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The reaction between differently substituted borasiloxanes and 2,5-bis(3-pyridylethynyl)thiophene provided the first example of luminescent borasiloxane-based chiral helices held together by N-B bonds. The starting building blocks and the helices were fully characterized, and the nature of the N-B bond rationalized by means of theoretical calculations.

The synthesis of 5-hydroxy-2-(hydroxymethyl)pyridin-4(1H)-one (P1) is presented, together with the evaluation of its coordination ability towards Fe(3+), studied by a combination of chemical, computational, and animal approaches. The use of complementary analytical techniques has allowed us to give evidence of the tautomeric changes of P1 as a function of pH, and to determine their influence on the coordinating ability of P1 towards Fe(3+). The pFe(3+) value 22.0 of P1-iron complexes is noticeably higher than that of deferiprone (20.6), one of the three clinical chelating agents in therapeutic use for iron overload diseases. This is due on one side to the tautomeric change to the catechol form, and on the other to the lower protonation constant of the OH group. Bio-distribution studies on mice allowed us to confirm in vivo the efficacy of P1. Furthermore the coordinating ability toward Al(3+), Cu(2+) and Zn(2+) has been studied to evaluate the possible use of P1 against a second toxic metal ion (Al(3+)), and to envisage its potential influence on the homeostatic equilibria of essential metal ions. The chelating ability of P1 toward these ions, not higher than that of the corresponding deferiprone, contributes to render P1 a more selective iron chelator.

Reactions between methyldiphenylphosphane selenide, SePPh2Me, and different group 11 metal starting materials {CuCl, [CuNO 3(PPh3)2], AgOTf, [AgOTf(PPh3)] (OTf = OSO2CF3), [AuCl(tht)], [Au(C6F 5)(tht)] and [Au(C6F5)3(tht)] (tht = tetrahydrothiophene)} were performed in order to obtain several new species with metal-selenium bonds. The new complexes [CuCl(SePPh2Me)] (1), [AgOTf(SePPh2Me)] (2), [AuCl(SePPh2Me)] (5), [Au(C 6F5)(SePPh2Me)] (6) and [Au(C6F 5)3(SePPh2Me)] (7) were isolated and structurally characterized in solution by multinuclear NMR spectroscopy ( 1H, 31P, 77Se and 19F where appropriate). Solid products were isolated also from the reactions between SePPh2Me and [CuNO3(PPh3)2] or [AgOTf(PPh3)], respectively. NMR experiments, including low temperature 1H and 31P NMR, revealed for them a dynamic behaviour in solution, involving the transfer of selenium from PPh2Me to PPh3. In case of the isolated silver(i) containing solid an equilibrium between, respectively, monomeric [AgOTf(PPh3)(SePPh 2Me)] (3) and [AgOTf(PPh2Me)(SePPh3)] (4), and dimeric [Ag(PPh3)(μ-SePPh2Me)]2(OTf) 2 (3a) and [Ag(PPh2Me)(μ-SePPh3)] 2(OTf)2 (4a) species was observed in solution. In case of the isolated copper(i) containing solid the NMR studies brought no clear evidence for a similar behaviour, but it can not be excluded in a first stage of the reaction. However the transfer of selenium between the two triorganophosphanes takes place also in this case, but the NMR spectra suggest that the final reaction mixture contains the free triorganophospane selenides SePPh2Me and SePPh3 as well as the complex species [CuNO3(PPh3)2], [CuNO3(PPh 2Me)2] and [CuNO3(PPh3)(PPh 2Me)] in equilibrium. Single-crystal X-ray diffraction studies revealed monomeric structures for the gold(i) 6 and gold(iii) 7 complexes. In case of compound 6 weak aurophilic gold(I)***gold(I) contacts were also observed in the crystal. DFT calculations were performed in order to understand the solution behaviour of the silver(I) and copper(i) species containing both P(iii) and P(v) ligands, to verify the stability of possible dimeric species and to account for the aurophilic interactions found for 6. In addition, the nature of the electronic transitions involved in the absorption/emission processes observed for 6 and 7 in the solid state were also investigated by means of TD-DFT calculations. This journal is © The Royal Society of Chemistry., Financial support from the Ministry of Education and Research of Romania (CNCSIS, Research Project ID-2404/2008) and the Ministerio de Ciencia e Innovación (CTQ2010-20500-C02-01) is greatly appreciated. A. Pop thanks the European Social Fund for a Scholarship (Education and Training Program 2008-2013, POSDRU/6/1.5/S/3).

