15N NMR Research Articles

Raman, ATRIR and NMR spectra, conformational stability, vibrational assignments, normal coordinates analysis and DFT calculations of hydrochlorothiazide drug

The Raman (4000-50 cm−1), attenuated total reflectance (ATR) infrared (4000-400 cm−1) spectra of Hydrochlorothiazide (C7H8ClN3O4S2; HCTZ) have been recorded in the solid state in addition to LCMS in the dimer and trimer ranges. The 1H, 13C and 15N NMR spectra were also recorded in addition to DEPT (45, 90 and 135) of HCTZ sample dissolved DMSO‑d6. Initially, three conformers resulting from the rotation of -SO2NH2 moiety around C9-S11 were proposed, namely gauche, trans and cis conformers. And then Density Functional Theory (DFT) calculations for an isolated molecule were carried out employing both B3LYP and P3PW91 methods at 6-31G(d), 6-311+G(d), 6–311++G(d,p) basis set. The cis isomer is a transition state owing to the prediction of an imaginary wavenumber, while the gauche being more stable than trans by ∼438–538 cm−1 (∼1.25–1.54 kcal) employing the afore-mentioned computations. Moreover, we carried out a potential surface scan for the gauche to determine SO2NH2 barriers to internal rotations and to ensure the optimal gauche is the most stable conformer. Aided by normal coordinate analysis (NCA) in addition to the atomic displacements in Cartesian coordinates (ADCC), confident vibrational assignment of the observed infrared and Raman bands are proposed for all fundamentals of the gauche rotamer. Nevertheless, force constants (FCs) in internal coordinates were also estimated using the above-mentioned methods and basis sets as well. The 1H, 13C and 15N chemical shifts were also correlated to their corresponding atoms. The results are reported herein and compared with HCTZ and its cocrystals whenever appropriate.

Investigation of hydrogen bonds in proton transfer complexes derived from the reaction of 2- and 4-(N,N-dimethylamino)pyridines with chloranilic acid

New complexes of 2-(N,N-dimethylamino)pyridine with chloranilic acid (2-DMAP + CLA) and 4-(N,N-dimethylamino)pyridine with chloranilic acid (4-DMAP + CLA) were synthesized and characterized by single crystal X-ray diffraction, infrared spectroscopy, thermal analysis methods and 1H, 13C and 15N NMR spectroscopy. The NMR spectroscopies were carried out in both, DMSO solution and in the solid state (CPMAS NMR). The 2-DMAP + CLA and 4-DMAP + CLA complexes crystallize in centrosymmetric P-1 and P21/c space group, respectively.In both complexes, the phenomenon of proton transfer is observed, which results in the formation of strong N+–H···O– hydrogen bonds. Thermal decompositions of 2-DMAP + CLA and 4-DMAP + CLA complexes were studied by thermogravimetric analysis. Temperature dependent IR spectra revealed that methyl groups of 4-DMAP + CLA perform fast stochastic reorientational motion at room temperature which is slowed on cooling while in 2-DMAP + CLA reonrientational motion of CH3 groups is much slower due to steric effects.

Interaction of electrolyte molecules with the surface of porous carbon: NMR study

Electrochemical double-layer capacitors use porous carbons as the electrode material, and improving their performance requires an understanding of the electrolyte−carbon surface interactions. 13C, 14N, and 11B NMR spectroscopy were used to investigate the behaviour of the electrolytes [C(OCH3)3NH3]+Cl- and [N(CH2CH3)]+BF4- on the surface of porous carbon in D2O solutions. A chemical shift of 13C has been found in the fragments N–C, indicating electron density redistribution between nitrogen atoms and alkyl fragments. The presence of a signal with a chemical shift of d = 7.7 confirms the structuring of the electrolytic layer of water solution [N(CH2CH3)]+BF4-.

Bonding and Reactivity of d0 Transition Metal Imido Complexes Encoded in Their 15N NMR Signatures.

