Francesco A. Devillanova

Template self-assembly of polyiodide networks

A range of metal thioether macrocyclic complexes has been used as templating agents in the preparation of extended multi-dimensional polyiodide arrays. A selection of unusual and intriguing polyiodides is described, and the role played by the size, shape and charge of the metal macrocyclic complex discussed.

On the Use of Raman Spectroscopy in the Characterization of Iodine in Charge-Transfer Complexes

FT-Raman spectra of some polyiodides and of a series of D · I2 charge-transfer complexes (where D is a molecule containing the thione or selone groups as donors), all characterized by x-ray diffraction, are reported. For the adducts with the thione compounds, which can be considered weak or medium-weak complexes, an empirical linear correlation between the frequency of the v(I-I) stretching vibrations and the d(I-I) bond distances has been found. Some polyiodides show FT-Raman spectra that are indistinguishable with respect to those displayed by the neutral complexes of weak or medium-weak strength; in such cases, the polyiodide can be regarded as a diiodine molecule, perturbed by an I n (n = 1,3,…) donor. Polyiodides of this type show Raman absorptions falling in the linear correlation.

Tuning seleniumiodine contacts: from secondary soft–soft interactions to covalent bonds

Selenium to iodine contacts ranging from the sum of the Se and I van der Waals distances to strong covalent bonds are reviewed with the help of recent structural determinations of compounds exhibiting SeI distances from 384 to 244 pm, with emphasis on ‘less clear-cut’ cases, in terms of different extents of ‘hypervalent’ 3c–4e (10-Se-3) and (10-I-2) interactions. Within a continuum of SeI interactions from undisturbed single bonds via n->σ*(SeI) interactions and typical 3c–4e XSeI or SeIX systems to van der Waals contacts, any desired SeI distances can be tuned by an appropriate choice of the particular substituents and ligands attached to the SeI moiety.

CHARGE-TRANSFER ADDUCTS BETWEEN DONORS CONTAINING CHALCOGENS (S AND SE) AND DI-IODINE : SOLUTION STUDIES

Abstract The solution equilibria related to the 1:1 charge-transfer adduct formation between molecular iodine and several substrates containing sulfur and selenium donor atoms have been reviewed and the corresponding thermodynamic parameters ( K and Δ H °) reported for a series of thiones, selones, sulfides and selenides. A survey of the several calculation methods, based on UV–vis and in some cases 13 C-NMR spectroscopies, is also reported. Although the methods and techniques employed are very different, some correlations between the thermodynamic parameters and other experimental data, such as ν (II) Raman frequencies or UPS-binding energies, are reviewed and general conclusions drawn.

Photoinduced conductivity and nonlinear optical properties of [M(R,R′timdt)2] dithiolenes (M=Ni, Pd, Pt; R,R′timdt=monoreduced imidazolidine-2,4,5-trithione) as materials for optically driven switches and photodetectors

Abstract The unusual NIR-photoconducting properties of [M(Et,Pent-timdt)2] neutral dithiolenes (M=Ni, Pd, Pt; Et,Pent-timdt=monoreduced N-ethyl,N′-pentylimidazolidine-2,4,5-trithione) have been investigated with the aim of developing wavelength-selective air-stable photodetectors. In addition, the ps time-resolved dynamics of the absorption saturation has been studied on the Pd-complex by means of pump–probe experiments.

FT-Raman Study on Charge-Transfer Polyiodide Complexes and Comparison with Resonance Raman Results

