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Papers by Andreas Scheurer

Research paper thumbnail of Low-Spin to Low-Spin Valence Tautomeric Transition in Cobalt Dioxolenes

Research paper thumbnail of Electronic structure study by means of x-ray spectroscopy and theoretical calculations of the “ferric star” single molecule magnet

Journal of Chemical Physics, Jan 24, 2006

Research paper thumbnail of Kohlenwasserstoffverbrückte Metallkomplexe. LI. Ein Bis(ferrocenyl-1,3-diketonat)-Kupfer(II)-Chelatkomplex als Wirt für Calcium- und Alkalimetallionen

Zeitschrift für anorganische und allgemeine Chemie, Oct 1, 2007

Research paper thumbnail of Reductive disproportionation of nitric oxide mediated by low-valent uranium

Chemical Communications, 2016

Research paper thumbnail of Unprecedented pairs of uranium (<scp>iv</scp>/<scp>v</scp>) hydroxido and (<scp>iv</scp>/<scp>v</scp>/<scp>vi</scp>) oxido complexes supported by a seven-coordinate cyclen-anchored tris-aryloxide ligand

Research paper thumbnail of A complete series of uranium(<scp>iv</scp>) complexes with terminal hydrochalcogenido (EH) and chalcogenido (E) ligands E = O, S, Se, Te

Dalton Transactions, 2019

Research paper thumbnail of A Pair of Cobalt(III/IV) Terminal Imido Complexes

Angewandte Chemie International Edition, 2021

The reaction of the cobalt(I) complex [(TIMMNmes)CoI](BPh4) (2) (TIMMNmes=tris‐[2‐(3‐mesitylimida... more The reaction of the cobalt(I) complex [(TIMMNmes)CoI](BPh4) (2) (TIMMNmes=tris‐[2‐(3‐mesitylimidazolin‐2‐ylidene)methyl]amine) with 1‐adamantylazide yields the cobalt(III) imido complex [(TIMMNmes)CoIII(NAd)](BPh4) (3) with concomitant release of dinitrogen. The N‐anchor in diamagnetic 3 features an unusual, planar tertiary amine, which results from repulsive electrostatic interaction with the filled d(z2)‐orbital of the cobalt ion and negative hyperconjugation with the neighboring methylene groups. One‐electron oxidation of 3 with [FeCp2](OTf) provides access to the rare, high‐valent cobalt(IV) imido complex [(TIMMNmes)CoIV(NAd)](OTf)2 (4). Despite a half‐life of less than 1 h at room temperature, 4 could be isolated at low temperatures in analytically pure form. Single‐crystal X‐ray diffractometry and EPR spectroscopy corroborate the molecular structure and the d5 low‐spin, S= , electron configuration. A computational analysis of 4 suggests high covalency within the CoIV=NAd bond ...

Research paper thumbnail of Phenanthroline-Based Molecular Switches for Prospective Chemical Grafting: A Synthetic Strategy and Its Application to Spin-Crossover Complexes

Inorganic Chemistry, 2019

Research paper thumbnail of C2-Symmetric (SO)N(SO) Sulfoxide Pincer Complexes of Mg and Pd: Helicity Switch by Ambidentate S/O-Coordination and Isolation of a Chiral Pd-Sulfenate

Research paper thumbnail of Uranium(iv) terminal hydrosulfido and sulfido complexes: insights into the nature of the uranium–sulfur bond

Chemical Science, 2016

We report the synthesis and characterization of terminal uranium(iv) hydrosulfido and sulfido com... more We report the synthesis and characterization of terminal uranium(iv) hydrosulfido and sulfido complexes, supported by the hexadentate, tacn-based ligand (Ad,MeArO)3tacn3−.

Research paper thumbnail of Self-Assembly Of 1D- And 3D-Networks Through Non-Coordination Intermolecular Forces: Synthesis And Crystal Structures Of Copper(I) Complexes Based On Pyridazine-Type Ligands