Terminal imido complexes containing metal-nitrogen multiple bonds have been widely used in organometallic chemistry and homogeneous catalysis. The role of terminal imido ligands spans from reactive sites to spectator motifs, largely depending on the nature of the metal center and its specific coordination sphere. Aiming at identifying reactivity descriptors for M-N multiple bonds, we herein explore solid-state 15N NMR spectroscopy (ssNMR) on early transition metal terminal imido complexes augmented by computational studies and show that the asymmetry parameter, κ (skew, 1 ≥ κ ≥ -1), readily available from experiments or calculations, is diagnostic for the reactivity of M-N multiple bonds in imido complexes. While inert imido ligands exhibit skew values (κ) close to 1, highly reactive imido moieties display significantly lower skew values (κ ≪ 1) as found in metallocene or bis-imido complexes. Natural chemical shielding analysis shows that skew values away from 1 are associated with an asymmetric development of π-orbitals around the M-N multiple bond of the imido moiety, with a larger double-bond character for reactive imido. Notably, this descriptor does not directly relate to the M-N-C bond angle, illustrating the shortcoming of evaluating bonding and hybridization from geometrical parameters alone. Overall, this descriptor enables to obtain direct experimental evidence for the π-loading effect seen in bis(imido) and related complexes, thus explaining their bonding/reactivity.

14N NMR of magnetically oriented microcrystals

14N NMR of magnetically oriented microcrystals is reported. With a home-built 1H–13C–14N probe capable of modulating the rotation of the sample around the axis normal to the magnetic field, magnetically oriented microcrystal suspension (MOMS) of l-alanine is made. 14N NMR spectra acquired with various timings during intermittent rotation lead to a rotation pattern of the MOMS similar to that of a single crystal. The effect of orientational distribution of the microcrystals to broadening of the resonance line is discussed.

Symmetry of a partially-ligated state maintained by dynamics in a negatively cooperative system

Symmetry was a key concept underlying the MWC model for allostery advanced in 1965 by Monod, Wyman, and Changeux. The reciprocal interactions of symmetrically-arranged identical subunits were proposed to stabilize multimeric assemblies together with the free energy from bound ligands that progressively favor a monomer-like state. Structural symmetry of subunits was assumed to be maintained in the partially-ligated states, even if ligand placement itself is not symmetric. Partially-ligated states can be populated sufficiently for experimental study only in negatively cooperative systems, which were not considered in the MWC model. The work reported here uses 1H, 13C, 15N, and 19F NMR to evaluate the structural symmetry of the hexameric arginine repressor of E. coli, a negatively cooperative system, with a single bound L-arginine ligand. The analysis indicates that the singly-ligated hexamer maintains structural symmetry as probed by these four NMR nuclei. The results are consistent with earlier molecular dynamics simulations suggesting that the global dynamics of the singly-ligated assembly are harnessed to maintain structural symmetry. The results extend MWC symmetry concepts to this negatively cooperative system, and indicate a role for global dynamics in allostery.

N-Acetonitrile functionalized 3-nitrotriazole: Precursor to nitrogen rich stable and insensitive energetic materials

In the field of energetic materials, prime attention has been given to the synthesis of environmentally compatible energetic materials having an adequate balance between energy and stability. For this purpose, nitrogen-rich heterocyclic rings have contributed as pivotal frameworks. Nitro-functionalized 1,2,4-triazoles have been profusely used as a constituent for synthesizing high-performing energetic materials (EMs) due to their high nitrogen content, good thermal stability, and modifiable sites via functionalization. Combination with a different energetic scaffold may provide an opportunity for accessible tailoring. In this work, in an effort to investigate the potential of 3-nitrotriazoles, its N-acetonitrile derivative 2 was synthesized, which was further converted to various explosophores. N-methylene-C bridged asymmetrically connected tetrazole (3) and 1,2,4-oxadiazole (9 and 10) based EMs have been synthesized. Further tuning of energetic properties via salt formation strategy was employed for the synthesis of compounds 4–7, 11 and 12. 1,2,4-oxadiazole-based compound 9 was also confirmed via X-ray diffraction analysis, and 10 was analyzed with 15N NMR spectroscopy. Compounds 3, 4, 5, 7 and 9 exhibited high thermal stabilities and were found to be insensitive towards impact and friction. Compounds 5, 6, and 10 exhibited detonation performance comparable to the conventional insensitive explosive TATB.

The Scope of the Applicability of Non-relativistic DFT Calculations of NMR Chemical Shifts in Pyridine-Metal Complexes for Applied Applications.

