Synthesis of a Novel Zn-Salphen Building Block and Its Acrylic Terpolymer Counterparts as Tunable Supramolecular Recognition Systems

Abstract

In this work, we present the synthesis of a novel Zn-Salphen complex containing an allyl group, which was used as building block in the further preparation of a new family of functional terpolymers. These polymers were obtained through radical co-polymerization with methyl metacrylate (MMA) and n-butyl acrylate (nBuA) in different ratios. The supramolecular recognition behavior of each polymer was evaluated via potentiometric measurements against selected anions in aqueous media. Interestingly, this proof of concept study shows that these systems were selective against only fluoride (F−) or both, fluoride and acetate (OAc−), by tailoring the relative content of Zn-Salphen monomer, thus making them a promising starting point for modular design of chemical sensors through straightforward synthetic approaches.

Acrylic Polymers Containing a Nickel Salphen Complex: An Approach to Supramolecular and Macromolecular Systems

“…In our previous work, [29] we found that similar counterparts at 0 % of Salphen component ( i. e . only the acrylic backbone n BuA:MMA at 80 : 20 in mass) yielded also one T g , but such transition occurred at −28.6 °C, a lower temperature if compared to the values in the present study.…”

“…[28] Also, we have shown that unsymmetrical Zn-Salphen derivatives bearing an allyl moiety attached to the aldimine aromatic ring, could efficiently copolymerize together with acrylic monomers n-butyl acrylate (nBuA) and methyl methacrylate (MMA) at different ratios. [29] In those experiments, an nBuA:MMA mass ratio of 80 : 20 exhibited an optimal performance in anion detection and disposable potentiometric sensors. Such ratio maximized the material's anion-discrimination through the polymerized Zn-Salphen binding site, thanks to an enhanced balance in ion permeation inside the polymer phase derived from a favorable internal environment.…”

“…[38] Complex 1 and polymers 2 and 3 were synthesized following previously reported methodologies with some modifications. [29] All nuclear magnetic resonance (NMR) measurements were carried out on a Varian V NMRS 400 MHz spectrometer at ambient temperature unless otherwise stated, and chemical shifts are given in parts per million versus TMS. Thermogravimetric analyses (TGA) were performed under nitrogen flow with a ramp of 10°C min À 1 on a Perkin Elmer TGA4000 apparatus; starting temperature 30°C, final temperature 500°C.…”

“…Compound ( E )‐2‐(((2‐aminophenyl)imino)(phenyl)methyl) phenol (ketimine, I) was prepared using a previously reported methodology [38] . Complex 1 and polymers 2 and 3 were synthesized following previously reported methodologies with some modifications [29] . All nuclear magnetic resonance (NMR) measurements were carried out on a Varian V NMRS 400 MHz spectrometer at ambient temperature unless otherwise stated, and chemical shifts are given in parts per million versus TMS.…”

“…For that purpose, we followed a solvent-free radical polymerization approach in the presence of azobisisobutyronitrile (AIBN) as initiator, as shown in Scheme 1, according to environmentally-friendly protocols developed in our group. [29,30] In the corresponding 1 H NMR spectra of these polymers ( Figures S3 and S4 in the Supporting Information), characteristic broad signals for the different aliphatic hydrogens are located in the regions 0.75-2.5 ppm and 3.5-4.2 ppm. It is interesting to mention the presence of a few aromatic signals around 6.5-7.7 ppm and a singlet at 8.07 ppm typical to the CH of the aldimine present in the Ni-Salphen units.…”