Dynamic Behavior, Electrochromism, and Two-Photon Absorption of Dicyanomethylenated Quinacridone

Synthesis, structures and properties of two donor-acceptor acridone-based compounds

Two donor-acceptor acridone-based compounds, namely, 2-{10-[4-(diphenylamino)phenyl]acridin-9-ylidene}malononitrile (TPA-AD-DCN), C34H22N4, and 2-{10-[4-(9H-carbazol-9-yl)phenyl]acridin-9-ylidene}malononitrile (CzPh-AD-DCN), C34H20N4, have been synthesized in high yield and their structures determined. TPA-AD-DCN and CzPh-AD-DCN crystallized in the centrosymmetric space groups P-1 and P21/c, respectively. Both molecules adopt a `butterfly-like' configuration of the common part of the structure and differences occur within the substituents on the acridine N atom. A Hirshfeld surface analysis showed that the H...H and C...H/H...C contacts constitute a high percentage of the intermolecular interactions. The optical and electrochemical properties, as well as theoretical calculations, of TPA-AD-DCN and CzPh-AD-DCN support the structural characterization of these materials. As crystallization-induced emission materials, TPA-AD-DCN and CzPh-AD-DCN are anticipated to be of potential use in the construction of promising optoelectronic materials.

Dynamics of proton, ion, molecule, and crystal lattice in functional molecular assemblies

Dynamic molecular processes, such as short- or long-range proton (H⁺) and ion (M⁺) motions, and molecular rotations in electrical conducting and magnetic molecular assemblies enable the fabrication of electron-H⁺ (or M⁺) coupling systems, while crystal lattice dynamics and molecular conformation changes in hydrogen-bonded molecular crystals have been utilised in external stimuli responsive reversible gas-induced gate opening and molecular adsorption/desorption behavior. These dynamics of the polar structural units are responsible for the dielectric measurements. The H⁺ dynamics are formed from ferroelectrics and H⁺ conductors, while the dynamic M⁺ motions of Li⁺ and Na⁺ involve ionic conductors and coupling to the conduction electrons. In n-type organic semiconductors, the crystal lattices are modulated by replacing M⁺ cations, with cations such as Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺. The use of polar rotator or inversion structures such as alkyl amides, m-fluoroanilinium cations, and bowl-shaped trithiasumanene π-cores enables the formation of ferroelectric molecular assemblies. The host-guest molecular systems of ESIPT fluorescent chromic molecules showed interesting molecular sensing properties using various bases, where the dynamic transformation of the crystal lattice and the molecular conformational change were coupled to each other.

Color-tunable arylaminoanthraquinone dyes through hydrogen-bond-assisted charge transfer interaction

We prepared a series of arylaminoanthraquinone derivatives, including those with electron-accepting sulfone units and/or with electron-donating dialkylamino units. A color-tunable anthraquinone library that reached into the NIR region could be prepared through the precise control of frontier orbitals. Fine color-tuning was achieved through proper selection and positioning of the substituents. Effective intramolecular hydrogen-bond-assisted charge transfer interaction between electron-donating aniline/p-phenylenediamine and electron-accepting anthraquinone substructures induced a significant bathochromic shift of anthraquinone. The number and position of the substituents and the molecular conformation also significantly contributed to determining photophysical properties.

A color-tunable anthraquinone library based on arylaminoanthraquinone was prepared through hydrogen-bond-assisted charge transfer interaction.

Some Products from C=O Condensations of Quinacridones

Quinacridone chemistry has been developed which provides a source of new compounds that have potential application in organic photovoltaic (OPV) devices. Phosphoryl chloride is used for the conversion of carbonyl groups in N,N′-dialkylquinacridones, generating reactive intermediates that enable selective condensation with either one or two nucleophilic molecules under mild conditions.