Zeitschrift für Naturforschung B, 2007

Reaction of [Cu2(H3CCN)2(μ-pydz)3][PF6]2 (1) with an excess of pyridazine or phthalazine yielded ... more Reaction of [Cu2(H3CCN)2(μ-pydz)3][PF6]2 (1) with an excess of pyridazine or phthalazine yielded the novel dinuclear complexes [Cu2(μ-pydz)3(pydz)2][PF6]2 (2) and [Cu2 (μ- pydz)(μ-phtz)2(phtz)2][PF6]2 (5), respectively. Depolymerisation of the coordination polymer 1 ∞ {[Cu(μ-pydz)2][PF6]} (3) in dichloromethane by addition of an excess of benzo[c]cinnoline afforded the dinuclear copper(I) salt [Cu2(μ-pydz)2(pydz)2(benzo[c]cinnoline)2][PF6]2 (4). Furthermore, a new route for the preparation of bis(benzonitrile)tris(μ-phthalazine)dicopper(I) bis(trifluoromethanesulfonate), [Cu2(C6H5CN)2(μ-phtz)3][CF3SO3]2 (7), was established from {[Cu(CF3SO3)]2 ・C6H5Me}, phthalazine and benzonitrile via the very air-sensitive intermediate [Cu2(CF3SO3)2(μ-phtz)3] (6). Copper(I) compounds 2, 4, and 7 were completely characterised and the molecular structures confirmed in the solid state by single-crystal X-ray structure determination. The analysis of the packing of the molecules in crystals of 4 and 7 ...

Research paper thumbnail of Magnetic Ground-State and Systematic X-ray Photoreduction Studies of an Iron-Based Star-Shaped Complex

The Journal of Physical Chemistry Letters, 2011

Research paper thumbnail of Uranium-mediated reductive conversion of CO2 to CO and carbonate in a single-vessel, closed synthetic cycle

Chemical Communications, 2012

Research paper thumbnail of Synthesis, magnetic properties, and STM spectroscopy of an unprecedented octanuclear chloro-bridged nickel(ii) double cubane

Dalton Transactions, 2012

Research paper thumbnail of Synthesis of Camphor-Derived Bis(pyrazolylpyridine) Rhodium(III) Complexes: Structure–Reactivity Relationships and Biological Activity

Inorganic Chemistry, Dec 19, 2018

Two novel rhodium(III) complexes, namely, [Rh III (X)Cl 3 ] (X = 2 2,6-bis((4S,7R)-7,8,8-trimethy... more Two novel rhodium(III) complexes, namely, [Rh III (X)Cl 3 ] (X = 2 2,6-bis((4S,7R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-1H-4,7-methanoindazol-3-yl)pyridine or 2,6-bis((4S,7R)-1,7,8,8-tetramethyl-4,5,6,7-tetrahydro-1H-4,7-methanoindazol-3-yl)pyridine), were synthesized from camphor derivatives of a bis(pyrazolylpyridine), tridentate nitrogen-donor chelate system, giving [Rh III (H 2 L*)-Cl 3 ] (1a) and [Rh III (Me 2 L*)Cl 3 ] (1b). A rhodium(III) terpyridine (terpy) ligand complex, [Rh III (terpy)Cl 3 ] (1c), was also synthesized. By single-crystal X-ray analysis, 1b crystallizes in an orthorhombic P2 1 2 1 2 1 system, with two molecules in the asymmetric unit. Tridentate coordination by the N,N,N-donor localizes the central nitrogen atom close to the rhodium(III) center. Compounds 1a and 1b were reactive toward L-methionine (L-Met), guanosine-5′-monophosphate (5′-GMP), and glutathione (GSH), with an order of reactivity of 5′-GMP > GSH > L-Met. The order of reactivity of the Rh III complexes was: 1b> 1a > 1c. The Rh III complexes showed affinity for calf thymus DNA and bovine serum albumin by UV−vis and emission spectral studies. Furthermore, 1b showed significant in vitro cytotoxicity against human epithelial colorectal carcinoma cells. Since the Rh III complexes have similar coordination modes, stability differences were evaluated by density functional theory (DFT) calculations (B3LYP(CPCM)/LANL2DZp). With (H 2 L*) and (terpy) as model ligands, DFT calculations suggest that both tridentate ligand systems have similar stability. In addition, molecular docking suggests that all test compounds have affinity for the minor groove of DNA, while 1b and 1c have potential for DNA intercalation.

