Dithiocarbamate Complexes of Platinum Group Metals: Structural Aspects and Applications

Insight into stability of dithiocarbamate-modified adsorbents: Oxidation of dithiocarbamate

We previously reported that monoalkyl dithiocarbamate-modified cellulose (DMC) exhibited excellent adsorption performance for arsenite (AsIII), cadmium (CdII), lead (PbII), gold (AuIII), silver (AgI), platinum (PtIV), and palladium (PdII). However, its adsorption capability for AsIII decreased by 96.4% after two weeks of storage at 40 °C under an air atmosphere. This decrease in adsorption ability could occur for other metals that dithiocarbamates can extract. In this study, we investigated the adsorption performance of DMC for various metals before and after storage and proposed a possible mechanism for this decrease. We found significant decreases in the adsorption abilities of PbII (11.4%), AgI (39.5%), PtIV (65.5%), and PdII (69.6%), whereas AuIII and CdII adsorption was largely retained, with decreases of 1.1% and 4.0%, respectively. FTIR analysis of the stored DMC revealed the formation of S-S bonds and the retention of dithiocarbamate peaks, indicating the formation of dithiocarbamate dimers (thiuram disulfides). To further support thiuram disulfide formation, dialkyl thiuram disulfides were tested for the adsorption of the seven employed metals. The metal adsorption behavior of dialkyl thiuram disulfides was almost identical to that of the stored adsorbent, ensuring thiuram disulfide formation. In conclusion, the loss of adsorption capability can be mainly attributable to the formation of thiuram disulfide.

Synthesis and Crystal Structures of Bis(diallydithiocarbamato)zinc(II) and Silver(I) Complexes: Precursors for Zinc Sulfide and Silver Sulfide Nanophotocatalysts

We report the preparation and crystal structures of bis(diallydithiocarbamato)zinc(II) and silver(I) complexes. The compounds were used as single-source precursors to prepare zinc sulfide and silver sulfide nanophotocatalysts. The molecular structure of bis(diallydithiocarbamato)zinc(II) consists of a dimeric complex in which each zinc(II) ion asymmetrically coordinates with two diallydithiocarbamato anions in a bidentate chelating mode, and the centrosymmetrically related molecule is bridged through the S-atom that is chelated to the adjacent zinc(II) ion to form a distorted trigonal bipyramidal geometry around the zinc(II) ions. The molecular structure of bis(diallydithiocarbamato)silver(I) formed a cluster complex consisting of a trimetric Ag₃S₃ molecule in which the diallydithiocarbamato ligand is coordinated to all the Ag(I) ions. The complexes were thermolyzed in dodecylamine, hexadecylamine, and octadecylamine (ODA) to prepare zinc sulfide and silver sulfide nanoparticles. The powder X-ray diffraction patterns of the zinc sulfide nanoparticles correspond to the hexagonal wurtzite while silver sulfide is in the acanthite crystalline phase. The high-resolution transmission electron microscopy images show that quantum dot zinc sulfide nanoparticles are obtained with particle sizes ranging between 1.98 and 5.49 nm, whereas slightly bigger silver sulfide nanoparticles are obtained with particle sizes of 2.70-13.69 nm. The surface morphologies of the ZnS and AgS nanoparticles capped with the same capping agent are very similar. Optical studies revealed that the absorption band edges of the as-prepared zinc sulfide and silver sulfide nanoparticles were blue-shifted with respect to their bulk materials with some surface defects. The zinc sulfide and silver sulfide nanoparticles were used as nanophotocatalysts for the degradation of bromothymol blue (BTB) and bromophenol blue (BPB). ODA-capped zinc sulfide is the most efficient photocatalyst and degraded 87% of BTB and 91% of BPB.

