Interfacial adsorption and stripping of ions as a reason of stimuli responsive luminescence of Tb-doped silica nanoparticles

Herein we introduce the "on-off-on" switching of Tb-centered luminescence as a result of reversible adsorption of Fe III ions at the silica/water interface of Tb-doped silica nanoparticles and the stripping effect of anions. The interfacial adsorption of Fe III ions results in the charge neutralization and aggregation of Tb-doped silica nanoparticles, accompanied by significant quenching of Tb-centered luminescence. The analysis of the steady state and time resolved quenching measurements reveals both static and dynamic quenching mechanisms. The addition of EDTA and some phosphates, including ATP results in the deaggregation of nanoparticles due to the complex formation with Fe III ions and following stripping of FeIII ions from the silica surface. The "off-on" switching of Tb-centered luminescence resulted from the stripping effect of biorelevant phosphates is a good basis for further bioanalytical application. © 2011 Elsevier B.V. All rights reserved

Solubility, acid-base and complexation properties of calix[4]resorcinarene in aqueous solutions of nonionic surfactants

Solubility and acid-base properties of calix[4]resorcinarene (H8L) in aqueous solutions of nonionic surfactants Triton X-100, Triton X-405, and Brij-35, as well as isopropanol were studied by pH-potentiometry. The dependence of the amount of a nonionic surfactant necessary to dissolve H8L on the length of ethylene oxide chain was found. The dissociation constants of macrocycle for the first four steps are low sensitive to the medium nature (micellar or water-alcohol solutions). Complexation ability of the [H8-nL]n- anions with respect to tetramethyl- and tetraethylammonium, N-methylpyridinium, and [Co(En)2(C2O4)]+ cations was studied by pH-potentiometry. A noticeable increase in the selectivity of guest-host binding was found on going from aqueous or water-alcohol to micellar solutions

The outer-sphere association of p-sulfonatothiacalix[4]arene with some Co(III) complexes: The effect on their redox activity in aqueous solutions

The effect of the ion-pairing of Co(III) complexes with p-sulfonatothiacalix[4]arene (STCA) on Fe(II)-Co(III) electron transfer rate was evaluated from the analysis and comparison of kinetic data in double Co(III)-Fe(II) and triple Co(III)-Fe(II)-STCA systems at various concentration conditions. Complexes [Co(en)3]3+(1), [Co(en) 2ox]+(2), [Co(dipy)3]3+ (3), [Co(His)2]+(4) and [Fe(CN)6]4- were chosen as Co(III) and Fe(II) compounds. The effect of STCA was found to correlate with the association mode. The outer-sphere association with STCA was found to exhibit the insignificant effect on Fe(II)-Co(III) electron transfer k et constants for complexes 3 and 4 with bulky and rigid chelate rings, while more sufficient inclusion of flexible ethylendiaminate rings of 1 and 2 into the cavity of STCA results in the unusual increase of k et. © 2007 Springer Science+Business Media, Inc

Heterometallic complex formation on p-sulfonatothiacalix[4]arene platform resulting in pH- and redox-modification of [Ru(bpy)3]2+ luminescence

The pH-dependent heterometallic complex formation with p-sulfonatothiacalix[4]arene (TCAS) as bridging ligand in aqueous solutions was revealed by the use of spectrophotometry, nuclear magnetic relaxation and fluorimetry methods. The novelty of the structural motif presented is that the appendance of emission metal center ([Ru(bpy)3]2+) is achieved through the cooperative non-covalent interactions with the upper rim of TCAS. The second metal block (Fe(III), Fe(II) and Mn(II)), bound with the lower rim of TCAS in the inner sphere coordination mode is serving as quencher of [Ru(bpy)3]2+ emission. The difference between the complex ability of Fe(III) and Fe(II) ions provides pH conditions for redox-dependent emission of [Ru(bpy)3]2+. © 2009 Elsevier B.V. All rights reserved

Photophysical and electrochemical properties of the outer-sphere associate of [Ru(bipy)3]2+ with p-sulfonatothiacalix[4]arene

1H NMR titration and X-ray diffraction analysis revealed that [Ru(bipy)3]2+ forms an outer-sphere inclusion complex with p-sulfonatothiacalix[4]arene in a ratio of 1: 1 in both aqueous solutions and the solid state. According to cyclic voltammograms and fluorimetric data, the outer-sphere association of [Ru(bipy)3]2+ with p-sulfonatothiacalix[4]arene changes the reversible character of the electrochemical oxidation of [Ru(bipy)3]2+ and lowers its emission intensity. © 2008 Springer Science+Business Media, Inc

Outer-sphere association of p-sulfonatothiacalix[4]arene and tetrasulfonatomethylated calix[4]resorcinarene with cobalt(III) tris(dipyridyl): the effect on the spectral and electrochemical properties of the latter