Research paper thumbnail of New monofunctional platinum(II) and palladium(II) complexes: Studies of the nucleophilic substitution reactions, DNA/BSA interaction, and cytotoxic activity

Journal of Inorganic Biochemistry, Dec 1, 2018

Four new complexes [Pd(H 2 L tBu)Cl]Cl (Pd1), [Pt(H 2 L tBu)Cl]Cl (Pt1), [Pd(Me 2 L tBu)Cl]Cl (Pd... more Four new complexes [Pd(H 2 L tBu)Cl]Cl (Pd1), [Pt(H 2 L tBu)Cl]Cl (Pt1), [Pd(Me 2 L tBu)Cl]Cl (Pd2) and [Pt (Me 2 L tBu)Cl]Cl (Pt2) (where H 2 L tBu = 2,6-bis(5-(tert-butyl)-1H-pyrazol-3-yl)pyridine and Me 2 L tBu = 2,6-bis(5-(tert-butyl)-1-methyl-1H-pyrazol-3-yl)pyridine) were synthesized and characterized by elemental microanalysis, IR, 1 H NMR and ESI-MS methods. The reactivity of complexes towards thiourea (Tu), L-methionine (L-Met), Lcysteine (L-Cys) and guanosine-5′-monophosphate (5′-GMP) was investigated. The obtained order was established as follows: Tu > L-Cys > L-Met > 5′-GMP. Complexes Pd1 and Pt1, that contain H 2 L tBu as chelator, showed higher reactivity towards biomolecules than those with Me 2 L tBu. The interaction of complexes with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) was studied by UV-Vis and fluorescence spectroscopy. The results have shown that complexes can bind to DNA exhibiting high binding constants (K b = 10 4 M −1). Obtained results during the examination of competitive reaction with ethidium bromide (EB) showed that complexes can replace EB-bound DNA. High values of binding constants indicate good binding affinity of complexes towards BSA. We evaluated the stability differences between complexes based on terpy as well as H 2 L tBu /Me 2 L tBu by DFT calculations (B3LYP(CPCM)/LANL2DZp), showing that both tridentate ligand systems lead to complexes of similar stability. The results of biological testing showed that all complexes exert moderate to high selective cytotoxicity, inducing apoptosis and autophagy in HeLa and PANC-1 tumor cell lines. Pd1 exhibited the strongest cytotoxic effect. Finally, cell cycle analysis showed that in HeLa cells Pd1, Pd2 and Pt1 induced accumulation of cells in S phase, whereas in PANC-1 cells Pd2 and Pt1 induced G2/M cycle arrest and Pd1 induced G0/G1 arrest. 1. Introduction Platinum-based drugs are widely used anticancer agents with a broad range of antitumor activities [1,2]. Although, cisplatin, cis-[Pt (NH 3) 2 Cl 2 ], is one of the most common chemotherapy drugs, the acquired resistance and serious side effects limit its clinical use [3-5]. These limitations have stimulated the investigations for improvement of existing platinum antitumor drugs and development of new derivatives that display better therapeutic properties. Therefore, a significant number of different platinum complexes were synthesized with the goal to overcome the disadvantages of cisplatin [6-11]. However, the long-term application of platinum complexes was leading to examination of complexes of some other metals, such as palladium [12-14]. It is well established that palladium(II) complexes

Research paper thumbnail of Saalfrank-type {Fe<sub>2</sub>L<sub>3</sub>} host–guest complexes – prediction of ion selectivity by quantum chemical calculations VII

Journal of Coordination Chemistry, Sep 2, 2015

Based on density functional calculations (B3LYP/LANL2DZp (LANL2DZp=LANL2DZ augmented with polariz... more Based on density functional calculations (B3LYP/LANL2DZp (LANL2DZp=LANL2DZ augmented with polarization functions on non-hydrogen atoms)), the selectivity of the {2}-metallocryptand [Fe2L3] (L2− = 2,6-dibutane-1,3-dionylpyridine dianion) was investigated and the experimentally known K+, Sr2+ and Ba2+ cation selectivity rationalized. The rigidity of L2−, visible in the small torsion angles compared to previously investigated classical organic cryptands, can be identified as the origin of this discrimination. Derived from the hosted alkali and alkaline earth cations, the size of the {2}-metallocryptand’s [Fe2L3] cavity is analogous to the cryptand [2.2.phen]. Additionally, the quantum chemical calculations identified the {2}-metallocryptand [Fe2L3] as the first experimentally verified metalloproton sponge (calculated (B3LYP/LANL2DZp) proton affinity −259.8 kcal mol−1). This high gas-phase proton affinity clearly explains why empty [Fe2L3] was never observed, and only [(HN)3Fe2L3]3+ or [MFe2L3]m+ are known. Graphical abstract