Heavy metals are toxic, but it is impossible to stop using them. Considering the variety of molecular systems in which they can be present, the multicomponent nature and disorder of the structure of such systems, one of the most effective methods for studying them is NMR spectroscopy. This determines the need to calculate NMR chemical shifts for expected model systems. For elements beyond the third row of the periodic table, corrections for relativistic effects are necessary when calculating NMR parameters. Such corrections may be necessary even for light atoms due to the shielding effect of a neighboring heavy atom. This work examines the extent to which non-relativistic DFT calculations are able to reproduce experimental 15N and 113Cd NMR chemical shift tensors in pyridine-metal coordination complexes. It is shown that while for the calculation of 15N NMR chemical shift tensors there is no real need to consider relativistic corrections, for 113Cd, on the contrary, none of the tested calculation methods could reproduce the experimentally obtained tensor to any extent correctly.

Spectroscopic Study on the Complexation of trivalent Actinide and Lanthanide ions with TEDGA in Solution

AbstractNMR spectroscopy studies on the complexation of La(III), Sm(III), Lu(III), Y(III) and Am(III) with N,N,N′,N′‐tetraethyldiglycolamide (TEDGA) have been performed. Initial studies concerning the stoichiometry of the complexes prove the formation of [M(TEDGA)3]3+ in D2O and [M(TEDGA)1‐3]3+ in CD3CN. Decreasing the solvent polarity translates to an increase of the complex stability as shown by complementary TRLFS studies with Cm(III). Due to delocalization of the lone electron pair of the amide nitrogen atom, the M(III)−O interaction has been studied indirectly by collecting 13C and 15N NMR data. The observed chemical shifts prove that the interaction of the trivalent ions, An(III) and Ln(III), and TEDGA is almost identical.

Experimental and Theoretical Studies on the Reactions of Aliphatic Imines with Isocyanates.

In the context of a project aiming at the replacement of the 3-substituted β-lactam ring in classical β-lactam antibiotics by an N(3)-acyl-1,3-diazetidinone moiety, we have investigated the reaction of isocyanates with imines derived from allyl glycinate and differently substituted propionaldehydes. Imines of aromatic aldehydes with anilines have been reported to react with acyl isocyanates to give 1,3-diazetidinones or 2,3-dihydro-4H-1,3,5-oxadiazin-4-ones, via [2+2] or [4+2] cycloaddition, respectively. However, neither of these products was formed with imines derived from allyl glycinate and 2-(mono)methyl propionaldehydes. α,α-Dimethylation of the imine enabled the [4+2] cycloaddition pathway, but the desired 1,3-diazetidinone products were not observed. Surprisingly, the imines obtained from thioesters of 2,2-dimethyl 3-oxo propionic acid reacted with aryl isocyanates or with benzyl isocyanate to give 5,5-dimethyl-2,4-dioxo-6-(aryl-/alkylthio)tetrahydropyrimidines, via thiol displacement and re-addition to a putative six-membered iminium intermediate. These experimental results obtained for the reactions could be rationalized by DFT calculations. In addition, we have shown that N(3)-acyl-1,3-diazetidinone and 2,3-dihydro-4H-1,3,5-oxadiazin-4-one products can be distinguished based on experimental IR data in combination with theoretical reference spectra employing the IR spectra alignment (IRSA) algorithm. This discrimination was not possible by means of 1 H, 13 C, or 15 N NMR spectroscopy.

Microwave-assisted synthesis of crosslinked ureido chitosan for hemostatic applications

In this study, we present a facile method for introducing hydrophilic ureido groups (NH2-CO-NH-) into chitosan using a microwave-assisted reaction with molten urea, with the aim of enhancing chitosan's interaction with blood components for improved hemostasis. The formation of the ureido groups through nucleophilic addition reaction between the amine groups in chitosan and in situ generated isocyanic acid was confirmed by FTIR, CP/TOSS 13C NMR, and CP/MAS 15N NMR spectroscopic techniques. However, in stark contrast to the glucans, the said modification introduced extensive crosslinking in chitosan. Spectroscopic studies identified these crosslinks as carbamate bridges (-NH-COO-), which were likely formed by the reaction between the ureido groups and hydroxyl groups of adjacent chains through an isocyanate intermediate. These carbamate bridges improved ureido chitosan's environmental stability, making it particularly resistant to changes in pH and temperature. In comparison to chitosan, the crosslinked ureido chitosan synthesized here exhibited good biocompatibility and cell adhesion, rapidly arrested the bleeding in a punctured artery with minimal hemolysis, and induced early activation and aggregation of platelets. These properties render it an invaluable material for applications in hemostasis, particularly in scenarios that necessitate stability against pH variations and degradation.

