Thiourea Metal Complexes Research Articles

Synthesis of New Thiourea-Metal Complexes with Promising Anticancer Properties.

In this work, two thiourea ligands bearing a phosphine group in one arm and in the other a phenyl group (T2) or 3,5-di-CF3 substituted phenyl ring (T1) have been prepared and their coordination to Au and Ag has been studied. A different behavior is observed for gold complexes, a linear geometry with coordination only to the phosphorus atom or an equilibrium between the linear and three-coordinated species is present, whereas for silver complexes the coordination of the ligand as P^S chelate is found. The thiourea ligands and their complexes were explored against different cancer cell lines (HeLa, A549, and Jurkat). The thiourea ligands do not exhibit relevant cytotoxicity in the tested cell lines and the coordination of a metal triggers excellent cytotoxic values in all cases. In general, data showed that gold complexes are more cytotoxic than the silver compounds with T1, in particular the complexes [AuT1(PPh3)]OTf, the bis(thiourea) [Au(T1)2]OTf and the gold-thiolate species [Au(SR)T1]. In contrast, with T2 better results are obtained with silver species [AgT1(PPh3)]OTf and the [Ag(T1)2]OTf. The role played by the ancillary ligand bound to the metal is important since it strongly affects the cytotoxic activity, being the bis(thiourea) complex the most active species. This study demonstrates that metal complexes derived from thiourea can be biologically active and these compounds are promising leads for further development as potential anticancer agents.

Insights into the use of metal complexes of thiourea derivatives as highly efficient adsorbents for ciprofloxacin from contaminated water

Despite the wide use of synthesised metal complexes of thiourea and their derivatives in medicine and corrosion inhibition, a paucity of research exists on their application as adsorbents for pollutants. This study was aimed at investigating the adsorption potential of the copper (II) and zinc (II) complexes of 4-nitro-substituted thiourea derivatives of aminophenol for ciprofloxacin (CPF). The metal complexes were synthesised and characterised. Fourier transform infrared spectroscopy, scanning electron microscopy and a BET surface area analyzer were utilised to determine the surface structure and properties of the synthesised adsorbents. Isotherms were conducted by the application of Langmuir, Freundlich and Scatchard models and revealed a heterogeneous multilayer adsorption process. Kinetic evaluation showed best fit with the pseudo second order model (R2 > 0.991) compared to the pseudo first order and Bangham equations. Thermodynamics showed an endothermic spontaneous abstraction process. The metal complexes showed over 80% desorption of CPF using 0.2 M NaOH and were stable over three cycles of regeneration and reuse. This research revealed the potential of the metal complexes of thiourea as adsorbents for CPF supported by the high adsorption capacity compared to other reported adsorbents.

Studying the kinetics of electrode reactions on copper, silver and gold in acid thiourea-citrate electrolytes

The kinetics of electrode reactions that take place on copper, silver and gold electrode in acid thiourea-citrate electrolytes has been studied. It is established that the anodic dissolution of metals is accompanied by the formation of stable thiourea metal complexes of a cation-type complex. The citric acid provides the acidic pH-value of the solutions and contributes to the active dissolution of anodes. The ionization rate is limited by the diffusion of charged particles into the electrolyte volume. The cathode reduction of metals obeys the mechanisms of mixed kinetics that includes the diffusion and the preceding chemical complexes dissociation reaction. The charge of the complex ions of copper, silver and gold is +1. Therefore, their dissolution at the anode and reduction at the cathode occurs with the maximum possible electrochemical equivalent.

Design and synthesis of novel thiourea metal complexes with controllable antibacterial properties

A new bidentate O,S donor thiourea ligand (L1), namely N‐(2‐hydroxyethyl)‐N′‐2‐chlorobenzoylthiourea, and its oxazolidine derivative (L2) were synthesized. Derivative L2 was used for the preparation of Ni(L2)2 and Cu(L2)2 complexes. The compounds were investigated using X‐ray crystallography and Fourier transform infrared, 1H NMR and UV–visible spectroscopies. Single‐crystal X‐ray analysis showed strong hydrogen bonding interactions between carbonyl oxygen and N(10) ─ H in the L1 ligand. In addition, the antibacterial activities of these compounds were evaluated against Gram‐positive and Gram‐negative bacteria, measured using the colony count method. The Cu(L2)2 complex exhibited a significant antibacterial activity while the activity of the other compounds was much lower. Finally, the relationship between the structure and antibacterial properties of these compounds was investigated using highest occupied and lowest unoccupied molecular orbital energies calculated by density functional theory method based on the 6‐31G*/LANL2DZ basis set.

