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

Abstract

A novel Cu(I) cluster compound has been synthesized by reacting CuI with the 2,2′-dithiobis(5-nitropyridine) ligand under solvothermal conditions. During the reaction, the original ligand breaks into the 5-nitropyridine-2-thiolate moiety, which acts as the coordinating ligand with both N- and S-sites, leading to a distorted octahedral Cu 6 S 6 cluster. The structure has been determined by single-crystal X-ray diffraction and FT-IR analysis, and the photophysical properties have been determined in the solid state by means of steady-state and time-resolved optical techniques. The cluster presents a near-infrared emission showing an unusual temperature dependence: when passing from 77 to 298 K, a blue-shift of the emission band is observed, associated with a decrease in its intensity. Time-dependent-density functional theory calculations suggest that the observed behavior can be ascribed to a complex interplay of excited states, basically in the triplet manifold.

Eight-Electron Superatomic Cu31 Nanocluster with Chiral Kernel and NIR-II Emission

“…One of the most studied and fascinating properties of metal nanoclusters is their photoluminescence, which can be applied in sensing, biological imaging, and optical devices. , Cu­(I) complexes are well known as good luminescent materials. ,− The emission peaks of the Cu­(I) complexes always lie in the visible range because of their d 10 electronic structures and favorable low-energy ligand-to-metal charge transfer or cluster-centered transition. The extension of the emission wavelength from the first near-infrared (750–950 nm, NIR-I) to the second near-infrared (1000–1700 nm, NIR-II) window is beneficial to deeper tissue imaging and reduced photon scattering when applied in bioimaging and thus is highly desirable but hard to be accessible. − Several copper clusters were reported to have emissions in the near-infrared (NIR) region. − [Cu 15 ( t BuCC) 14 NO 3 ] featured a board NIR emission band centered at 871 nm, which is, to the best of our knowledge, the longest emission wavelength of all atomically precise copper clusters . While gold, silver, and alloy nanoclusters have been demonstrated to possess NIR-II emissions, − as cheaper congeners, there are no NIR-II emissive copper nanoclusters being reported yet …”

Molecularly Engineered Room-Temperature Phosphorescence for Biomedical Application: From the Visible toward Second Near-Infrared Window

“…237 A distorted octahedral Cu 6 kernel stabilized by rigid and multiple coordination structures was found that had strong red room-temperature phosphorescence with a maximum at about 765 nm. 298 The emission spectrum sharpened and further red-shifted at 77 K, exhibiting a band at 815 nm. To achieve large electronic delocalization, 299 a heterometallic Au 11 @Cu 1 cluster was prepared that showed up-converted anti-Stokes fluorescence and phosphorescence.…”

“…The ultimate kernel size is likely located within single-atom scale, which would permit simpler yet more efficient alterations of electronic radiative and nonradiative processes . A distorted octahedral Cu 6 kernel stabilized by rigid and multiple coordination structures was found that had strong red room-temperature phosphorescence with a maximum at about 765 nm . The emission spectrum sharpened and further red-shifted at 77 K, exhibiting a band at 815 nm.…”

Solvent-Mediated Hetero/Homo-Phase Crystallization of Copper Nanoclusters and Superatomic Kernel-Related NIR Phosphorescence

“…The metal nanoclusters that emit in the near-infrared (NIR > 750 nm) region are attracting increasing attention for their potential applications in optoelectronics, sensors, and telecommunications. − Their atomically precise geometric structures and well-defined compositions offer ideal platforms for understanding the relationship between structure and photoluminescence (PL). Considerable advancements in the PL mechanism and applications of NIR-emissive gold and silver nanoclusters have been made in the past decades. − Nevertheless, as their lighter congeners, the synthesis of copper nanoclusters (Cu NCs) encounters formidable challenges, primarily attributed to their inherent poor stability, not to mention the investigations on their NIR PL. − So far, only very few Cu NCs have been discovered to emit in the NIR region under ambient conditions.…”