Search

Monoanionic gold bis(dithiolene) complexes were recently shown to display activity against ovarian cancer cells, Gram-positive bacteria, Candida strains and the rodent malaria parasite, P. berghei. To date, only monoanionic gold(III) bis(dithiolene) complexes with a thiazoline backbone substituted with small alkyl chains have been evaluated for biomedical applications. We now analyzed the influence of the length and the hydrophobicity vs. hydrophilicity of these complexes' alkyl chain on their anticancer and antiplasmodial properties. Isomer analogues of these monoanionic gold(III) bis(dithiolene) complexes, this time with a thiazole backbone, were also investigated in order to assess the influence of the nature of the heterocyclic ligand on their overall chemical and biological properties. In this report we present the total synthesis of four novel monoanionic gold(III) bis(dithiolene) complexes with a long alkyl chain and a polyoxygenated (PEG) chain aiming to improve their solubility and biological properties. Our results showed that the complexes with a PEG chain showed promising anticancer and antiplasmodial activities beside improved solubility, a key parameter in drug discovery and development. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of two bis(dithiolene) proligands involving heteroatomic linkers such as 1,4-dithiine and dihydro-1,4-disiline between the two protected dithiolene moieties are described. Two bimetallic complexes involving these heteroatomic bridges between two redox active bis(cyclopentadienyl)molybdenum dithiolene moieties have been synthesized and characterized by electrochemistry, spectroelectrochemistry, and their properties rationalized with (TD-)DFT. Cyclic voltammetry experiments show sequential oxidation of the two redox centers with ΔE values between successive one-electron transfers varying according to the nature of the bridge. Depending on the nature of the heteroatomic bridge, the bis-oxidized complexes exhibit either a diradical character with both radicals essentially localized on the metallacycles, or a closed-shell dicationic state. [ABSTRACT FROM AUTHOR]

Benzene‐1,2,4,5‐tetrathiolate (btt) has been used as a bridging ligand to prepare a redox active (molybdenocene dithiolene)‐based bimetallic complex Cp2Mo(btt)MoCp2, which exhibits four successive electron transfers up to the tetracation. Spectro‐electrochemical investigations together with DFT and TD‐DFT calculations evidence that the two electroactive MoS2C2 metallacycles are electronically coupled in the monocationic as in the dicationic state. Two salts of the dication [Cp2Mo(btt)MoCp2]2+ have been structurally characterized with PF6− and HSO4− counterions, showing different chair or boat conformations associated with variable folding angles of the two MoS2C2 metallacycles along the S−S hinge. The bis‐oxidized dicationic complex exhibits a diradical character, with both radicals essentially localized on the metallacycles and with antiferromagnetic coupling evidenced from magnetic susceptibility measurements. [ABSTRACT FROM AUTHOR]

Tetrathiafulvalenes (TTFs) functionalized with groups able to increase non-covalent intermolecular interactions through either hydrogen, halogen or chalcogen bonding were investigated. For that purpose, we designed several appropriate precursors, fused dithiole-2-one/thiazoles, which under homocoupling led to symmetrically substituted TTFs or through heterocoupling to dissymmetrically substituted TTFs. The electrochemical investigations allowed the assessment of the electronic effect of these substituents on the overall donating ability of the TTFs. In addition two charge transfer salts have been prepared involving two of these TTFs with TCNQF4 as the electron acceptor, (4c)2(TCNQF4) and (4b)(TCNQF4). Furthermore the crystal structures of the neutral TTFs and of the charge transfer salts allowed us to study the stacking mode and the different non-covalent interactions taking place in the crystals, in connection with the calculated electrostatic surface potential (ESP) of the investigated molecules. All the data provide information about non-covalent bonding interactions in the solid state and about their potential contribution to direct to some extent crystallographic intermolecular organization. [ABSTRACT FROM AUTHOR]

