Bismuth-Based Coordination Polymers with Efficient Aggregation-Induced Phosphorescence and Reversible Mechanochromic Luminescence.

Two bismuth coordination polymers (CPs), (TBA)[BiBr4 (bp4mo)] (TBA=tetrabutylammonium) and [BiBr3 (bp4mo)2 ], which are based on the rarely used simple ditopic ligand N-oxide-4,4'-bipyridine (bp4mo), show mechanochromic luminescence (MCL). High solid-state phosphorescence quantum yields of up to 85 % were determined for (TBA)[BiBr4 (bp4mo)] (λem =540 nm). Thorough investigations of the luminescence properties combined with DFT and TDDFT calculations revealed that the emission is due to aggregation-induced phosphorescence (AIP).

Photo- and thermochromic and adsorption properties of porous coordination polymers based on bipyridinium carboxylate ligands.

The zwitterionic bipyridinium carboxylate ligand 1-(4-carboxyphenyl)-4,4'-bipyridinium (hpc1) in the presence of 1,4-benzenedicarboxylate anions (BDC(2-)) and Zn(2+) ions affords three porous coordination polymers (PCPs): [Zn5(hpc1)2(BDC)4(HCO2)2]·2DMF·EtOH·H2O (1), [Zn3(hpc1)(BDC)2(HCO2)(OH)(H2O)]·DMF·EtOH·H2O (2), and [Zn10(hpc1)4(BDC)7(HCO2)2(OH)4(EtOH)2]·3DMF·3H2O (3), with the formate anions resulting from the in situ decomposition of dimethylformamide (DMF) solvent molecules. 1 and 3 are photo- and thermochromic, turning dark green as a result of the formation of bipyridinium radicals, as shown by electron paramagnetic resonance measurements. Particularly, crystals of 3 are very photosensitive, giving an eye-detectable color change upon exposure to the light of the microscope in air within 1-2 min.

Aggregation induced phosphorescent N-oxyde-2,2'-bipyridine bismuth complexes and polymorphism-dependent emission.

Unprecedented bismuth complexes, based on the rarely used ditopic ligand N-oxide-2,2'-bipyridine (bp2mo), crystallizing as three polymorphs, α- (), β- () and γ-[BiBr3(bp2mo)2] (), exhibit phosphorescence with a quantum yield up to 17% for the crystal phase (), while the complex displays a weak fluorescence in solution. A study of the luminescence properties combined with DFT/TDDFT calculations reveals that the lighting phenomenon originated by aggregation induced phosphorescence correlated with the weak intermolecular interactions present in the different crystal phases.

Unprecedented stacking of MV2+ dications and MV˙+ radical cations in the mixed-valence viologen salt (MV)2(BF4)3 (MV = methylviologen).

Using a slow liquid-gas diffusion method, the mixed-valence viologen salt (MV)2(BF4)3 (1) and the radical cation salt (MV)(BF4) (2) are crystallized. Both structures contain regular stacks of MV˙(+) radical cations (2) or alternating MV˙(+) and MV(2+) entities (1). A short intrastack intermolecular separation (3.