Atoms Of Ligand Research Articles

Effect of Substituents in Functional Bipyridonate Ligands on Ruthenium‐Catalyzed Dehydrogenative Oxidation of Alcohols: An Experimental and Computational Study

AbstractA series of hexamethylbenzene (HMB)–Ru complexes 2–5 bearing a 4,4’‐functionalized 2,2’‐bipyridine‐6,6’‐dionate (bpyO) ligand, which exhibits metal‐ligand cooperative catalysis, was prepared with the aim of developing excellent catalyst for dehydrogenative oxidation of alcohols. Interestingly, the catalytic activity increased in the order 3 (CF3) <4 (OMe)<2 (H) <5 (NMe2), where substituents at 4,4’‐positions of bpyO ligand are in parentheses. This is different from the order of simple electron‐donating ability. DFT calculations revealed that the rate‐limiting step is the concerted proton/hydride transfer from the alcohol to the complex. The activation energy decreases as the interaction between the alcoholic proton and the O atom of the bpyO ligand becomes stronger; hence, the introduction of the NMe2 group decreases the activation energy, whereas that of the CF3 group increases it. The unexpectedly lower catalytic ability of 4 than that of 2 results from the enthalpy–entropy compensation effect.

Dynamics of Formation of Binuclear Metal Complexes: A New Cu(I) Compound with N‐(2‐thiophenecarbonyl)‐N’‐(3‐Cl, 4‐F‐phenyl)thiourea as Ligand

AbstractHerein we report the synthesis and characterization of a new copper(I) complex with triphenylphosphine (PPh3) and N‐(2‐thiophenecarbonyl)‐N’‐(3‐Cl, 4‐F‐phenyl)thiourea (HL), as ligands. The complex was characterized by vibrational (FTIR and FT‐Raman) and multinuclear (1H, 13C {1H}, 31P{1H}) NMR spectroscopies. The crystalline structure of the complex was determined by single‐crystal X‐ray diffraction, confirming that a neutral binuclear compound, identified as [Cu(PPh3)(L‐κ2‐N,μ‐S)]2, was obtained. The anionic thiourea ligand coordinates to the metal through the sulfur and nitrogen atoms in an unusual bidentate κ2‐N,μ‐S coordination mode. The complex is a dimer sited on a crystallographic center of symmetry. Each Cu2(μ‐S)2 cation bridges trough the sulfur atoms of two symmetry related thiourea moieties and is also coordinated to the nitrogen atom of the thiourea ligand and the phosphorus atom from PPh3 co‐ligand, forming a slightly distorted tetrahedral geometry. An intramolecular N−H⋅⋅⋅O=C hydrogen bond is observed in the anionic ligand, forming a six‐membered ring that stabilizes the N−H thioamide group. Hirshfeld surface analysis shows that the molecules are connected by weak intermolecular contacts C⋅⋅⋅C, H⋅⋅⋅C and H⋅⋅⋅H which add to the stability of the crystalline packing. The in vitro cytotoxicity study of the complex indicates that it is more active against human lung carcinoma cells (A549), when compared to the free ligand.

Synthesis and crystal structure of trans-di-aqua(1,4,8,11-tetra-aza-undeca-ne)copper(II) isophthalate monohydrate.

In the title hydrated mol-ecular salt, [Cu(C7H20N4)(H2O)2](C8H4O4)·H2O, the metal ion is coordinated by the two primary and two secondary N atoms of the amine ligand and the mutually trans O atoms of the water mol-ecules in a tetra-gonally distorted octa-hedral geometry. The average equatorial Cu-N bond lengths (2.013 and 2.026 Å for Cu-Nprim and Cu-Nsec, respectively) are substanti-ally shorter than the average axial Cu-O bond length (2.518 Å). The tetra-amine ligand adopts its energetically favored conformation with its five- and six-membered chelate rings in gauche and chair conformations, respectively. In the crystal, the N-H donor groups of the tetra-amine, the acceptor carboxyl-ate groups of the isophthalate dianion and both the coordinated water mol-ecules and the water mol-ecule of crystallization are involved in numerous N-H⋯O and O-H⋯O hydrogen bonds, resulting in the formation of electroneutral layers oriented parallel to the ac plane.