Comparative Study of Thiourea Metal Complexes Crystals

Abstract: The thiourea is an interesting inorganic matrix modifier. Recently, researchers are focusing on growing metal complexes of thiourea crystals. Some of the examples are bis thiourea zinc chloride (BTZC) , tetrakis thiourea potassium iodide (TTPI) , tetra thiourea potassium iodide (TTPI) , tetra thiourea cobalt chloride (TTCoC) , bis thiourea cadmium chloride (BTCC) etc., G.Anand et al , S.Gopinath et al and M.Mariappan et al have reported the growth and characterization of metal complexes of urea thiourea. This paper aims to compare the optical , mechanical and thermal properties of these crystals.

Thermal, anisotropic microhardness and laser induced surface damage studies on certain metal complexes of thiourea

Single crystals of thiourea metal complexes with selected group II metal ions, zinc and cadmium, have been grown by solvent evaporation technique and characterized by XRD studies. The thermal, mechanical and laser induced surface damage properties of thiourea and its metal complexes in (1 0 0) plane were studied. From the improved photopyroelectric technique the thermal properties of the metal complexes were evaluated. Due to larger heat capacity ZTS (382.4 J kg −1 K −1) has better thermal stability than BTCC (304.09 J kg −1 K −1), TTCS (293.5 J kg −1 K −1) and BTZC (255.24 J kg −1 K −1). Vickers hardness studies reveal that the materials have reverse indentation size effect and belong to soft material type. Elastic stiffness was found to be very large for ZTS (8.05) than TTCS (5.38), BTCC (1.57 GPa) and BTZC (0.76 GPa). Multi-shot laser damage studies reveal that ZTS (40 GW/cm 2) has higher laser damage threshold and the roles of the group II metal ions in improving the mechanical and thermal stability of the metal complexes are discussed.

χ(3) measurement and optical limiting properties of metal complexes of thiourea using Z-scan

The third order NLO properties of thiourea and its metal complexes were measured using a 532 nm second harmonic of diode pumped Nd:YAG laser (1064 nm, 50 mW) by employing the Z-scan technique. The magnitude of nonlinear refractive index, nonlinear absorption coefficient and third order susceptibility was found to be in the order of 10 −8 cm 2 W −1, 10 −3 cm W −1 and 10 −6 esu respectively. The Z-scan reflects the negative nonlinearity of the samples and hence self defocusing nature is responsible for the optical limiting behavior in the regime of interest. The response time was found to be in the order of milliseconds.

Mechanical, thermal and laser damage threshold analyses of II group metal complexes of thiourea

Single crystals of thiourea metal complexes with selected Group II metal ions, Zinc and Cadmium, have been grown by solvent evaporation technique. The crystals grown are bisthiourea zinc chloride (BTZC) and bisthiourea cadmium chloride (BTCC). Following an improved photopyroelectric technique, the thermal transport properties have been determined. It is found that BTCC has a higher heat capacity (304.09 J kg −1 K −1) than BTZC (255.24 J kg −1 K −1), and hence BTCC has better thermal stability. Vicker's microhardness measurements reveal that these materials have reverse indentation size effect and belong to the category of soft materials. Elastic stiffness is found to be higher for BTCC (1.57 GPa) than BTZC (0.76 GPa). The roles of the Group II metal ions in improving the mechanical and thermal stability of the metal complexes are discussed. Multi-shot laser damage studies on these materials reveal that BTCC has a higher laser damage threshold (15 GW cm −2) than BTZC (6 GW cm −2).

