In 1913 Alfred Werner received the Nobel Prize in Chemistry for his work that was of great importance for the development of coordination chemistry. In the years that followed numerous complexes ...consisting of metal ions and organic ligands were isolated, thus building a strong connection between inorganic and organic chemistry. Coordination compounds have many interesting properties which find diverse applications in numerous aspects of human life. Fourteeen contributions were received for this Special Issue covering very different aspects of metal complexes and their practical applications. The highest number of manuscripts deals with the biological activity of complexes which might potentially be used in the clinical practice. Authors have tested their cytotoxicity, antibacterial activity and enzyme inhibition. Their optical properties were studied in view of their potential use in photodynamic therapy. Moreover, optical properties could also be used for bioanalysis. It is also known that metal complexes are useful catalysts and a few such examples are also described herein. Many other interesting properties and facts about the isolated and described complexes are also reported (radioactivity, design of metal-organic frameworks, etc.).
In this review several types of interactions between metal ions and DNA are given, starting from basic binding to the use of metal complexes in cancer treatment and diagnostics. Metal cations help to ...neutralize the negative charge of DNA and thus enable the normal functions of DNA but many other interactions are also possible and are discussed in this paper. Various consequences of such interactions can be reversible (e. g. conformational changes) or irreversible (e. g. cleavage). It is known that some metal ions can also damage DNA which can provoke mutations and in some cases leads to cancer. It is clear that we know a lot about metal-DNA interactions but much more information is needed to understand the role of metal ions completely and to use this knowledge successfully.
Selective photochemical oxidation of styrene was performed in an active acetonitrile medium, using H
O
with or without ultraviolet (UV) light radiation. Pyrithione metal complexes (M-Pth: M = Cu(II), ...Ni(II), Ru(II); Pth = 2-mercaptopyridine-N-oxide) were used as catalysts. Catalytic testing measurements were done by varying the time, chemical reaction temperature and H
O
concentration with or without UV energy. Epoxide styrene oxide (SO), benzaldehyde and acetophenone were the major synthesized products. A high batch rate, conversion and selectivity towards SO was shown in the presence of UV. A minor constant formation of CO
was observed in the stream. Coordinated Ru-based compounds demonstrated the highest process productivity of SO at 60 °C. The effect of the functional alkyl substituent on the ligand Pth, attached to the specific ruthenium(II) centre, decreased the activity of the substance. Ni-Pth selectively yielded benzaldehyde. The stability of the catalysts was examined by applying nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis coupled with mass spectrometry. Tested metal complexes with pyrithione (M-Pth) exhibited excellent reuse recyclability up to 3 cycles.
Two new Zn(II) complexes with tridentate hydrazone-based ligands (condensation products of 2-acetylthiazole) were synthesized and characterized by infrared (IR) and nuclear magnetic resonance (NMR) ...spectroscopy and single crystal X-ray diffraction methods. The complexes
,
and recently synthesized Zn
(NCS)
(
= (
)-
,
,
-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium) complex
were tested as potential catalysts for the ketone-amine-alkyne (KA
) coupling reaction. The gas-phase geometry optimization of newly synthesized and characterized Zn(II) complexes has been computed at the density functional theory (DFT)/B3LYP/6-31G level of theory, while the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO and LUMO) energies were calculated within the time-dependent density functional theory (TD-DFT) at B3LYP/6-31G and B3LYP/6-311G(d,p) levels of theory. From the energies of frontier molecular orbitals (HOMO-LUMO), the reactivity descriptors, such as chemical potential (
), hardness (
), softness (
), electronegativity (
) and electrophilicity index (
) have been calculated. The energetic behavior of the investigated compounds (
and
) has been examined in gas phase and solvent media using the polarizable continuum model. For comparison reasons, the same calculations have been performed for recently synthesized Zn
(NCS)
complex
. DFT results show that compound
has the smaller frontier orbital gap so, it is more polarizable and is associated with a higher chemical reactivity, low kinetic stability and is termed as soft molecule.
Heavy metal ions can disrupt biological functions via multiple molecular mechanisms, including inhibition of enzymes. We investigate the interactions of human papain-like cysteine endopeptidases ...cathepsins L, K, and S with gallium and cerium ions, which are associated with medical applications. We compare these results with zinc and lead, which are known to inhibit thiol enzymes. We show that Ga3+, Ce3+, and Ce4+ ions inhibit all tested peptidases with inhibition constants in the low micromolar range (between 0.5 µM and 10 µM) which is comparable to Zn2+ ions, whereas inhibition constants of Pb2+ ions are one order of magnitude higher (30 µM to 150 µM). All tested ions are linear specific inhibitors of cathepsin L, but cathepsins K and S are inhibited by Ga3+, Ce3+, and Ce4+ ions via hyperbolic inhibition mechanisms. This indicates a mode of interaction different from that of Zn2+ and Pb2+ ions, which act as linear specific inhibitors of all peptidases. All ions also inhibit the degradation of insoluble elastin, which is a common target of these peptidases in various inflammatory diseases. Our results suggest that these ions and their compounds have the potential to be used as cysteine cathepsin inhibitors in vitro and possibly in vivo.