Research paper thumbnail of Bis(triazinyl)pyridine complexes of Pt(II) and Pd(II): studies of the nucleophilic substitution reactions, DNA/HSA interactions, molecular docking and biological activity

Journal of Biological Inorganic Chemistry, Jul 15, 2021

Four new complexes of Pt(II) and Pd(II), [Pd(L1)Cl]Cl 1, [Pd(L2)Cl]Cl 2, [Pt(L1)Cl]Cl 3 and [Pt(L... more Four new complexes of Pt(II) and Pd(II), [Pd(L1)Cl]Cl 1, [Pd(L2)Cl]Cl 2, [Pt(L1)Cl]Cl 3 and [Pt(L2)Cl]Cl 4 (where L1 = 2,6-bis(5,6-diphenyl-1,2,4-triazin-3-yl)pyridine and L2 = 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine), were synthesized. Characterization of the complexes was performed using elemental analysis, IR, 1H NMR spectroscopy and MALDI-TOF mass spectrometry. The substitution reactions of 1-4 complexes with L-methionine (L-met), L-cysteine (L-cys) and guanosine-5'-monophosphate (5'-GMP), were studied spectrophotometrically at physiological conditions. Complexes with ligand L1 (1 or 3) were more reactive than those with ligand L2 (2 or 4) by a factor ranging up to 1.57 and 3.71, respectively. The order of reactivity of the nucleophiles was: L-met > L-cys > 5'-GMP. The interactions of complexes with calf thymus-DNA (CT-DNA) and human serum albumin (HSA) were studied by Uv-Vis absorption and fluorescence emission spectroscopy. Competitive binding studies with intercalative agent ethidium bromide (EB) and minor groove binder Hoechst 33258 were performed as well. All studied complexes can interact with DNA through the intercalation and minor groove binding, where the latter was preferred. The binding constants (103 and 104 M-1) for the interaction of complexes with HSA indicate the moderate binding affinity of complexes 1-4 to protein. The trends in the experimental results of binding studies between complexes 3 and 4 with DNA and HSA were compared to those obtained from the molecular docking study. Biological evaluation of cytotoxicity of 1 and 2 on HCT-116 and MDA-MB-231 cell lines showed significant cytotoxic and prooxidative character, while 2 also exerted extraordinary selectivity towards colon cancer in comparison to breast cancer cells. The nucleophilic substitution reactions, DNA/HSA interactions, molecular docking and biological activity of bis(triazinyl)pyridine complexes of Pt(II) and Pd(II) were studied.

Research paper thumbnail of The influence of the bridgehead in Saalfrank-type cryptands: prediction of ion selectivity by quantum chemical calculations XII†

Journal of Coordination Chemistry, 2020

We examined the cation selectivity of the Saalfrank-type f2g-metallocryptands [Ga 2 R 3 ] and [Fe... more We examined the cation selectivity of the Saalfrank-type f2g-metallocryptands [Ga 2 R 3 ] and [Fe 2 R 3 ] (R: 1,1'-(pyridine-2,6-diyl)bis(2-(1H-tetrazol-5-yl)ethan-1-one)) with alkaline and earth alkaline metal ions by means of DFT calculations (B3LYP/LANL2DZp) to obtain a better insight into the influence of the bridge head metal ions responsible for the cryptands ion selectivity. Based on our DFT calculations, notably the application of model equations and geometric features regarding the flexibility of the f2g-metallocryptands, we identified K þ , Sr 2þ and Ba 2þ as the best fitting ions. While [Fe 2 R 3 ] has a cavity a bit larger than [Ga 2 R 3 ], it prefers the Ba 2þ cation, whereas [Ga 2 R 3 ] selects the smaller Sr 2þ cation. The good flexibility of the investigated hosts is provided by the oxygen-donor moieties of the f2g-metallocryptands.

Research paper thumbnail of Experimental and quantum chemical study оn the DNA/protein binding and the biological activity of a rhodium(iii) complex with 1,2,4-triazole as an inert ligand

Dalton Transactions, 2020

A rhodium(iii) complex with 1,2,4-triazole and a pincer type nitrogen-donor ligand was synthesize... more A rhodium(iii) complex with 1,2,4-triazole and a pincer type nitrogen-donor ligand was synthesized, and its interaction with biomolecules was examined.