Design and synthesis of novel heterocyclic pivalamide ligands and their copper(II) complexes: Structure, BSA/DNA interactions and SOD synzyme activity

Four new heterocyclic pivalamide based ligands (L1-L4) and their respective mononuclear copper(II) complexes (C1 = [Cu(N-(thiazol-2-yl)pivalamide)2], C2 = [Cu(N-(5-methylthiazol-2-yl)pivalamide)2], C3 = [Cu(N-(benzothiazol-2-yl)pivalamide)2], C4 = [Cu(N-(benzoimidazol-2-yl)pivalamide)2]) were synthesized to serve as low molecular weight SOD mimics. The complexes were characterized by single crystal XRD, Hirshfeld surface analysis, FT-IR, UV–vis, EPR and ESI-MS studies. C1 crystallizes out in a triclinic system with P-1 space group, while C2 and C4 belong to P21/c and P21/n space groups respectively, from monoclinic system. The crystal structures indicate nearly square planar geometry where mononuclear copper(II) metal ions have coordinated with O and N donor atoms of the pivalamide ligands in trans fashion. All the complexes can scavenge superoxide concentration at low concentrations, in the order C2 < C3 < C1 < C4. The interaction of all the complexes with BSA (bovine serum albumin) protein investigated using fluorescence titration method indicated a static quenching mechanism (KBSA values of the order 105 M−1). The ability of the complexes to bind with calf thymus DNA were also evaluated using absorption and fluorescence titration methods and an intercalative interaction mode of the complexes with DNA was established (Kb values of the order 104 M−1). The complexes have a strong ability to cleave supercoiled plasmid DNA.

Silyl-Osmium(IV)-Trihydride Complexes Stabilized by a Pincer Ether-Diphosphine: Formation and Reactions with Alkynes.

Complex OsH4{κ3-P,O,P-[xant(PiPr2)2]} (1) activates the Si-H bond of triethylsilane, triphenylsilane, and 1,1,1,3,5,5,5-heptamethyltrisiloxane to give the silyl-osmium(IV)-trihydride derivatives OsH3(SiR3){κ3-P,O,P-[xant(PiPr2)2]} [SiR3 = SiEt3 (2), SiPh3 (3), SiMe(OSiMe3)2 (4)] and H2. The activation takes place via an unsaturated tetrahydride intermediate, resulting from the dissociation of the oxygen atom of the pincer ligand 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(PiPr2)2). This intermediate, which has been trapped to form OsH4{κ2-P,P-[xant(PiPr2)2]}(PiPr3) (5), coordinates the Si-H bond of the silanes to subsequently undergo a homolytic cleavage. Kinetics of the reaction along with the observed primary isotope effect demonstrates that the Si-H rupture is the rate-determining step of the activation. Complex 2 reacts with 1,1-diphenyl-2-propyn-1-ol and 1-phenyl-1-propyne. The reaction with the former affords Os{C≡CC(OH)Ph2}2{=C=CHC(OH)Ph2}{κ3-P,O,P-[xant(PiPr2)2]} (6), which catalyzes the conversion of the propargylic alcohol into (E)-2-(5,5-diphenylfuran-2(5H)-ylidene)-1,1-diphenylethan-1-ol, via (Z)-enynediol. In methanol, the hydroxyvinylidene ligand of 6 dehydrates to allenylidene, generating Os{C≡CC(OH)Ph2}2{=C=C=CPh2}{κ3-P,O,P-[xant(PiPr2)2]} (7). The reaction of 2 with 1-phenyl-1-propyne leads to OsH{κ1-C,η2-[C6H4CH2CH=CH2]}{κ3-P,O,P-[xant(PiPr2)2]} (8) and PhCH2CH=CH(SiEt3).

