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

Abstract

1 H 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.Polypyridyl complexes of ruthenium(II) are of particu lar interest among other transition metal complexes be cause of their unique redox and photophysical properties, rigid three dimensional structures, and kinetic inertness. 1,2 They are employed as probes in DNA structure determina tion 3,4 and as building blocks for the design of molecular machines and devices. 5-9 Water soluble calixarenes, es pecially their sulfonate derivatives, constitute a novel class of macrocyclic compounds under intensive development, which can be regarded as a new type of outer sphere ligands for charged coordinatively saturated transition metal com plexes. 10-16 For instance, the study 16,17 of the influence of outer sphere association of p sulfonatocalix[4(8)]arenes with [Ru(bipy) 3 ] 2+ on the photophysical properties of the metal complex revealed an increased emission intensity of [Ru(bipy) 3 ] 2+ in the case of p sulfonatocalix[8]arene 16 and emission quenching in the case of p sulfonatocalix[4] arene. 17 The causes behind such different effects still re main unclear. The sulfur analog of p sulfonatocalix[4] arene (TCAS) has virtually the same inclusive ability as its classic analog 11,13,14,18,19 but is superior in the complexing ability toward metal ions. 20-22 In turn, this provides a pre requisite for the formation of heterometallic complexes in which the metal centers are bound by the calixarene plat form by means of both the inclusive ability of the upper rim and the electron donating groups of the lower rim of TCAS. In the present work, we investigated outer sphere coordination of [Ru(bipy) 3 ] 2+ with TCAS in solutions and in the solid state, determined the stability of the resulting outer sphere associate, and examined the photophysical and electrochemical properties of the [Ru(bipy) 3 ] 2+ -TCAS associate in aqueous solution.Experimental TCAS was prepared as described earlier; 23 calix[4] and calix[8]arene 4 sulfonic acids were synthesized according to a known procedure 24 and further converted into tetra (CAS4) and octasodium salts (CAS8) by neutralization with appro priate amounts of NaOH. The complex [Ru(bipy) 3 ]Cl 2 •6H 2 O was an Acros Organics chemical. The complex C 24 H 12 O 16 S 8 •2(C 30 H 24 N 6 Ru)•8H 2 O (1) was isolated from an aqueous solution of [Ru(bipy) 3 ] 2+ (1.5•10 -3 mol L -1 ) and TCAS (1.0•10 -3 mol L -1 ) at pH 4-5.1 H NMR spectra were recorded in D 2 O on a Bruker DRX 600 spectrometer (600.13 MHz). The pH value was maintained con stant with a Tris buffer (1•10 -2 mol L -1 , pH 6.8) at 293 K. 1 H chemical shifts were measu...

Redox-switchable binding of ferrocyanide with tetra(viologen)calix [4] resorcine

“…Calixarene electro-switchable host-guest systems described in literature [37][38][39][40][41][42][43] operate through the reversible redox switching of guests. Our results obtained previously [53] and in this investigation demonstrate the possibility of creating switchable systems with the redox-conversion of calixarene containing redox-active groups.…”

“…(Thia)calix[n]arenas and calix [4] resorcines, as macrocyclic polyphenols, are electrochemically active compounds with a tendency for oxidation [37][38][39][40][41][42][43]. But these oxidation reactions are reversible only under specific conditions, and in most cases they are irreversible.…”

Dual Visible and Near-Infrared Luminescent Silica Nanoparticles. Synthesis and Aggregation Stability

“…This decrease does not result from Yb(III), because p -sulfonatothiacalix[4]arene itself provides the same quenching. The quenching of [Ru(dipy) 3 ] 2+ emission by p -sulfonatocalix[4]arene and p -sulfonatothiacalix[4]arene was discussed in more detail in ref . The obtained data indicate the lack of Ru−Yb energy transfer and the quenching effect of [Ru(dipy) 3 ] 2+ on Yb(III)-centered luminescence of [YbHL] 4− in aqueous solutions resulting from their ion pairing.…”

Multiple molecular logic gate arrays in one system of (2-(2′-pyridyl)imidazole)Ru(ii) complexes and trimeric cyclophanes in water

“…85 Perching binding is known in previous cases where the macrocycle cavity is constricted, although the individual interactions are noticeably different. [86][87][88][89][90] Since we have previously shown that redox interconversions of alcohols and ketones correspond in logic terms to a Reset-Set ip-op, 85 the two different modes of inclusive binding with trialcohol 2 and perching binding with triketone 1 can be represented as outputs in this situation (Fig. 3A).…”