. This is in good agreement with the theory we described in recent works.     

Features of sensitized phosphorescence and delayed annihilation fluorescence spectra of coronene in frozen solutions

We have studied the sensitized phosphorescence spectra of coronene in toluene and its delayed annihilation fluorescence spectra in n-decane at 77 K. We show that as a result of perturbation of electronic states by exchange interactions, intensity redistribution occurs in both the sensitized phosphorescence spectrum and the delayed annihilation fluorescence spectrum. The nonzero probability of the symmetry-forbidden radiative 0–0 transition is explained by the lower symmetry of the bimolecular system compared with the symmetry of the coronene molecule.     

Influence of the mineral component in biotissues affected by calcinosis on their laser-induced fluorescence spectrum

Laser-induced fluorescence (LIF) spectra of human cardiac-valve tissues affected by calcinosis and of macroscopic calcinosis formations produced from resected cardiac valves with such pathology were investigated by comparison with analogous spectra of bone and myocardial tissue of an animal, LIF was excited by an excimer laser with λ=248 nm. In the spectrum of macroscopic calcinosis formations, luminescence bands of the mineral component were separted from the band of protein tissues when these tissues were subjected to heat treatment at 700°C. The investigations have shown that the LIF spectrum of a calcified tissue contains fluorescence bands of tryptophan and fluorescence bands of the mineral component (hydroxylapatite). A change in the spectrum of tissues with pathological processes can be cause not only by a relative change in the concentration of collagen elastin, but also by the additional fluorescenced of the hydroxylapatite mineral that is absent in a healthy cardiac tissue. It was found that the change in the spectrum characterized by the ratio of the LIF intensity at λ=330 nm to the LIF intensity at λ=450 nm is sufficiently large. This makes it possible to use measurements of the relative intensity of fluorescence at these wavelengths to control the degree of calcination of cardiac tissue. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 846–849, November–December, 1999.     

Comparative Studies of Two Araceous Lectins by Steady State and Time-Resolved Fluorescence and CD Spectroscopy

Transitions in the tryptophan microenvironment and secondary structure of two monocot lectins from Sauromatum guttatum and Arisaema tortuosum under different denaturing conditions were studied by steady state and time resolved fluorescence and CD spectroscopy. The lectins exist as tetramers with a single tryptophan residue estimated per monomer, present in a polar environment. Quenching with ionic quenchers showed predominantly electropositive environment for tryptophan residues. Acrylamide had maximum quenching effect. A decrease in KI quenching due to lectin denaturation indicated redistribution of charges as a result of possible conformational change. The two values for lifetimes of tryptophanyl population (1.2–1.4 and 6.3–6.4 ns) reduced substantially on quenching or denaturation. Similarly, both the lectins showed a drastic loss of secondary structure in 5 M Gdn-HCl or 6 M Urea or at pH 2.0 and below. For the first time araceous lectins, like legume lectins are shown to bind adenine. The presence of a compact structure at alkaline pH 10.0–12.0 was observed in CD spectra.     

Spectral properties of anionic form of 3-hydroxyflavone

The spectral and temporal characteristics of the fluorescence of the anionic form of some 3-hydroxiflavones in different solvents are studied. This form is observed under selective excitation in the region of the long-wavelength slope of the main absorption band, and its spectrum consists of a wide structureless band lying between the short- and long-wavelength fluorescence bands of these molecular probes. The fluorescence excitation spectra of the anionic form differ from the corresponding spectra of the normal and tautomeric forms. The addition of water to the solution leads to a gradual fluorescence quenching which is static or belongs to the second kind according to Vavilov’s classification, i.e., occurs in the ground state.     

Synthesis,X-Ray Crystal Structures and Optical Properties of Novel Substituted Pyrazoly 1,3,4-Oxadiazole Derivatives

Novel pyrazoly 1,3,4-oxadiazole derivatives were synthesized and characterized by ¹H NMR, IR, HRMS and X-ray diffraction analysis. UV–vis absorption and fluorescence properties of these compounds in different solutions showed that the maximum absorption wavelength was not significantly changed in different solvents; however, maximal emission wavelength was red-shifted with the increase of solvent polarity. Absorption λ_max and emission λ_max was less correlated with substituent groups on aryl rings.     

Electron impact excitation of luminescence of uracil

We have measured the luminescence spectra of isolated uracil molecules in the wavelength range of 200–500 nm that were excited by slow electrons. The spectrum contains more than 20 spectral bands and lines. We show that the luminescence spectrum of uracil is formed by processes of dissociative excitation of molecules, dissociative excitation with ionization, and excitation of electronic states of the initial molecule and molecular ion.     

Molecular probe FET: Long-wavelength fluorescence excitation effect and proton transfer reaction

We studied the steady-state fluorescence spectra of solutions of FET (4′-(diethylamino)-3-hydroxyflavone) in acetonitrile that were excited at different temperatures by quanta with different energies located in the range of the main absorption band and in its long-wavelength wing. We found that, at room temperature, the emission intensity ratio of the bands of the normal and tautomeric forms, which are located at 505 and 570 nm, respectively, depends on the excitation wavelength. In the range of the main absorption band 300–360 nm, this ratio remains nearly the same, i.e., 1.45, while, upon excitation in the range of the long-wavelength wing 360–380 nm of the main band, it decreases to 1.33 at a wavelength of 460 nm. In this same range, a long-wavelength excitation effect that is unusual for liquid inviscid solvents at room temperature, i.e., a bathochromic shift of the entire short-wavelength emission band by 11 nm, manifests itself. We propose to explain these dependences using energy diagrams, which take into account the dependence of free energy on the orientational polarization of the polar solvent. The observed effect of the long-wavelength shift of the fluorescence spectrum with increasing excitation wavelength is explained in terms of the inhomogeneous broadening of electronic spectra of polar solutions, and it should be described using the scheme of energy states that takes into account sublevels of orientational broadening due to orientational dipole-dipole interactions of the fluorophore with nearest molecules of the polar solvent, as well as the relation between the fluorophore lifetime in the excited state and the dielectric relaxation time of solvent molecules in the field of the fluorophore dipole.     

Fluorescence spectroscopy of potential electroluminescent materials: Substituent effects on DSB and segmented PPV derivatives

The absorption and fluorescence of substituted distyrylbenzene (DSB) derivatives and segmented poly(phenylene vinylene) (PPV) derivatives are characterized by long-wavelength absorption maxima and absorption coefficients of λ_a = 380–450 nm, ε = 20,000–60,000 M⁻¹ cm¹ and fluorescence maxima, quantum yields, and decay times of λ_r = 440–530 nm, Φ_f = 0.2–0.9, and Τ = 0.8–2.5 ns, respectively. Alkoxy substituents at the central phenylene ring of DSB groups increase the bathochromic shift in the spectra in comparison to DSB, without a significant decrease in the high DSB fluorescence quantum yield. Both phenyl and cyano substitutions at the vinylene bridge lead to a further bathochromic shift of the fluorescence and a decrease in the quantum yield to ca. 0.4. The DSB derivatives and the related segmented PPV derivatives show nearly the same absorption spectra, fluorescence spectra, and radiative rate constantsk _f= Φ_f/Τ, indicating the efficacy of the segmentation of the polymer chain. The radiative rate constants determined by the Φ_f and Τ values and by the Strickler/Berg formula are in reasonable agreement. This supports the possibility of interpreting the properties of the polymers in terms of their DSB units. The decrease in the emission anisotropy can be ascribed to multistep energy transfer processes between different oriented segments.