Addressing the gaps in homeostatic mechanisms of copper and copper dithiocarbamate complexes in cancer therapy: a shift from classical platinum-drug mechanisms

The platinum drug, cisplatin, is considered as among the most successful medications in cancer treatment. However, due to its inherent toxicity and resistance limitations, research into other metal-based non-platinum anticancer medications with diverse mechanisms of action remains an active field. In this regard, copper complexes feature among non-platinum compounds which have shown promising potential as effective anticancer drugs. Moreover, the interesting discovery that cancer cells can alter their copper homeostatic processes to develop resistance to platinum-based treatments leads to suggestions that some copper compounds can indeed re-sensitize cancer cells to these drugs. In this work, we review copper and copper complexes bearing dithiocarbamate ligands which have shown promising results as anticancer agents. Dithiocarbamate ligands act as effective ionophores to convey the complexes of interest into cells thereby influencing the metal homeostatic balance and inducing apoptosis through various mechanisms. We focus on copper homeostasis in mammalian cells and on our current understanding of copper dysregulation in cancer and recent therapeutic breakthroughs using copper coordination complexes as anticancer drugs. We also discuss the molecular foundation of the mechanisms underlying their anticancer action. The opportunities that exist in research for these compounds and their potential as anticancer agents, especially when coupled with ligands such as dithiocarbamates, are also reviewed.

Trends in dithiocarbamates food research: A bibliometric vision

Dithiocarbamate Fungicides (DTFs) are widely analyzed and studied mainly due to the fact that they play an important role in the cultivation of fruits and vegetables. This manuscript aims to display the results of a bibliometric analysis based on the Web of Science© database, performed in the DTF and food research area. A total of 374 publications were examined. The most scientific production was concentrated between 2012 and 2021, showing a decrease of 32% over the last two years. The Journal of Agricultural and Food Chemistry, India, and Sardar Vallabhbhai National Institute of Technology were the most productive journal, country, and institution, respectively. Reference Publication Year Spectroscopy index showed a decrease of 95% in the last last years studied. Finally, current and future trends should focus on keywords such as individual DTF (Mancozeb, Thiram and Maneb), metabolites (Ethylenethiourea, Propilenthiourea) and a change in the analysis methodology: HPLC versus traditional GC.

Cross-linked dithiocarbamate-modified cellulose with enhanced thermal stability and dispersibility as a sorbent for arsenite removal

Numerous reports have described dithiocarbamate (DTC)-modified cellulose sorbents that can selectively separate metal ions from water. We have previously synthesized a novel sorbent modified with DTC containing N-heterocycles in the backbone for the selective removal of hazardous metal ions. The sorbent was found to partially dissolve and aggregate in solution, reducing its sorption capacity. In this study, to prepare the sorbent for use as a soli-phase extraction material for the removal of arsenite (As^III) ions, we attempted to decrease the solubility of the sorbent. The sorbent was cross-linked with epoxy or complexed with iron, and the quantities of the modifiers were varied between 3.0 and 10 mol%. As a result, the iron-complexed sorbents were still partially soluble, and cross-linkage with 6.0 mol% of epoxy made the sorbent almost insoluble and dispersed in solution. This sorbent also exhibited the highest As^III sorption performance among the sorbents synthesized in this study. Although DTC-modified polymers are reported to lose their sorption capability after storage at 40 °C, the sorbent was found to be thermally stable. The optimum contact time and pH for As^III removal were 20 min and 3.0, respectively. The maximum sorption capacity of the epoxy-cross-linked sorbent, calculated from the Langmuir isotherm equation, was 600 μmol g^-1 (45 mg g^-1) at 25 °C. Additionally, the sorbent was highly selective toward As^III compared with previously reported sorbents and capable of removing approximately 97% of As^III from environmental water. In conclusion, cross-linking enhances the stability of the sorbents in solutions, which facilitates the removal of As^III from environmental water.

