Simple Polyphenyl Zirconium and Hafnium Metallocene Room-Temperature Lumophores for Cell Imaging

Abstract

Zirconium and hafnium metallocene dihalides based on simple polyphenyl cyclopentadienes are stable room-temperature lumophores with large Stokes shifts, emitting from states with substantial LMCT character. Their synthesis is described, including by a rapid solvent-free approach compatible with the lifetime of PET-active isotopes (89Zr). Preliminary experiments indicate the viability of these species as lumophores for fluorescence cell-imaging microscopy.

Progress with, and prospects for, metal complexes in cell imaging

“…14 Very recently a simplified example of a rigidified system based on polyphenyl cyclopentadienes was reported which retains room temperature emission due to the retarded vibrations in these sterically hindered cases. 15 The steric hindrance also leads to a reduction in the moisture sensitivity of the complexes, which has allowed application in cell imaging, (Fig. 3) although this work is at too early a stage to allow any general rules regarding patterns of uptake, localisation of toxicity to be deduced.…”

Photoluminescence of Seven‐Coordinate Zirconium and Hafnium Complexes with 2,2′‐Pyridylpyrrolide Ligands

“…[17] Much attention in this area has been devoted to 1str ow late transition metals [18][19][20][21][22][23][24][25][26][27] and low-valent groups 6a nd 7m etals [28][29][30][31][32][33] that retain the fundamental design principle of photoinduced charge separation via MLCT. [34] In pronouncedc ontrast, luminescent metalc omplexes relying on alternative mechanisms such as ligand-tometal charget ransfer (LMCT), [35][36][37][38][39][40][41][42][43] ligand-to-ligand charge transfer (LLCT), [44,45] or metal-centered excitations( i.e. d-d, f-f, or d-f) [46][47][48][49][50][51][52] are not as well-studied, but offer the potentialt o expand the palette of metals suitable for photosensitizer development.…”

Functional imaging of a model unicell: Spironucleus vortens as an anaerobic but aerotolerant flagellated protist

“…Complexes of the most lipophilic ligands could potentially be adapted for use as radio-imaging agents(e.g., as 99m Tc(I) analogues while still being useful using confocal microscopy in cellular imaging studies. Zirconium and hafnium metallocene dihalides based on simple polyphenyl cyclopentadienes with a large Stokes shifts and good room temperature stability with emission from triplet states are also promising cell imaging compounds (Pritchard et al, 2013). Incubation with MCF-7 human adenocarcinoma gave images showing incorporation into peripheral extra-nuclear organelles and satisfactory maintenance of cellular integrity indicated low toxicity Application of phosphorescence imaging to S. vortens has proved useful in the selection of complexes of freely permeable derivatives with toxicity characteristics with emission well separated from routinely employed fluorescent probes, thereby enabling colocalisation studies.…”