Research paper thumbnail of Low-Spin to Low-Spin Valence Tautomeric Transition in Cobalt Dioxolenes

Research paper thumbnail of Electronic structure study by means of x-ray spectroscopy and theoretical calculations of the “ferric star” single molecule magnet

Journal of Chemical Physics, Jan 24, 2006

Research paper thumbnail of Kohlenwasserstoffverbrückte Metallkomplexe. LI. Ein Bis(ferrocenyl-1,3-diketonat)-Kupfer(II)-Chelatkomplex als Wirt für Calcium- und Alkalimetallionen

Zeitschrift für anorganische und allgemeine Chemie, Oct 1, 2007

Research paper thumbnail of Reductive disproportionation of nitric oxide mediated by low-valent uranium

Chemical Communications, 2016

Research paper thumbnail of Unprecedented pairs of uranium (<scp>iv</scp>/<scp>v</scp>) hydroxido and (<scp>iv</scp>/<scp>v</scp>/<scp>vi</scp>) oxido complexes supported by a seven-coordinate cyclen-anchored tris-aryloxide ligand

Research paper thumbnail of A complete series of uranium(<scp>iv</scp>) complexes with terminal hydrochalcogenido (EH) and chalcogenido (E) ligands E = O, S, Se, Te

Dalton Transactions, 2019

Research paper thumbnail of A Pair of Cobalt(III/IV) Terminal Imido Complexes

Angewandte Chemie International Edition, 2021

The reaction of the cobalt(I) complex [(TIMMNmes)CoI](BPh4) (2) (TIMMNmes=tris‐[2‐(3‐mesitylimida... more The reaction of the cobalt(I) complex [(TIMMNmes)CoI](BPh4) (2) (TIMMNmes=tris‐[2‐(3‐mesitylimidazolin‐2‐ylidene)methyl]amine) with 1‐adamantylazide yields the cobalt(III) imido complex [(TIMMNmes)CoIII(NAd)](BPh4) (3) with concomitant release of dinitrogen. The N‐anchor in diamagnetic 3 features an unusual, planar tertiary amine, which results from repulsive electrostatic interaction with the filled d(z2)‐orbital of the cobalt ion and negative hyperconjugation with the neighboring methylene groups. One‐electron oxidation of 3 with [FeCp2](OTf) provides access to the rare, high‐valent cobalt(IV) imido complex [(TIMMNmes)CoIV(NAd)](OTf)2 (4). Despite a half‐life of less than 1 h at room temperature, 4 could be isolated at low temperatures in analytically pure form. Single‐crystal X‐ray diffractometry and EPR spectroscopy corroborate the molecular structure and the d5 low‐spin, S= , electron configuration. A computational analysis of 4 suggests high covalency within the CoIV=NAd bond ...

Research paper thumbnail of Phenanthroline-Based Molecular Switches for Prospective Chemical Grafting: A Synthetic Strategy and Its Application to Spin-Crossover Complexes

Inorganic Chemistry, 2019

Research paper thumbnail of C2-Symmetric (SO)N(SO) Sulfoxide Pincer Complexes of Mg and Pd: Helicity Switch by Ambidentate S/O-Coordination and Isolation of a Chiral Pd-Sulfenate

Research paper thumbnail of Uranium(iv) terminal hydrosulfido and sulfido complexes: insights into the nature of the uranium–sulfur bond

Chemical Science, 2016

We report the synthesis and characterization of terminal uranium(iv) hydrosulfido and sulfido com... more We report the synthesis and characterization of terminal uranium(iv) hydrosulfido and sulfido complexes, supported by the hexadentate, tacn-based ligand (Ad,MeArO)3tacn3−.

Research paper thumbnail of Self-Assembly Of 1D- And 3D-Networks Through Non-Coordination Intermolecular Forces: Synthesis And Crystal Structures Of Copper(I) Complexes Based On Pyridazine-Type Ligands

