Three-dimensionally organized sulfonamide groups have been demonstrated to show an anion signaling ability using poly(phenylacetylene) with L-aspartic acid and sulfonamide functionalities (poly-1). The polymerization of N-(4-ethynylphenylsulfonyl)-L-aspartic acid diethyl ester (1) was carried out using Rh + (2,5-norbornadiene)[(η 6 -C 6 H 5 )B -(C 6 H 5 ) 3 ] (Rh(nbd)BPh 4 ) as a catalyst to afford poly-1. The biased helical conformation of poly-1 was demonstrated through Cotton effects in the circular dichroism (CD) spectra. The addition of the anions including perchlorate (ClO 4 -), nitrate (NO 3 -), azide (N 3 -), and bromide (Br -) anions had fundamentally no effect on both the CD and UV profiles of poly-1. On the other hand, the addition of the anions including acetate and fluoride anions (CH 3 COOand F -) into the poly-1 solution intensified the CD responses of the poly-1, showing that the anion recognition of sulfonamide groups induced distinct changes in the poly(phenylacetylene) backbone. In addition, a distinct red shift was observed for poly-1 in the presence of these two anions; i.e., the λ max value for CH 3 COOchanged from 408 to 447 nm, and that for Fchanged from 408 to 482 nm. The guest specificity observed in the solution color change of poly-1 with counteranions clearly correlated with the guest basicity.

Three-dimensionally organized amide groups have been demonstrated to show a high sensitivity toward anionic guests using poly(phenylacetylene)s with L-leucine and amide functionalities (poly-PA-Leu). The poly-PA-Leu was prepared from the N-(4-ethynylphenylcarbonyl)-L-leucine ethyl ester (PA-Leu) using Rh + (2,5-norbornadiene)[(η 6 -C 6 H 5 )B -(C 6 H 5 ) 3 ] (Rh(nbd)BPh 4 ) 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 acetate, fluoride, benzoate, azide, and bromide (CH 3 COO -, F -, C 6 H 5 COO -, N 3 -, and Br -, respectively) into the poly-PA-Leu solution intensified the CD responses of the poly-PA-Leu, indicative of the polyacetylene helicity changes triggered by anion recognition of the amide groups. The efficient anion binding was observed for poly-PA-Leu with CH 3 COO -, whose apparent binding constant was estimated to be 1.1 × 10 3 (mol -1 • L). On the other hand, the anions including perchlorate (ClO 4 -), nitrate (NO 3 -), chloride (Cl -), and iodide (I -) had essentially no effects on both the CD and UV profiles of poly-PA-Leu. The guest specificity observed in the CD spectra of poly-PA-Leu with counteranions clearly correlated with the guest-basicity.

A r a t i o n a l l y d e s i g n e d p o l y -(phenylenebutadiynylene) bearing urea functionalities (poly-1) was demonstrated to be a novel fluorescence turn-on probe for various anions. Poly-1 itself exhibits an extremely weak emission that was undetectable by the naked eye, whereas the fluorescence emission of poly-1 was significantly enhanced by the addition of anions. Based on the NMR, dynamic light scattering, and fluorescence decay measurements, the observed fluorescence turn-on response was determined to be realized by the fluorescence recovery based on the disassembly of the poly-1 aggregates, which was originally triggered by the anion recognition event at the urea units of poly-1.

A colorimetric detection of guest counteranions has been demonstrated using poly(phenylacetylenes)s with urea functionalities and R-amino acids, such as L-leucine, L-glutamic acid, L-aspartic acid, L-phenylalanine, L-isoleucine, and L-alanine (PPA-Leu, PPA-Glu, PPA-Asp, PPA-Phe, PPA-Ile, and PPA-Ala, respectively). The polymers were prepared by the polymerization of the N-(4-ethynylphenylcarbamoyl)-L-amino acids ethyl ester (PA-Leu, PA-Glu, PA-Asp, PA-Phe, PA-Ile, and PA-Ala) using Rh + (2,5norbornadiene)[(η 6 -C 6 H 5 )B -(C 6 H 5 ) 3 ] (Rh(nbd)BPh 4 ) as the catalyst. The biased helical conformations of all the urea-functionalized polymers were demonstrated through Cotton effects in the circular dichroism (CD) spectra. The addition of various ammonium salts including tetra-n-butylammonium acetate (TBAA), benzoate (TBAB), nitrate (TBAN), azide (TBAN 3 ), fluoride (TBAF), chloride (TBACl), and bromide (TBABr) to a solution of all the urea-functionalized polymers intensified the CD responses of the polymers, indicative of the chiral adjustability of the anion recognition using urea groups. The anion signaling property of the urea-functionalized polymers was different from each other. In particular, the signs of the induced Cotton effect for the urea-functionalized polymers in the presence of anions were strongly dependent on the pendant structure of the R-amino acids.

The colorimetric detection of anionic species has been studied for a-amino acid-conjugated poly(phenylacetylene)s, which were prepared by the polymerization of the ethyl esters of N-(4-ethynylphenylsulfonyl)-L-alanine, L-isoleucine, L-valine, L-phenylalanine, L-aspartic acid, and L-glutamic acid using Rh þ (2,5-norbornadiene)[(g 6 -C 6 H 5 )B À (C 6 H 5 ) 3 ] as the catalyst in CHCl 3 . The one-handed helical conformations of all the sulfonamide-functionalized polymers were characterized by Cotton effects in the circular dichroism spectra. The addition of anions with a relatively high basicity, such as tetra-n-butylammonium acetate and fluoride, induced drastic changes in both the optical and chiroptical properties. On the other hand, anions with a relatively low basicity, such as tetra-n-butylammonium nitrate, azide, and bromide, had essentially no effects on the helical conformation of all the sulfonamide-functionalized polymers. The anion signaling property of the sulfonamide-functionalized polymers possessing a-amino acid moieties was significantly affected by the installed residual amino acid structures.