Nitrogen Donor Atoms Research Articles

Arene ruthenium, rhodium and iridium complexes containing benzamide derivative ligands: Study of interesting bonding modes, antibacterial, antioxidant and DNA binding studies

The benzamide derivative ligands of benzothiazole (L1) and benzimidazole (L2) upon reaction with halide bridged metal precursors of platinum group yielded a series of complexes (1-6) formulated as [(arene)M(κ1(N)-L)Cl2], where, L = L1 and L2, M = Ru, Rh and Ir, arene = Cp*, p-cymene. Structural studies revealed the bonding of the ligands to the metal centers takes through the nitrogen donor atom of the benzothiazole and benzimidazole moiety in a monodentate fashion. Further reaction of rhodium and iridium complexes with NaN3 in methanol yielded di-azido κ1(N3) monodentate complexes by substituting two chlorides. In the case of ruthenium, azido complexes could not be isolated. Additional treatment of the di-azido complexes with diethyl acetylene dicarboxylate (DEAD) yielded two different bonded triazolo complexes of rhodium (11 and 13) and iridium (12 and 14). In rhodium triazolo complexes, the ligands displayed a chelating mode of bonding through the carbonyl oxygen and the nitrogen atom of the benzothiazole/benzimidazole ring while in iridium triazolo complexes, the ligands retained a monodentate bonding through the nitrogen atom of the benzothiazole/benzimidazole ring and formed two triazole rings. All these complexes were characterized by various spectroscopic techniques. NMR analysis revealed the triazolo ring coordinated to the metal center via the central nitrogen in both the rhodium and iridium triazolo complexes. These complexes as well as the ligands have been studied for antibacterial, antioxidant activity as well as DNA binding studies where a few of the compounds have shown good activity. Amongst these compounds, complex 7 possessed the highest antibacterial and radical scavenging activity while ligand L1 and complexes 1 and 2 showed good affinity as DNA binders.

Short Strong Hydrogen Bonds can Hinder Complex Formation: A Stability and Structure Study of Copper(II) Alkyl-N-iminodiacetic Acid Complexes in Aqueous Systems and Solid State

In the present study the solution and coordination chemistry of copper(II)–alkyl-N-iminodiacetate systems are studied in aqueous solution by potentiometry, using ion selective copper and pH electrodes, EXAFS (extended X-ray absorption fine structure) and dye probe molecular absorption spectrophotometry. Alkyl-N-iminodiacetates with varying alkyl chain length, methyl (CH3–), n-hexyl (C6H13–), n-dodecyl (C12H25–) and n-octadecyl (C18H37–) were used to tune the amphiphilic properties of the ligands. The polar head groups have both oxygen (hard Lewis base) and nitrogen donor (border-line Lewis base) atoms. This means that metal ions with different bonding characteristics may bind these ligands differently. Furthermore, the chelating properties of the polar head group may be regulated by pH as the acid–base properties of the imine and carboxylic acid groups are different. Copper(II) forms two stable complexes with alkyl-N-iminodiacetates with short alkyl chains, present as monomers in aqueous solution, log10β1 = 11.10(2), log10β2 = 19.5(2) for methyl-N-iminodiacetate, and log10β1 = 12.22(4), log10β2 = 21.9(2) for n-hexyl-N-iminodiacetate. n-Octadecyl-N-iminodiacetic acid, present as large aggregates in acidic aqueous solution, has short strong hydrogen bonds between carboxylic acid and carboxylate groups in the surface of the aggregates, which hinder complex formation at pH values below 4, obstructs it in the pH region 4–7, while the complex formation behaves as for short-chained alkyl-N-iminodiacetates at pH > 7. The structure around copper in copper(II)–alkyl-N-iminodiacetate complexes in aqueous solution and solid state formed at different pH values and copper(II):alkyl-N-iminodiacetate ratios has been determined by EXAFS. The coordination chemistry of copper(II) shows four strong bonds in the equatorial plane, and two different Cu–O/N bond distances, ca. 0.2 Å apart, in the axial positions of a non-centrosymmetric tetragonally elongated octahedron.

Computational Study of Actinyl Ion Complexation with Dipyriamethyrin Macrocyclic Ligands.