Alcoholate and Mixed Alcoholate/Iodide Supported Hexanuclear Niobium Cluster Compounds with a Mixed Face-Bridged/Edge-Bridged Cluster Pair Example

Chemical reactions of ball-mill activated [Nb6I11] with alcohol solutions of Mg alcoholates result in the formation of the three new hexanuclear Nb cluster compounds [Nb6I8(HOCH3)6][Nb6(OCH3)18]·2CH3OH (1), (PPh4)2[Nb6(OC2H5)12I6]·C2H5OH (2) and (PPN)2[Nb6(OC2H5)12I6] (3). They contain cluster anions, which have the edges of the Nb6 octahedra, i.e. the inner coordination sites, μ2-bridged by the O atoms of methanolato or ethanolato ligands. Thereby, they represent further characterized members of the so far very small group of hexanuclear cluster alcoholates. The terminal metal sites are bonded to further methanolato (1) or iodido ligands (2 and 3). Sterically demanding organic cations (PPh4+, PPN+, 2 and 3) or a cationic Nb6 cluster complex with terminal methanol ligands [Nb6I8(HOCH3)6]2+ in 1 compensate the negative charges of the cluster anions. Compound 1 is the first example of a M6 cluster ion pair of both the text-book known edge-bridged [M6X12] and face-bridged [M6X8] cluster units. The structures of the three title compounds were determined by means of single-crystal X-ray structure analysis.Graphical

Substituent’s Effects of PNP Ligands in Ru(II)-Catalyzed CO2 Hydrogenation to Formate: Theoretical Analysis Considering Steric Hindrance and Promotion of Hydrogen Bonding

This paper investigates the effects of substituents in PNP-type ruthenium complexes in the catalytic hydrogenation of CO2 to formate using the DFT method. Six groups were considered as substituents linked to the P atom of the PNP ligand: hydrogen, methyl, iso-propyl, tert-butyl, cyclopentyl, and cyclohexyl. The substituent effects were analyzed from the perspectives of steric hindrance and promotion of hydrogen bonding. With the joint functions of steric hindrance and hydrogen bonding promotion during the CO2 coordination step, hydride addition step, and HCOO− rotation step, these groups exhibited very different substituent effects. The results showed that the methyl group was the most favorable substituent when the solvent’s effects were not included, as it formed hydrogen bonding with relatively weak steric hindrance. The second favorable substituent was the iso-propyl group, while the tert-butyl group was the most unfavorable one, due to remarkable steric hindrance. When the substituent was cyclopentyl or cyclohexyl, the complex provided a wider open space for the reaction compared with the tert-butyl-substituted complex, because cyclopentyl and cyclohexyl are cyclic groups. Therefore, the principle for choosing the substituent in PNP-type complexes allowing the design of highly efficient catalysts for CO2 hydrogenation indicates that more hydrogen atoms but wider open space are ideal. In addition, the substituent’s effects can be markedly impacted by the solvent used.

Design of a Novel Series of Hetero-Binuclear Superhalogen Anions MM'X4 - (M = Li, Na; M' = Be, Mg, Ca; X = Cl, Br).

A series of hetero-binuclear superatom motifs involving chloride/bromide ligands, that is, MM′X4 − (M = Li, Na; M′ = Be, Mg, Ca; X = Cl, Br) anions, have been characterized by using many-body perturbation theory calculations. Large vertical electron detachment energies (VDEs, 5.470–6.799 eV) confirm the superhalogen identity of these anions. A larger VDE value can be obtained by introducing small M or large M′ central atoms and small halogen ligand atoms. Thus, one isomer of LiCaCl4 − possesses the largest VDE value. Besides, when the extra electron is shared by all ligand atoms or three bridging ligand atoms, the isomers have relatively larger VDE values.

Synthesis and crystal structure of bis-[trans-di-aqua-(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N 1,N 4,N 8,N 11)nickel(II)] trans-(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N 1,N 4,N 8,N 11)bis-[4,4',4''-(1,3,5-tri-methyl-benzene-2,4,6-tri-yl)tris-(hydrogen phenyl-phospho-nato-κO)]nickel(II) deca-hydrate.

