Poly(Zn-salphen)-alt-(p-phenyleneethynylene)s as Dynamic Helical Metallopolymers: Luminescent Properties and Conformational Behavior

Abstract

The synthesis of soluble, conjugated poly­(Zn-salphen)-alt-(p-phenyleneethynylene)­s with a coilable structure and bearing acetylated sugar substituents is described, and their photophysical properties and conformational behavior have been investigated. Their CD spectra confirm that these systems are chiral, and signify ordered (helical) coiling of the polymer backbone arising from chirality transfer from the β-d-glucopyranosyl groups. The consequences of varying side-chain substituents as well as the extent of inter- and intrachain [π-stacking and Zn···O­(salphen)] interactions have been studied, and comparisons with the corresponding linear-rod and Pt-based congeners have been made. Analysis of the effects of different solvents on these systems by UV–vis absorption, emission, and CD spectroscopy indicates that low-polarity solvents give a tighter, more compressed helical structure with increased CD intensities, while coordinating solvents can perturb the folded conformation to afford a more extended coiled structure with decreased Cotton effects. These observations, together with variable-temperature CD experiments, point to the flexibility and dynamic nature of the helical conformation.

Dissymmetric Chiral Poly(diphenylacetylene)s: Secondary Structure Elucidation and Dynamic Luminescence

“…These studies are inspired by the structure/function relationships present in biomacromolecules such as peptides, proteins, DNA or polysaccharides. Among non‐natural helical scaffolds, dynamic helical polymers constitute a very interesting family due to the possibility of tuning their helical sense or elongation through external stimuli [19–23] . The use of non‐natural building blocks to synthetize these polymers allows the creation of smart materials with applications in different fields such as sensing, [24–31] asymmetric synthesis, [32–36] chiral recognition [37] and separation [38–41] .…”

“…Among nonnatural helical scaffolds, dynamic helical polymers constitute a very interesting family due to the possibility of tuning their helical sense or elongation through external stimuli. [19][20][21][22][23] The use of non-natural building blocks to synthetize these polymers allows the creation of smart materials with applications in different fields such as sensing, [24][25][26][27][28][29][30][31] asymmetric synthesis, [32][33][34][35][36] chiral recognition [37] and separation. [38][39][40][41] However, in molecular engineering it is mandatory to establish structure/function relationships for these materials, a fact that will allow to determine and, if possible, refine the structural features involved in the functionality of the material.…”

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

“…However, the use of Zn-Salphen building blocks as a broadly applicable strategy for developing molecularly tunable materials in polymer science is still in its early stages [29]. In the literature, these building blocks have been incorporated into polymeric systems using two main strategies: supramolecular functionalization to obtain Zn-Salphen-composites [30,31,32] and homo-polymerization to produce covalently linked Zn-Salphen oligomers [33,34]. Nevertheless, to date, their potential as a supramolecular tool for tailoring the functional properties of more complex co-polymer materials has remained underexploited.…”

Saccharide‐Functionalized Poly(Zn‐salphen)‐alt‐(m‐ and p‐phenyleneethynylene)s as Dynamic Helical Metallopolymers

“…We have developed shape‐persistent cofacial (M‐salphen) 2 (M=Pt, [18] Zn [19] ) coordination architectures, which give selective photophysical responses to guest analytes attributable to perturbations in conformation and intramolecular interactions [20] . Extension of this approach led to the development of coilable poly(M‐salphen)‐ alt ‐( p ‐phenylene‐ethynylene) (M=Pt, [21] Zn [22] ) systems bearing acetylated glucosyl substituents. These materials are optically active as revealed by CD spectroscopy, indicating ordered coiling of the polymer backbone arising from chirality transfer from the β ‐D‐glucopyranosyl units.…”