Relativistic density functional theory has been employed to characterize [AnO2(L)]0/-1 complexes, where An = U, Np, Pu, and Am, and L is the recently reported hexa-aza porphyrin analogue, termed dipyriamethyrin, which contains six nitrogen donor atoms (four pyrrolic and two pyridine rings). Shorter axial (An═O) and longer equatorial (An-N) bond lengths are observed when going from AnVI to AnV. The actinide to pyrrole nitrogen bonds are shorter as compared to the bonds to the pyridine nitrogens; the former also play a dominant role in the formation of the actinyl (VI and V) complexes. Natural population analysis shows that the pyrrole nitrogen atoms in all the complexes carry higher negative charges than the pyridine nitrogens. Upon binding actinyl ions with the ligand a significant ligand-to-metal charge transfer takes place in all the actinyl (VI and V) complexes. The formation energy of the actinyl(VI,V) complexes in the gas-phase is found to decrease in the order of UO2L > PuO2L > NpO2L > AmO2L. This trend is consistent with results for the formation of complexes in dichloromethane solution. The calculated ΔG and ΔH values are negative for all the complexes. Energy decomposition analysis (EDA) indicates that the interactions between actinyl(V/VI) and ligand are mainly controlled by electrostatic components over covalent orbital interactions, and the covalent character gradually decreases from U to Am for both pentavalent and hexavalent actinyl complexes.

Synthetic Approach, Structural Performance and in vitro Antibacterial Activity: Nitrogen and Oxygen Donor Atoms containing Bidentate Schiff Base Ligand and its Mononuclear Complexation with Co(II) and Cu(II) Metal Ions

A synthetic approach has been designed and followed for the synthesis of new bidentate Schiff base ligand 2-acetylthiophenenicotinic hydrazone (L) (which possessed nitrogen and oxygen donor atoms) and its Co(II) and Cu(II) mononuclear complexes. All the compounds were examined IR, 1H NMR, mass, EPR, conductivity, elemental analysis, etc. Octahedral geometry has been assigned to all synthesized compounds on the basis of magnetic, IR and electronic spectral analysis. In vitro activity i.e. antibacterial (E. coli and P. aeruginosa) and antifungal (A. niger, M. phasolina and P. glomerata) had been examined for these compounds following well diffusion and poisoned food methods, respectively. During the performance of antifungal activity, antifungal agent was incorporated into the molten agar at various concentrations and mixed well. After performance of in vitro activity, it has been resulted out that metal(II) complexes exhibited remarkable activity than free ligand but less active compared to the standard drugs..

Synthesis, Spectral Characterization and Biological Evaluation of Metal Complexes of 2-Thioxoquinoline Aminophenol

A series of novel 2-thioxoquinoline aminophenol Schiff base based Co(II), Ni(II), Cu(II) and Zn(II) metal complexes [M(L)2], (M = Co2+, Ni2+, Cu2+ & Zn2+; L = 2-thioxoquinoline aminophenol) were synthesized and characterized by elemental analysis and spectral studies (FT-IR, UV-Vis, 1H NMR, ESR and ESI-Mass). All experimental results showed that in these metal complexes, the central metal atom was coordinated by oxygen, nitrogen and sulfur donor atoms of deprotonated Schiff base. Further, the ligand and its metal(II) complexes were screened against Gram-positive (Staphylococcus aureus), Gram-negative (Escherichia coli) bacteria and fungus (Candida albicans) strains. in vitro Anticancer activity of ligand and its metal(II) complexes were also screened against HeLa cells (Human cervical cancer cells).

Recent advances in the supramolecular assembly of cyclophosphazene derivatives.

