Photo-reversible and selective Cu2+ complexation of a spiropyran-carrying sulfobetaine copolymer in saline solution

Abstract

A sulfobetaine copolymer (1) carrying a photochromic spiropyran residue was synthesized, which reversibly isomerized between the closed and open forms in pure water and in saline by irradiation with visible light. The thermodynamic stability of the open form of the spiropyran methacrylate (SPMA) units of compound 1 was reduced upon increasing NaCl concentration. In addition, photo-reversible and selective Cu 2+ complexation in saline solution ([NaCl] ¼ 1.0 wt%) was achieved using compound 1 with metal ions (Cu 2+ , Zn 2+ , Ni 2+ , or Co 2+ ). Covalently cross-linked compound 1 showed selective Cu 2+ adsorption in pure water. In contrast, the other metal ions were increasingly adsorbed as NaCl concentration increased, resulting in lower selectivity of Cu 2+ ion adsorption with 1, e.g., the ratios of adsorption of Cu 2+ , Zn 2+ , Ni 2+ , and Co 2+ with 1 in 10 wt% saline were 73, 20, 10, and 3%, respectively, while only Cu 2+ adsorption was observed in a solution of 1.0 wt% NaCl. Because the stability of the open form of the SPMA units and the metal complexation of 1 were influenced by NaCl concentration, the electrostatically cross-linked networks of the zwitterionic sulfobetaine units of 1 may be loosened by NaCl addition, resulting in easy entry of metal ions into the network. The order of metal complexation among the four metals corresponded to the Irving-Williams series. Hydrogen-bonded networks of water molecules also may contribute to the relatively ineffective selective adsorption of Cu 2+ ions by 1 compared to the electrically neutral spiropyran-carrying copolymer of N-isopropylacrylamide, 2.

Hydroxyethylcellulose‐graft‐poly(2‐(dimethylamino)ethyl methacrylate) as physically adsorbed coating for protein separation by CE

“…Although the poor selectivity of the SP‐polymers is still considered as a drawback on these systems, good selectivity was reported in the case of Cu 2+ when a sulfobetaine‐methacrylate‐functionalised SP copolymers, linear or covalently crosslinked (Table 1, no. 5) were used 69. However, even in this case, NaCl concentration in the system was found to play an important role, since high NaCl concentrations results in inefficient metal ion sensitivity.…”

Synthesis and Characterizations of Bis-Spiropyran Derivatives

“…[4][5][6][7][8][9][10][11][12][13][14][15] However, the synthesis and characterization of oligomers or polymers containing spiropyran moieties in the main backbone have not been well investigated. [16][17][18][19][20][21][22][23] Herein, we report the synthesis and characterization of conjugated bis-spiropyran derivatives.…”

Swelling–shrinking behavior of hydrated noncross‐linked copolymer films in response to photoreversible isomerizaton and metal complexation of spiropyran units of the copolymers

“…2‐hydroxypropyl methacrylate and N ‐isopropylmethacrylamide (NIPMAm) were purchased from Wako Pure Chemical Industries, Ltd. (1‐2 Doshomachi 3‐Chome, Chuo‐ku, Osaka 540‐8605, Japan) and Sigma‐Aldrich, Inc., (3050 Spruce St., St. Louis, MO 63103, USA) respectively. 1′,3′,3′‐trimethyl‐6‐methacryloylspiro[ 2H ‐1‐benzopyran‐2,2′‐indoline] (SPMA) was synthesized as described previously . ( E )‐4‐{[4‐(Dimethylamino)phenyl]diazenyl}phenol was purchased from Tokyo Chemical Industry Co., Ltd. (4‐10‐2 Nihonbashi‐honcho, Chuo‐ku, Tokyo 103‐0023, Japan).…”

“…We have reported on photoreversible metal complexation in water with polymeric spiropyrans . The attractive features of photochromic spiropyrans have prompted several studies of derivatives of these compounds and their metal‐binding characteristics .…”

“…[2] We have reported on photoreversible metal complexation in water with polymeric spiropyrans. [3][4][5] The attractive features of photochromic spiropyrans have prompted several studies of derivatives of these compounds and their metal-binding characteristics. [6][7][8][9] Upon irradiation with ultraviolet (UV) or visible light, spiropyrans isomerize between open forms (OFs) and closed forms (CFs), as shown in Fig.…”