Hydrogen-Bonded Organic Frameworks as a Tunable Platform for Functional Materials

As a novel class of porous crystalline materials, hydrogen-bonded organic frameworks (HOFs), self-assembled from organic or metal-organic building blocks through intermolecular hydrogen-bonding interactions, have attracted more and more attention. Over the past decade, a number of porous HOFs have been constructed through judicious selection of H-bonding motifs, which are further enforced by other weak intermolecular interactions such as π-π stacking and van der Waals forces and framework interpenetration. Since the H-bonds are weaker than coordinate and covalent bonds used for the construction of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), HOFs have some unique features such as mild synthesis condition, solution processability, easy healing, and regeneration. These features enable HOFs to be a tunable platform for the construction of functional materials. Here, we review the H-bonding motifs used for constructing porous HOFs and highlight some of their applications, including gas separation and storage, chiral separation and structure determination, fluorescent sensing, heterogeneous catalysis, biological applications, proton conduction, photoluminescent materials, and membrane-based applications.

Endohedral dynamics of push-pull rotor-functionalized cages

A series of [Pd2L4] coordination cages featuring endohedral functionalities in central backbone positions was synthesized. Although attached via C[double bond, length as m-dash]C double bonds, the substituents behave as molecular rotors. This is explained by their pronounced donor-acceptor character which lowers rotational barriers and allows for electronic control over the spinning rates inside the cage. The dynamic behaviour of the free ligands, assembled cages and host-guest complexes is compared with the aid of NMR experiments, X-ray structure analysis and molecular modelling.

Organic Electron Acceptors Comprising a Dicyanomethylene-Bridged Acridophosphine Scaffold: The Impact of the Heteroatom

Stable two-electron acceptors comprising a dicyanomethylene-bridged acridophosphine scaffold were synthesized and their reversible reduction potentials were efficiently tuned through derivatization of the phosphorus center. X-ray crystallographic analysis combined with NMR, UV/Vis, IR spectroscopic, and electrochemical studies, supported by theoretical calculations, revealed the crucial role of the phosphorus atom for the unique redox, structural, and photophysical properties of these compounds. The results identify the potential of these electron deficient scaffolds for the development of functional n-type materials and redox active chromophores upon further functionalization.

New quinacridone derivatives with π-extended conjugation in central core

A novel synthetic strategy for the preparation of quinacridone derivatives with extended conjugation in central aromatic core is proposed allowing for fine tuning of their electronic properties.

Internal dynamics and guest binding of a sterically overcrowded host

Substituent control in self-assembled host systems allows for a fine-tuning of structure, dynamics and guest preference. Flat banana-shaped ligands L1 assemble with Pd(ii) cations into the interpenetrated coordination cage dimer [3BF4@Pd4L18], capable of sequential guest uptake. In contrast, the introduction of bulky adamantyl groups in ligand L2 prevents dimerization and results in the clean formation of monomeric cage species [Pd2L24]. Owing to steric crowding, the adamantyl substituent is considerably bent sideways with respect to the ligand backbone, and is rapidly flipping between both faces of the free ligand giving rise to two energetically degenerate conformers. Surprisingly, the flipping is preserved in the cage, albeit at a lower rate due to entropic reasons. Despite the very dense packing within the self-assembled structure, the cage is able to encapsulate a series of bis-anionic guests in an induced-fit fashion. Electronic structure calculations revealed a substantial contribution from dispersion interactions between the guest and the surrounding adamantyl groups that stabilize the host-guest complex. Guest exchange kinetics were quantified and the influence that encapsulated guests imparted on the ligand flipping dynamics was examined by a series of 2D NMR experiments. Four synchrotron X-ray structures of the cage and its host-guest complexes are presented, allowing for unprecedented insight into the host-guest interactions of a sterically overcrowded host and its guest-induced distortion.

Large π-Conjugated Quinacridone Derivatives: Syntheses, Characterizations, Emission, and Charge Transport Properties

Two 11-ring-fused quinacridone derivatives, TTQA and DCNTTQA, have been synthesized by ferric chloride mediated cyclization and Knoevenagel reaction. Replacement of the carbonyl groups (in TTQA) with dicyanoethylene groups (in DCNTTQA) not only red-shifted the emission to the near-infrared region but also led to a nonplanar skeleton that significantly improved the solubility of DCNTTQA. Moreover, dicyanoethylene groups rendered DCNTTQA low-lying HOMO and LUMO levels. DCNTTQA-based solution-processed field-effect transistors showed a hole mobility up to 0.217 cm(2) V(-1) s(-1).

Structure–property relationship of donor–acceptor acridones – an optical, electrochemical and computational study

The effect of changing acceptor strength on intramolecular charge transfer absorption and its implication towards organic materials are investigated.