Supramolecular Self-Assembly as a Tool To Preserve the Electronic Purity of Perylene Diimide Chromophores

Perylene Diimide-Embedded Chiral Carbaporphyrin

Herein, we report the synthesis of a novel carbaporphyrin incorporating perylene diimide (PDI) and dipyrromethane units. The twisted plane of the PDI subunits imbues carbaporphyrin with intriguing conformational chirality and stable chiroptical properties. Both experimental and theoretical studies reveal that the unique properties arise from the rigidly conjugated macrocyclic architecture and the reduced interchromophoric distance. This work successfully integrates PDIs into carbaporphyrins, thereby expanding their structural diversity and functional potential.

Investigating the diastereoselective synthesis of a macrocycle under Curtin-Hammett control

This work sheds new light on the stereoselective synthesis of chiral macrocycles containing twisted aromatic units, valuable π-conjugated materials for recognition, sensing, and optoelectronics. For the first time, we use the Curtin-Hammett principle to investigate a chiral macrocyclisation reaction, revealing the potential for supramolecular π-π interactions to direct the outcome of a dynamic kinetic resolution, favouring the opposite macrocyclic product to that expected under reversible, thermodynamically controlled conditions. Specifically, a dynamic, racemic perylene diimide dye (1 : 1 P : M) is strapped with an enantiopure (S)-1,1'-bi-2-naphthol group (P-BINOL) to form two diastereomeric macrocyclic products, the homochiral macrocycle (PP) and the heterochiral species (PM). We find there is notable selectivity for the PM macrocycle (dr = 4 : 1), which is rationalised by kinetic templation from intramolecular aromatic non-covalent interactions between the P-BINOL π-donor and the M-PDI π-acceptor during the macrocyclisation reaction.

Helical Cage Rotors Switched on by Brake Molecule with Variable Fluorescence and Circularly Polarized Luminescence

While chiral molecular rotors have unique frames and cavities to possibly generate switchable chiroptical functions, it still remains a formidable challenge to precisely restrict their rotations to activate certain functions such as fluorescence as well as circularly polarized luminescence (CPL), which are strongly related to the local molecular rotations. Herein, we design a pair of enantiopure helical cage rotors, which emit light neither at the molecular state nor in the crystal or aggregation states, although they contain luminophore groups. However, upon mounting with fluoroaromatic borane (TFPB) as a molecular brake, the phenyl rotation of the helical cage can be effectively hindered and fluorescence and CPL activities of the molecular cage are switched on. Crystal structure analysis reveals that the rotation is restricted through synergistic B-O-H-N bonding and a fluoroaromatic-aromatic (ArF-Ar) dipole interaction. Moreover, the helical cages are switched on stepwise with color-variable fluorescence and CPL by the inner brake in the molecular state and the outer brake in the supramolecular assemblies, respectively. This work not only provides the design idea of chiroptical molecular rotors but also unveils how fluorescence and CPL could be generated in cage rotor systems.

Excited-Multimer Mediated Supramolecular Upconversion on Multicomponent Lanthanide-Organic Assemblies

Upconversion (UC) is a fascinating anti-Stokes-like optical process with promising applications in diverse fields. However, known UC mechanisms are mainly based on direct energy transfer between metal ions, which constrains the designability and tunability of the structures and properties. Here, we synthesize two types of Ln8L12-type (Ln for lanthanide ion; L for organic ligand L1 or L2R/S) lanthanide-organic complexes with assembly induced excited-multimer states. The Yb8(L2R/S)12 assembly exhibits upconverted multimer green fluorescence under 980 nm excitation through a cooperative sensitization process. Furthermore, upconverted red emission from Eu3+ on the heterometallic (Yb/Eu)8L12 assemblies is also realized via excited-multimer mediated energy relay. Our findings demonstrate a new strategy for designing UC materials, which is crucial for exploiting photofunctions of multicomponent lanthanide-organic complexes.

Engineering Soluble Diketopyrrolopyrrole Chromophore Stacks from a Series of Pd(II)-Based Ravels

A strategy to engineer the stacking of diketopyrrolopyrrole (DPP) dyes based on non-statistical metallosupramolecular self-assembly is introduced. For this, the DPP backbone is equipped with nitrogen-based donors that allow for different discrete assemblies to be formed upon the addition of Pd(II), distinguished by the number of π-stacked chromophores. A Pd3 L6 three-ring, a heteroleptic Pd2 L2 L'2 ravel composed of two crossing DPPs (flanked by two carbazoles), and two unprecedented self-penetrated motifs (a Pd2 L3 triple and a Pd2 L4 quadruple stack), were obtained and systematically investigated. With increasing counts of stacked chromophores, UV/Vis absorptions red-shift and emission intensities decrease, except for compound Pd2 L2 L'2 , which stands out with an exceptional photoluminescence quantum yield of 51 %. This is extraordinary for open-shell metal containing assemblies and explainable by an intra-assembly FRET process. The modular design and synthesis of soluble multi-chromophore building blocks offers the potential for the preparation of nanodevices and materials with applications in sensing, photo-redox catalysis and optics.