The prototypical [Ni(dmit)2] complex (dmit: 1,3-dithiole-2-thione-4,5-dithiolate) is modified here by combining the N–R substitution found in [Ni(R-thiazdt)2] complexes (R-thiazdt: N-alkyl-thiazoline-2-thione-4,5-dithiolate) and the selone substitution found in [Ni(dmiSe)2] complex (dmiSe: 1,3-dithiole-2-selone-4,5-dithiolate) to give a novel N-methyl substituted, radical anionic complex formulated as [Ni(Me-thiazSe-dt)2]1− (Me-thiazSe-dt: N-methyl-thiazoline-2-selone-4,5-dithiolate). Both this anionic complex and its mixed-valence Et4N+ salt crystallize with a rare cis arrangement of the two dithiolene ligands around the Ni atom. In the 1 : 2 [Et4N][Ni(Me-thiazSe-dt)2]2 salt, the complexes organize into dimerized chains well isolated from each other, giving the salt a strong one-dimensional character. It shows however a high RT conductivity of 4.6 S cm−1 and small activation energy of 33 meV, indicating a possible Mott insulator behavior, which is not suppressed under pressures up to 10 GPa. [ABSTRACT FROM AUTHOR]

A major challenge in the field of neurocomputing is to mimic the brain's behavior by implementing artificial synapses and neurons directly in hardware. Toward that purpose, many researchers are exploring the potential of new materials and new physical phenomena. Recently, a new concept of the Leaky Integrate and Fire (LIF) artificial neuron was proposed based on the electric Mott transition in the inorganic Mott insulator GaTa4Se8. In this work, we report on the LIF behavior in simple two-terminal devices in three chemically very different compounds, the oxide (V0.89Cr0.11)2O3, the sulfide GaMo4S8, and the molecular system [Au(iPr-thiazdt)2] (C12H14AuN2S8), but sharing a common feature, their Mott insulator ground state. In all these devices, the application of an electric field induces a volatile resistive switching and a remarkable LIF behavior under a train of pulses. It suggests that the Mott LIF neuron is a general concept that can be extended to the large class of Mott insulators. [ABSTRACT FROM AUTHOR]

As shown in Figure 4, the [Ni( I i i Pr-thiazdt) SB 2 sb ] complex adopts a I cis i configuration, while the [Ni(NMe SB 2 sb -thiazdt) SB 2 sb ] complex adopts a I trans i configuration. First, the Ni complexes were prepared under the dianionic state, [PPh SB 4 sb ] SB 2 sb [Ni(R-thiazdt) SB 2 sb ], by deprotecting the thiolate functions of B 1-R b in the presence of sodium methanolate followed by the addition of NiCl SB 2 sb and PPh SB 4 sb Cl (Scheme 2). Another possibility to generate the monoanionic complex from the dianionic ones consist in adding one equivalent of [Cp SB 2 sb Fe][PF SB 6 sb ] to a dichloromethane solution of [PPh SB 4 sb ] SB 2 sb [Ni(R-thiazdt) SB 2 sb ] under inert atmosphere. SCE, are collected in Table 1 together with the complexes, previously investigated [PPh SB 4 sb ][Ni(R-thiazdt) SB 2 sb ] (R=Et, Me).[19] For all the investigated complexes three redox processes can be observed on the cyclic voltammogram. [Extracted from the article]

A series of crown ether substituted vinylogous tetrathiafulvalenes (TTFVs) is synthesized via oxidative coupling of bisdithiafulvenes. The rigidification of the crown ether ring after complexation has appeared as a decrease of the apparent electron-transfer kinetics and has little effect on the thermodynamics as the crown ether is far from the redox center.

Cyclic vinylogous tetrathiafulvalenes (TTFs) where the two dithiole rings are linked through the outer sulfur atoms with an alkyl chain of various lengths were synthesized by oxidative intramolecular coupling of bis (dithiafulvenes). This additional steric strain induces an opposite conformational change upon oxidation to the stretch one observed for the unlinked vinylogous TTFs.