No abstract

Materials used in current technological approaches for the removal of mercury lack selectivity. Given that this is one of the main features of supramolecular chemistry, receptors based on calix[4]arene and calix[4]resorcarene containing functional groups able to interact selectively with polluting ions while discriminating against biologically essential ones were designed. Thus two receptors, a partially functionalized calix[4]arene derivative, namely, 5,11,17,23-tetra-tert-butyl [25-27-bis(diethyl thiophosphate amino)dihydroxy] calix[4]arene (1) and a fully functionalized calix[4]resorcarene, 4,6,10,12,16,18,22,24-diethyl thiophosphate calix[4]resorcarene (2) are introduced. Mercury(II) was the identified target due to the environmental and health problems associated with its presence in water Thus following the synthesis and characterization of 1 and 2 in solution ((1)HNMR) and in the solid state (X-ray crystallography) the sequence of experimental events leading to cation complexation studies in acetonitrile and methanol ((1)H NMR, conductance, potentiometric, and calorimetric measurements) with the aim of assessing their behavior as mercury selective receptors are described. The cation selectivity pattern observed in acetonitrile follows the sequence Hg(II) > Cu(II) > Ag(I). In methanol 1 is also selective for Hg(II) relative to Ag(I) but no interaction takes place between this receptor and Cu(II) in this solvent. Based on previous results and experimental facts shown in this paper, it is concluded that the complexation observed with Cu(II) in acetonitrile occurs through the acetonitrile-receptor adduct rather than through the free ligand. Receptor 2 has an enhanced capacity for uptaking Hg(II) but forms metalate complexes with Cu(II). These studies in solution guided the inmobilization of receptor 1 into a silica support to produce a new and recyclable material for the removal of Hg(II) from water. An assessment on its capacity to extract this cation from water relative to Cu(II) and Ag (I) shows that the cation selectivity pattern of the inmobilized receptor is the same as that observed for the free receptor in methanol. These findings demonstrate that fundamental studies play a critical role in the selection of the receptor to be attached to silicates as well as in the reaction medium used for the synthesis of the new decontaminating agent.

No abstract

No abstract

contrast to traditional solution studies, this technique readily affords metal complexes in crystalline form to allow their X-ray structural characterization. Using co-deposition, we have successfully prepared the first metal complexes of corannulene [1], dibenzo [a,g]corannulene [2], and hemifullerene [3]. X-ray structural analysis revealed an 2 -rim coordination of the above fullerene fragments in their Rh(II) and Ru(I) complexes. Importantly, multiple metal coordination to a ligand was readily achieved under gas phase conditions to force rare polydentate bridging modes of fullerene fragments. This has resulted in unique complexes ranging from discreet to extended 1D, 2D, and 3D networks. The type of supramolecular architecture is dictated by the geometry and curvature of the fullerene fragment.[ We are grateful for financial support from the National Natural Science Foundation of China (No. 20431010 and 20171012 (3) reflections with I>2 (I) collected at T=100 K, and refined to R1-factors of 0.054 (1), 0.049 (2) and 0.090 (3). In all compounds, a pair of strong O-H…O(pend) bonds in the lower rim produces relatively open chalices. This, in turn, promotes the hydrophobic interaction with the solvent molecules found included in these cavities. The upper half of the EPS pendant arms is anchored by N-H…O(ox) intramolecular bonds where now the phenol oxydryl oxygen atoms act as H-bond acceptors. Despite the relative rigidity of the upper half of the hydrophilic cavity, the lower half is pre-organized towards soft metal ion complexation at the thiophosphorous sulphur binding site by unhindered torsion movements, mainly around the N-P -bond. The silver(I) complex with EPS, exhibits an approximate C 2 symmetry around the calix axis. The Ag(I) ion is sited on this axis, linearly coordinated to the sulphur atoms of the pendant arms [Ag-S distances of 2.414(2) and 2.422(2) Å, (S-Ag-S)=171.99 (8) [4]arene ligand in both complexes shows hydrophobic cavities with a quite similar squashed cone conformation. In contrast, the hydrophilic cavities exhibit substantial differences in the conformation adopted by the opposite sulfur-containing pendant arms: in LHg(ClO 4 ) 2 they are roughly related by a pseudo two-fold axis, while in LHg(ClO 4 ) 2 .2MeCN these pendant arms are approximately related through a local mirror plane. Despite these lower rim conformational differences, the Hg(II) ion in both complexes is in a similar environment, trans coordinated to the sulfur atoms of the opposite pendant arms, conforming a nearly linear S-Hg-S bond. We thank FAPESP (Brazil) and EU (Contract ICA CT 2000-30006) USP, C.P. 780, 13560-970, São Carlos-S.P., Brazil. 2 Instituto de Química de Araraquara, UNESP, C.P. 355, 14801-970, Araraquara-S.P., Brazil. E-mail: janagofe@iqsc.usp.br The X-ray structure determinations showed that the coordination polymers [Cd(µ-Cl) 2 (HPz) 2 ] n (1) and [Cd(µ-1,3-SCN) 2 (HPz) 2 ] n (2) (HPz = pyrazole) exhibited chain structures made by linear arrays of Cd(II) bridged by chlorine (1) (see Fig. 1)...