Guest‐Modulated Circularly Polarized Luminescence by Ligand‐to‐Ligand Chirality Transfer in Heteroleptic Pd^II Coordination Cages

Abstract

Multicomponent metallo‐supramolecular assembly allows the rational combination of different building blocks. Discrete multifunctional hosts with an accessible cavity can be prepared in a non‐statistical fashion. We employ our shape‐complementary assembly (SCA) method to achieve for the first time integrative self‐sorting of heteroleptic PdII cages showing guest‐tunable circularly polarized luminescence (CPL). An enantiopure helicene‐based ligand (M or P configuration) is coupled with a non‐chiral emissive fluorenone‐based ligand (A or B) to form a series of Pd2L2L′2 assemblies. The modular strategy allows to impart the chiral information of the helicenes to the overall supramolecular system, resulting in CPL from the non‐chiral component. Guest binding results in a 4‐fold increase of CPL intensity. The principle offers potential to generate libraries of multifunctional materials with applications in molecular recognition, enantioselective photo‐redox catalysis and information processing.

Self-Sorting of Transient Polymer Networks by the Selective Formation of Heteroleptic Metal–Ligand Complexes

“…From the electronic interaction between metal ions and surrounding ligands, exceptional electrochemical, optical, magnetic, and catalytic features emerge that have resulted in unique properties and applications of SCCs . As static units, they are capable of harvesting and transforming the solar energy, catalysis, and illuminance, whereas as dynamic units, they can undergo structural rearrangements in response to variety of external stimuli such as pH, light, temperature, redox reactions, and the introduction of competing ligands or metal ions. − Therefore, they have potential applications in drug delivery, soft robotics, sensors, and variety of molecular machines.…”

“…However, the advances in the design and applications of SCCs are barely utilized in the development of MSPNs . A prime example is the control over coordination geometry that is highly developed in designing complex SCCs by the so-called self-sorting mechanisms, ,,, although being limited to choosing the coordination number in standard homoleptic complexes between bis and tris in the polymer field. − The control over coordination geometry in MSPNs is typically realized by the pH-induced variation of the protonation state in case of protic ligands or according to the coordination geometry preference of the utilized metal ion in aprotic ligands. , For instance, Rowan and co-workers have reported that depending on the type of the counterion, the tridentate 2,6-bis­( N -methylbenzimidazoyl) pyridine ligand forms strong bis-complexes with transition-metal ions, while it can form weak tris-complexes with lanthanides . We have also demonstrated that the bidentate phenanthroline ligand preferentially forms tris-complexes in the presence of Fe 2+ , while Co 2+ and Ni 2+ , respectively, show higher affinities toward bis-complexes. , Moreover, we have shown that phenanthroline and terpyridine ligands are capable of forming heteroleptic complexes in the presence of Co 2+ , whereas Zn 2+ and Fe 2+ exclusively form a mixture of homoleptic complexes .…”

Tunable Circularly Polarized Luminescence via Chirality Induction and Energy Transfer from Organic Films to Semiconductor Nanocrystals

“…However, over the past decades increasing interest in CPL translated to rapid technological advancements. The variety of (i) materials, e.g., conjugated polymers, − gels, − liquid crystals, − metal-organic, and covalent organic frameworks and cages, (ii) phenomena, e.g., thermally activated delayed fluorescence, , room-temperature phosphorescence, − and aggregation-induced emission (AIE), − and (iii) approaches on imparting chirality, e.g., covalent and supramolecular, ,− utilized within this field, is truly broad. Among the different approaches, achieving CPL in multicomponent systems exhibiting simultaneous chirality induction (induction of chiroptical properties of an achiral component) and energy transfer between constituents ,,− has been very recently shown to be particularly attractive.…”

“…However, over the past decades increasing interest in CPL translated to rapid technological advancements. The variety of (i) materials, e.g., conjugated polymers, 12−14 gels, 15−17 liquid crystals, 18−22 metal-organic, 23 and covalent organic frameworks 24 and cages, 25 (ii) phenomena, e.g., thermally activated delayed fluorescence, 26,27 room-temperature phosphorescence, 28−30 and aggregation-induced emission (AIE), 31−33 and (iii) approaches on imparting chirality, e.g., covalent and supramolecular, 15,34−38 and energy transfer between constituents 15,19,39−44 has been very recently shown to be particularly attractive. Such sophisticated systems enable advanced regulation, 39 drastic amplification, 13 and dynamic tunability 15,45,46 of CPL fueling future research toward this way.…”

Evolution of Multicomponent [Pd2ABCD] Cages

“…Multifunctional assemblies based on the contribution from two different components are still in their infancy, e.g. systems featuring circularly polarized luminescence (CPL) by intraassembly chirality transfer 18 , charge-transfer in donor-acceptor systems 19 , and cooperative catalysis [20][21][22] . In only few of the most complicated self-assembled systems reported to date, more than two differentiable functionalities, situated on separate components, have been involved 20,23,24 .…”