Synthesis, Electrochemistry, and Photophysical Studies of Ruthenium(II) Polypyridine Complexes with D–π–A–π–D Type Ligands and Their Application Studies as Organic Memories

Abstract

A new class of ruthenium(II) polypyridine complexes with a series of D-π-A-π-D type (D=donor, A=acceptor) ligands was synthesized and characterized by H NMR spectroscopy, mass spectrometry, and elemental analysis. The photophysical and electrochemical properties of the complexes were also investigated. The newly synthesized ruthenium(II) polypyridine complexes were found to exhibit two intense absorption bands at both high-energy (λ=333-369 nm) and low-energy (λ=520-535 nm) regions. They are assigned as intraligand (IL) π→π* transitions of the bipyridine (bpy) and π-conjugated bpy ligands, and IL charge-transfer (CT) transitions from the donor to the acceptor moiety with mixing of dπ(Ru )→π*(bpy) and dπ(Ru )→π*(L) MLCT characters, respectively. In addition, all complexes were demonstrated to exhibit intense red emissions at approximately λ=727-744 nm in degassed dichloromethane at 298 K or in n-butyronitrile glass at 77 K. Nanosecond transient absorption (TA) spectroscopy has also been carried out, establishing the presence of the charge-separated state. In order to understand the electrochemical properties of the complexes, cyclic voltammetry has also been performed. Two quasi-reversible oxidation couples and three quasi-reversible reduction couples were observed. One of the ruthenium(II) complexes has been utilized in the fabrication of memory devices, in which an ON/OFF current ratio of over 10 was obtained.

Design and Synthesis of Solution-Processable Donor–Acceptor Dithienophosphole Oxide Derivatives for Multilevel Organic Resistive Memories

“…With the structural diversity offered by the D−π–A structure, these materials have been continuously explored as the active materials for organic electronics, including organic photovoltaics, , organic light-emitting diodes, − and organic field-effect transistors . In light of their success in organic optoelectronics, interests in the functionalization of the D−π–A-based materials for resistive memory devices have also attracted growing attention for the past decade. − Possessing a simple two-electrode device structure, organic resistive memories are believed to have outstanding downscaling potential . Together with the solution processability of organic active materials, the manufacturing cost of organic resistive memory devices can be potentially lowered by the simple fabrication processes including spin-coating and inkjet printing, allowing the design and fabrication of memory devices readily achievable for flexible electronics, such as e-textiles and future electronics .…”

1,10‐Phenanthroline Ruthenium(II) Complexes as Model Systems in the Search for High‐Performing Triplet Photosensitisers: Addressing Ligand versus Metal Effects

“…This increase in absorptivity in the visible region has been noted before for TPA‐containing complexes as has the shift of the absorbance band to longer wavelengths ( λ abs =454 nm ( Ru‐3 ) compared to λ abs =481 nm ( Ru‐2 )). This red‐shift can result in the 1 ILCT (singlet intraligand charge transfer) overlapping with the 1 MLCT (singlet metal to ligand charge transfer) of Ru II polyimine complexes and give rise to the enhanced absorbance in the visible region of the spectrum …”

Hexaarylbenzene based high-performance p-channel molecules for electronic applications

“…Organic memory devices (OMDs) came as an ultimate key solution. Though many organic molecules have been used for OMDs, the report by Ming, 21 explains the application of ruthenium( ii ) complexes which employed in donor–π–acceptor–π–donor (DπAπD) type molecular system. Herein, bipyridine appended triarylamine ligand connected to polyphenylene moiety, where polyphenylene moiety is equipped as an electron donor and central Ru-biphenyl segment served as acceptor.…”

“…15 Unique properties of HAB have stimulated researchers from many areas such as supramolecular chemistry, bio-medical, environmental sensing, material chemistry, synthetic and organometallic chemistry. 8,[16][17][18][19][20][21] Since the pioneering work of Dilthey in 1933 on the synthesis of hexaphenylbenzene (HPB) through Diels-Alder cycloaddition reaction, polyaromatic psystems have been the subject of tremendous exploration. 22 Among the reported multiply substituted aromatic compounds, HPBs are highly signicant due to their structural diversity and optical properties.…”