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Examples of pyridyl‐N‐heterocyclic carbene (NHC) ruthenium(II) complexes: (a) homoleptic complexes 4a–b and (b) heteroleptic complexes 4c–f
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This Minireview presents and discusses recent developments in photoactive/photoluminescent N‐heterocyclic carbene (NHC) transition metal complexes and their viability as catalysts in bond‐forming photocatalysis. Specifically, we summarise key structural motifs adopted by photoactive NHC transition metal complexes and highlight some of their photoph...
Citations
... , ipso-C of Ph), 134.1 (d, 2 J PC = 21.5 Hz,, 129.1 (s, p-Ph), 127.9 (d,3 J PC = 5.8 Hz, m-Ph), 124.2 (s, C 5 Me 5 ), 117.9 (d, 3 J PC = 4.2 Hz, C 5 H 4 ), 110.2 (s, C 5 H 4 ), 39.0 (d, 1 J PC = 20.7 Hz, CMe 2 ), 25.5 (d, 2 J PC = 18.0 Hz, CMe 2 ), 12.5 (s, C 5 Me 5 ); 31 P{ 1 H}: δ 32.ZrCl 2 ] (2-O). Complex 1 (100 mg, 0.17 mmol) was dissolved in toluene, the solution cooled to −20°C and t-BuOOH (37 μL, 0.20 mmol, 5.5 M in hexanes) was added. ...
An electrochemical synthesis of gold(I)‐N‐heterocyclic carbene (Au‐NHC) complexes has been developed. The electrochemical methodology uses only imidazolium salts, gold metal electrodes, and electricity to produce these complexes with hydrogen gas as the only by‐product. This high‐yielding and operationally simple procedure has been used to produce eight mononuclear and three dinuclear Au‐NHC complexes. The electrochemical procedure facilitates a clean reaction with no by‐products. As such, Au‐NHC complexes can be directly transferred to catalytic reactions without work‐up or purification. The Au‐NHC complexes were produced on‐demand and tested as catalysts in a vinylcyclopropanation reaction. All mononuclear Au‐NHC complexes performed similarly to or better than the isolated complexes.
The development of efficient and operationally simple synthetic routes to dinuclear gold(I)-amido complexes bearing aromatic/aliphatic-bridges are reported. This family of complexes was prepared utilizing environmentally friendly and sustainable reagents under...
Bioactive NHC-transition metal complexes have shown promise as anti-cancer agents, but their potential use as radiosensitizers has been neglected so far. We disclose here a new series of bimetallic platinum(II) complexes displaying NHC-type bridging ligands, (bis-NHC)[trans-Pt(RNH2)I2]2, that have been synthesized via a simple, two-step procedure. They display cytotoxicity in the micromolar range on cancerous cell lines, accumulate in cells, and bind to genomic DNA, by inducing DNA damages. Notably, these bimetallic complexes demonstrate significant radiosensitizing effects on both ovarian cells A2780 and nonsmall lung carcinoma cells H1299. Further investigations revealed that bimetallic species make irradiation-induced DNA damages more persistent by inhibiting repair mechanisms. Indeed, a higher and persistent accumulation of both γ-H2AX and 53BP1 foci post-irradiation was detected, in the presence of the NHC-Pt complexes. Overall, we provide the first in vitro evidence for the radiosensitizing properties of NHC-platinum complexes, which suggests their potential use in combined chemo-radio therapy protocols.
A series of Ru(III)-NHC complexes, identified as [RuIII(PyNHCR)(Cl)3(H2O)] (1a-c), have been prepared, starting from RuCl3·3H2O following a base-free route. The Lewis acidic Ru(III) centre operates via a halide-assisted, electrophilic C-H activation for carbene generation. The best results were obtained with azolium salts having the I- anion, while ligand precursors with Cl-, BF4-, and PF6- gave no complex formation and those with Br- gave a product with mixed halides. The structurally simple, air and moisture-stable complexes represent rare examples of paramagnetic Ru(III)-NHC complexes. Furthermore, these benchtop stable Ru(III)-NHC complexes were shown to be excellent metal precursors for the synthesis of new [RuII(PyNHCR)(Cl)2(PPh3)2] (2a-c) and [RuII(PyNHCR)(CNCMe)I]PF6 (3a-c) complexes. All the complexes have been characterised using spectroscopic methods, and the structures of 1a, 1b, 2c, and 3a have been determined using the single-crystal X-ray diffraction technique. This work allows easy access to new Ru-NHC complexes for the study of new properties and novel applications.
Two novel halogenated (Br- and F-) quinazoline derivatives, namely [(E)-4-(2-((6-bromopyridin-2-yl)methylene)hydrazinyl)quinazoline] (L1) and [(E)-4-(2-((3-fluoropyridin-2-yl)methylene)hydrazinyl) quinazoline] (L2), were synthesized and characterized. Their interaction with a series of metal(II) ions (= Mn(II), Ni(II), Cu(II), Zn(II) and Cd(II)) resulted in the formation of six mononuclear complexes characterized by spectroscopic techniques and single-crystal X-ray crystallography. The complexes bear the formulae [Ni(L1)2](NO3)2 (1), [Zn(L2)2](NO3)(PF6) (2), [Cd(L2)(H2O)(CH3OH)(NO3)](NO3) (3), [Cu(L2)Cl2] (4), [Ni(L2)2](NO3)2 (5) and [Mn(L2)(CH3OH)(Cl)2] (6). The biological activity of the compounds was further evaluated in vitro regarding their interaction with calf-thymus DNA, their cleavage ability towards supercoiled circular pBR322 plasmid DNA in the absence or presence of irradiation at various wavelengths (UVA, UVB and visible light), their affinity to bovine serum albumin and their ability to scavenge 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radicals and to reduce H2O2. In silico molecular docking calculations were employed to study the behavior of the complexes towards calf-thymus DNA and bovine serum albumin.