Optical limiting behavior of certain thiourea metal complexes under CW laser excitation

Optical nonlinearity of thiourea and its metal complexes (Zn and Cd) in water is studied in the regime of low laser power using a continuous wave diode pumped Nd:YAG laser (532 nm, 50 mW). The Z-scan technique was used to measure the nonlinearity of the medium and it is found that the predominant mechanism of nonlinearity is thermal in origin. The nonlinear refractive index and nonlinear absorption coefficient of the samples are found to be in the order of 10 −8 cm 2/W and 10 −3 cm/W respectively. The inclusion of metal has improved the optical nonlinearity of the samples than its parent molecule. The third-order nonlinear susceptibility was found to be in the order of 10 −6 esu. The self-defocusing effect observed was used to demonstrate the optical limiting action at 532 nm using the same cw laser beam.

Tuning the dielectric properties of thiourea analog crystals for efficient nonlinear optical applications

Materials with low dielectric constant have attracted a great deal of interest in the field of nonlinear applications and microelectronic industry. Metal complexes of thiourea with group II transition metals (Zn, Cd) as central atom and period III elements (S, Cl) were synthesized by chemical reaction method and single crystals were grown from aqueous solution by slow evaporation method. By parallel plate capacitor technique, the dielectric response, dissipation factor, ac conductivity and impedance of virgin and metal complexes have been studied in the frequency (100 Hz to 5 MHz) and temperature (303–423 K) ranges. Metal complexes of thiourea with cadmium substitute have a low dielectric constant less than 10. Also the presence of chlorine in the metal complex induces noncentro symmetric structure. Hence the role of group II transition metals and period III elements in tuning the dielectric properties for efficient nonlinear applications has been studied.

Thermal decomposition of thiourea complexes of Cu(I), Zn(II), and Sn(II) chlorides as precursors for the spray pyrolysis deposition of sulfide thin films

Comparative study on thermal decomposition of four thiourea–metal complexes, solid precursors for spray pyrolysis deposition (SPD) methods, had been carried out by using thermoanalytical and X-ray diffraction (XRD) methods in combination. [Cu2(tu)6]Cl2·2H2O (1), ZnCl2(tu)2 (2), Sn2Cl4(tu)5·2H2O (3), and SnCl2(tu) (4) prepared from aqueous thiourea (tu) solutions, had been decomposed in a simultaneous thermogravimetric/differential thermoanalytical (TG/DTA) apparatus, while XRD phase analysis of solid residues obtained at various temperatures had been performed. In static air, a main degradation step between 200°C and 300°C led to the formation of Cu9S5 (digenite), ZnS (zinc blende), and SnS2 (berndtite), respectively. Unfortunately, some chemical species with low volatility still remained in condensed phase, while above 400°C, primary oxidation products of sulfides such as Cu2O(SO4) (dolerophanite), ZnO, and SnO2 also occurred. Nevertheless, intermittent spray pyrolysis depositions of Cu2SnS3 and Cu2ZnSnS4 films from some thiourea solutions with Cu(I), Zn(II), and Sn(II) onto glass substrates, with temperature ranging between 225°C and 300°C, were successful.

Metal complex catalyzed reactions of anils. II. Transimination

The exchange of aromatic residues between anilines and anils (transimination) has been shown to be efficiently catalyzed by metal complexes of thiourea. This reaction can be conveniently studied by nmr spin saturation transfer techniques. Experiments of this type using both CW and FT nmr spectrometers are reported. The rate of the reaction is about two orders of magnitude greater than the rates of reactions involving anil formation and hydrolysis with the same substrates and catalysts. The effectiveness of the catalysts vary in the same manner as they do for anil formation and the reaction is similarly subject to inhibition by competing ligands. The rate of exchange of the two inequivalent methyl groups in acetone anils is similarly catalyzed and may be studied by spin saturation transfer experiments. The lifetime of an anil molecule for methyl group exchange is approximately twice that for transimination suggesting that the rate determining process for transimination results in free rotation about the C—N bond so that the methyl groups have an equal probability of retaining or exchanging their environments.

X-ray photoelectron spectra of inorganic molecules. : XX. Observations concerning the sulfur 2p binding energies in metal complexes of thiourea

X-ray photoelectron spectra of inorganic molecules. : XX. Observations concerning the sulfur 2p binding energies in metal complexes of thiourea