The components of the title compound, [Ni(C10H24N4)(H2O)2]2[Ni(C10H24N4)(C27H24O9P3)2]·10H2O are two centrosymmetric [Ni(C10H24N4)(H2O)2]2+ dications, a centrosymmetric [Ni(C10H24N4)(C27H24O9P3)2]4- tetra-anion and five crystallographically unique water mol-ecules of crystallization. All of the nickel ions are coordinated by the four secondary N atoms of the macrocyclic cyclam ligands, which adopt the most energetically stable trans-III conformation, and the mutually trans O atoms of either water mol-ecules in the cations or the phospho-nate groups in the anion in a tetra-gonally distorted NiN4O2 octa-hedral coordination geometry. Strong O-H⋯O hydrogen bonds between the protonated and the non-protonated phospho-nate O atoms of neighboring anions result in the formation of layers oriented parallel to the bc plane, which are linked into a three-dimensional network by virtue of numerous N-H⋯O and O-H⋯O hydrogen bonds arising from the sec-NH groups of the macrocycles, phospho-nate O atoms and coordinated and non-coordinated water mol-ecules.

Synthesis and characterization of nonlinear optical metal organic frame work – Cadmium di glycinate monohydrate

The new non-linear optical single crystal of Cadmium di glycinate monohydrate have been synthesized by the slow evaporation solution growth technique and it was characterized by SXRD,powderXRD,SEM, FTIR, UV-Vis-NIR, TG/DTA and SHG measurements. In the polymeric structure the metal ion Cd (II) has coordinated with carboxylate oxygen atom and glycine ligand nitrogen atom. The crystalline nature of the material was proved by PXRD pattern. The lattice strain produced by the bimetallic cadmium is found to be 0.0042. The functional groups are confirmed by FTIR analysis, again the force constant of C-C bond was enhanced to 316 Nm−1. The UV-Visible spectrum reveals the optical qualities such as band gap, transmittance and refractive index of the grown crystal. The lower cut off wavelength was found to be 213 nm. The TG-DTA analyses were carried out to determine the thermal stability as well as the decomposition temperature. The Cadmium-Glycine frame work shows void morphology. The title compound shows superior SHG efficiency compared to standard KDP.

Synthesis, Characterization and Anti-Cancer Activity of gold (III) and Nickel (II) Metal Ion Complexes Derived from Tetrazole-Triazole Compound

This research is for academic understanding to work out new ligand behavior4-({(5-(4-hydroxyphenyl)-3-sulfanyl-1H-1,2,4-triazol-1-yl)amino}(1H-tetrazol-5-yl)methyl)-2-methoxyphenol (L) with gold (III) and nickel (II) metal ions. Ligand (L) has been synthesized from cyclization of the interaction of (4-hydroxy-3-methoxyphenyl){[5-(4-hydroxyphenyl)-3-sulfanyl-1H-1,2,4-triazol-1-yl]amino}acetonitrile (F) with sodium azide. α-Amino nitrile compound (F) intern synthesized from interaction of aldehyde amine and KCN acidic medium as three components one put reaction. The presence of well oriented donor atoms (N2-type) of ligand (L) interacted with gold (III) and nickel (II) ions under reflux to prepare [1:2] [M:L]Cl electrolytic complexes, the complexes [Au (L)3]Cl3and [Ni (L)2]Cl2were suggested to have square planar geometry. The resulting products were characterized via technical1H-NMR, UV-Vis, IR spectroscopy, conductivity and EDX. The cytotoxic effect was studied on a breast cancer cell line (MCF-7 cell line). At different concentrations for both complexes. The results showed that gold(III) complex has higher cytotoxicity than nickel(II) complex against cancer cell line.

Characterization of [Ru(bpy)2(diamine)]2+ complexes and their DNA binding and cleavage, BSA interaction, cytotoxic, and anticancer mechanistic properties