Sensitivity-enhanced NMR 15N R1 and R1ρ relaxation experiments for the investigation of intrinsically disordered proteins at high magnetic fields

NMR relaxation experiments provide residue-specific insights into the structural dynamics of proteins. Here, we present an optimized set of sensitivity-enhanced 15N R1 and R1ρ relaxation experiments applicable to fully protonated proteins. The NMR pulse sequences are conceptually similar to the set of TROSY-based sequences and their HSQC counterpart (Lakomek et al., J. Biomol. NMR 2012). Instead of the TROSY read-out scheme, a sensitivity-enhanced HSQC read-out scheme is used, with improved and easier optimized water suppression. The presented pulse sequences are applied on the cytoplasmic domain of the SNARE protein Synpatobrevin-2 (Syb-2), which is intrinsically disordered in its monomeric pre-fusion state. A two-fold increase in the obtained signal-to-noise ratio is observed for this intrinsically disordered protein, therefore offering a four-fold reduction of measurement time compared to the TROSY-detected version. The inter-scan recovery delay can be shortened to two seconds. Pulse sequences were tested at 600 MHz and 1200 MHz 1H Larmor frequency, thus applicable over a wide magnetic field range. A comparison between protonated and deuterated protein samples reveals high agreement, indicating that reliable 15N R1 and R1ρ rate constants can be extracted for fully protonated and deuterated samples. The presented pulse sequences will benefit not only for IDPs but also for an entire range of low and medium-sized proteins.

T-Shaped Palladium and Platinum {MNO}10 Nitrosyl Complexes.

The synthesis and characterization of a homologous series of T-shaped {MNO}10 nitrosyl complexes of the form [M(PR3)2(NO)]+ (M = Pd, Pt; R = tBu, Ad) are reported. These diamagnetic nitrosyls are obtained from monovalent or zerovalent precursors by treatment with NO and NO+, respectively, and are notable for distinctly bent M-NO angles of ∼123° in the solid state. Adoption of this coordination mode in solution is also supported by the analysis of isotopically enriched samples by 15N NMR spectroscopy. Effective oxidation states of M0/NO+ are calculated, and metal-nitrosyl bonding has been interrogated using DFT-based energy decomposition analysis techniques. While a linear nitrosyl coordination mode was found to be electronically preferred, the M-NO and P-M-P angles are inversely correlated to the extent that binding in this manner is prevented by steric repulsion between the bulky ancillary phosphine ligands.

NMR analysis of structural geometry and molecular dynamics in perovskite-type N(CH3)4CdBr3 crystal near high-temperature phase transition.

The NMR chemical shifts, linewidths, spin-lattice relaxation times in the rotating system T1ρ, and spin-lattice relaxation times in the laboratory system T1 were evaluated for the perovskite-type N(CH3)4CdBr3 crystal, aiming to understand the changes in the structural geometry and molecular dynamics from phase I to phase II. From the temperature-dependence of the 1H, 13C, 14N, and 113Cd NMR chemical shifts, the structural geometry underwent a continuous change, without anomalous changes around (TC = 390 K). However, the linewidths in phase I were narrower than those in phase II, indicating that the motional averaging effects were caused by the rapid rotation of the N(CH3)4 group. Sudden changes in T1 and T1ρ were observed near TC, for which the activation energy Ea in phase I was approximately 12 times larger than that in phase II; the small Ea values in phase II indicate a large degree of freedom for the methyl group and CdBr6 octahedra, whereas the large Ea in phase I was primarily attributed to the overall N(CH3)4 and the 113Cd in the CdBr6 groups. Consequently, the phase transition mechanisms of N(CH3)4CdBr3 are related to reorientation of the N(CH3)4 group and the arrangement of the CdBr6 groups.

Role of ancillary ligands in S-nitrosothiol and NO generation from nitrite-thiol interactions at mononuclear zinc(ii) sites.