Synthesis, Structural, Thermal, and Hirshfeld Surface Analysis of In(III) Tris (N-Methyl-N-Phenyl Dithiocarbamate)

The reaction of ammonium N-methyl-N-phenyl dithiocarbamate with In3+ resulted in the In(III) tris (N-methyl-N-phenyldithiocarbamate) complex. The spectroscopic characterization of the complex was carried out using FTIR, 1H, and 13C NMR spectroscopy. Single-crystal X-ray diffraction analysis (SCXRD) revealed that the complex crystallizes in a triclinic system with a centrosymmetric P-1 space group. The stabilization of the structure was via weak hydrogen bonds and C-H···π contacts. The non-covalent interactions in the crystal network were identified using computational analysis based on SCXRD data, such as Hirshfeld surface analysis. The thermal decomposition behaviour of the complex was studied by thermogravimetric analysis, which showed a one-step decomposition to yield In2S3 at 380 °C.

Domino assembly of dithiocarbamates via Cu-catalyzed denitrogenative thiolation of iodotriazole-based diazo precursors

An efficient domino approach to assemble benzoxazoles and anthranilamides bearing dithiocarbamate moieties has been developed. The proposed route represents a Cu-catalyzed three-component reaction between readily available 5-iodo-1,2,3-triazoles, amines, and CS₂. The cascade transformation is based on a denitrogenative coupling of in situ formed dithiocarbamic acids with diazo intermediates, generated via annulation-triggered triazole ring-opening. This method is applicable to nucleophilic secondary amines and features good functional group compatibility.

Synthesis of a Highly Selective Scavenger of Precious Metals from a Printed Circuit Board Based on Cellulose Filter Paper Functionalized with a Grafted Polymer Chain Bearing N-Methyl-2-hydroxyethylcarbamothioate Moieties

We report the synthesis and practical application of a novel scavenger for precious metals. The scavenger was prepared from cellulose filter paper with grafted chains of poly(glycidyl methacrylate) modified with a novel ligand group of N-methyl-2-hydroxyethylcarbamothioate moieties, introduced by the reaction with O-1-mercapto-3-phenoxypropan-2-yl N-methyl-2-hydroxyethylcarbamothioate. Batch experiments were performed to evaluate the capability of the scavenger in ranges of pH and acid concentration as well as to determine the kinetics and isotherm models. The scavenger was found to adsorb only Ag(I), Pd(II), and Au(III) from an aqueous media in the presence of coexisting ions of different bases and precious metals at wide ranges of pH and acid concentration. The adsorption rates fit a pseudo-second-order kinetic equation, and the adsorption reached equilibrium within 60 min. The isotherm studies indicated that the obtained data were a good fit with the Langmuir model. The maximum adsorption capacities of Ag(I), Pd(II), and Au(III) were 126.95, 124.67, and 230.67 mg g-1, respectively. Regeneration experiments indicated that the adsorbent maintained 97% of its initial efficiency even after five adsorption/desorption cycles. The scavenger was effectively utilized to recover Ag(I), Pd(II), and Au(III) from an aqua regia solution of waste printed circuit boards.

Coordination Chemistry of the Parent Dithiocarbamate H2NCS2-: Organometallic Chemistry and Tris-Chelates of Group 9 Metals

Two tris-chelate complexes of cobalt and rhodium and two complexes of Ru(II) of dithiocarbamate, [S₂CNH₂]^-, were synthesized. The complexes were spectroscopically characterized by IR, NMR, UV-vis, and MS and structurally characterized by X-ray diffraction. The structural features of the rhodium complex were compared to those of other tris-chelate Rh(III) dithiocarbamate complexes and are characterized by a change in the ground-state geometry in comparison to expected octahedral tris-chelate complexes. This was confirmed both experimentally by X-ray diffraction and theoretically using DFT calculations. The inversion barriers of Rh(Bz₂dtc)₃, Ir(Bz₂dtc)₃, and Rh(Et₂dtc)₃ were determined using VT-NMR in DMSO. These barriers were found to be surprisingly low for heavy group 9 elements of d⁶ tris-chelate complexes: values of 16.7, 17.1, and 16.4 kcal/mol were calculated, respectively. By comparing structural features, we are able to determine that the activation barrier for the inversion of stereochemistry of Rh(H₂dtc)₃ must have a similarly low value. A modified version of the Bailar twist involving an intermediate with C_3h geometry was proposed as the mechanism of inversion.