Zeitschrift für Naturforschung B, 2007

Reaction of [Cu2(H3CCN)2(μ-pydz)3][PF6]2 (1) with an excess of pyridazine or phthalazine yielded ... more Reaction of [Cu2(H3CCN)2(μ-pydz)3][PF6]2 (1) with an excess of pyridazine or phthalazine yielded the novel dinuclear complexes [Cu2(μ-pydz)3(pydz)2][PF6]2 (2) and [Cu2 (μ- pydz)(μ-phtz)2(phtz)2][PF6]2 (5), respectively. Depolymerisation of the coordination polymer 1 ∞ {[Cu(μ-pydz)2][PF6]} (3) in dichloromethane by addition of an excess of benzo[c]cinnoline afforded the dinuclear copper(I) salt [Cu2(μ-pydz)2(pydz)2(benzo[c]cinnoline)2][PF6]2 (4). Furthermore, a new route for the preparation of bis(benzonitrile)tris(μ-phthalazine)dicopper(I) bis(trifluoromethanesulfonate), [Cu2(C6H5CN)2(μ-phtz)3][CF3SO3]2 (7), was established from {[Cu(CF3SO3)]2 ・C6H5Me}, phthalazine and benzonitrile via the very air-sensitive intermediate [Cu2(CF3SO3)2(μ-phtz)3] (6). Copper(I) compounds 2, 4, and 7 were completely characterised and the molecular structures confirmed in the solid state by single-crystal X-ray structure determination. The analysis of the packing of the molecules in crystals of 4 and 7 ...

Research paper thumbnail of Magnetic Ground-State and Systematic X-ray Photoreduction Studies of an Iron-Based Star-Shaped Complex

The Journal of Physical Chemistry Letters, 2011

Research paper thumbnail of Uranium-mediated reductive conversion of CO2 to CO and carbonate in a single-vessel, closed synthetic cycle

Chemical Communications, 2012

Research paper thumbnail of Synthesis, magnetic properties, and STM spectroscopy of an unprecedented octanuclear chloro-bridged nickel(ii) double cubane

Dalton Transactions, 2012

Research paper thumbnail of Synthesis of Camphor-Derived Bis(pyrazolylpyridine) Rhodium(III) Complexes: Structure–Reactivity Relationships and Biological Activity

Inorganic Chemistry, Dec 19, 2018

Two novel rhodium(III) complexes, namely, [Rh III (X)Cl 3 ] (X = 2 2,6-bis((4S,7R)-7,8,8-trimethy... more Two novel rhodium(III) complexes, namely, [Rh III (X)Cl 3 ] (X = 2 2,6-bis((4S,7R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-1H-4,7-methanoindazol-3-yl)pyridine or 2,6-bis((4S,7R)-1,7,8,8-tetramethyl-4,5,6,7-tetrahydro-1H-4,7-methanoindazol-3-yl)pyridine), were synthesized from camphor derivatives of a bis(pyrazolylpyridine), tridentate nitrogen-donor chelate system, giving [Rh III (H 2 L*)-Cl 3 ] (1a) and [Rh III (Me 2 L*)Cl 3 ] (1b). A rhodium(III) terpyridine (terpy) ligand complex, [Rh III (terpy)Cl 3 ] (1c), was also synthesized. By single-crystal X-ray analysis, 1b crystallizes in an orthorhombic P2 1 2 1 2 1 system, with two molecules in the asymmetric unit. Tridentate coordination by the N,N,N-donor localizes the central nitrogen atom close to the rhodium(III) center. Compounds 1a and 1b were reactive toward L-methionine (L-Met), guanosine-5′-monophosphate (5′-GMP), and glutathione (GSH), with an order of reactivity of 5′-GMP > GSH > L-Met. The order of reactivity of the Rh III complexes was: 1b> 1a > 1c. The Rh III complexes showed affinity for calf thymus DNA and bovine serum albumin by UV−vis and emission spectral studies. Furthermore, 1b showed significant in vitro cytotoxicity against human epithelial colorectal carcinoma cells. Since the Rh III complexes have similar coordination modes, stability differences were evaluated by density functional theory (DFT) calculations (B3LYP(CPCM)/LANL2DZp). With (H 2 L*) and (terpy) as model ligands, DFT calculations suggest that both tridentate ligand systems have similar stability. In addition, molecular docking suggests that all test compounds have affinity for the minor groove of DNA, while 1b and 1c have potential for DNA intercalation.

