Recent Advances of Near-Infrared (NIR) Emissive Metal Complexes Bridged by Ligands with N- and/or O-Donor Sites

Abstract

Near-infrared (NIR) emissive metal complexes have shown potential applications in optical communication, chemosensors, bioimaging, and laser and organic light-emitting diodes (OLEDs) due to their structural tunability and luminescence stability. Among them, complexes with bridging ligands that exhibit unique emission behavior have attracted extensive interests in recent years. The target performance can be easily achieved by NIR light-emitting metal complexes with bridging ligands through molecular structure design. In this review, the luminescence mechanism and design strategies of NIR luminescent metal complexes with bridging ligands are described firstly, and then summarize the recent advance of NIR luminescent metal complexes with bridging ligands in the fields of electroluminescence and biosensing/bioimaging. Finally, the development trend of NIR luminescent metal complexes with bridging ligands are proposed, which shows an attractive prospect in the field of photophysical and photochemical materials.

Charge‐Transfer und Spin‐Flip‐Zustände als sich ergänzende Gegensätze

“…So ermöglichte beispielsweise eine Kombination aus elektronenreichen Liganden zur Destabilisierung der d‐Orbitale und einem elektronenarmen Liganden zur Bereitstellung eines niederenergetischen π*‐Akzeptororbitals NIR‐Phosphoreszenz [128] . Andere Strategien umfassen unter anderem erweiterte aromatische Systeme auf den Liganden und polynukleare Komplexe [129, 130, 132–134] . In jedem Fall leiden die für die NIR‐Emission erforderlichen niederenergetischen angeregten Zustände unter erhöhten Raten für strahlungslose Deaktivierung gemäß dem Energielückengesetz (energy gap law), was sich negativ auf Lebensdauer und Quantenausbeute auswirkt [135] .…”

714 nm emission with 12.25% efficiency from iridium complexes with low iridium content by the strategy of rigid coordination core and amplifying shell

“…In recent years, near-infrared (NIR) organic light-emitting diodes (NIR-OLEDs) with emission wavelengths from 700 to 2500 nm have shown potential applications in optical communication, bioimaging, chemosensors, night-vision, photodynamic therapy, etc. 1–4 Over the past two decades, in order to meet practical application, many NIR-emitting materials, including donor–acceptor (D–A) organic small molecules, 5,6 conjugated polymers, 7,8 transition metal complexes 9–16 and lanthanide–metal complexes, 17,18 have been developed. However, with increasing emission wavelengths, these NIR emitters usually displayed significantly descending luminescence efficiency because of the exponentially increased non-radiative deactivation pathways according to the “energy-gap law”.…”

Novel Cu(I)-5-nitropyridine-2-thiol Cluster with NIR Emission: Structural and Photophysical Characterization

“…Solid materials and coordination compounds emitting in the near-infrared (NIR) have emerged as promising and challenging materials with potential applications in optoelectronics, sensors, and telecommunications. − Cu­(I) compounds are a special class of materials for their remarkable photophysical and electronic properties. − In particular, polynuclear Cu­(I) clusters are an intriguing family of materials that are being investigated for promising applications in optoelectronics and luminescence signaling. − Among them, hexacopper­(I) clusters formulated as [Cu 6 S 6 ], constitute a rarely explored family of polynuclear complexes, with high potential in the design of NIR luminescent materials. − …”