ABSTRACT
Herein we report the synthesis and investigation of the properties of two tris-cyclometalated luminescent iridium complexes. These complexes are the simple derivatives of fac-[Ir(ppy)3] bearing amino alkyl groups on one of the phenylpyridine rings. The complexes are highly emissive and exhibit structured emission peaks in aqueous solution while having only broad unstructured emission in organic solvents. The complexes have been shown to be taken up by NIH-3T3 and PC3 cells, where they localize in the lysosomes and remain emissive with lifetimes in the microsecond domain.
Subject(s)
Aminopyridines/chemistry , Iridium/chemistry , Luminescent Agents/chemistry , Organometallic Compounds , Animals , Cell Membrane/metabolism , Endocytosis , Humans , Luminescence , Lysosomes/chemistry , Mice , Molecular Structure , NIH 3T3 Cells , Organometallic Compounds/chemical synthesis , Organometallic Compounds/chemistryABSTRACT
Reaction of [Co(TC-n,m)]+ with (Me4N)(SC6F5), where (TC-n,m) is a tropocoronand with n and m linker chain methylene groups, yielded the thiolate complexes [Co(SC6F5)(TC-3,3)] (1a), and [Co(SC6F5)(TC-4,4)] (2a), which were structurally characterized. Use of more electron-releasing thiolates afforded the [Co(TC-n,m)] reduction product and the corresponding disulfide. The bent nitrosyl complexes [Co(NO)(TC-3,3)] (1b) and [Co(NO)(TC-4,4)] (2b) were synthesized from [Co(TC-n,m)] and NO and their structures were also determined. Compounds 1a and 1b have square-pyramidal geometry like all other structurally characterized [MX(TC-3,3)] complexes. Compounds 2a and 2b have trigonal-bipyramidal stereochemistry, formerly rare for Co(III). Although 1a, 1b, and 2a are paramagnetic, 2b is diamagnetic due to the strong antibonding pi-interaction between the metal and NO pi* orbitals. In the presence of excess NO, [Co(TC-4,4)] exhibited novel reactivity in which a putative Co(N2) adduct formed.
ABSTRACT
A family of new fluorescently labeled ligands, HRDATI, was prepared to develop transition-metal-based NO sensing strategies. The ligands are composed of aminotroponiminates (ATIs) with a dansyl fluorophore on one of the imine nitrogen atoms and an alkyl substituent, either i-Pr (8), t-Bu (9), or Bz (10), on the other. Bis(chelate) Co2+ ([Co(i-PrDATI)2] (12), [Co(t-BuDATI)2] (14), [Co(BzDATI)2] (15)) and Zn2+ ([Zn(i-PrDATI)2] (13)) complexes were prepared and characterized by X-ray crystallography. The bis(ATI) complex [Co(i-Pr2ATI)2] (11) was also prepared and its X-ray crystal structure determined. Cyclic voltammetry reveals reversible redox waves at -2.57 and -0.045 V (vs Cp2Fe/Cp2Fe+) in THF for the Co2+/Co+ and Co3+/Co2+ couples, respectively, of 11. Only a Co2+/Co+ wave at -2.09 V is observed for 12. When excited at 350 nm, the HRDATI ligands and the diamagnetic Zn2+ complex 13 fluoresce around 500 nm, whereas the paramagnetic Co2+ complexes quench the fluorescence. These air-stable cobalt compounds react with nitric oxide to dissociate a DATI ligand and form neutral dinitrosyl complexes, [Co(NO)2(RDATI)]. The release of the fluorophore-containing ligand is accompanied by an increase in fluorescence intensity, thus providing a strategy for fluorescent NO sensing. Linking two DATI moieties via a tetramethylene chain affords the ligand H2DATI-4 (18). The Co2+ complex [Co(DATI-4)] (19) reacts more readily with NO than the bis(DATI) compounds and also displays an increase in fluorescence intensity upon NO binding.