Research paper thumbnail of New monofunctional platinum(II) and palladium(II) complexes: Studies of the nucleophilic substitution reactions, DNA/BSA interaction, and cytotoxic activity

Journal of Inorganic Biochemistry, Dec 1, 2018

Four new complexes [Pd(H 2 L tBu)Cl]Cl (Pd1), [Pt(H 2 L tBu)Cl]Cl (Pt1), [Pd(Me 2 L tBu)Cl]Cl (Pd... more Four new complexes [Pd(H 2 L tBu)Cl]Cl (Pd1), [Pt(H 2 L tBu)Cl]Cl (Pt1), [Pd(Me 2 L tBu)Cl]Cl (Pd2) and [Pt (Me 2 L tBu)Cl]Cl (Pt2) (where H 2 L tBu = 2,6-bis(5-(tert-butyl)-1H-pyrazol-3-yl)pyridine and Me 2 L tBu = 2,6-bis(5-(tert-butyl)-1-methyl-1H-pyrazol-3-yl)pyridine) were synthesized and characterized by elemental microanalysis, IR, 1 H NMR and ESI-MS methods. The reactivity of complexes towards thiourea (Tu), L-methionine (L-Met), Lcysteine (L-Cys) and guanosine-5′-monophosphate (5′-GMP) was investigated. The obtained order was established as follows: Tu > L-Cys > L-Met > 5′-GMP. Complexes Pd1 and Pt1, that contain H 2 L tBu as chelator, showed higher reactivity towards biomolecules than those with Me 2 L tBu. The interaction of complexes with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) was studied by UV-Vis and fluorescence spectroscopy. The results have shown that complexes can bind to DNA exhibiting high binding constants (K b = 10 4 M −1). Obtained results during the examination of competitive reaction with ethidium bromide (EB) showed that complexes can replace EB-bound DNA. High values of binding constants indicate good binding affinity of complexes towards BSA. We evaluated the stability differences between complexes based on terpy as well as H 2 L tBu /Me 2 L tBu by DFT calculations (B3LYP(CPCM)/LANL2DZp), showing that both tridentate ligand systems lead to complexes of similar stability. The results of biological testing showed that all complexes exert moderate to high selective cytotoxicity, inducing apoptosis and autophagy in HeLa and PANC-1 tumor cell lines. Pd1 exhibited the strongest cytotoxic effect. Finally, cell cycle analysis showed that in HeLa cells Pd1, Pd2 and Pt1 induced accumulation of cells in S phase, whereas in PANC-1 cells Pd2 and Pt1 induced G2/M cycle arrest and Pd1 induced G0/G1 arrest. 1. Introduction Platinum-based drugs are widely used anticancer agents with a broad range of antitumor activities [1,2]. Although, cisplatin, cis-[Pt (NH 3) 2 Cl 2 ], is one of the most common chemotherapy drugs, the acquired resistance and serious side effects limit its clinical use [3-5]. These limitations have stimulated the investigations for improvement of existing platinum antitumor drugs and development of new derivatives that display better therapeutic properties. Therefore, a significant number of different platinum complexes were synthesized with the goal to overcome the disadvantages of cisplatin [6-11]. However, the long-term application of platinum complexes was leading to examination of complexes of some other metals, such as palladium [12-14]. It is well established that palladium(II) complexes

Research paper thumbnail of Saalfrank-type {Fe<sub>2</sub>L<sub>3</sub>} host–guest complexes – prediction of ion selectivity by quantum chemical calculations VII

Journal of Coordination Chemistry, Sep 2, 2015

Based on density functional calculations (B3LYP/LANL2DZp (LANL2DZp=LANL2DZ augmented with polariz... more Based on density functional calculations (B3LYP/LANL2DZp (LANL2DZp=LANL2DZ augmented with polarization functions on non-hydrogen atoms)), the selectivity of the {2}-metallocryptand [Fe2L3] (L2− = 2,6-dibutane-1,3-dionylpyridine dianion) was investigated and the experimentally known K+, Sr2+ and Ba2+ cation selectivity rationalized. The rigidity of L2−, visible in the small torsion angles compared to previously investigated classical organic cryptands, can be identified as the origin of this discrimination. Derived from the hosted alkali and alkaline earth cations, the size of the {2}-metallocryptand’s [Fe2L3] cavity is analogous to the cryptand [2.2.phen]. Additionally, the quantum chemical calculations identified the {2}-metallocryptand [Fe2L3] as the first experimentally verified metalloproton sponge (calculated (B3LYP/LANL2DZp) proton affinity −259.8 kcal mol−1). This high gas-phase proton affinity clearly explains why empty [Fe2L3] was never observed, and only [(HN)3Fe2L3]3+ or [MFe2L3]m+ are known. Graphical abstract

