Alternating Poly(Pt‐salphen)‐(p‐phenyleneethynylene) as Phosphorescent Conjugated Linear‐Rod and Coilable Sensory Materials

Abstract

Phosphorescent conjugated polymers consisting of alternating p-phenylene-ethynylene and 'para-' or 'meta-type' Pt(II)-salphen luminophore units have been synthesized. Side-arms bearing different substituents (n-alkoxy and acetylated-sugar) have afforded contrasting emission properties that are attributed to the polymer conformation, extent of π-stacking interactions and differences in chemical structure. Intriguing selectivity in luminescent sensing of metal ions has been observed.

Metal Salen- and Salphen-Containing Organic Polymers: Synthesis and Applications

“…Furthermore, by the variation of the substitution pattern of the halogens at the salphen units, helical or zig-zag-type polysalphen chains with Zn 2þ , Ni 2þ , and Cu 2þ 104b as well as with Pt 2þ centers have been realized. 105 Furthermore, different external substituents like saccharines were used as well. 105,106 An interesting example of a 1D salphen polymer with an ordered 3D structure was presented by Liu and coworkers in 2015 by condensing a bissalicylaldehyde and phenazine diamine with zinc acetate.…”

“…105 Furthermore, different external substituents like saccharines were used as well. 105,106 An interesting example of a 1D salphen polymer with an ordered 3D structure was presented by Liu and coworkers in 2015 by condensing a bissalicylaldehyde and phenazine diamine with zinc acetate. 107 It is suggested that due to the extended aromatic backbone of the precursors, the resulting polymer chains pack in an ordered fashion to form crystalline supramolecular 3D networks.…”

“…In addition to the as-discussed applications, salen-and salphen-containing polymers were used for example as light-emitting materials in solution. [103][104][105][106]141 While some of the polymers were only investigated phenomenologically, 103 MacLachlan's linear 1D Zn(II)-containing poly(salphenyleneethynylenes) showed a fluorescence enhancement upon addition of Lewis bases such as pyridine, proving a potential application as a fluorescent sensor for such. 104b This was further underlined by a series of poly(Pt-salphen)-(para-phenyleneethynylenes) providing low-energy emission (λ Em $ 580-700 nm) with a selective fluorescence quenching in the presence of Cu 2þ ions, while other main group and transition metals did not influence the emission properties.…”

“…104b This was further underlined by a series of poly(Pt-salphen)-(para-phenyleneethynylenes) providing low-energy emission (λ Em $ 580-700 nm) with a selective fluorescence quenching in the presence of Cu 2þ ions, while other main group and transition metals did not influence the emission properties. 105 Another example for the use of 1D salen polymers is the metal-free polymer P1, which was used to enantiodiscriminate chiral α-hydroxyl carboxylic acids. For instance, for mandelic acid an enantiomeric fluorescence difference ratio (ef) 142 of up to 8.41 in preference to the (L)enantiomer was found (Figure 8).…”

New Trends in the Optical and Electronic Applications of Polymers Containing Transition‐Metal Complexes

“…Sensory materials that can selectively detect Cu 2+ ions are of interest,12 but reports about phosphorescent Cu 2+ sensors are few. A series of conjugated polymers composed of alternating p ‐phenylene‐ethynylene and “para‐” ( p ‐ P2 and p ‐ P3 ) or “meta‐type” ( m ‐ P2 and m ‐ P3 ) Pt(II)‐ salphen complex units was synthesized by Chan et al13 The side‐arms bearing acetylated‐sugar afforded contrasting emission properties that were attributed to differences in the polymer conformation, the extent of π‐stacking interactions and the chemical structure. The luminescent responses of the p ‐ and m ‐ P3 to different metal ions in CH 3 CN indicates the good selectivity to Cu 2+ , which may be assigned to the judicious choice of the side‐arm receptor groups.…”