Generation of S-nitrosothiol (RSNO) and nitric oxide (NO) mediated by zinc(ii) coordination motifs is of prime importance for understanding the role of zinc(ii)-based cofactors in redox-signalling pathways. This study uniquely employs a set of mononuclear [L2ZnII]2+ cores (where L = Me4PzPz/Me2PzPy/Me2PzQu) for introducing subtle alterations of the primary coordination sphere and investigates the role of ligand tuning in the transformation of NO2 - in the presence of thiols. Single crystal X-ray diffraction (SCXRD) analyses on [L2ZnII-X](X) (where X = perchlorate/triflate) illustrate consistent changes in the bond distances, thereby showing variations of the metal-ligand interactions depending on the nature of the heterocyclic donor arms (pyrazole/pyridine/quinoline). Moreover, such tuning of the ligands affects the Lewis-acidity of the [L2ZnII]2+ cores as evaluated by 31P NMR and SCXRD studies on the 1 : 1 acid-base adducts [L2ZnII(OPEt3)]2+. Crystallographic and 15N NMR spectroscopic analyses on the nitrite complexes [L2ZnII(κ2-nitrite)](ClO4) reveal that the chemical environments of the nitrite anions in these complexes are nearly identical, despite the dissimilarity in the Lewis-acidity of the [L2ZnII]2+ cores. Interestingly, RSNO and NO generation from the reactions of [L2ZnII(κ2-nitrite)](ClO4) with 4-tert-butylbenzylthiol ( t BuBnSH) exhibits that the [(Me2PzQu)2ZnII]2+ core is the most efficient in promoting nitrite-thiol interactions due to the ease of available hemilabile coordination sites at the Lewis acidic [ZnII]. Detailed UV-vis studies in tandem with computational investigation, for the first time, provide an unambiguous demonstration of the nitrous acid (HNO2) intermediate generated through an intramolecular proton-transfer from thiol to nitrite at zinc(ii).

Optimisation of dynamic nuclear polarisation using "off-the-shelf" Gd(III)-based polarising agents.

Complexes of paramagnetic metal ions, in particular Gd3+, have been demonstrated as efficient polarising agents for magic-angle spinning (MAS) dynamic nuclear polarisation (DNP). We recently demonstrated that commercially available and inexpensive Gd(NO3)3 is suitable for use as an "off-the-shelf" MAS DNP polarising agent, providing promising sensitivity enhancements to 1H, 13C, and 15N NMR signals. Here we expand upon this approach by investigating the impact of the Gd(NO3)3 concentration and by exploring a larger range of readily available Gd3+ sources. We found that a Gd(NO3)3 concentration of 20 mM in the case of 1H and 13C, and 40 mM in the case of 15N, offers optimum signal enhancements and is rationalised as a trade-off between DNP enhancements, polarisation build-up times, and electron paramagnetic resonance (EPR) spin-spin relaxation times. We determined that a range of different gadolinium compounds (GdCl3, Gd2(SO4)3, GdBr3, and Gd(OAc)3) are also suitable for use as polarising agents and yield 1H, 13C, and 15N signal enhancements of variable values. Gd(OAc)3 yields lower signal enhancements, which is proposed to be the result of greater local asymmetry at the Gd3+ centre leading to EPR line broadening, and the methyl group in the acetate ion acting as a relaxation sink and limiting the nuclear polarisation available.

Structure and dynamics of the proton-selective histidine and the gating tryptophan in an inward rectifying hybrid influenza B and A virus M2 proton channel.

The M2 proteins of influenza A and B viruses form acid-activated proton channels that are essential for the virus lifecycle. Proton selectivity is achieved by a transmembrane (TM) histidine whereas gating is achieved by a tryptophan residue. Although this functional apparatus is conserved between AM2 and BM2 channels, AM2 conducts protons exclusively inward whereas BM2 conducts protons in either direction depending on the pH gradient. Previous studies showed that in AM2, mutations of D44 abolished inward rectification of AM2, suggesting that the tryptophan gate is destabilized. To elucidate how charged residues C-terminal to the tryptophan regulates channel gating, here we investigate the structure and dynamics of H19 and W23 in a BM2 mutant, GDR-BM2, in which three BM2 residues are mutated to the corresponding AM2 residues, S16G, G26D and H27R. Whole-cell electrophysiological data show that GDR-BM2 conducts protons with inward rectification, identical to wild-type (WT) AM2 but different from WT-BM2. Solid-state NMR 15N and 13C spectra of H19 indicate that the mutant BM2 channel contains higher populations of cationic histidine and neutral τ tautomers compared to WT-BM2 at acidic pH. Moreover, 19F NMR spectra of 5-19F-labeled W23 resolve three peaks at acidic pH, suggesting three tryptophan sidechain conformations. Comparison of these spectra with the tryptophan spectra of other M2 peptides suggests that these indole sidechain conformations arise from interactions with the C-terminal charged residues and with the N-terminal cationic histidine. Taken together, these solid-state NMR data show that inward rectification in M2 proton channels is accomplished by tryptophan interactions with charged residues on both its C-terminal and N-terminal sides. Gating of these M2 proton channels is thus accomplished by a multi-residue complex with finely tuned electrostatic and aromatic interactions.