Research paper thumbnail of Bis(triazinyl)pyridine complexes of Pt(II) and Pd(II): studies of the nucleophilic substitution reactions, DNA/HSA interactions, molecular docking and biological activity

Journal of Biological Inorganic Chemistry, Jul 15, 2021

Four new complexes of Pt(II) and Pd(II), [Pd(L1)Cl]Cl 1, [Pd(L2)Cl]Cl 2, [Pt(L1)Cl]Cl 3 and [Pt(L... more Four new complexes of Pt(II) and Pd(II), [Pd(L1)Cl]Cl 1, [Pd(L2)Cl]Cl 2, [Pt(L1)Cl]Cl 3 and [Pt(L2)Cl]Cl 4 (where L1 = 2,6-bis(5,6-diphenyl-1,2,4-triazin-3-yl)pyridine and L2 = 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine), were synthesized. Characterization of the complexes was performed using elemental analysis, IR, 1H NMR spectroscopy and MALDI-TOF mass spectrometry. The substitution reactions of 1-4 complexes with L-methionine (L-met), L-cysteine (L-cys) and guanosine-5'-monophosphate (5'-GMP), were studied spectrophotometrically at physiological conditions. Complexes with ligand L1 (1 or 3) were more reactive than those with ligand L2 (2 or 4) by a factor ranging up to 1.57 and 3.71, respectively. The order of reactivity of the nucleophiles was: L-met > L-cys > 5'-GMP. The interactions of complexes with calf thymus-DNA (CT-DNA) and human serum albumin (HSA) were studied by Uv-Vis absorption and fluorescence emission spectroscopy. Competitive binding studies with intercalative agent ethidium bromide (EB) and minor groove binder Hoechst 33258 were performed as well. All studied complexes can interact with DNA through the intercalation and minor groove binding, where the latter was preferred. The binding constants (103 and 104 M-1) for the interaction of complexes with HSA indicate the moderate binding affinity of complexes 1-4 to protein. The trends in the experimental results of binding studies between complexes 3 and 4 with DNA and HSA were compared to those obtained from the molecular docking study. Biological evaluation of cytotoxicity of 1 and 2 on HCT-116 and MDA-MB-231 cell lines showed significant cytotoxic and prooxidative character, while 2 also exerted extraordinary selectivity towards colon cancer in comparison to breast cancer cells. The nucleophilic substitution reactions, DNA/HSA interactions, molecular docking and biological activity of bis(triazinyl)pyridine complexes of Pt(II) and Pd(II) were studied.

Research paper thumbnail of The influence of the bridgehead in Saalfrank-type cryptands: prediction of ion selectivity by quantum chemical calculations XII†

Journal of Coordination Chemistry, 2020

We examined the cation selectivity of the Saalfrank-type f2g-metallocryptands [Ga 2 R 3 ] and [Fe... more We examined the cation selectivity of the Saalfrank-type f2g-metallocryptands [Ga 2 R 3 ] and [Fe 2 R 3 ] (R: 1,1'-(pyridine-2,6-diyl)bis(2-(1H-tetrazol-5-yl)ethan-1-one)) with alkaline and earth alkaline metal ions by means of DFT calculations (B3LYP/LANL2DZp) to obtain a better insight into the influence of the bridge head metal ions responsible for the cryptands ion selectivity. Based on our DFT calculations, notably the application of model equations and geometric features regarding the flexibility of the f2g-metallocryptands, we identified K þ , Sr 2þ and Ba 2þ as the best fitting ions. While [Fe 2 R 3 ] has a cavity a bit larger than [Ga 2 R 3 ], it prefers the Ba 2þ cation, whereas [Ga 2 R 3 ] selects the smaller Sr 2þ cation. The good flexibility of the investigated hosts is provided by the oxygen-donor moieties of the f2g-metallocryptands.

Research paper thumbnail of Experimental and quantum chemical study оn the DNA/protein binding and the biological activity of a rhodium(iii) complex with 1,2,4-triazole as an inert ligand

Dalton Transactions, 2020

A rhodium(iii) complex with 1,2,4-triazole and a pincer type nitrogen-donor ligand was synthesize... more A rhodium(iii) complex with 1,2,4-triazole and a pincer type nitrogen-donor ligand was synthesized, and its interaction with biomolecules was examined.