ABSTRACT
A family of five neutral cyclometalated iridium(III) tetrazolato complexes and their methylated cationic analogues have been synthesised and characterised. The complexes are distinguished by variations of the substituents or degree of π conjugation on either the phenylpyridine or tetrazolato ligands. The photophysical properties of these species have been evaluated in organic and aqueous media, revealing predominantly a solvatochromic emission originating from mixed metal-to-ligand and ligand-to-ligand charge transfer excited states of triplet multiplicity. These emissions are characterised by typically long excited-state lifetimes (â¼hundreds of ns), and quantum yields around 5-10 % in aqueous media. Methylation of the complexes caused a systematic red-shift of the emission profiles. The behaviour and the effects of the different complexes were then examined in cells. The neutral species localised mostly in the endoplasmic reticulum and lipid droplets, whereas the majority of the cationic complexes localised in the mitochondria. The amount of complexes found within cells does not depend on lipophilicity, which potentially suggests diverse uptake mechanisms. Methylated analogues were found to be more cytotoxic compared to the neutral species, a behaviour that might to be linked to a combination of uptake and intracellular localisation.
Subject(s)
Coordination Complexes/chemistry , Iridium/chemistry , Tetrazoles/chemistry , Animals , Cations/chemistry , Cell Line , Cell Survival/drug effects , Coordination Complexes/metabolism , Coordination Complexes/toxicity , Crystallography, X-Ray , Endoplasmic Reticulum/chemistry , Endoplasmic Reticulum/metabolism , Fluorescent Dyes/chemical synthesis , Fluorescent Dyes/chemistry , Fluorescent Dyes/metabolism , Ligands , Light , Microscopy, Fluorescence , Molecular Conformation , Photolysis/radiation effects , Pyridines/chemistry , RatsABSTRACT
The first examples of anionic Ir(iii) bis-tetrazolate complexes and their combination with a cationic Ir(iii)tetrazole derivative forming "fully tetrazolate" Ir(iii) based soft salts as O2-sensitive white emitters are described herein.
ABSTRACT
In order to exploit their potential as versatile luminescent sensors, four new Re(I)-tetrazolato complexes with the general formula fac-[Re(CO)3(diim)(L)], where diim is 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen) and L(-) is either the anion 5-(2'-pyridyl)tetrazolato (2-PTZ(-)) or 5-(2'-quinolyl)tetrazolato (2-QTZ(-)), were prepared and fully characterized. In all cases, the regioselective coordination of the Re(I) center through the N2 atom of the tetrazolato ring was observed. This particular feature ensures the availability of the diiminic (N^N) site that was systematically incorporated into the structure of the 2-PTZ(-) and 2-QTZ(-) ligands for further coordination with metal cations. Such a diimine-type coordination mode was preliminarily tested by using the mononuclear Re(I) complexes as N^N ligands for the preparation of two [(N^N)Cu(POP)] cationic species, where POP is the chelating diphosphine bis[2-(diphenylphosphino)phenyl]ether. The X-ray structures of the resulting Re(I)-Cu(I) dyads revealed that the Re(I) mononuclear complexes effectively behaved as chelating N^N ligands with respect to the [Cu(POP)](+) fragment, the coordination of which also resulted in significant modification of the Re(I)-centered luminescence. With these data in hand, the luminescent sensing abilities of the four new Re(I) tetrazolato complexes were screened with respect to divalent metal ions of toxicological and biological importance such as Zn(II), Cd(II) and Cu(II). The interaction of the Re(I) complexes with Zn(II) and Cd(II) was witnessed by the evident blue shift (Δλmax = 22-36 nm) of the emission maxima, which was also accompanied by a significant elongation of the emission lifetimes. On the contrary, the addition of the cupric ion caused substantial quenching of the radiative processes originating from the Re(I) luminophores.
ABSTRACT
The coordination of 2-pyridyltetrazolate and ortho-xylene-linked bis(NHC)cyclophane to Pt(II) yielded a novel complex characterised by enhanced pure deep-blue emission, whose intensity can be modulated via methylation of the tetrazole ring.
