Synthesis, Crystal Structures, Magnetic Properties and Photoconductivity of C60 and C70 Complexes with Metal Dialkyldithiocarbamates M(R2dtc)x, where M = CuII, CuI, AgI, ZnII, CdII, HgII, MnII, NiII, and PtII; R = Me, Et, andnPr

Copper Dithiocarbamates: Coordination Chemistry and Applications in Materials Science, Biosciences and Beyond

Copper dithiocarbamate complexes have been known for ca. 120 years and find relevance in biology and medicine, especially as anticancer agents and applications in materials science as a single-source precursor (SSPs) to nanoscale copper sulfides. Dithiocarbamates support Cu(I), Cu(II) and Cu(III) and show a rich and diverse coordination chemistry. Homoleptic [Cu(S2CNR2)2] are most common, being known for hundreds of substituents. All contain a Cu(II) centre, being either monomeric (distorted square planar) or dimeric (distorted trigonal bipyramidal) in the solid state, the latter being held together by intermolecular C···S interactions. Their d9 electronic configuration renders them paramagnetic and thus readily detected by electron paramagnetic resonance (EPR) spectroscopy. Reaction with a range of oxidants affords d8 Cu(III) complexes, [Cu(S2CNR2)2][X], in which copper remains in a square-planar geometry, but Cu–S bonds shorten by ca. 0.1 Å. These show a wide range of different structural motifs in the solid-state, varying with changes in anion and dithiocarbamate substituents. Cu(I) complexes, [Cu(S2CNR2)2]−, are (briefly) accessible in an electrochemical cell, and the only stable example is recently reported [Cu(S2CNH2)2][NH4]·H2O. Others readily lose a dithiocarbamate and the d10 centres can either be trapped with other coordinating ligands, especially phosphines, or form clusters with tetrahedral [Cu(μ3-S2CNR2)]4 being most common. Over the past decade, a wide range of Cu(I) dithiocarbamate clusters have been prepared and structurally characterised with nuclearities of 3–28, especially exciting being those with interstitial hydride and/or acetylide co-ligands. A range of mixed-valence Cu(I)–Cu(II) and Cu(II)–Cu(III) complexes are known, many of which show novel physical properties, and one Cu(I)–Cu(II)–Cu(III) species has been reported. Copper dithiocarbamates have been widely used as SSPs to nanoscale copper sulfides, allowing control over the phase, particle size and morphology of nanomaterials, and thus giving access to materials with tuneable physical properties. The identification of copper in a range of neurological diseases and the use of disulfiram as a drug for over 50 years makes understanding of the biological formation and action of [Cu(S2CNEt2)2] especially important. Furthermore, the finding that it and related Cu(II) dithiocarbamates are active anticancer agents has pushed them to the fore in studies of metal-based biomedicines.

Self-Assembly of a Chiral Cubic Three-Connected Net from the High Symmetry Molecules C60 and SnI4

The design of new chiral materials usually requires stereoselective organic synthesis to create molecules with chiral centers. Less commonly, achiral molecules can self-assemble into chiral materials, despite the absence of intrinsic molecular chirality. Here, we demonstrate the assembly of high-symmetry molecules into a chiral van der Waals structure by synthesizing crystals of C₆₀(SnI₄)₂ from icosahedral buckminsterfullerene (C₆₀) and tetrahedral SnI₄ molecules through spontaneous self-assembly. The SnI₄ tetrahedra template the Sn atoms into a chiral cubic three-connected net of the SrSi₂ type. Our results represent the remarkable emergence of a self-assembled chiral material from two of the most highly symmetric molecules, demonstrating that almost any molecular, nanocrystalline, or engineered precursor can be considered when designing chiral assemblies.

Exploring the crystallization landscape of cadmium bis(N-hydroxyethyl, N-isopropyldithiocarbamate), Cd[S2CN(iPr)CH2CH2OH]2