In resonance Raman (RR) spectroscopy, the laser excitation sources have often been found to be destructive towards polyiodides if compared with the milder conditions under which the Fourier transform Raman (FT-R) technique operates. In fact, our FT-R spectra of some model polyiodides—[(CH3)4N]I5 (I5− bent), [(C2H5)4N]I7, and [(CH3)4N]I9—are significantly different from the literature RR data, give evidence of decomposition of the samples in RR, and are in agreement, respectively, with the I− · 2I2, I3− · 2I2 and (I− · 2I2) · 2I2 descriptions. In addition to the above-cited cases, the FT-R spectra of (Mn(modtc)3]Is (modtc = morpholine carbodithioato) and (moH]I5 (moH = morpholinium) are reported. The crystal structures indicate that in these two compounds the I5 anions can be properly described as I− · 2I2 and I3− · I2, respectively, and FT-R spectra agree well with this formulation. Moreover, the first FT-R spectrum of an I164– anion in [mo2ttl]2I16, ([mo2ttl]2+ = 3,5-di(N-morpholinio)-1,2,4-trithiolane), whose X-ray structure shows a sequence of two I3− … I2 … I− ·I2 (I82–) interacting anions, is reported. A close correlation of the FT-Raman peaks with the molecular species, identified by the interatomic distances, is also observed in this case. Thus, a combination of X-ray structural data and FT-R data can provide a reasonable interpretation of the nature of the acceptor iodine moiety in charge-transfer polyiodide complexes.

New perspectives in phosphonodithioate coordination chemistry. Synthesis and X-ray crystal structure of trans-bis-[O-ethyl-(4-methoxyphenyl)phosphonodithioato] nickel(II)

Abstract Attempts to optimise the synthesis of a new class of nickel(II) dithiolene complexes starting from 1,3-dialkylimidazolidine-2-thione-4,5-dione (1) and Lawessons reagent (2) have afforded a new and easy one-step synthesis of phosphonodithioate nickel(II) complexes. This consists of the direct reaction between NiCl2 and Lawessons reagent in the appropriate alcohol R′OH (R=Me, Et, i-Pr, Bu, Bz) as solvent, to give the bis-[O-alkyl/aryl-(4-methoxyphenyl)phosphonodithioato] nickel(II) complexes (5a–e) with high yields (64–91%). Among them, trans-bis-[O-ethyl-(4-methoxyphenyl)phosphonodithioato] nickel(II) (5b) was characterised by means of X-ray diffraction measurements on a single crystal. The compound crystallises in the triclinic, P 1 space group with a=6.4840(7), b=7.6032(9), c=13.055(2) A, α=99.481(9), β=99.43(1), γ=104.487(9)° and Z=1. The compound is centrosymmetric and exhibits discrete monomeric units with the ligand acting as S,S-bidentate. To explain the reactivity of Lawessons reagent, the formation of 4-methoxyphenyldithiophosphorane (6) as intermediate has been suggested. The reaction was also tested for Pd(II) and Pt(II), but in these cases the yields were not as satisfactory as for Ni(II).

Redox chemosensors: coordination chemistry towards CuII, ZnII, CdII, HgII, and PbII of 1-aza-4,10-dithia-7-oxacyclododecane ([12]aneNS2O) and its N-ferrocenylmethyl derivativeElectronic supplementary information (ESI) available: synthetic details including analytical and spectroscopic data for the isolated complexes. Ortep views of the coordination sphere around the metal centres in 1, 2 and 5. See http://www.rsc.org/suppdata/dt/b2/b210806m/

The coordination chemistry of the mixed donor 12-membered macrocyclic ligand 1-aza-4,10-dithia-7-oxacyclododecane ([12]aneNS2O) with CuII, ZnII, CdII, HgII, and PbII has been investigated both in water solution and in the solid state. The protonation constant for [12]aneNS2O and stability constants with the aforementioned metal ions have been determined potentiometrically and compared with those reported for other mixed N/S/O-donor tetradentate 12-membered macrocycles. The measured values are consistent with trends observed previously for aza macrocycles as secondary N-donors are replaced by O- and S-donors. In particular our results show that HgII in water has the highest affinity for [12]aneNS2O followed by CuII, CdII, PbII, and ZnII. For each considered metal ion, 1 ∶ 1 complexes of [12]aneNS2O have been isolated in the solid state; those of CuII, HgII, and CdII have also been characterised by X-ray crystallography. In the cases of copper(II) and cadmium(II) complexes the ligand adopts a folded [2424] conformation, whereas a more planar [3333] conformation is observed in the case of the mercury(II) complex. The macrocycle [12]aneNS2O and its structural analogue [12]aneNS3 have then been used as receptor units in the design and synthesis of the new ferrocene-containing redox-active ionophores N-ferrocenylmethyl 1-aza-4,10-dithia-7-oxacyclododecane (L1) and N-ferrocenylmethyl 1-aza-4,10,7-trithiacyclododecane (L2). Electrochemical studies carried out in MeCN in the presence of increasing amounts of CuII, ZnII, CdII, HgII, and PbII showed that the wave corresponding to the Fc/Fc+ couple of the uncomplexed ionophores L1 and L2 is gradually replaced by a new reversible wave at more positive potentials and corresponding to the Fc/Fc+ couple of the complexed ionophores. The maximum shift of the ferrocene oxidation wave was found for L1 in the presence of ZnII (230 mV) and PbII (220 mV), whereas for L2 a selective sensing response for CuII over the other guest metal cations was observed with an oxidation peak shift of 230 mV.