The ruthenium(II) complexes of the type [Ru(bpy)2(diamine)](PF6)21–3, where diamine is ethylenediamine (en, 1) or N,N-dimethylethylenediamine (dmen, 2) and N,N-diethyl-ethylenediamine (deen, 3) and bpy is 2,2′-bipyridine has been isolated and characterized. The X-ray crystal structures of 1 and 2 reveal that the compounds possess a distorted octahedral geometry composed of two amine nitrogen atoms of the diamine ligand (1, en; 2, dmen) and four nitrogen atoms of the two bpy ligands, which selectively forms a “cis-α” (2) or “cis-β” (1) isomer. The 1H and 13C NMR spectral data of the complexes disclose the nature of metal-ligand bonding, conformations of the chelate rings, and absolute configurations, which indicate that the two bpy ligands maintain their tendency to form geometrical isomers even in solution. They exhibit dπ → π* MLCT transitions, show a ligand-based radical anion (3MLCT) luminescence, and display one quasi-reversible and one non-reversible metal-based oxidative process corresponding to RuII/RuIII and RuIII/RIV redox couples respectively. They interacted with calf thymus (CT) DNA and the mode of interaction was found to be groove binding, as determined by various spectral and redox techniques. Upon interaction with CT DNA 1–3 show a decrease in current and less positive shift in the formal potential in the differential pulse voltammograms suggesting that they are involved in electrocatalytic guanine oxidation. Interestingly, 1–3 alters the DNA superhelicity upon binding with supercoiled pUC19 plasmid DNA with a reductant. Further, the quenching of the tryptophan emission of BSA in the presence of 1–3 is static. The binding is mainly entropy-driven and hydrophobic forces played a major role. The DNA and protein binding affinity and the DNA cleavage activity is in the order 2 > 3 > 1, and the higher DNA and protein binding affinity and DNA cleavage activity of 2 and 3 illustrates the strong involvement of the methyl (dmen) and ethyl (deen) groups in the hydrophobic interaction with the DNA and protein. Furthermore, the ruthenium(II) complexes, 2 and 3 exhibit moderate cytotoxicity against human breast adenocarcinoma MCF-7 and human cervical carcinoma HeLa (IC50: 48 h, 28–45 μM) cells, whereas 2 displays the best activity (IC50: 48 h, 28 μM) for MCF-7 cancer cells, which is better than that of cisplatin. Both the complexes displayed excellent selectivity by being relatively inactive against the Madin-Darby bovine kidney (MDBK) normal cells with selectivity index (SI) values ranging from 5.6 to 8.9. They block the cell cycle progression of MCF-7 cells in the G1 (2) and S (3) phases. FACSVerse analyses are suggestive of reactive oxygen species (ROS) generation and apoptotic cell death induced by 2 and 3. The induction of apoptosis in MCF-7 cells was shown by Annexin V with propidium iodide (PI) and 4’,6-diamidino-2-phenylindole (DAPI) staining methods.

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

Synthesis and crystal structure of di-aqua-(1,4,8,11-tetra-aza-cyclo-tetra-deca-ne)zinc(II) bis-(hydrogen 4-phospho-natobiphenyl-4'-carboxyl-ato)(1,4,8,11-tetra-aza-cyclo-tetra-deca-ne)zinc(II).

In the asymmetric unit of the title compound, trans-di-aqua-(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N 1,N 4,N 8,N 11)zinc(II) trans-bis-(hydrogen 4-phospho-natobiphenyl-4'-carboxyl-ato-κO)(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N 1,N 4,N 8,N 11)zinc(II), [Zn(C10H24N4)(H2O)2][Zn(C13H9O5P)2(C10H24N4)], both Zn atoms lie on crystallographic inversion centres and the atoms of the macrocycle in the cation are disordered over two sets of sites. In both macrocyclic units, the metal ions possess a tetra-gonally elongated ZnN4O2 octa-hedral environment formed by the four secondary N atoms of the macrocyclic ligand in the equatorial plane and the two trans O atoms of the water mol-ecules or anions in the axial positions, with the macrocyclic ligands adopting the most energetically favourable trans-III conformation. The average Zn-N bond lengths in both macrocyclic units do not differ significantly [2.112 (12) Å for the anion and 2.101 (3) Å for the cation] and are shorter than the average axial Zn-O bond lengths [2.189 (4) Å for phospho-nate and 2.295 (4) Å for aqua ligands]. In the crystal, the complex cations and anions are connected via hydrogen-bonding inter-actions between the N-H groups of the macrocycles, the O-H groups of coordinated water mol-ecules and the P-O-H groups of the acids as proton donors, and the O atoms of the phospho-nate and carboxyl-ate groups as acceptors, resulting in the formation of layers lying parallel to the (110) plane.

