Size-specific, colorimetric detection of counteranions by using helical poly(phenylacetylene) conjugated to L-leucine groups through urea acceptors.
A colorimetric detection susceptible to the dimensions of guest counteranions has been demonstrated by using poly(phenylacetylene) with L-leucine and urea functionalities (poly-PA-Leu). Poly-PA-Leu was prepared from N-(4-ethynylphenylcarbamoyl)-L-leucine ethyl ester (PA-Leu) by using [Rh(+){eta(6)-C(6)H(5))B(-)(C(6)H(5))(3)}(2,5-norbornadiene)] as a catalyst. The biased helical conformation of poly-PA-Leu was demonstrated through Cotton effects in the circular dichroism (CD) spectra. The addition of ammonium salts, including tetra-n-butylammonium acetate, tetra-n-butylammonium chloride, and tetra-n-butylammonium bromide anions (CH(3)COO(-), Cl(-), and Br(-)), into the poly-PA-Leu solution intensified the CD responses of poly-PA-Leu, which is indicative of the chiral adjustability of anion recognition by using urea groups. In addition, the combination of poly-PA-Leu with the CH(3)COO(-), Cl(-), and Br(-) anions promoted large redshifts in the absorption spectra, thus providing dramatic color changes from pale yellow to red. Guest dependency in the CD and UV/Vis spectra was clearly correlated with the size of the counteranions. Fundamentally, the addition of tetra-n-butylammonium nitrate, tetra-n-butylammonium hydrogen sulfate, tetra-n-butylammonium perchlorate, tetra-n-butylammonium azide, tetra-n-butylammonium fluoride, and tetra-n-butylammonium iodide anions (NO(3) (-), HSO(4) (-), ClO(4) (-), N(3) (-), F(-), and I(-)) has no effect on either the CD or UV/Vis profiles of poly-PA-Leu. The guest specificity observed in the CD and UV/Vis spectra clearly demonstrated the guest-dimension selectivity of poly-PA-Leu in counteranion recognition.
Division of Biotechnology and Macromolecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo, Japan. kakuchi@poly-bm.eng.hokudai.ac.jp
Ryohei
R
Kakuchi
Sachiko
S
Nagata
Ryosuke
R
Sakai
Issei
I
Otsuka
Hiroshi
H
Nakade
Toshifumi
T
Satoh
Toyoji
T
Kakuchi
D000114:Acetylene / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D000838:Anions / Q000737:chemistry; D002942:Circular Dichroism; D003124:Colorimetry; D007930:Leucine / Q000737:chemistry*; D015394:Molecular Structure; D008970:Molecular Weight; D013053:Spectrophotometry; D014508:Urea / Q000737:chemistry*
D000838:Anions; C519145:poly(phenylacetylene); D014508:Urea; D007930:Leucine; D000114:Acetylene