Dipyrrolyldiketone PtII Complexes: Ion-Pairing π-Electronic Systems with Various Anion-Binding Modes.

A variety of π-electronic ion-pairing assemblies can be constructed by combining anion complexes of π-electronic systems and countercations. In this study, a series of anion-responsive π-electronic molecules, dipyrrolyldiketone PtII complexes containing a phenylpyridine ligand, were synthesized. The resulting PtII complexes exhibited phosphorescence emission, with higher emission quantum yields (0.30-0.42) and microsecond-order lifetimes, and solution-state anion binding, as revealed by our spectroscopic analyses. These PtII complexes displayed solid-state ion-pairing assemblies, exhibiting various anion-binding modes, which derived from pyrrole-inverted and pyrrole-non-inverted conformations, and packing structures, with the contribution of charge-by-charge assemblies, which were dependent on the substituents in the PtII complexes and the geometries and electronic states of their countercations.

Nitro-Substituted Dipyrrolyldiketone BF2 Complexes as Electronic-State-Adjustable Anion-Responsive π-Electronic Systems.

Nitro-substituted π-electronic molecules are fascinating because of their unique electronic and optical properties and the ease of their transformation into various functional derivatives. Herein, nitro-introduced dipyrrolyldiketone BF2 complexes as anion-responsive π-electronic molecules were synthesized, and their electronic properties and anion-binding abilities were investigated by spectroscopic analyses and theoretical studies. The obtained nitro-substituted derivatives showed solvent-dependent UV/vis spectral changes and high anion-binding affinities due to the easily pyrrole-inverted conformations and polarized pyrrole NH sites upon the introduction of electron-withdrawing moieties.

Arylpyrrolyldiketone Boron Complexes Exhibiting Various Anion-Binding Modes Based on Dynamic Conformation Changes.

Arylpyrrolyldiketone boron complexes as anion-responsive π-electronic molecules were synthesized by Claisen condensations of acetylpyrrole and corresponding aryl esters. The synthesized π-electronic molecules exhibited anion-binding behavior with various binding modes including pyrrole-inverted and non-inverted [1+1]-type anion complexes as well as [2+1]-type complexes owing to the presence of only a single pyrrole ring. Furthermore, solid-state ion-pairing assemblies, comprising receptor-anion complexes and countercations, were constructed based on fairly planar [2+1]-type complexes.

Conjunction of Pyrrole and Amide Moieties: Highly Anion-Responsive π-Electronic Molecules Forming Ion-Free and Ion-Pairing Assemblies.

Dipyrrolyldiketone BF2 complexes with amide units at pyrrole α-positions were synthesized in modest yields and showed extremely high anion-binding affinities because of multiple hydrogen-bonding interactions. The phenyl-amide-substituted derivative formed solid-state chiral helical structures, wherein π planes were oriented parallel to the helical directions. Examination of anion-binding behavior using 1 H NMR spectroscopy combined with theoretical studies suggested fast pyrrole inversions, particularly for the phenyl-amide-substituted derivative. The anion complexes behaved as building units of ion-pairing assemblies in combination with planar and bulky cations.