Sensing and photocatalytic properties of a new 1D Zn(II)-based coordination polymer derived from the 3,5-dibromosalicylaldehyde nicotinoylhydrazone ligand

A new 1D coordination polymer, [Zn(dsn)(HO2CCH3)]n (1), has been synthesized by reacting the Schiff base ligand 3,5-dibromosalicylaldehyde nicotinoylhydrazone (H2dsn) with Zn(O2CCH3)2·6H2O. The polymer has been characterized using FTIR spectroscopy and single crystal X-ray diffraction analysis. The single crystal X-ray analysis reveals that the immediate geometry around the Zn(II) ion is five-coordinate, that is satisfied by a pyridyl nitrogen atom of one dsn ligand, the imine-N, carbonyl-O and phenoxo-O atoms of the other dsn ligand, as well as the acetate oxygen atom, which generate a trigonal bipyramidal geometry. Furthermore, the dsn ligand coordinated by the pyridyl nitrogen atom also coordinates to another Zn(II) ion by its imine-N, carbonyl-O and phenoxo-O atoms to generate a zig-zag lD polymer chain. The 1D chain is held by weak non-conventional interactions in the solid state to engender a 2D supramolecular layer. The photoluminescent (PL) property of 1 has been investigated and the polymer has been exploited as a sensitive and selective fluorescent sensor to detect metronidazole (MDZ) with limit of detection (LOD) of 9.39 × 10−7 M amongst a variety of related antibiotics. Also, 1 has been used as a photocatalyst and displays excellent photocatalytic degradation of methylene blue (MB), decomposing 86.3% in 100 min under UV light irradiation. The plausible mechanisms which polymer 1 executed for the sensing of MDZ and photodegradation of MB have been explained with the aid of theoretical calculations.

Isolation and structural comparison of RuII-dnp complexes [dnp = 2,6-bis-(1,8-naphthyridin-2-yl)pyridine] with axially or equatorially coordinating NCS ligands.

The mol-ecular and crystal structures of two ruthenium(II) complexes, viz. cis-aqua-[2,6-bis-(1,8-naphthyridin-2-yl)pyridine-κ3 N,N',N''](thio-cyanato-κN)(tri-phen-yl-phosphine-κP)ruthenium(II) hexa-fluorido-phosphate-acetone-water (1/0.5/1), [Ru(NCS)(C21H13N5)(C18H15P)(H2O)]PF6·0.5C3H6O·H2O (I) and trans-[2,6-bis-(1,8-naphthyridin-2-yl)pyridine-κ3'N,N',N'']bis-(pyridine-κN)(thiocyanato-κN)ruthenium(II) thio-cyanate, [Ru(NCS)(C21H13N5)(C5H5N)2]NCS (II), with an N-coordinating thio-cyanato group and a tridentate polypyridyl supporting ligand, are reported. The RuII atom in each of the cationic complexes adopts a distorted octa-hedral coordination sphere, defined by an N atom of the thio-cyanato ligand, three N atoms from the tridentate polypyridyl ligand, and an O and P atom in (I) or two pyridine-N atoms in (II) derived from monodentate ligands. The thio-cyanato ligand in (I) coordinates in an axial manner to the {Ru-dnp} unit [dnp = 2,6-bis-(1,8-naphthyridin-2-yl)pyridine], whereas it coordinates in an equatorial manner in (II). In the crystal structure of compound (I), intra-molecular C-H⋯O, C-H⋯N and O-H⋯N hydrogen bonds as well as π-π contacts are present, in addition to inter-molecular C-H⋯F, C-H⋯O and O-H⋯O hydrogen bonds. In the crystal structure of compound (II), intra-molecular C-H⋯N hydrogen bonds are observed along with inter-molecular C-H⋯N and C-H⋯S hydrogen bonds as well as a π-π inter-action.

