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Tytuł:
Transformacje strukturalne w kryształach wywołane reakcjami fotochemicznymi
Structural transformations in crystals induced by photochemical reactions
Autorzy:
Turowska-Tyrk, I.
Bąkowicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/171650.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
reakcje fotochemiczne w kryształach
struktura kryształu
struktura cząsteczki
zmiany strukturalne
rentgenowska analiza strukturalna
krystalografia
photochemical reactions in crystals
crystal structures
molecular structure
structural changes
X-ray structure analysis
crystallography
Opis:
Structural changes induced in crystals by photochemical reactions were presented. The changes concern: a) the distances between neighbouring reactant molecules and their mutual orientation in the case of intermolecular reactions, b) the distances and angles between fragments of a molecule for intramolecular reactions, c) the position of molecules in crystals, d) geometry of hydrogen bonds, e) cell constants, and f) the content of product molecules in crystals. For most intramolecular reactions, the distances between reactive atoms are constant for a long time in phototransformation and decrease rapidly at its end (Figs. 3 and 5). In the case of intermolecular reactions, the distances between reactive atoms of reactant molecules decrease linearly along with the phototransformation of crystals (Fig. 7). Additionally, unreacted molecules become, to a certain degree, similar to product molecules in terms of their shape (Figs, 4 and 8). Reactant and product molecules do not assume a fixed place in crystals. Product molecules change their orientation towards that of which is observed in a pure product crystal and reactant molecules gradually move away from the position they took in pure reactant crystals. All this has an influence on the geometry of hydrogen bonds existing in crystals (Fig. 9). The above-mentioned structural transformations find their expression in values of cell constants (Fig. 10). The factors influencing the photoreactivity of molecules in crystals were also described. Knowledge of crystal and molecular structures of partly reacted crystals, determined thanks to X-ray structure analysis which is a branch of crystallography, reveals the behaviour of molecules in crystals in which photochemical reactions proceed and helps to understand a pathway of these reactions.
Źródło:
Wiadomości Chemiczne; 2014, 68, 5-6; 381-402
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Struktura pochodnych benzo[ b]furanu i kumaryny oraz ich kompleksów z miedzią (II) i cynkiem(II)
The structure of benzo[b]furan and courmarin derivatives and their copper (II) and zinc (II) complexes
Autorzy:
Drzewiecka, A.
Powiązania:
https://bibliotekanauki.pl/articles/172518.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
pochodne benzo[b]furanu
pochodne kumaryny
kompleks Cu(II)
kompleks Zn(II)
struktura kryształu
badania XAS
benzo(b)furan derivatives
coumarin derivatives
Cu(II) complex
Zn(II) complex
crystal structure
XAS study
Opis:
Selected benzo[b]furan and coumarin derivatives with proven and potential antibacterial, anticancer and antiarrhythmic activities have been investigated [1–3] (Figs. 1 and 2). The stereochemical description of their molecules in the solid and gas phase as well as intra- and intermolecular-interactions in crystals have been determined [4–6]. The structural studies of analyzed molecules indicated the planarity of the benzo[b]furan and coumarin ring systems. The oxygen or carbon atoms of the substituents, –OH, –OCH3, –C(=O)CH3 and –COO H, are nearly coplanar with the aromatic ring. The hydroxyl and acetyl groups, being in the ortho position, are coplanar with the aromatic ring and the formation of the intramolecular O–H…O hydrogen bond in all three states of matter is observed. Its strength is around 18 kcal/mol. Several conformers of studied compounds, differing in the orientation of the methoxy, acetyl and/or carboxyl groups, were analyzed. Next, the electrochemical method was used to synthesize novel copper and zinc complexes with the oxygen donor benzo[b]furan and coumarin derivatives. The Cu(II) and Zn(II) complexes have been obtained with carboxylic acids as ligands whereas hydroxy ligands reacted only with copper [6]. The geometry of metal-ligand interaction of new compounds has been determined using a single crystal X-ray crystallography and an X-ray absorption spectroscopy [7, 8]. The combination of these two methods revealed that for some compounds cation environment could depend on the form of the solid sample. In the microcrystalline zinc complexes (studied by EXAFS) the cation is penta-coordinated (ZnO5) with the Zn–O distances being ca 1.98(3) Ĺ. In the recrystallized complex (analyzed by the X-ray diffraction) it was found that zinc is tetra-coordinated (ZnO4). The Cu(II) cation in the singlecrystal form of the complex with the carboxylic acid 5 is penta-coordinated to the carboxylate groups and the ethanol molecule. The bridging COO – groups stabilize the dinuclear complex center Cu2O10. The powdered form of this complex is based on the Cu2O8 units, indicating the absence of the ethanol molecule in the coordination sphere. In the series of the Cu(II) complexes with the hydroxy derivatives of benzo[b]furan and coumarin a centrosymmetric coordination polyhedron of metal exhibits a square-planar geometry (CuO4). Two ligands are bonded to the copper cation via the acetyl and deprotonated hydroxyl O atoms.
Źródło:
Wiadomości Chemiczne; 2012, 66, 3-4; 355-369
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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