In Situ Hyperpolarization Enables 15N and 13C Benchtop NMR at Natural Isotopic Abundance.

Without employing isotopic labeling, we demonstrate the generation of 15N and 13C NMR signals for molecules containing -NH2 motifs using benchtop NMR spectrometers (1-1.4 T). Specifically, high-SNR (>50) detection of ammonia, 4-aminopyridine, benzylamine, and phenethylamine dissolved in methanol or dichloromethane is demonstrated after only 10 s of parahydrogen bubbling using signal amplification by reversible exchange and applying a pulse sequence based on spin-lock-induced crossing. Optimization of the sequence parameters allows us to achieve up to 12% 15N and 0.4% 13C polarization in situ without the need for the sample transfer typically employed in other hyperpolarization methods. Moreover, hyperpolarization is generated continuously without having to stop the parahydrogen bubbling to reset magnetization, paving the way toward fast 2D spectroscopic methods and relaxometry. The provided methodology may find application for the identification of diluted chemicals relevant to industry and research with the aid of affordable benchtop NMR spectrometers.

Green synthesis of novel pyrano[2,3-c]pyrazole-5-carbonitrile analogues by using Fe5(PW10V2O40)3 nanocatalyst through a one-pot Knoevenagel condensation and Michael addition mechanism

A swift and green one-pot method was improved for the preparation of new pyranopyrazole analogues using iron-doped heteropoly acid [(Fe5(PW10V2O40)3] (FePWV) as an efficient catalyst at room temperature and ethanol as the solvent. The one-pot, multi-component reaction combining substituted aldehyde, malononitrile,ethyl acetoacetate, and hydrazine hydrate produces remarkable yields (varying from 88 % to 98 %) for this highly selective technique. Using P-XRD, TGA, BET, FT-IR, TEM, and SEM studies, the synthesized FePWV catalyst was fully characterized. Several spectroscopic methods, including 1H NMR, 15N NMR, 13C NMR, and HRMS, were used to confirm the target molecules' structural information.This environmentally benign method also has other benefits, such as operational simplicity, a stable catalyst with great reusability (up to 7 times), quick reaction times (<20 min), and the absence of chromatographic separations. The proposed method is sustainable and affordable as a result of these properties taken together.

Structural characteristics and biological properties of new pseudo-octahedral ruthenium(II) complexes containing a biphenyl moiety

Three new ruthenium(II) complexes with biphenyl (bip), and disubstituted 1,2,4-triazolo[1,5-a]pyrimidine (dstp) of the general formula [(η6-bip)Ru(dstp)Cl2], where dstp – dmtp–5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine for (1), dptp–5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine for (2), or ibmtp–7-isobutyl-5-methyl-1,2,4-triazolo[1,5-a]pyrimidine for (3) have been synthesized and fully characterized by an elemental analysis and spectroscopic methods (1H, 13C, 15N NMR; IR; X–ray). The crystal sructures of two complexes have been solved. To determine the therapeutic potential of the newly synthesized compounds, examinations of their biological properties such as lipophilicity and in vitro cytotoxicity towards T47D (breast cancer), A549 (non-small cell lung cancer), LoVo (colon cancer), and one healthy cell line mouse fibroblasts–BALB3T3 were preformed. The results show that all the tested ruthenium(II) complexes present higher lipophilicity (logP = 0.79–1.43) than Cisplatin (−2.31). From among all the newly obtained complexes,(2)(IC50 = 25 – 29 µM) exhibits the highest cytotoxicity.Based on the own results and literature data we reported earlier, it can be confirmed that the in vitro cytotoxicity of ruthenium(II) complexes increases with an increase in the size of the arene ligand.