2,2-Difluoro-4-phenyl-1,3,2-dioxaborolo[4,5-c]chromen-5-ium-2-ide

In the crystal, the inversely oriented mol­ecules of the title compound, C15H9BF2O3, form stacks along the a axis via π–π inter­actions between parallel phenyl­chromenium fragments. Linked by a network of C—H⋯F inter­actions, the stacks form layers in the ac plane that are dispersively stabilized in the crystal structure. Two F atoms bonded to the B atom are located in the plane perpendicular to the planar skeleton of the mol­ecule made rigid by two intra­molecular C—H⋯O inter­actions

3-Hy­droxy-2-(4-meth­oxy­phen­yl)-4H-chromen-4-one

In the title compound, C16H12O4, the benzene ring is twisted at an angle of 12.3 (1)° relative to the 4H-chromene skeleton, and an intramolecular O—H⋯O hydrogen bond occurs. The meth­oxy group is almost coplanar with the benzene ring [1.5 (1)°]. In the crystal, inversely oriented mol­ecules are arranged in double (A, A′) columns, along the b axis, and are linked by a network of inter­molecular O—H⋯O hydrogen bonds (between A and A′) and C—H⋯π contacts (within A or A′). The 4H-chromene cores are parallel within A or A′, but make a dihedral angle of 88.6 (1)° between A and A′

2-(4-Fluoro­phen­yl)-3-hy­droxy-4H-chromen-4-one

In the crystal structure of the title compound, C15H9FO3, inversely oriented mol­ecules form inversion dimers through pairs of O—H⋯O hydrogen bonds. The benzene ring is twisted at an angle of 12.0 (1)° relative to the 4H-chromene skeleton of the mol­ecule. Adjacent 4H-chromene units are parallel in a given column or oriented at an angle of 50.0 (1)° in neighboring, inversely oriented, columns, forming a herringbone pattern

Characterization of Coupled Ground State and Excited State Equilibria by Fluorescence Spectral Deconvolution

Fluorescence probes with multiparametric response based on the relative variation in the intensities of several emission bands are of great general utility. An accurate interpretation of the system requires the determination of the number, positions and intensities of the spectral components. We have developed a new algorithm for spectral deconvolution that is applicable to fluorescence probes exhibiting a two-state ground-state equilibrium and a two-state excited-state reaction. Three distinct fluorescence emission bands are resolved, with a distribution of intensities that is excitation-wavelength-dependent. The deconvolution of the spectrum into individual components is based on their representation as asymmetric Siano-Metzler log-normal functions. The application of the algorithm to the solvation response of a 3-hydroxychromone (3HC) derivative that exhibits an H-bonding-dependent excited-state intramolecular proton transfer (ESIPT) reaction allowed the separation of the spectral signatures characteristic of polarity and hydrogen bonding. This example demonstrates the ability of the method to characterize two potentially uncorrelated parameters characterizing dye environment and interactions

Синтез нового ряду хромонів на основі формілтіазолів

A preparative approach to thiazole-containing chromone derivatives has been developed by modifying the corresponding aldehydes with their further transformation into propenone derivatives, and finally introducing them into the Algar-Flynn-Oyamada reaction. Several methods for obtaining propenones have been analyzed, and the most effective and practically convenient one has been found. The thiazole-containing analogs of chromones obtained have a great potential as probes for a wide range of studies.Розроблено препаративний підхід до тіазолвмісних похідних хромону шляхом модифікації відповідних альдегідів та наступним одержанням на їх основі похідних пропенонів, які було застосовано в реакції Альгара-Флінна-Оямади. Проаналізовано декілька методів одержання пропенонів та виявлено найбільш ефективний та практично зручний. Отримані тіазолвмісні аналоги хромонів мають великий потенціал як зонди для широкого спектра досліджень

7‑Hydroxyflavone Revisited. 2. Substitution Effect on Spectral and Acid–Base Properties in the Ground and Excited States

Three derivatives of 7-hydroxy-2-phenyl-4<i>H</i>-chromen-4-one (7-hydroxyflavone), containing chloro, methoxy, and dimethylamino substituents at position 4′, were synthesized and investigated from the view of their ground-state and electronically excited-state behavior. Spectral and fluorescent properties in a wide range of pH/<i>H</i>₀, thermodynamics of the ground and S₁ states, and kinetics of the excited-state deactivation of the compounds were investigated by means of steady-state electronic absorption, steady-state, and time-resolved fluorescent spectroscopies as well as by computational methods. The results are rationalized from the point of view of the substituent effect. In spite of a similar structure and the same acid–base centers, the compounds strongly differ in fluorescence characteristics as well as in the dependence of fluorescent properties on pH/<i>H</i>₀ of the media. Various protolytic/tautomeric forms of the compounds investigated absorb light in the 300–500 nm range and fluoresce in the whole visible range of spectra. The electron-releasing substituents at position 4′ of 7-hydroxyflavone immensely affect spectral properties as well as the excited-state thermodynamics and kinetics, whereas the electron-withdrawing ones cause minimal effect

2-(4-Hydroxyphenyl)-3-methoxy-4H-chromen-4-one

In the title compound, C16H12O4, the substituent benzene ring and methoxy group are twisted relative to the 4H-chromene skeleton by 24.1&#8197;(1) and 61.3&#8197;(1)&#176;, respectively. In the crystal, molecules are connected by classical O&#8212;H...O and weak C&#8212;H...O hydrogen bonds, forming chains parallel to [201]. The 4H-chromene ring systems of adjacent molecules are either parallel or inclined at an angle of 28.9&#8197;(1)&#176;