Four new fluorescent chemosensors for metal ions based on 8-hydroxyquinoline (8-HDQ) derivatives and sulfur-containing macrocyclic units were synthesized and characterized, namely 1-(5-chloro-8-hydroxy-7-quinolinylmethyl)-1-aza-4,7,10-trithiacyclododecane (L1), 1-(5-chloro-8-hydroxy-7-quinolinylmethyl)-1-aza-4,13-dithia-7,10-dioxacyclopentadecane (L2), 1-(8-hydroxy-2-quinolinylmethyl)-1-aza-4,7,10-trithiacyclododecane (L3), and 1-(8-hydroxy-2-quinolinylmethyl)-1-aza-4,13-dithia-7,10-dioxacyclopentadecane (L4). Preliminary fluorimetric titrations indicated L1 as the only member of the family of ligands to give a selective CHEF-type response to the presence of Zn(2+) in MeCN-H2O (1:1, v/v) solutions, which allowed imaging of this metal ion in Cos-7 cells in vitro. The other ligands either did not show any fluorescence response (L3, L4) to any of the metal ions considered (Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+)) or gave (L2) a CHEF-type response also to the presence of Cd(2+). The coordination properties of L1 towards Zn(2+) were, therefore, fully investigated by potentiometric measurements and absorption and emission spectroscopy at different pH values, which indicated that the formation of 2:1 L1/Zn(2+) complexes is responsible for the CHEF-type effect observed. The complexes [Zn(L1)2H2O](BF4)2 and [Zn(L3)](ClO4)2 were characterized in the solid state by X-ray crystallography, and DFT calculations were performed to understand the origin of the Zn(2+)/Cd(2+) optical discrimination of the 8-HDQ-based "conjugate" fluorescent chemosensors reported.

The I(2)-adducts of drugs propylthiouracil (PTU) and methimazole (MeImSH) oxidize liquid mercury in dichloromethane to separate in good yield the neutral complexes [HgI(2)(PTU)(2)·MeOH] (1), [HgI(2)(PTU)(2)·HgI(2)] (2), and [Hg(2)I(4)(MeImSH)(2)] (3). The single crystal X-ray diffraction analysis of 1-2 shows that the Hg(II) center is coordinated by two sulfur atoms and by two iodine atoms in a tetrahedral geometry. In complex 2 almost linear molecules of HgI(2) result encapsulated in the crystal packing enfolded by the hydrophobic propyl appendages of coordinated units of PTU. X-ray analysis of complex 3 shows the presence of dimeric [Hg(2)I(4)(MeImSH)(2)] molecules to form Hg(2)S(2)I(4) cores. The intra- and intermolecular hydrogen bonds concerning PTU and MeImSH have been evaluated. The oxidation of Hg(0) to Hg(II) requires a two-electron transfer process accomplished by an oxidative addition from the "activated" iodine moiety. The oxidizing and complexing properties of PTU-I(2) and MeImSH-I(2) have been interpreted considering the S-donor to I(2) interaction that leads to a charge separation between the sulfur-bound iodine atom S-I and the terminal I atom. Compounds 1, 2, and 3 react with tetraethylammonium iodide to separate the compound (Et(4)N)(2)[HgI(4)] with the release of free PTU and MeImSH, respectively. The reported dissolution technique could be applied to the recovery of mercury from waste electrical and electronic equipment (WEEE) scrap, the nature of complexes 1-3 makes it possible the easy separation of the mercury as tetraiodomercurate anion and the recycling of the donors.