Rhenium(I) tricarbonyl complexes with bispyridine ligands attached to sulfur-rich core: Syntheses, structures and properties

Nanoparticles Functionalised with Re(I) Tricarbonyl Complexes for Cancer Theranostics

Globally, cancer is the second (to cardiovascular diseases) leading cause of death. Regardless of various efforts (i.e., finance, research, and workforce) to advance novel cancer theranostics (diagnosis and therapy), there have been few successful attempts towards ongoing clinical treatment options as a result of the complications posed by cancerous tumors. In recent years, the application of magnetic nanomedicine as theranostic devices has garnered enormous attention in cancer treatment research. Magnetic nanoparticles (MNPs) are capable of tuning the magnetic field in their environment, which positively impacts theranostic applications in nanomedicine significantly. MNPs are utilized as contrasting agents for cancer diagnosis, molecular imaging, hyperfusion region visualization, and T cell-based radiotherapy because of their interesting features of small size, high reactive surface area, target ability to cells, and functionalization capability. Radiolabelling of NPs is a powerful diagnostic approach in nuclear medicine imaging and therapy. The use of luminescent radioactive rhenium(I), 188/186Re, tricarbonyl complexes functionalised with magnetite Fe3O4 NPs in nanomedicine has improved the diagnosis and therapy of cancer tumors. This is because the combination of Re(I) with MNPs can improve low distribution and cell penetration into deeper tissues.

2-Azabutadiene complexes of rhenium(I): S,N-chelated species with photophysical properties heavily governed by the ligand hidden traits

The reaction of [Re(CO)3(THF)(μ-Br)]2 or [Re(CO)5X] (X = Cl, Br, I) with the diaryl-2-azabutadienes [(RS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CAr2] containing two thioether arms at the 4,4-position forms the luminescent S,N-chelate complexes fac-[(OC)3ReX{(RS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CAr2}] (1a-h). The halide abstraction by silver triflate converts [(OC)3ReCl{(PhS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CPh2}] (1c) to [(OC)3Re(OS([double bond, length as m-dash]O)2CF3){(PhS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CPh2}] (1j) bearing a covalently bound triflate ligand. The cyclic voltammograms reveal reversible S^N ligand-centred reduction and irreversible oxidation waves for all complexes. The crystal structures of nine octahedral complexes have been determined along with that of (NaphtylS)2C[double bond, length as m-dash]C(H)-N[double bond, length as m-dash]CPh2 (L6). A rich system of weak non-covalent intermolecular secondary interactions through CHX(Cl, Br)Re, CHO, COπ(Ph), CHπCO, CHO and CHS contacts has been evidenced. The photophysical properties have been investigated by steady-state and time-resolved absorption (fs transient absorption, fs-TAS) and emission (ns-TCSPC and ps-Streak camera) spectroscopy in 2-MeTHF solution at 298 and 77 K. The emission bands are composed of either singlet (450 < λmax < 535 nm) and/or triplet emissions (at 77 K only, λmax < 640 nm, or appearing as a tail at λ > 600 nm), which decay in a multiexponential manner for the fluorescence (short ps (i.e. <IRF) < τF < 1.9 ns at 298 and 77 K) and monoexponentially for the phosphorescence (4.0 < τP < 7.0 ns at 77 K). The fs-TAS data reveal the presence of 2 to 4 transient species decaying in four narrow time windows (generally 125-165 fs, 370-685 fs, 3-6 ps, 30-45 ps). The complexity of these kinetics was explained by studying the photophysical behaviour of ligand L6. Its behaviour is the same as the complexes thus indicating that the ligand dictates the kinetic traits of the Re-species, except for the triplet emission as L6 is not phosphorescent. The triplet lifetime (4.0 < τP < 7.0 ns) is considered very short but not unprecedented. Furthermore, the nature of the lowest energy excited states of these chelate compounds and L6 has been addressed using DFT and TDDFT calculations and been assigned to metal-to-ligand (MLCT) and/or intraligand charge-transfer (ILCT).

Novel Re(I) tricarbonyl coordination compounds based on 2-pyridyl-1,2,3-triazole derivatives bearing a 4-amino-substituted benzenesulfonamide arm: synthesis, crystal structure, computational studies and inhibitory activity against carbonic anhydrase I, II, and IX isoforms†

In this work, two bidentate 2-pyridyl-1,2,3-triazole ligands (3a and 3b) containing a 4-substituted benzenesulfonamide pharmacophore prepared by classical click chemistry procedures, as well as their corresponding rhenium complexes, 4a and 4b of general formula [ReCl(CO)3(L)] (L = 3a or 3b) were prepared and fully characterised by spectroscopic methods (IR, NMR, MS, UV-Vis), elemental analysis, X-ray diffraction, and theoretical studies using DFT and TD-DFT methods. In particular, we showed that, in the solid state, the pyridine and the triazole rings of 3b adopted an uncommon cis configuration which stems from intermolecular hydrogen bonds. Preliminary assays demonstrated a promising nanomolar inhibitory activity against carbonic anhydrase isoform IX for both ligands and complexes with a strong affinity Ki of 2.8 nM for ligand 3a. More interestingly, complex 4b exhibited a pronounced selectivity against hCA IX over the off-targets hCA I and hCA II which makes this compound a promising potential anticancer drug candidate.

Photocatalytic Hydrogen Evolution by tris-dithiolene tungsten complexes

Herein, we report on the homogeneous photocatalytic evolution of hydrogen by using as reductive catalysts the prismatic symmetric tris – dithiolene complexes of the tungsten, namely [W{S2C2(Ph)2}3] (1) and its monoanion [W{S2C2(Ph)2}3](TBA) (2). Complex 2 is fully characterized by elemental analysis, ESI-MS, IR, UV-Vis and fluorescence spectrophotometry as well as cyclic voltammetry. The photocatalytic system consists of [ReBr(CO)3(bpy)] as a photosensitizer, triethanolamine as a sacrificial electron donor and acetic acid as the proton source. Although the activity of the photocatalytic system is rather small (TON=18), it indicates that the homoleptic tris dithiolene complexes can act as proton reductive catalysts with their monoanion form to be more active in accordance with the findings for the bis - dithiolene complexes.

New dinuclear hydrido-carbonyl rhenium complexes designed as photosensitizers in dye-sensitized solar cells

Dye-sensitized solar cells based on dinuclear hydrido-carbonyl rhenium complexes have been developed, achieving an overall solar conversion efficiency of 1.0%.