FUNDAMENTAL ASPECTS OF COORDINATION CHEMISTRY OF TRANSITION METALS WITH FUNCTIONALLY SUBSTITUTED THIOAMIDES (PART 2)

In the second part of the analytical review, the influence of polydentate and N-allyl-substituted thiamides on the course of complexation reactions with platinum metal ions and Ag(I) was analyzed. The potential of the obtained coordination compounds for their application in medical and analytical chemistry is also demonstrated. The presented results are obtained on the basis of joint research performed in the Department of "Chemistry of Complex Compounds" of the V.I. Vernadsky Institute of General and Inorganic Chemistry NAS of Ukraine together with the staff of the Department of “Chemistry of Heterocyclic Compounds” of the Institute of Organic Chemistry NAS of Ukraine. The example of the reaction of polydentate thioureas with metal ions shows that the increase in functional groups does not always lead to their simultaneous coordination with metal ions. For example, the migration of double bonds, which is characteristic of H2 L5 thioureas, contributes to the stiffness of heterocycles, which in turn reduces the dentat capacity of these thioureas as ligands, despite the localization of donor atoms in a favorable position for metallocycle formation. In addition, an increase in the number of donor centers in the thioamide molecule can lead to their intramolecular rearrangement under conditions of complexation, and to the occurs of redox reactions. It has been shown that the formation of a π coordination bond involved in the formation of a six-membered chelated metalocycle occurs only when, together with the C=C allyl moiety, other donor atoms of the organic ligand are at an unfavorable geometric location for metalocycle formation. Otherwise, the allyl group does not participate in the coordination to the central metal ion. A characteristic indicator of the formation of the π coordination bond is the splitting of the C3 H2 signal of allylic group protons in 1 H NMR spectra into two doublets with the same spin-spin interaction constant, as well as high-frequency shift of absorption bands of valence vibrations νas(CH)allyl, νs (CH) allyl in the IR spectra of π,n-chelate complexes.It was found that regardless of the stoichiometry of the starting components, the reaction of N-allyl-substituted thioamides HL10-12 with platinum metal ions leads to the formation of complexes only in the ratio M:L=1:1, due to the strong "trans-effect" of the allylic fragment. It was found that a number of n,π-chelate complexes of palladium(II) and platinum(II) with general formula [Pd/Pt(HL10-12)Hal2 ] (Hal = Cl-, Br- , I- ), which are structurally analogous to the known antitumor agent cisplatin, show effective antitumor action: antiproliferative, cytotoxic, anti-metastatic, proapoptotic. However, unlike cisplatin, they have proven to be much more effective: they are stable over a wide pH range; have the ability to overcome the resistance of pathogenic cells to the action of antitumor agents and show a wider range of action. The method of molecular docking was used to study the possible mechanism of interaction of the studied complexes, ie the most probable orientation and location of the complex molecule relative to the protein site of DNA binding was determined by mathematical modeling. Thioamide H2 L1 has been found to be an effective universal analytical reagent for the determination, extraction and separation of Ru(III), Rh(III) and Pd(II) from model solutions of their chlorides. The difference in the formation of anionic complexes of these metals and their ionic associations with the cationic dye atrafloxin is the basis of the developedmethod of extraction-photometric determination and stepwise separation of Ru(III), Rh(II) and Pd(II), which is important for applied aspects chemistry.

Nitrato(5,10,15,20-tetra-phenyl-porphinato)manganese(III)-benzene-n-hexa-ne (2/1/1).

The crystal structure of solvated [Mn(TPP)(NO3)] (TPP = 5,10,15,20-tetra-phenyl-porphyrinato, C44H28N4), [Mn(C44H28N4O3)(NO3)]·0.5C6H14·0.5C6H6, has been determined in the space group Pccn. The MnIII atom has a distorted square-pyramidal environment, being coordinated by four pyrrole N atoms of the porphyrin ligand in the basal plane and an O atom of the nitrato ligand in the apical site. The MnIII atom is displaced out of the porphyrin plane by 0.22 (4) Å with the average Mn-Np distance being 2.011 (6) Å (where Np is a porphyrin N atom). The Mn-O bond length is 2.1246 (18) Å. Two kinds of inter-molecular C-H⋯O hydrogen bonds exist in the crystal structure, with the apical nitrato ligands inter-acting with solvent mol-ecules and adjacent mol-ecules, respectively.