Synthesis, X-ray and spectroscopic characterization of obtained throught the one-step reaction of mbit·2I2 with tin metal powder (mbit = 1,1′-bis(3-methyl-4-imidazoline-2-thione)methane)

Abstract The reaction of the adduct mbit·2I2 (mbit = 1,1′-bis(3-methyl-4-imidazoline-2-thione)methane) with tin metal powder produces Sn(mbit)2I9, in mild conditions. An X-ray diffraction study on a crystal showed that the compound consists of a cation [SnI2(mbot)2]2+ having two I2 as counterions, interacting with two disordered diiodine molecules. In the cation, the metal atom lying on a symmetry centre exhibits a slightly distorted octahedral coordination with the two iodides at the apices in trans position, and with the two mbit molecules acting as bidentate chelating ligands through the sulfur atoms and forming an eight-membered ring, the tin metal atom included. The counterions I1 are slightly bent (I(2)–I(3)–I(4) 176.0(1)) and so asymmetric (I(2)–I(3) 2.841(6) I(3)−I(4) 3.016(5) A) that they can be better described as I ·I2 adducts. The presence of the two independent, centrosymmetric and disordered diiodine molecules as guests in the channel running parallel to [III] brings about I82 units of the type I2·I✓I2✓I·I2, here two triiodide ions realted by a sym centre are linked only for one third to I(5)–I(510), that is one of the two disordered guest I2 molecules (I(4)✓I(5) 3.22(I) A). Two I82 units related by a symmetry centre are held together through a non-negligible interaction (I(4)✓I(6) 3.55(1) A) involving the other disordered diiodine molecule (I(6)–I(6m)) giving rise to an octadecaioddide. Crystallographic data for C18H24N8S4I90Sn are as follows: the crystal is trigonal. M = 1783.77 space group R3, Z = 3, V = 3146(4) A ′, a = 18.100(6) A , α = 115.55(2)°, R = 0.0584 . In accordance with a description of the counterions as a sequence of the type I2·I✓I2✓I·I2. FT-Raman spectra do not show the peaks generally found in conventional triiodides, but those related to perturbed diiodine molecules.

Charge transfer complexes of benzoxazole-2(3H)-thione and benzoxazole-2(3H)-selone with diiodine: X-ray crystal structure of benzoxazole-2(3H)-thione bis(diiodine)

Abstract Solids of stoichiometry 1·I2 (C7H5I2NOS; I), 1·2I2 (C7H5I4NOS; II), 2·I2 (C7H5I2NOSe; III) and 2·2I2 (C7H5I4NOSe; IV) have been obtained by reacting respectively benzoxazole-2(3H)-thione (1) and benzoxazole-2(3H)-selone (2) with molecular diiodine in a 1:1 or 1:2 molar ratio in CH2Cl2 solution. Crystals suitable for X-ray structure determination have been obtained only for II and contain units formed by one diiodine molecule bonded almost linearly [178.44(4)°] to the thionic sulphur atom of 1 and another diiodine molecule weakly interacting with the former. The FT-Raman spectrum in the characteristics v(I-I) region shows two bands for compound II at 176 and 159 cm−1, in accordance with the presence of two differently perturbed diiodine molecules [ I (1)– I (2) = 2.769(1) A , I (3)– I (4) = 2.729(1) A ] . The FT-IR and FT-Raman spectra of compounds I, III and IV are discussed in comparison with the spectrum of II and with those reported for similar charge transfer complexes.