抄録
In order to study the supramolecular formations of guest-responsive cavitand derivatives in aqueoussolution, synthesis of water-soluble fluorogenic cavitands, which are modified with mono- and bis-pyreneunits (1 and 2, respectively), and their metal sensing abilities have been investigated. Compound 2 showedmonomer and excimer emissions in both an organic and aqueous, which was contained a 10 vol.% DMF, solution, whereas compound 1 indicated these two emissions in only aqueous solution. The fluorescencespectral patterns of compounds 1 and 2 were changed depending on DMF concentrations in an aqueoussolution. The extent of the excimer emission of 2 was the highest in a 50 vol.% DMF, whereas drasticdecrease of this excimer emission was observed in over 60 vol.% DMF. On the other hand, compound 1showed the highest excimer emission intensity between 10-30 vol.% DMF and middle emission wasrecognized in 30 vol% DMF. Finally, in over 50 vol.% DMF, no excimer emission of 1 was observed. Themovements of the appended units of these compounds in various DMF concentrations were studied by thefluorescence and UV spectra and MM2-minimized structures. A ratio of excimer and monomer emissionintensities of 1 and 2 were varied in 10-40 vol.% and 10-50 vol.% DMF contents in water, respectively. TheUV spectra patterns of 1 or 2 were different between in 10-40 vol.%, 50 vol.% and over 60 vol.% or 10-50vol.%, 60 vol.% and over 70 vol.% DMF aqueous solutions, respectively. The variations of fluorescence andUV spectra suggested that compounds 1 and 2 formed association dimer in 10-40 vol.% and 10-50 vol.%DMF aqueous solutions, respectively, and the canceling of these dimer formations was observed withincreasing DMF content or metal concentration. Furthermore, fluorescent spectral changes and MM2-minimized structures suggested that the association dimer of 2, which formed one pair pyrene excimer in 10vol.% DMF aqueous solution, was transformed into different configuration of association dimer makingplural pyrene excimer pairs in 20-50 vol.% DMF aqueous solutions. In order to evaluate the metal sensingabilities of 1 and 2 in a 10 vol.% DMF aqueous solution, the ratio of decrement of an intensity of excimeremission with an addition of metal cation was used as a detecting parameter. Compounds 1 and 2 exhibitedthe highest sensing abilities for Na2+ and Co2+, respectively.
