Ion-pairing Assemblies Research Articles

Ion-Pairing Assemblies of Anion-Responsive π-Electronic Systems That Have Noncovalently Assisted Expanded Planar Region.

Arylethynyl-substituted dipyrrolyldiketone BF2 complexes as anion-responsive π-electronic molecules exhibited characteristic electronic properties derived from conformation changes upon anion binding, which caused an increase in UV/vis absorption and associated two-photon absorption. The anion complexes showed expanded planar regions assisted by intramolecular interactions, resulting in charge-by-charge ion-pairing assemblies in the solid state.

Ion-pairing assemblies of π-extended anion-responsive organoplatinum complexes

ABSTRACT PtII complexes of π-extended dipyrrolyldiketones were synthesized as anion-responsive π-electronic molecules. The dipyrrolyldiketone PtII complexes exhibited red-shifted absorption and photoluminescence properties. In the solid state, [1 + 1]-type anion complexes formed charge-by-charge ion-pairing assemblies when combined with countercations. Detailed theoretical studies of the packing structures revealed favorable interactions between the planar anion complexes and π-electronic cations. Statement of Novelty PtII complexes of π-extended dipyrrolyldiketones, introducing arylethynyl substituents, in the form of anion complexes exhibited the formation of charge-by-charge assemblies with π-electronic cations via i π– i π interactions.

Enhanced solid-state phosphorescence of organoplatinum π-systems by ion-pairing assembly.

Anion binding and ion pairing of dipyrrolyldiketone PtII complexes as anion-responsive π-electronic molecules resulted in photophysical modulations, as observed in solid-state phosphorescence properties. Modifications to arylpyridine ligands in the PtII complexes significantly impacted the assembling behaviour and photophysical properties of anion-free and anion-binding (ion-pairing) forms. The PtII complexes, in the presence of guest anions and their countercations, formed various anion-binding modes and ion-pairing assembled structures depending on constituents and forms (solutions and crystals). The PtII complexes emitted strong phosphorescence in deoxygenated solutions but showed extremely weak phosphorescence in the solid state owing to self-association. In contrast, the solid-state ion-pairing assemblies with tetraalkylammonium cations exhibited enhanced phosphorescence owing to the formation of hydrogen-bonding 1D-chain PtII complexes dispersed by stacking with aliphatic cations. Theoretical studies revealed that the enhanced phosphorescence in the solid-state ion-pairing assembly was attributed to preventing the delocalisation of the electron wavefunction over PtII complexes.

Anion-dependent ion-pairing assemblies of triazatriangulenium cation that interferes with stacking structures.

Ion pairs of N-(2,6-dimethylphenyl)-substituted triazatriangulenium (TATA+) cation with various counteranions were synthesized to investigate the interactions for the bulky cation. Single-crystal X-ray analysis of the TATA+ ion pairs revealed solid-state ion-pairing assemblies without stacking at the cationic π-planes. The TATA+ cation showed counteranion-dependent assembly structures, with smaller counteranions located at the top of TATA+ and bulkier counteranions displaced from the TATA+ plane to interact with the surrounding TATA+.

Bidipyrrin AuIII Complex as a Helical Charged π-Electronic System.

A series of ion pairs based on a bidipyrrin-AuIII complex that acts as a stable helical π-electronic cation have been prepared via ion-pair metathesis. The helical cation, which exhibits NIR absorption and phosphorescence emission, formed solid-state ion-pairing assemblies, whose assembling modes depended on the properties of coexisting counteranions.

Borylated β-Fluorinated Pyrroles

Borylated β-fluorinated pyrroles, which are molecules with the potential to be converted into π-extended derivatives, were synthesized using IrI-catalyzed reactions and their solid-state assembled structures via hydrogen bonding between the pyrrole NH and Bpin-O were revealed. The deprotonated species detected by ESI-TOF-MS suggest the formation of anionic species, which are promising building blocks for ion-pairing assemblies. Borylated β-fluorinated pyrroles, which are molecules with the potential to be converted into π-extended derivatives, were synthesized using IrI-catalyzed reactions and their solid-state assembled structures via hydrogen bonding between the pyrrole NH and Bpin-O were revealed. The deprotonated species detected by ESI-TOF-MS suggest the formation of anionic species, which are promising building blocks for ion-pairing assemblies.

