Abstract
A new malonate possessing two pyrene moieties was synthesized as a fluoroionophore, and its structure and fluorescence spectroscopic properties were investigated. When excited at 344 nm in acetonitrile/chloroform (9:1, v/v), the synthesized bispyrenyl malonate has the fluorescence of intramolecular excimer (λem = 467 nm) emissions and not a pyrene monomer emission (λem = 394 nm). A large absolute fluorescence quantum yield was obtained in the solid state (ΦPL = 0.65) rather than in solution (ΦPL = 0.13). X-ray crystallography analysis clarified the molecular structure and alignment of the bispyrenyl malonate in the crystal phase, elucidating its fluorescence spectroscopic properties. Such analysis also suggests there are intramolecular C–H···π interactions and intermolecular π···π interactions between the pyrenyl rings. Interestingly, the synthesized bispyrenyl malonate exhibits excellent fluorescence sensing for the Cu2+ ion. Remarkable fluorescence intensity enhancement was only observed with the addition of the Cu2+ ion.
Highlights
In recent years, research on ion sensing by fluoroionophores has attracted considerable attention [1,2,3,4,5]
The molecular diagrams of bispyrenyl malonate 1 in Figure 3 indicate that the molecules are linked by the π·· π is within the range of the typical distance for 3π···
Fluorescence intensity enhancement of the bispyrenyl malonates by the Cu ions could be interpreted as follows: the binding of the Cu 2+ ion to ester moieties of a bispyrenyl malonate is interpreted as follows: the binding of the Cu ion to ester moieties of a bispyrenyl malonate is considered to shorten the distance between the intramolecular pyrenyl rings, resulting in fluorescence considered to shorten the distance between the intramolecular pyrenyl rings, resulting in fluorescence intensity enhancement of the pyrene excimer emissions
Summary
Research on ion sensing by fluoroionophores has attracted considerable attention [1,2,3,4,5]. For more highly sensitive sensing, improvement demonstrated that sandwich-type ion recognition compounds indicatestudies, excellentition selectivity and that of the fluorescence quantum yield is necessary. Inmoieties, this study, we havethe malonate affect the dihedral between two recognition designed and synthesized new malonate possessing twomoieties pyrene [48] In this we have designed dihedral angles between the two possessing pyrenyl rings the fluorescent are controlled the and synthesized a new malonate two of pyrene moieties as aprobe fluoroionophore. Theby dihedral substituents introduced into pyrenyl the C2-position thefluorescent malonate spacers, leading to by the the improvement angles between the two rings ofofthe probe are controlled substituents of introduced the pyreneinto excimer emissionsofand fluorescence quantum yield. We have reported the the C2-position the malonate spacers, leading the improvement of the pyrene synthesis, fluorescence properties, andHere, the we structure of the bis excimer emissions andspectroscopic fluorescence quantum yield. Have reported the (1-pyrenemethyl)-2synthesis, fluorescence benzyl-2-methylmalonate spectroscopic properties,1.and the structure of the bis (1-pyrenemethyl)-2-benzyl-2-methylmalonate 1
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