Cyclophosphazenes are a fascinating group of inorganic heterocyclic compounds whose rings are constituted by the repetition of phosphorus and nitrogen atoms. They have received particular attention due to their easy functionalization and thermal stability and as an excellent core for the preparation of advanced materials. Rigid trispirocyclic derivatives of cyclophosphazenes afford numerous supramolecular structures that are suitable for the formation of host-guest complexes with a variety of guest molecules such as gas molecules and molecular rotor compounds. Also, the donor nitrogen atoms of the cyclophosphazene ring can participate in non-covalent interactions such as hydrogen bonding and metal coordination. It can also be used in the construction of supramolecular dendrimeric or polymeric systems as either the starting compound or the carrier of supramolecular groups. Thus, cyclophosphazenes have been employed in the preparation of supramolecular systems for about past 30 years. This review focuses on the state of recent advances in the construction of cyclotriphosphazene-based supramolecular systems built by non-covalent interactions and their applications such as host-guest complexes, liquid crystals, coordination polymers and nanostructures. The future perspective of cyclophosphazene supramolecular assemblies is also discussed.

DFT Quantum-Chemical Modeling Molecular Structures of Cobalt Macrocyclic Complexes with Porphyrazine or Its Benzo-Derivatives and Two Oxygen Acido Ligands.

Based on the results of a quantum chemical calculation using the DFT method with the OPBE/TZVP and B3PW91/TZVP levels, the possibility of the existence of three cobalt heteroligand complexes containing in the inner coordination sphere porphyrazine, di[benzo]- and tetra[benzo]porphyrazine, and two oxygen (O2−) ions with probable oxidation state VI of Co, which is unknown for this element at the present time, was shown. Data on the structural parameters are presented. It was shown that CoN4 chelate nodes as well as all metal-chelate and non-chelate cycles in each of these complexes, were strictly planar. Besides, the bond angles formed by two donor nitrogen atoms and a Co atom were close or equal to 90°, while the bond angles formed by donor atoms N, Co, and O, in most cases, albeit insignificantly, differed from this value. Good agreement between the calculated data obtained using the above two versions of the DFT method was found. Standard thermodynamic parameters of formation (standard enthalpy ΔH0f, 298, entropy S0f, 298 and Gibbs’s energy ΔG0f, 298) for the indicated complexes were presented too.

Enhanced Near-Infrared Emission from Eight-Coordinate vs Nine-Coordinate YbIII Complexes Using 2-(5-Methylpyridin-2-yl)-8-hydroxyquinoline.

Enhanced near-infrared (NIR) luminescence from two structurally related heterobinuclear NaIYbIII eight-cooridnate and heterobinuclear YbIIINaI eight-coordinate (CN = 8) complexes is reported and compared to a nine-coordinate (CN = 9) homoleptic complex. For the heteroleptic complex, [Yb(MPQ2)(acac)], the YbIII cation is coordinated to two tridentate 2-(5-methylpyridin-2-yl)-8-quinolinate (MPQ) anions, with a bidentate acetylacetonate (acac) anion completing the coordination sphere. Instead, the heterobinuclear [NaYb(MPQ)4] complex comprises a total of four anionic MPQ ligands, two of which exhibit κ3-coordination to the YbIII cation. The remaining two MPQ anions are unidentate toward the lanthanide and form μ2-bridges via the deprotonated quinolinate oxygens to a bound NaI cation which is also coordinated to the remaining nitrogen donor atoms. The structural properties of these complexes were evaluated by single-crystal X-ray diffraction (SXRD), continuous shape measure (CShM) analysis, and 1H NMR spectroscopy using a diamagnetic LuIII analogue. The corresponding photophysical properties were examined in CH2Cl2 solution by using absorption and emission spectroscopy. For both the complexes, characteristic YbIII emission is observed at ca. 980 nm, with recorded photoluminescence quantum yields (Φobs) and NIR luminescence lifetimes (τobs) of 2.0% and 14.0 μs vs 1.5% and 11.6 μs for the [NaYb(MPQ)4] and [Yb(MPQ)2(acac)] complexes, respectively. Interestingly, the eight-coordinate YbIII complexes both have higher photoluminescence quantum yields when compared to the homoleptic [Yb(MPQ)3] complex, which has a reported quantum yield of 1.0% and a NIR lifetime determined herein of 13.3 μs under identical conditions. These results have been rationalized by considering the overall efficiency of the ligand-centered sensitization process (ηsens = Φisc × Φeet), together with subsequent radiative (kr) and nonradiative (knr) deactivation of the YbIII cation. Moreover, the efficiency of the intersystem crossing (Φisc) and electronic energy transfer (Φeet) processes involved in the antennae effect have been quantified for the new complexes using a combination of nanosecond and femtosecond transient absorption techniques and have been compared to our previous results using [Ln(MPQ)3] complexes with Ln = Yb and Lu.

