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

Abstract

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.

Heterometallic CoIII–LnIII (Ln = Gd, Tb, Dy) Complexes on a p‐Sulfonatothiacalix[4]arene Platform Exhibiting Redox‐Switchable Metal‐to‐Metal Energy Transfer

“…[13] So, the effect of the additional stabilization is apparent only for the [Co(en) 3 complexes, forming inclusion complexes with TCAS with high binding efficiency (logβ Ն 4.5). [12,13] The NMR spectroscopic data in solution, [10] X-ray data in the solid state, [11,12] and quantum chemical calculations [34] indicate that the cavity is tuning up to provide the most efficient host-guest interaction. In particular, the pinched cone conformation becomes predominant in inclusion complexes both in the solid state and in solution, whereas cone conformation dominates for sulfonated calix [4]arene and its thia analogue with empty cavities.…”

“…Our previous data demonstrate that the inclusion of Co III complexes causes insignificant changes in the absorption spectrum of TCAS. [12,13] [28] and kinetic inertness [29] 3+ provides reversible waves in the CV curves, whereas reduction of other Co III complexes is nonreversible and occurs in a much more cathodic region. [28] Thus, [Co(dipy) 3 ] 3+ is a convenient Co III block from the viewpoint of the development of redox-dependent quenching.…”

“…The inclusion of an organic cation into the cavity along with metal-ion coordination by the hydroxy groups on the lower rim were estimated in both the solid state (from Xray data [20] ) and solutions. [19] It is worth noting that d metal complexes can be also bound by the upper rim of TCAS [11][12][13] and its classic analogue, [21,22] thus forming stable outer-sphere associates with calixarenes in both inclusive and noninclusive modes. The choice of Co III complexes as d blocks is conditioned by their chromophoric properties and kinetic inertness, as well as by our previous data.…”

“…The choice of Co III complexes as d blocks is conditioned by their chromophoric properties and kinetic inertness, as well as by our previous data. [12,13] According to these data, the outer-sphere association with TCAS can be considered as a way to fix the Co III block onto the TCAS platform, whereas the f center can be bound in the inner-sphere mode by the lower rim. Thus, the main goal of the work presented is to reveal the regularities of the formation of Co III + , which are known [11,12] to form outer-sphere associates with TCAS, were chosen as the d blocks.…”

Determination of Copper at a Glassy Carbon Electrode Modified with Langmuir–Blodgett Film of p‐tert‐Butylthiacalix[4]arene

“…Accordingly, much attention has been focused on the activity of thiacalixarenes and their metal complexes. Recently, many X-ray structures of thiacalixarene complexes with various transition metals have appeared in the literature [24,25]. However, the employment of calixarenes as effective analytical reagents is still rather restricted by almost unknown chemistry of these compounds.…”