Silver(I) and Gold(I) Monothiocarbonate Complexes: Synthesis, Structure, Luminescence

The monothiocarbonate ligand, [S(O)COR]−, is unusual and rare regarding its use in the formation of coordination compounds. Here, we report the synthesis and structures of the silver(I) and gold(I) monothiocarbonate complexes, [{Ag4(SC(O)OiPr)2(2,2′-bpy)4}(PF6)2]n (1) and [Au2{S(O)COiPr}2(dppe)]n (2), respectively. Both complexes are coordination polymers, with 1 being cationic and 2 neutral. The uniqueness of the ligand is that it is monoanionic and contains both a ‘hard’ O-donor ligand and a ‘soft’ S-donor ligand in a O-C-S manifold with, in principle, electron delocalization across the three atoms. However, for both complexes 1 and 2, it was found that the binding occurred exclusively through the S-donor atom, while the C=O portion remained dangling and was not involved in bonding. This bonding mode departs significantly from the symmetrical S-C-S type ligand such as dithiocarbamates. The structures were analysed and confirmed by NMR and X-ray crystallography.

The Versatility in the Applications of Dithiocarbamates

Dithiocarbamate ligands have the ability to form stable complexes with transition metals, and this chelating ability has been utilized in numerous applications. The complexes have also been used to synthesize other useful compounds. Here, the up-to-date applications of dithiocarbamate ligands and complexes are extensively discussed. Some of these are their use as enzyme inhibitor and treatment of HIV and other diseases. The application as anticancer, antimicrobial, medical imaging and anti-inflammatory agents is examined. Moreover, the application in the industry as vulcanization accelerator, froth flotation collector, antifouling, coatings, lubricant additives and sensors is discussed. The various ways in which they have been employed in synthesis of other compounds are highlighted. Finally, the agricultural uses and remediation of heavy metals via dithiocarbamate compounds are comprehensively discussed.

Selective Anticancer and Antimicrobial Metallodrugs Based on Gold(III) Dithiocarbamate Complexes

New dithiocarbamate cycloaurated complexes have been synthesized and their physicochemical and in vitro antitumor properties have been evaluated. All the performed studies highlighted good transport through the blood and biodistribution, according to the balance between the properties of hydrophilicity/lipophilicity and the binding of moderate strength to the BSA protein. Furthermore, none of the complexes exhibited reduction or decomposition reactions, presenting excellent physiological stability. The in vitro cytotoxic effect was evaluated on human colon cancer cell line Caco-2/TC7, and the complexes showed great antiproliferative activity and excellent selectivity, as much less effect was detected on normal Caco-2/TC7 cells. Most of the complexes exhibit antiproliferative activity that was better than or similar to auranofin, and at least nine times better than that of cisplatin. Its action mechanism is still under discussion since no evidence of cell cycle arrest was found, but an antioxidant role was shown for some of the selective complexes. All complexes were also tested as antimicrobial drugs, exhibiting good activity towards S. aureus and E. coli. bacteria and C. albicans and C. neoformans fungi.

The Coordination Chemistry of Imidomethanedithiolate Di-anions: A Structural Comparison with Their Dithiocarbamate Analogs

A review of the coordination chemistry along with the structural features of heavy element complexes of dithiocarbimate di-anions in the form of [(R)C=NCS2]2− for R = CN, alkyl, and aryl are described. This class of compound is far less studied compared with the well-explored dithiocarbamate mono-anions formulated as [R(R’)NCS2]− for R/R’ = H, alkyl, and aryl. The coordination chemistry of dithiocarbimate di-anions is dominated by a S,S-chelating mode; rare examples of alternative modes of coordination are evident. When comparisons are available, the structural motifs adopted by metal dithiocarbimate complexes match those found for their dithiocarbamate analogs, with only small, non-systematic variations in the M–S bond lengths.