The Role of Zinc(II) Ion in Fluorescence Tuning of Tridentate Pincers: A Review.

Tridentate ligands are simple low-cost pincers, easy to synthetize, and able to guarantee stability to the derived complexes. On the other hand, due to its unique mix of structural and optical properties, zinc(II) ion is an excellent candidate to modulate the emission pattern as desired. The present work is an overview of selected articles about zinc(II) complexes showing a tuned fluorescence response with respect to their tridentate ligands. A classification of the tridentate pincers was carried out according to the binding donor atom groups, specifically nitrogen, oxygen, and sulfur donor atoms, and depending on the structure obtained upon coordination. Fluorescence properties of the ligands and the related complexes were compared and discussed both in solution and in the solid state, keeping an eye on possible applications.

Intrinsic Effect of Pyridine-N-Position on Structural Properties of Cu-Based Low-Dimensional Coordination Frameworks.

Metal-organic assemblies have received significant attention for catalytic and other applications, including gas and energy storage, due to their porosity and thermal/chemical stability. Here, we report the synthesis and physicochemical characterization of three metallosupramolecular assemblies consisting of isomeric ambidentate pyridyl-β-diketonate ligands L1–L3 and Cu(II) metal ions. It has been demonstrated that the topology and dimensionality of generated supramolecular aggregates depend on the location of the pyridine nitrogen donor atom in L1–L3. This is seen in characterization of two distinct 2D polymeric assemblies, i.e., [Cu(L1)2]n and [Cu(L2)2]n, in which both β-diketonate and pyridine groups are coordinated to the Cu(II) center, as well as in characterization of the mononuclear 1D complex Cu(L3)2, in which the central atom is bound only by two β-diketonate units.

Synthesis, silver (I) extraction and silver (I) binding studies of novel N1,N3-bis(2-(benzylthio)ethyl)propanediamide derivatives

Solvent or liquid–liquid extraction represents a highly valuable technique for the selective recovery of metals from the aqueous phase due to the ease of operation and short turnaround times. Ligands bearing soft donor atoms including nitrogen and sulfur are ideal candidates for selective silver recovery due to their preference for silver binding. Herein, novel N1,N3-bis(2-(benzylthio)ethyl)propanediamide derivatives bearing sulfur and nitrogen donor atoms were prepared in low to high yields and tested for Ag+ extraction from ternary aqueous solutions also containing Cu2+ and Pb2+ following a well-established solvent extraction protocol. It was observed that electronics effects at the 4-aryl position in the propanediamide (or malondiamide) derivatives had a significant effect on the selectivity, but little effect on the efficiency of Ag+ extraction with the 4-methoxy analogue proving the most selective. Steric hindrance provided by dimethyl substitutions at the α-positions to the sulfur atoms had negative effects on Ag+ extraction efficiency and selectivity, while diethyl steric hindrance at the methylene center lowered selectivity but increased extraction efficiency for Ag+. Detailed binding studies reveal that one of the malondiamide derivatives which lacked the electronic and steric hindrance groups studied coordinated Ag+ in a 1:1 fashion suggesting a tetrahedral complex geometry. Overall, the results show that simple modification of the electronics and sterics of the N1,N3-bis(2-(benzylthio)ethyl)propanediamides, can improve their selectivity for Ag+ recovery from the aqueous phase.

Structure vs chemistry: Tribological behavior of TiN films in the nitrogen atmosphere

Traditional view holds that transition metal nitride films have high friction coefficient and difficult to regulate. It is very challenging to obtain low friction consumption, which limits their wide application. Here, the tribological behavior of TiN films prepared by multi-arc ion plating and GCr15 steel balls under nitrogen atmosphere have been systematically investigated. It is interesting that TiN film in an alternating atmosphere shows a good adaptability similar to that of H-DLC films in the atmosphere of nitrogen. Specifically, the friction coefficient is higher in vacuum, but lower in nitrogen atmosphere. The multi-cycle variation in the frictional environment confirms the adsorption of nitrogen molecules at the sliding interface. The X-ray photoelectron spectroscopy results from the wear tracks show the formation of oxide and the adsorption of nitrogen at the sliding interface. In addition, the synergistic mechanism of N2 molecule as electron donor and electrostatic repulsion and nitrogen atoms and tribo-transfer film was established. It provides a general strategy for the regulation of hard films in nitrogen atmosphere.