Ion-Pairing Assemblies of Dithienylnitrophenol-Based π-Electronic Anions Stabilized by Intramolecular Interactions

Dithienylnitrophenols were synthesized as precursors of π-electronic anions, which were stabilized by intramolecular chalcogen bonding, forming various ion pairs in combination with cations. The modes of solid-state charge-by-charge assemblies, along with solution-state stacking and photoinduced electron transfer behaviors, were modulated by the constituent ionic species.

Anion-Responsive Boron-Spiro-Centered π-Electronic Systems That Form Ion-Pairing Assemblies.

A variety of naphthalenediolates were orthogonally introduced to the boron unit of dipyrrolyldiketone boron complexes, exhibiting electronic properties that depended on the substituting positions of the naphthyl moieties. Combining the anion complexes with countercations resulted in the formation of ion-pairing assemblies with supporting stacking interactions of the naphthyl units.

Ion-pairing assemblies comprising porphyrin–AuIII complexes and helical π-system–anion complexes

Ion pairs of tetraphenylporphyrin–Au[Formula: see text] complex as a [Formula: see text]-electronic cation with helical [Formula: see text]-electronic receptor–anion complexes were prepared. In the crystalline-state ion-pairing assemblies, the receptor–anion complexes exhibited single-helical structures based on the [1+1]-type Cl[Formula: see text]complexes. [Formula: see text]–[Formula: see text] Interactions, mainly consisting of electrostatic and dispersion forces, effectively induced the ordered arrangement of [Formula: see text]-electronic cation and helical pseudo-[Formula: see text]-electronic anions.

Ion-pairing assemblies of self-associating pyrrole-based anion-responsive π-electronic molecules

Dipyrrolylbenzenes bearing a tethered carboxylate unit with a countercation have been synthesized as components of anion-binding self-assemblies via hydrogen bonding between the anionic moieties and pyrrole NH units. The 1D-chain self-assembled structures, as negatively charged supramolecular polymers, provide solid-state ion-pairing assemblies, whose assembly modes depend on the coexisting cations.

Ordered Arrangement of Charged Porphyrins in π-Electronic Ion-Pairing Assemblies

π-Electronic ions with appropriate geometries and peripheral substituents provide assemblies through the interactions between charged building subunits, resulting in fascinating electronic properties. Structures and properties of the assemblies can be controlled by the combined negatively and positively charged species in the assemblies. Thus far, diverse π-electronic ions along with ion-responsive π-electronic systems have afforded dimension-controlled ion-pairing assemblies as crystals, supramolecular gels, and thermotropic liquid crystals.[1] Highly ordered arrangement of charged species has been found to be a key factor to exhibit the enhanced performance as fascinating electronic materials. In fact, ion pairs of porphyrin–AuIII complexes as π-electronic cations, prepared with the combination of various anions including π-electronic anions, formed dimension-controlled assemblies as thermotropic liquid crystals, whose ionic components were highly organized by i π– i π interactions (mainly electrostatic and dispersion forces).[2] Furthermore, π-electronic ion pairs comprising porphyrin-based π-electronic anions[3] have exhibited characteristic assembling modes via i π– i π interactions and resulting electronic properties such as solid-state absorption, which was correlated with the arrangement of constituent charged π-systems, and photoinduced electron transfer.[4]References[1] Recent reviews: (a) Haketa, Y. et al. Mol. Syst. Des. Eng. 2020, 5, 757; (b) Yamasumi, K. et al. Bull. Chem. Soc. Jpn. 2021, 94, 2252. [2](a) Haketa, H. et al. iScience 2019, 14, 241; (b) Tanaka, H. et al. Chem. Asian J. 2019, 14, 2129; (c) Tanaka, H. et al. Chem. Asian J. 2020, 15, 494; (d) Fumuto, N. et al. Org. Lett. 2021, 23, 3897; (e) Kuno, A. et al. Chem. Eur. J. 2021, 27, 10068. [3](a) Sasano, Y. et al. Dalton Trans. 2017, 46, 8924. (b) Sasano, Y. et al. Chem. Eur. J. 2019, 25, 6712. [4] Sasano, Y.; Tanaka, H. et al. Chem. Sci. 2021, 12, 9645.