We report that 1-(2-picolyl)-1,2,3-triazole (click triazole) forms stable complexes with transition-metal ions in which the coordination involves the triazole N2 nitrogen atom and the pendant ...2-picolyl group. This is exemplified by model compound 1-(2-picolyl)-4-phenyl-1H-1,2,3-triazole (L x ) and its complexes with transition-metal ions of PtII, PdII, CuII, RuII, and AgI. The coordination was investigated experimentally and theoretically. Ligand L x easily reacted at room temperature with cis-PtCl2(DMSO)2, Pd(CH3CN)4(BF4)2, CuCl2, RuCl(μ-Cl)(η6-p-cymene)2, and AgNO3 to give stable chelates PtCl2 L x (1), Pd(L x )2(BF4)2 (2), CuCl2(L x )2 (3), RuCl(η6-p-cymene)L x OTf (4), and Ag2(L x )2(NO3)2 (5), respectively, in 60−98% yield. The structures of 1−5 were unambiguously confirmed by NMR spectroscopy and single-crystal X-ray diffraction analysis. Density functional theory calculations were carried out in order to theoretically investigate the stabilization factors in 1−5. A comparison of the chelating properties of ligand L x was made with structurally similar and isomeric 1-(2-aminoethyl)-substituted 1,2,3-triazole (L y ) and 4-(2-aminoethyl)-substituted 1,2,3-triazole (L z ). The complexation affinity of L x was attributed to π-back-donation from the metal to the pendant pyridine side arm, whereas the stability of the complexes involving L y and L z mainly originates from efficient π-back-donation to the triazole ring.
Enzyme butyrylcholinesterase (BChE) shows increased activity in some brain regions after progression of Alzheimer's disease and is therefore one of the therapeutic targets for symptomatic treatment ...of this neurodegenerative disorder. The organoruthenium(II) complex (η
-
-cymene)Ru(II)(1-hydroxy-3-methoxypyridine-2(1
)-thionato)ptaPF
(
) was designed based on the results of our previous structure-activity studies. Inhibitory activity toward cholinesterase enzymes shows that this complex selectively, competitively, and reversibly inhibits horse serum BChE (hsBChE) with an IC
value of 2.88 µM. When tested at supra-pharmacological concentrations (30, 60, 90, and 120 µM),
had no significant effect on the maximal amplitude of nerve-evoked and directly elicited single-twitch and tetanic contractions. At the highest tested concentration (120 µM),
had no effect on resting membrane potential, but significantly decreased the amplitude of miniature end-plate potentials (MEPP) without reducing their frequency. The same concentration of
had no effect on the amplitude of end-plate potentials (EPP), however it shortened the half-decay time of MEPPs and EPPs. The decrease in the amplitude of MEPPs and shortening of the half-decay time of MEPPs and EPPs suggest a possible weak inhibitory effect on muscle-type nicotinic acetylcholine receptors (nAChR). These combined results show that, when applied at supra-pharmacological concentrations up to 120 µM,
does not importantly affect the physiology of neuromuscular transmission and skeletal muscle contraction.
Zinc pyrithione (1a), together with its analogues 1b-h and ruthenium pyrithione complex 2a, were synthesised and evaluated for the stability in biologically relevant media and anti-SARS-CoV-2 ...activity. Zinc pyrithione revealed potent in vitro inhibition of cathepsin L (IC
50
=1.88 ± 0.49 µM) and PL
Pro
(IC
50
=0.50 ± 0.07 µM), enzymes involved in SARS-CoV-2 entry and replication, respectively, as well as antiviral entry and replication properties in an ex vivo system derived from primary human lung tissue. Zinc complexes 1b-h expressed comparable in vitro inhibition. On the contrary, ruthenium complex 2a and the ligand pyrithione a itself expressed poor inhibition in mentioned assays, indicating the importance of the selection of metal core and structure of metal complex for antiviral activity. Safe, effective, and preferably oral at-home therapeutics for COVID-19 are needed and as such zinc pyrithione, which is also commercially available, could be considered as a potential therapeutic agent against SARS-CoV-2.
Two acetazolamide (AAZ) complexes with ruthenium(II) η
6
-p-cymene chloride were synthesised, characterised and tested for their inhibitory effects on several carbonic anhydrase (CA, EC 4.2.1.1) ...isoforms with pharmacological applications. Against human (h) isoform hCA I, the two complexes showed inhibition constants in the range of 8.5-23.4 nM (AAZ has a K
I
of 250 nM), against hCA II of 0.48-4.2 nM, whereas against hCA IX of 0.63-3.8 nM and against hCA XII of 0.04-0.52 nM, respectively. These highly effective ruthenium acetazolamide derivatives against the tumour-associated CA isoforms IX and XII warrant further in vivo studies, in hypoxic tumours overexpressing these enzymes.
Four novel ruthenium organometallic complexes: (η⁶-
-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)Cl (
), (η⁶-
-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)ptaPF₆ (
), ...(η⁶-
-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)Cl (
) and (η⁶-
-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)ptaPF₆ (
) were synthesized and characterized by elemental analysis, infrared (IR), UV-Vis, NMR and mass spectroscopy and single-crystal X-ray diffraction. The crystal structures and spectroscopic data were compared to the previously published complexes (η⁶-
-cymene)Ru(4,4,4-trifluoro-1-(4-chloro-phenyl)-1,3-butanedione)Cl (
) and (η⁶-
-cymene)Ru(4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butanedione)ptaPF₆ (
). The pairs of complexes
and
as well as
and
are isostructural, with the former crystallizing in triclinic P-1 and the latter in monoclinic P2₁/c. The ruthenium(II) ion is found in a pseudo-octahedral "piano-stool" geometry in all compounds. Bond lengths and angles are consistent with other complexes of this type. Complexes
and
exhibit some moderate dynamic disorder. The lack of hydrogen bonding and major π-π interactions means that most of intramolecular interactions are fairly weak and involve halogen atoms present. This was further confirmed by ¹H-NMR spectra, where a significant difference is observed only on the ligand near the halogen atom, following an expected trend. The combined data show that the difference in any activity depends substantially on the type of the ligand's substituted halogen atom.
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