Long-Lived Near-Infrared Luminescent Lanthanide Complexes of Imidodiphosphinate “Shell” Ligands

Abstract

Near-infrared emitting complexes of Nd(III), Er(III), and Yb(III) based on hexacoordinate lanthanide ions with an aryl functionalized imidodiphosphinate ligand, tpip, have been synthesized and fully characterized. Three tpip ligands form a shell around the lanthanide with the ligand coordinating via the two oxygens leading to neutral complexes, Ln(tpip)3. In the X-ray crystal structures of Er(III) and Nd(III) complexes there is evidence of CH-pi interactions between the phenyl groups. Photophysical investigations of solution samples of the complexes demonstrate that all complexes exhibit relatively long luminescence lifetimes in nondeuteurated solvents. Luminescence studies of powder samples have also been recorded for examination of the properties of NIR complexes in the solid state for potential material applications. The results underline the effective shielding of the lanthanide by the twelve phenyl groups of the tpip ligands and the reduction of high-energy vibrations in close proximity to the lanthanide, both features important in the design of NIR emitting lanthanide complexes.

Rare‐Earth Nitroquinolinates: Visible‐Light‐Sensitizable Near‐Infrared Emitters in Aqueous Solution

“…It seems that the four ligands form a very efficient shell around the lanthanide ion. [25,26] These values compare well with those found by Imbert et al [5] and Comby et al, [6] who reported luminescence decay times for neodymium(III) complexes of a hydroxyquinoline-containing podand in water of between 0.13 and 0.25 µs. In these reports, however, the efficiencies of the ytterbium(III) complexes are much better than those of the neodymium(III) complexes, which is in line with what one would expect.…”

Near-Infrared Luminescent Labels and Probes Based on Lanthanide Ions and Their Potential for Applications in Bioanalytical Detection and Imaging

“…The experimentally determined luminescence quantum yield of this complex reaches a record value of 3%, which is obviously low compared to lanthanide ions in glasses and crystals or organic dyes in solution whose quantum yields can often exceed 50%. A recent, supplementary strategy for maintaining NIR luminescence is the encapsulation of the ions in aromatic shells, which rigourously prevents quenching solvent molecules from approaching the lanthanide ion [28,29]. [23,24] contains a carbostyril sensitiser, excited at 320 nm.…”

“…Moreover, the ligand shell around the luminescent ion is made tight, hydrophobic and bulky (Fig. 7), in order to keep any diffusion quenchers (such as water molecules) at a distance [28,29]. An open challenge is to combine this ion-protecting architecture with the integration of an efficient and visible-light absorbing sensitiser at close proximity of the ion.…”

“…Fig. 7 Imidodiphosphinate "shell"-type ligands [28,29] providing a very tight shielding of the lanthanide ion against quenching molecules. When used with NIR luminescent lanthanide ions, the perfluorinated imidophosphinate ligand yields very long luminescence lifetimes and -presumablyhigh photoluminescence quantum yields…”

Structure and optical spectroscopy of Yb(III) complex with o-phenylenedioxydiacetic acid

“…Spectroscopic properties of Nd(III), Er(III) and Yb(III) complexes with near infrared range emission [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and a number of qualities have been increasingly studied in recent times because of their diagnostic or tagging applications. The range of research into NIRsensitised luminescence makes it impossible to quote even major papers; this is why the author would like to refer to recent review publications [26].…”