Ion-Pairing Assemblies of Anion-Responsive π-Electronic Systems Bearing Triazole Moieties Introduced by Click Chemistry.

In this study, the diverse derivatives of dipyrrolyldiketone boron complexes as anion-responsive π-electronic systems were synthesized via the Huisgen cycloaddition of an ethynyl-substituted anion receptor and azide derivatives. The obtained triazole-substituted anion receptors showed effective anion-binding behaviors and ion-pairing assemblies comprising receptor-anion complexes and countercations. Solid-state ion-pairing structures were modulated according to the introduced azide moieties along with coexisting bulky and π-electronic cations.

Ion-pairing assemblies of heteroporphyrin-based π-electronic cation with various counteranions.

Various counteranions of the thiaporphyrin-NiII complex as a π-electronic cation were exchanged for preparing stable ion pairs. The ion-pairing assembling modes, which included contributions of charge-by-charge and charge-segregated modes, and properties depended on the geometries and electronic states of the counteranions.

Dianion complexes of pyrrole-based anion receptors: [2+1]-Type complexes that form ion-pairing assemblies

[2+1]-Type receptor–dianion complexes were formed in the solid state by the interaction between dipyrrolyldiketone boron complexes and sulfate, forming different binding modes as sandwiched- and interlocked-types depending on the substituents of the anion receptors. The dianionic [2+1]-type complexes provided ion-pairing assemblies in combination with countercations.

Charged Porphyrins: π-Electronic Systems That Form Ion-Pairing Assembled Structures

Abstract Noncovalent interactions are important for determining the assembling modes of materials. Electronically neutral π-systems form stacking structures based on π–π interactions, which are mainly derived from dispersion forces. Introducing charges into π-systems would affect the interaction, owing to the increased contribution from electrostatic forces. This unique interaction, which we have proposed as iπ–iπ interaction, can provide ion pairs that form assembled structures. The number of possible combinations of ion pairs can be obtained as the product of the number of components being paired. As π-electronic ions, especially anions, are more reactive than electronically neutral π-systems, their stabilization is required. We have recently focused on porphyrins as platforms to stabilize π-electronic ions by charge delocalization over their large π-systems. In addition, the facile structural modifications of porphyrins enable tuning of the assembly modes and functionalization of the ion-pairing assemblies. In this account, progress of charged porphyrin derivatives and their ion-pairing assembly behaviors is summarized.

Cover Feature: Dipyrrolyldiketone PtII Complexes: Ion‐Pairing π‐Electronic Systems with Various Anion‐Binding Modes (Chem. Eur. J. 39/2021)

Synthesis of dipyrrolyldiketone PtII complexes, as phosphorescence anion-responsive π-electronic molecules, was motivated by the chemistry of previously investigated boron complexes. The PtII complexes displayed solid-state ion-pairing assemblies, exhibiting various anion-binding modes, derived from pyrrole-inverted and pyrrole-non-inverted conformations, and packing structures, with the contribution of charge-by-charge assemblies. More information can be found in the Full Paper by H. Maeda et al. (DOI: 10.1002/chem.202100855).

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.

Supramolecular Assemblies of Dipyrrolyldiketone CuII Complexes.

Dipyrrolyldiketones are essential building units of anion-responsive π-electronic molecules and ion-pairing assemblies. Here, we demonstrated that they form complexes with CuII characterized by planar geometries. The solid-state stacking assembled structures, as revealed by single-crystal X-ray analysis, were modulated by the substitution of pyrrole units. The rectangular shapes of the CuII complexes resulted in the formation of mesophases upon introduction of aliphatic chains.

Pyrrole-bridged quinones: π-electronic systems that modulate electronic structures by tautomerism and deprotonation.

A new series of π-extended quinone derivatives containing a pyrrole bridge exhibited NH/OH-type tautomerization and anion binding along with deprotonation that induced near-infrared absorption and ion-pairing assemblies.

Self-assemblies of anionic-unit-introduced anion-responsive π-electronic molecules.

The introduction of a carboxy unit onto dipyrrolyldiketone skeletons was achieved by complexation with arylfluoroboron moieties bearing an acid group. Carboxylate-appended anion-responsive π-electronic molecules, formed upon deprotonation, provided anion-binding self-assemblies, as anionic supramolecular polymers, resulting in ion-pairing assemblies.