Beyond Steric Crowding: Dispersion Energy Donor Effects in Large Hydrocarbon Ligands.

Interactions between sterically crowded hydrocarbon-substituted ligands are widely considered to be repulsive because of the intrusion of the electron clouds of the ligand atoms into each other's space, which results in Pauli repulsion. Nonetheless, there is another interaction between the ligands which is less widely publicized but is always present. This is the London dispersion (LD) interaction which can occur between atoms or molecules in which dipoles can be induced instantaneously, for example, between the H atoms from the ligand C-H groups.These LD interactions are always attractive, but their effects are not as widely recognized as those of the Pauli repulsion despite their central role in the formation of condensed matter. Their relatively poor recognition is probably due to the relative weakness (ca. 1 kcal mol-1) of individual H···H interactions owing to their especially strong distance dependence. In contrast, where there are numerous H···H interactions, a collective LD energy equaling several tens of kcal mol-1 may ensue. As a result, in some molecules the latent importance of the LD attraction energies emerges and assumes a prominence that can overshadow the Pauli effects (e.g., in the stabilization of high-oxidation-state transition-metal alkyls, inducing disproportionation reactions, or in the stabilization of otherwise unstable bonds).Despite being known for over a century, the accurate quantification of individual H···H LD effects in molecular species is a relatively recent phenomenon and at present is based mainly on modified DFT calculations. A few leading reviews summarized these earlier studies of the C-H···H-C LD interactions in organic molecules, and their effects on the structures and stabilities were described. LD effects in sterically crowded inorganic and organometallic molecules have been recognized.The author's interest in these LD effects arose fortuitously over a decade ago during research on sterically crowded heavier main-group element carbene analogues and two-coordinate, open-shell (d1-d9) transition-metal complexes where counterintuitive steric effects were observed. More detailed explanations of these effects were provided by dispersion-corrected DFT calculations in collaboration with the groups of Tuononen and Nagase (see below).This Account describes our development of these initial results for other inorganic molecular classes. More recently, the work has led us to move to the planned inclusion of dispersion effects in ligands to stabilize new molecular types with theoretical input from the groups of Vasko and Grimme (see below). Our approach sought to use what Grimme has described as dispersion effect donor (DED) groups (i.e., spatially close-lying, densely packed substituents either as ligands (e.g., -C6H2-2,4,6-Cy3, Cy = cyclohexyl) or as parts of ligands (e.g., a Cy substituent) that produce relatively large dispersion energies to stabilize these new compounds.We predict that the future design of sterically crowding hydrocarbon ligands will include the consideration and incorporation of LD effects as a standard methodology for directed use in the attainment of new synthetic targets.

Low-Dimensional Metal–Organic Frameworks with High Activity and Selectivity toward Electrocatalytic Chlorine Evolution Reactions

Chlorine gas plays a paramount role in modern industrial chemistry and is one of the most basic chemicals produced by the electrolysis of brine solution. In the past decades, the dimensionally stable anode (DSA) made of RuO2 is the benchmark catalyst for the chlorine evolution reaction (CER) with high activity. However, the drawbacks of the DSA, such as high cost and inferior selectivity, demand the development of low-cost and efficient electrocatalysts for CER. Herein, three low-dimensional Fe/Co/Ni-dithiolene metal–organic frameworks (MOFs) were systematically investigated using the density functional theory. Our calculation results predict that Ni-based dithiolene MOF can efficiently catalyze the CER with a low thermodynamic overpotential of 0.049 V via the Cl* intermediate. The electronic resonance structure of [Ni2+(L•–)(L2–)]− in the Ni-based dithiolene MOF leads to the electron transfer first from S atoms in ligands to Ni cations to achieve a stable electronic configuration, which leads to the most desirable Ni–Cl interaction strength for CER. Moreover, the selectivity to Cl2 generation is due to its high thermodynamic overpotential of oxygen evolution reaction. Our findings may, therefore, accelerate CER catalyst discoveries beyond DSAs with the optimized electronic structures.