Epoxy compounds usually have stronger nucleophilic ability, because the alkyl group on the oxygen atom makes the bond angle smaller, which makes the lone pair of electrons react more dissimilarly with the electron-deficient system. Compound: 5,6-Dichloropyrazine-2,3-dicarbonitrile, is researched, Molecular C6Cl2N4, CAS is 56413-95-7, about The role of the size of aza-crown recognition moiety in azaphthalocyanine fluorescence sensors for alkali and alkaline earth metal cations.SDS of cas: 56413-95-7.
A series of fluorescence sensors bearing one 1-aza-12-crown-4, 1-aza-15-crown-5, 1-aza-18-crown-6 or 1-aza-21-crown-7 as a recognition moiety and an aza-analog of phthalocyanine as a fluorophore was prepared All compounds absorbed and emitted light in the red region. Sensing properties based on intramol. charge transfer were studied via absorption and fluorescence titration experiments with alkali metal cations and alk. earth metal cations. Important relationships between aza-crown size and binding affinity were observed in the group of alkali metal cations. Affinity for lithium decreased in series from the smallest crown to the largest, 1-aza-15-crown-5 bound sodium and potassium similarly, and 1-aza-18-crown-6 had the highest affinity to potassium. Alk. earth metal cations were bound more tightly, which was obvious from more pronounced changes in the absorption spectra, and from the higher increase of fluorescence upon cation addition A limited size preference was observed in the group of alk. earth metal cations.
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Reference:
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate