Excited-State Dynamics in fac-[Re(CO)3(Me4phen)(L)]+

The impact of biomolecule interactions on the cytotoxic effects of rhenium(I) tricarbonyl complexes

Rhenium complexes show great promise as anticancer drug candidates. Specifically, compounds with a Re(CO)3(NN)(py)+ core in their architecture have shown cytotoxicity equal to or greater than that of well-established anticancer drugs based on platinum or organic molecules. This study aimed to evaluate how the strength of the interaction between rhenium(I) tricarbonyl complexes fac-[Re(CO)3(NN)(py)]+, NN = 1,10-phenanthroline (phen), dipyrido[3,2-f:2',3'-h]quinoxaline (dpq) or dipyrido[3,2-a:2'3'-c]phenazine (dppz) and biomolecules (protein, lipid and DNA) impacted the corresponding cytotoxic effect in cells. Results showed that fac-[Re(CO)3(dppz)(py)]+ has higher Log Po/w and binding constant (Kb) with biomolecules (protein, lipid and DNA) compared to complexes of fac-[Re(CO)3(phen)(py)]+ and fac-[Re(CO)3(dpq)(py)]+. As consequence, fac-[Re(CO)3(dppz)(py)]+ exhibited the highest cytotoxicity (IC50 = 8.5 μM for HeLa cells) for fac-[Re(CO)3(dppz)(py)]+ among the studied compounds (IC50 > 15 μM). This highest cytotoxicity of fac-[Re(CO)3(dppz)(py)]+ are probably related to its lipophilicity, higher permeation of the lipid bilayers of cells, and a more potent interaction of the dppz ligand with biomolecules (protein and DNA). Our findings open novel avenues for rational drug design and highlight the importance of considering the chemical structures of rhenium complexes that strongly interact with biomolecules (proteins, lipids, and DNA).

Multiple phenyl ring appended Re-based complexes for strong visible light absorption and DNA binding

A series of facial-Re(CO)₃-based acyclic complexes (1-3) possessing N∩O bis-chelating ligands and a triphenylphosphine oxide donor was synthesized and characterized. The most interesting structural feature of these complexes is that both the coordinated ligands are functionalized with external phenyl rings. Single crystal X-ray diffraction analysis confirms that each molecule demonstrates a variety of intermolecular supramolecular interactions via the external phenyl rings. All the complexes displayed strong absorption (ε = 14 000-40 000 M^-1 cm^-1) over wide visible region (400-600 nm). Due to the interesting structural and photophysical properties of the complexes, a satisfactory DNA binding ability was observed. The binding of the complexes with DNA grooves was confirmed by a significant increase in the absorption intensities of the complexes in the visible region, absorption enhancement of DNA and circular dichroism.

Towards better understanding of photophysical properties of rhenium(I) tricarbonyl complexes with terpy-like ligands

Series of Re(I) carbonyls complexes were designed and synthesized to explore the impact of the triimine skeleton and number of methoxy groups attached to aryl substituents on their optoelectronic and thermal properties. The chemical structures of the prepared complexes were confirmed by ¹H and ¹³C NMR spectroscopy, HR-MS, elemental anlsysis, and X-ray measurements. DSC measuremtns showed that they melted in the range of 198-325 °C. Some of them form stable molecular glasses with high glass transition temperatures (158-173 °C). Experimentally obtained optical properties were supported by DFT calculations. The UV-Vis spectra display a series of overlapping absorption bands in the range 200-350 nm, and much weaker broad band in the visible spectral region, due to intraligand and charge transfer transitions, respectively. All synthesized complexes were emissive in solution and in solid state as powder. Moreover, when applied in diodes, some of them exhibited ability for emission of light under external voltage with maximum of electroluminescence band located at 591-630 nm.

Spectroscopic characterization of a new Re(i) tricarbonyl complex with a thiosemicarbazone derivative: towards sensing and electrocatalytic applications

A novel Re(i) complex with a thiosemicarbazone derivative is described and fully characterized. Its was further explored as CO₂ reduction electrocatalyst, being the first complex with a thiosemicarbazone derivative applied to this goal.

Heteroleptic [Os(Cl)(CO)(P^P)(pbi)] complexes bearing bidentate phosphine and 2-(2-pyridyl)benzimidazolate ligands: impact of isomerism on their luminescence properties

Two isomeric series of osmium(ii) complexes exhibit significant differences in their luminescence properties.

Molecular engineered rhenium(i) carbonyl complexes to promote photoisomerization of coordinated stilbene-like ligands in the visible region

Novel fac-[Re(CO)₃(dmcb)(trans-stpyR)]⁺ complexes have been judiciously engineered to absorb at lower energies and sensitize trans-4-styrylpyridine (trans-stpy) or trans-4-(4-cyano)styrylpyridine (trans-stpyCN) photoisomerizable ligands up to 436 nm of irradiation.

Photoisomerization of di-nuclear rhenium(i) bpe-based compounds

Photoisomerization processes of [{(NN)(CO)₃Re}₂(trans-bpe)]²⁺ complexes showed the contribution of the singlet pathway in addition to the usually observed triplet one. The luminescence observed for the cis-complexes in CH₃CN is able to efficiently photosensitize the generation of ¹O₂.

Reversible trans ⇌ cis photoisomerizations of [Re(CO)3(ph2phen)(stpyCN)]+ towards molecular machines

The fac-[Re(CO)₃(ph₂phen)(stpyCN)]⁺ complex is capable of switching through extended trans- and contracted cis-configurations upon irradiation under proper energies.

Asymmetric rhenium tricarbonyl complexes show superior luminescence properties in live cell imaging

The synthesis and photophysical properties of a novel series of rhenium tricarbonyl complexes based on tridentate phenanthridinyl-containing ligands are described. Photophysical data reveal beneficial luminescence behaviour especially for compounds with an asymmetric ligand set. These advantageous properties are not limited to organic solvents, but indeed also improved in aqueous solutions. The suitability of our new rhenium complexes as potent imaging agents has been confirmed by fluorescence microscopy on living cancer cells, which also confirms superior long-time stability under fluorescence microscopy conditions. Colocalisation studies with commercial organelle stains reveal an accumulation of the complexes in the endoplasmic reticulum for all tested cell lines.

Contrasting photophysical properties of rhenium(i) tricarbonyl complexes having carbazole groups attached to the polypyridine ligand

The fac-[Re(CO)₃(cbz₂phen)(L)]^0/+1 complexes showed a remarkable presence of the ILCT_cbz2phen fluorescence in addition to the usually observed ³MLCT_{Re→cbz2phen}. In PMMA films the emission is completely turned into a triplet excited state manifold.

Rhenium(i) terpyridine complexes – synthesis, photophysical properties and application in organic light emitting devices

The structural and photophysical characterization of new Re(i) complexes was reported.

Synthesis and characterization of monometallic rhenium(i) complexes and their application as selective sensors for copper(ii) ions

Monometallic Re(i) complexes, selective and sensitive sensor of Cu(ii) ion, show substantial enhancement in the emission intensity, quantum yield, and lifetime due to the restriction of CN isomerization.

Spectroscopic trends in a series of Re(I) α-diimine complexes as a function of the antenna/photoisomerizable ligands: a TD-DFT and MS-CASPT2 study

The absorption spectra of 11 rhenium(I) complexes with photoisomerizable stilbene-like ligands have been investigated by means of density functional theory (DFT). The electronic structures of the ground and excited states were determined for [Re(CO)3(N,N)(L)]+ (N,N = bpy (2,2′-bipyridine), phen (1,10-phenanthroline), Me4phen (3,4,7,8-tetramethyl-1,10-phenanthroline), ph2phen (4,7-diphenyl-1,10-phenanthroline), or Clphen (5-chloro-1,10-phenanthroline); L = bpe (1,2-bis(4-pyrydil)ethylene), stpy (4-styrylpyridine), or CNstpy (4-(4-cyano)styrylpyridine)) at the time–dependent (TD) DFT/CAM-B3LYP level of theory in vacuum and acetonitrile to highlight the effects of both antenna N,N and isomerizable L ligands. The TD-DFT spectra of two representative complexes, namely [Re(CO)3(bpy)(stpy)]+ and [Re(CO)3(phen)(bpe)]+, have been compared with MS-CASPT2 spectra. The TD-DFT spectra obtained in vacuum and acetonitrile agree rather well both with the ab initio and experimental spectra. The absorption spectroscopy of this series of molecules is characterized by the presence of three low-lying metal to ligand charge transfer (MLCT) states absorbing in the visible energy domain. The nature of the isomerizable ligands (bpe, stpy, or CNstpy) and the type of antenna ligands (bpy, phen, and substituted phen) control the degree of mixing between the MLCT and intraligand excited states, their relative energies, as well as their intensities.

fac-[1,2-Bis(pyridin-4-yl)ethane-κN]tricarbon-yl(1,10-phenanthroline-κ(2) N,N')rhenium(I) hexa-fluorido-phosphate aceto-nitrile monosolvate

The asymmetric unit of the title compound, [Re(C12H8N2)(C12H12N2)(CO)3]PF6.·CH3CN, contains one cation, one hexa-fluorido-phosphate anion and one aceto-nitrile solvent mol-ecule. The Re(I) ion is coordinated by two N atoms from the 1,10-phenanthroline ligand and one N atom from the 1,2-bis-(pyridin-4-yl)ethane ligand [mean Re-N = 2.191 (15) Å] and by three carbonyl ligands [mean Re-C = 1.926 (3) Å] in a distorted octa-hedral geometry. The electrostatic forces and weak C-H⋯F(O) hydrogen bonds pack cations and anions into the crystal with voids of 82 Å(3), which are filled by solvent mol-ecules. The crystal packing exhibits short inter-molecular O⋯O distance of 2.795 (5) Å between two cations related by inversion.

The photophysics of fac-[Re(CO)3(NN)(bpa)]+ complexes: a theoretical/experimental study

The influence of the polypyridyl ligand on the photophysics of Re(i) tricarbonyl complexes was investigated by steady-state and time resolved spectroscopy as well as by theoretical calculations.