Crystallization of Cd[S2CN(iPr)CH2CH2OH]2 from ethanol yields the coordination polymer [{Cd[S2CN(iPr)CH2CH2OH]2}·EtOH]∞ (1) within 3 h. When the solution is allowed to stand for another hour, the needles begin to dissolve and prisms emerge of the supramolecular isomer (SI), binuclear {Cd[S2CN(iPr)CH2CH2OH]2}2·2EtOH (2). These have been fully characterized spectroscopically and by X-ray crystallography. Polymeric 1 has 2-fold symmetry and features dithiocarbamate ligands coordinating two octahedral Cd atoms in a μ 2 κ 2-tridentate mode. Binuclear 2 is centrosymmetric with two ligands being μ 2 κ 2-tridentate as for 1 but the other two being κ 2-chelating leading to square pyramidal geometries. The conversion of the kinetic crystallization product, 1, to thermodynamic 2 is irreversible but transformations mediated by recrystallization (ethanol and acetonitrile) to related literature SI species, namely coordination polymer [{Cd[S2CN(iPr)CH2CH2OH]2}3·MeCN]∞ and binuclear {Cd[S2CN(iPr)CH2CH2 OH]2}2·2H2O·2MeCN, are demonstrated, some of which are reversible. Three other crystallization outcomes are described whereby crystal structures were obtained for the 1:2 co-crystal {Cd[S2CN(iPr)CH2CH2OH]2}2:2[3-(propan-2-yl)-1,3-oxazolidine-2-thione] (3), the salt co-crystal [iPrNH2(CH2CH2OH)]4[SO4]2{Cd[S2CN(iPr)CH2CH2OH]2}2 (4) and the salt [iPrNH2(CH2CH2OH)]{Cd[S2CN(iPr)CH2CH2OH]3} (5). These arise as a result of decomposition/oxidation of the dithiocarbamate ligands. In each of 3 and 4 the binuclear {Cd[S2CN(iPr)CH2CH2OH]2}2 SI, as in 2, is observed strongly suggesting a thermodynamic preference for this form.

A concise synthesis of substituted thiourea derivatives in aqueous medium

An efficient method for the synthesis of symmetrical and unsymmetrical substituted thiourea derivatives by means of simple condensation between available building blocks such as amines and carbon disulfide in aqueous medium is presented. This protocol works smoothly with aliphatic primary amines to afford various di- and trisubstituted thiourea derivatives. The present method is also useful in synthesizing various substituted 2-mercapto imidazole heterocycles. This method proceeds through a xanthate (amino dithiol deivative) intermediate, unlike isothiocyanate as in an earlier known method.

Ionic and Neutral C60 Complexes with Coordination Assemblies of Metal Tetraphenylporphyrins, MIITPP2·DMP (M = Mn, Zn). Coexistence of (C60-)2 Dimers Bonded by One and Two Single Bonds in the Same Compound

Coordination assemblies of metal tetraphenylporphyrins, MIITPP2.DMP (M=Mn, Zn) were shown to form ionic multicomponent and neutral complexes with fullerene, {(MnIITPP)2.DMP}.(C60-)2.(DMETEP+)2.(C6H4Cl2)5 (1) and {(ZnTPP)2.DMP}.(C60)2.(C6H5Cl)4 (2), where DMP=N,N'-dimethylpiperazine and DMETEP+=the cation of N,N'-dimethyl-N'-ethylthioethylpiperazine. The crystal structure of 1 contains zigzag chains of the (C60-)2 dimers alternating with the DMETEP+ cations in the channels formed by the (MnIITPP)2.DMP units, whereas in 2 zigzag chains of the C60 molecules are separated by the (ZnTPP)2.DMP units and C6H5Cl molecules. The (MIITPP)2.DMP assemblies (M=Mn, Zn) have axial M-N(DMP) bonds of 2.315(2) and 2.250(2) A length, average equatorial M-N(DMP) bonds elongated to 2.141(3) and 2.077(2) A, and MII atoms displaced from the porphyrin plane toward the ligand by 0.677 and 0.485 A, respectively. The single-bonded sigma-(C60-)2 dimer coexists in 1 with the (C60-)2 dimer bonded by two single bonds with 86/14 occupancy factors. The sigma-(C60-)2 dimers are unusually stable and begin to dissociate only above a temperature of 320-330 K that results in the increase of the magnetic moment of 1 from 8.33 microB (320 K) to 8.66 microB (360 K). The electron paramagnetic resonance (EPR) signal of the dimeric phase (T<320 K) with the features spread over the range of 0-0.7 T was attributed to the interacting Mn2+ centers in the (MnIITPP)2.DMP units. The dissociation of the sigma-(C60-)2 dimers to the EPR-active C60*- radical anions manifests a new broad Lorenz signal above 320 K with g=2.0179 and DeltaH=65.5 mT. This signal can appear due to the exchange coupling between paramagnetic (MnIITPP)2.DMP and C60*- species. The vis-NIR spectrum of the sigma-(C60-)2 dimers is discussed.

Exploiting the dithiocarbamate ligand in metal-directed self-assembly

The dithiocarbamate (dtc) ligand has proved to be an extremely versatile and robust motif for metal-directed self-assembly. Its ease of formation and wide ranging coordination chemistry has led to the formation of an array of novel and complex supramolecular architectures. Well-defined structures such as macrocycles, cages, catenanes and nanodimensional assemblies can be generated using a variety of oligomeric dithiocarbamate constructs in combination with transition metals. Polymetallic assemblies containing appropriately designed host cavities have allowed the binding of cationic, anionic and neutral guest species to be investigated. The use of the dithiocarbamate ligand has recently expanded to stabilising gold nanoparticles and preparing multimetallic wires and arrays. This perspective highlights the considerable potential that this simple and versatile ligand has to offer.