Controlled Synthesis of PdII and PtII Supramolecular Copolymer with Sequential Multiblock and Amplified Phosphorescence

Abstract

Supramolecular copolymers constitute a fundamental new class of functional materials attracting burgeoning interest, but examples that display phosphorescence and long-lived excited states are rare. Herein, we describe the synthesis of sequential phosphorescent multi-block supramolecular copolymers in one and multiple dimensions using pincer Pt II and Pd II complexes as building blocks by manipulating out-of-equilibrium self-assemblies via the living supramolecular polymerization approach. Doping a small amount of Pt II complexes (2 mol %) into the Pd II assemblies significantly boosted the emission efficiency and radiative decay rate constant (F em = 3.7%, k r = 1.8 3 10 4 s À1 in Pd II assemblies; F em = 76.2%, k r = 58.6 3 10 4 s À1 in Pt II -Pd II co-assemblies), which is ascribed to an external heavy-atom spin-orbital coupling effect arising from the doped Pt II complex with a delocalized 3 [ds*/p*] excited state. The findings on Pt II and Pd II supramolecular copolymers with controlled sequences and greatly enhanced phosphorescence efficiencies open the door to new photofunctional and responsive luminescent metal-organic supramolecular materials.

Emerging applications for living crystallization-driven self-assembly

“…Other examples of molecular amphiphiles that undergo living supramolecular polymerization include amphiphilic square planar Pt(II) phenanthroline and related complexes, [225][226][227][228][229] perylene bisimides, 221,230 and a wide range of additional π-stacking and hydrogen-bonding species. 210,231,232 Complex architectures, such as well-defined supramolecular block copolymers, have also been successfully prepared and their study represents an exciting new area within the flourishing field of supramolecular polymers.…”

“…210,231,232 Complex architectures, such as well-defined supramolecular block copolymers, have also been successfully prepared and their study represents an exciting new area within the flourishing field of supramolecular polymers. 221,222,229,233,234 For example, A-B-A supramolecular block copolymers of amphiphilic perylene bisimides have been fabricated by seeded living polymerization (see Figure 5c). 221 Cooperative supramolecular block copolymerization has been achieved based on naphthalene diimide monomers with optically distinct green and red fluorescence (see Figure 5d).…”

Living supramolecular polymerization of fluorinated cyclohexanes

“…While there has been remarkable progress recently with preparing supramolecular block copolymers under thermodynamic control [60][61][62] or by slow cooling of monomer mixtures [63][64][65] , a growing number of such precision polymers has been prepared by LSP, which can provide superior structural and sequence control. However to date, these LSP approaches either rely on the modification of the polymerizable core, e.g., substituents are attached to the core of rylene dyes 16,66 or the complexation of different metal ions to identical ligands 67,68 . A modular approach based on the variation of the side chain, as pioneered by Otto, Faul, Manners and Sugiyasu 19,32,69 , would be complementary to these methods and could offer distinct advantages for applications in organic materials science.…”

Consequences of hidden kinetic pathways on supramolecular polymerization

“…Complex supramolecular polymerization behaviour of 1 Self-assembled structures of d 8 metal complexes exhibit particularly interesting photophysical properties [29][30][31][32][33] and the presence of the metal fragment oen enables multiple competing non-covalent interactions, which is benecial to create kinetic aggregates. [34][35][36][37] Preliminary self-assembly studies of the (S)-enantiomer of Pd complex 1, however, suggested the presence of a single supramolecular species if monomer solutions in methylcyclohexane (MCH) were cooled from 363 K to 283 K at a rate of 1 K min À1 .…”