According to the 1H NMR and X-ray data, the outer-sphere association of [Co(dipy)3]3+ with cyclophanic anions p-sulfonatothiacalix[4]arene and tetrasulfonatomethylated calix[4]resorcinarene is accompanied by the inclusion of the dipyridyl moiety of the former into the cavities of the cyclophanic anions in aqueous and aqueous-DMSO solutions and in the solid state. The first-step dissociation of p-sulfonatothiacalix[4]arene does not change the inclusion mode, but the increase in DMSO content leads to a shallower inclusion of [Co(dipy)3]3+. The electrochemical property changes of [Co(dipy)3]3+ with both receptors undergoing ion pairing indicate the stabilization of the tris-(dipyridyl) cobalt complexes in lower oxidation states. The effect of the cyclophanic anions on the cyclic voltammograms of [Co(dipy)3]3+ correlates with the efficiency of binding of the latter with tetrasulfonatomethylated calix[4]resorcinarene and p-sulfonatothiacalix[4]arene. © 2005 American Chemical Society [email protected] A. E. Arbuzov Institute of Organic & Physical Chemistry Kazan State University

Outer-sphere interactions between octahedral chiral cobalt(III) complexes and water-soluble calixarenes

The structures and stability of outer-sphere associates of sulfonate derivatives of thiacalix[4]arene and calix[4]resorcinarene with coordinatively saturated cobalt(iii) bis- and tris-chelates ([Co(L-His)2] +, [Co(en)2ox]+, [Co(en)3] 3+, and [Co(dipy)3]3+) were compared based on the data from UV, CD, 1D 1H NMR, and 2D (2D NOESY) 1H NMR spectroscopy and conductometry. Outer-sphere association is accompanied by partial penetration of the chelate rings of the complexes into the hydrophobic cavity of calixarene, which induces changes in the spectroscopic and spectropolarimetric properties of the cobalt(iii) complexes

Dual visible and near-infrared luminescent silica nanoparticles. Synthesis and aggregation stability

Novel silica nanoparticles exhibiting near-infrared (NIR) and dual NIR-visible emission were synthesized according to reverse microemulsion procedure through the encapsulation of Yb(III) complex with p- sulfonatothiacalix[4]arene (Yb) and [Ru(dipy)3]Cl2 (Ru) as NIR- and visible-emitting luminophores into silica matrix. The synthesis was carried out at various Yb:Ru molar ratio. The numbers of Ru and Yb complexes per one nanoparticle were calculated from both fluorimetric and inductively coupled plasma atomic emission spectroscopy data. The dynamic light scattering measurements of aqueous dispersions of Yb, Ru, and Ru-Yb nanoparticles elucidate the relationship between the complexes inserted into nanoparticles and their aqueous dispersity. The transmission electron microscopy images were used to measure the size of the nanoparticles. The atomic force microscopy images reveal the different aggregation morphology of Yb- and Ru-doped nanoparticles. © 2010 American Chemical Society

Heterometallic CoIII-LnIII (Ln = Gd, Tb, Dy) complexes on a p-sulfonatothiacalix[4]arene platform exhibiting redox-switchable metal-to-metal energy transfer

Nuclear magnetic relaxation along with pH metric data have been used to reveal pH-dependent heterometallic CoIII-LnIII (Ln = Gd, Tb, and Dy) complex formation on a p-sulfonatothiacalix[4]arene (TCAS) platform in aqueous solution. The previously obtained 1D and 2D 1H NMR spectroscopic and X-ray data prove the outer sphere binding of the Co III block with the upper rim of TCAS, whereas the LnIII ion is coordinated with the phenolate groups of the lower rim of TCAS. The inclusive outer-sphere binding of CoIII tris(dipyridyl) and tris(ethylendiaminate) complexes with the upper rim of TCAS favors binding of the inner-sphere lanthanide ions through the lower rim of TCAS, whereas noninclusive binding of CoIII bis(histidinate) provides no effect on the binding of lanthanide ions. The emission properties of [Co(dipy) 3]3+-LnIII (Ln = Gd, Tb, Dy) complexes indicate the quenching of 4f luminescence by the 3d block. This quenching can be switched off by electrochemical CoIII/CoII reduction with further switching on by reoxidation. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008

Solubility, acid-base and complexation properties of calix[4]resorcinarene in aqueous solutions of nonionic surfactants

Solubility and acid-base properties of calix[4]resorcinarene (H8L) in aqueous solutions of nonionic surfactants Triton X-100, Triton X-405, and Brij-35, as well as isopropanol were studied by pH-potentiometry. The dependence of the amount of a nonionic surfactant necessary to dissolve H8L on the length of ethylene oxide chain was found. The dissociation constants of macrocycle for the first four steps are low sensitive to the medium nature (micellar or water-alcohol solutions). Complexation ability of the [H8-nL]n- anions with respect to tetramethyl- and tetraethylammonium, N-methylpyridinium, and [Co(En)2(C2O4)]+ cations was studied by pH-potentiometry. A noticeable increase in the selectivity of guest-host binding was found on going from aqueous or water-alcohol to micellar solutions