Four silver-based coordination polymers,
{[Ag(L)2](BF4)}∞ (1), {[Ag(H2BTC)(L)]·(H3BTC)}∞ (2), {[Ag2(H2BTEC)(L)2]·3.33H2O}∞ (3), and
[Ag(H25SSA)(L)]∞ (4), were
synthesized using
thiomorpholine-4-carbonitrile (L) as the primary ligand and three
aromatic polyoxoacids as coligands: trimesic (H3BTC), pyromellitic
(H4BTEC), and 5-sulfosalicylic acid (H35SSA).
Compounds 1 and 3 are two-dimensional, while 2 and 4 are one-dimensional. L acts as a bis-monodentate
ligand, while the Ag(I) ion is three-coordinated in 2 and four-coordinated in all of the other compounds. The tetrahedral
coordination of Ag(I) in 3 leads to an almost complete
absence of intermolecular interactions with the metal center. All
compounds show reasonable photocatalytic activity for photocatalytic
degradation of mordant blue 9 dye, with reaction rates in the 0.036–0.056
min–1 range. Changes in the reaction rates can be
correlated with the type and coordination of the coligand. Complex 3 exhibits photoluminescence at 77 K, while 4 exhibits photoluminescence at both room temperature and 77 K. Luminescence
lifetimes indicate electronic transitions of singlet parentage, where
transitions are allowed. A TD-DFT study determined the contributions
of individual singlet–singlet electronic excitations to the
fluorescence, indicating that metal– intraligand transitions
are responsible for luminescence in both complexes.
Pt(II)
and Pd(II) complexes (1 and 2,
respectively) with thiomorpholine-4-carbonitrile (TM-CN), an N-substituted
thiomorpholine derivative, were synthesized from tetrachlorido precursors
in water. Structural analysis has shown that 1 represents
the first monomeric metal complex with this ligand type with an axial
M–S bond with respect to the TM-CN ring chair conformation,
while in 2 a typical equatorial M–S bond position
with respect to the ring chair conformation was observed. A detailed
DFT investigation revealed that axial conformers are more stable for
molecular forms of both metals, while intermolecular interactions
in the crystals stabilize the axial conformer for Pt(II) and the equatorial
conformer for Pd(II). The magnitude of this stabilization in the case
of 2 is large enough to change the most stable axial
conformer in the molecular form to the equatorial conformer in the
crystal. Further investigation of the strength of individual intermolecular
interactions revealed significant differences of some interactions
between the two structures. The likely cause of the difference in
the crystal structures of experimentally obtained complexes is the
fact that 1 and 2 exhibit different dominant
interactions: C–H/M and C–H/S are more dominant in 1 and C–H/Cl interactions are more dominant in 2. In addition, DFT calculations have shown that while the
axial position of the Pt–S bond with respect to the ring chair
conformation results in a significantly shorter C–H/Pt interaction
distance than that in the hypothetical equatorial conformer, there
is very little difference in C–H/Pd interaction distances in
conformers with axial and equatorial positions of Pd–S bond
with respect to the ring chair conformation.
Four silver-based coordination polymers {[Ag(L1)2]NO3}∞ (1), {[Ag(L1)2]ClO4}∞ (2), {[Ag(L2)2]NO3‧H2O}∞ (3) and {[Ag(L2)2]ClO4}∞ (4) were synthesized using thiomorpholine-4-carbonitrile (L1) and piperazine-1,4-dicarbonitrile (L2) ligands. Compounds 1 and 2 are two-dimensional, while 3...
Many articles in the literature deal with horseradish peroxidase (HRP) biomineralization, but none pay attention to the isoenzyme composition of commercial HRP or the influence of the carbohydrate component of the protein molecule on the biomineralization process. To study the impact of these factors, we performed periodate oxidation of commercial HRP and a purified HRP-C isoform for biomineralization within ZIF-8. With purified HRP, enzyme@ZIF-8 biocomposites with higher activity were obtained, while periodate oxidation of the carbohydrate component of both commercial HRP and purified HRP-C yields biocomposites with very high activity in acetate buffer that does not degrade the ZIF-8 structure. Using acetate instead of phosphate buffer can prevent the false high activity of HRP@ZIF-8 biocomposites caused by the degradation of ZIF-8 coating. At the same time, purification and especially oxidation of the carbohydrate component of enzymes prior to biomineralization lead to significantly improved activity of the biocomposites.
Modern workers' organisations, in order to survive successfully in today's society, have to adapt to the new conditions and demands and not lose, in the process, their basic goals. Key to the achievement of this seems to be to recognise that modern workers' unions are, in fact, at least akin to political parties and no longer simple associations of people with common interests. A new, modern union structure needs to be built following the action guidelines and elements of good public relations, which will facilitate the organisation of efficient action initiatives in the context of the new information society and the market conditions that have changed the way of functioning both of companies and of the workforce. New, efficient unions need to have a high PR profile, aided by the establishment on their staffs of appropriately-qualified professionals. In the process, they will create for themselves a prominent presence that will act on two fronts -towards gathering a new membership in addition to a strengthening of their public profile, image and credibility.
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