Synthesis, spectral characterization, quantum chemical calculations, thermal studies and biological screening of nitrogen and oxygen donor atoms containing Azo-dye Cu(II), Ni(II) and Co(II) complexes

Present research work focuses on the synthesis of novel azo-dye Cu(II), Ni(II) and Co(II) chelates of Schiff base based ligand having antimicrobial activities. Azo-dye Cu(II) and Zn(II) complexes derived 7-benzyl-4-(phenyldiazenyl)quinolin-8-ol (HBPDQ) was obtained and described by spectroscopic tools and TGA analysis. UV-visible, IR, 1H, 13C & 15N NMR spectra revealed that the HBPDQ uses its quinoline nitrogen ring and deprotonated hydroxyl group in coordination with Cu(II), Ni(II) and Co(II) ions. The Cu(II), Ni(II) and Co(II) chelates were predicted to be not electrolytic from the measured molar conductance values. Thermal properties and decomposition kinetics of the metal chelates are investigated using Coats-Redfern method. Magnetic susceptibility and electronic spectral data as well as quantum chemical calculations reveal the Cu(II), Ni(II) and Co(II) complexes are octahedral geometry. DFT studies revealed that geometries of metal complexes and azo-dye (HBPDQ) were entirely optimized in relation to use energy by 6-31+g (d,p) basis set. The kinetic parameters like activation energy (E*), pre-exponential factor (A) and entropy of activation (ΔS*) were quantified. Results of spectral studies of mass and TGA data confirmed the octahedral geometry for all chelates. The Cu(II), Ni(II) and Co(II) chelates were investigated for biological action against pathogenic fungi (C. krusei, C. albican) and bacteria (S. aureus, E. coli). The antimicrobial results confirmed that Cu(II), Ni(II) and Co(II) chelates possessed superior inhibition potential than the parent ligand (HBPDQ). The enhanced antimicrobial activity might be due to the chelation.

Density Functional Theory Modeling of Molecular Structures of Heteroligand 3d M(IV) Complexes with Porphyrazine and Oxo Anion

The molecular structures of (6666) macrotetracyclic (M(IV) chelates (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu) with the (NNNN)-donor ligand porphyrazine and the oxo ligand have been calculated by the DFT OPBE/TZVP method. Selected bond lengths and bond and nonbonded angles in the complexes have been reported. The standard enthalpies, entropies, and Gibbs energies of formation of these compounds have been calculated. All these complexes have a structure of a distorted tetragonal pyramid, where the complex-forming M(IV) atom is located above the base formed by the donor nitrogen atoms. It has been demonstrated that all six-membered metal chelate rings in each of these structures are identical to each other both in the sum of their bond angles and in their set, although none of them is flat. The images of the molecular structures of some of these coordination compounds are presented.

Thermodynamic studies of carbon nanotube interaction with Gemcitabine anticancer drug: DFT calculations

One of the main causes worldwide is cancer. One of the important approaches to cancer treatment is the use of chemotherapy drugs but nowadays, the use of smart drugs by researchers is being used to treat cancer. The most important carrier of drug delivery to cells is the use of carbon nanotubes. In this research, the possibility of formation of interactions between carbon nanotube and Gemcitabine anticancer drug is investigated with M06/6-311G level. The results obtained by M06/6-311G level indicate adsorption of the drug into nanotubes is physical. The obtained interaction energy and obtained bonding energy values with standard method were corrected by basis set superposition error (BSSE) on the same level of theory. The binding energy in the solvent phase is lower than the gas phase. Hence, the stability of the studied reaction increases in solvent phase with regard to the gas phase. The NBO analysis shows which the transfer electron can occur from the lone pair of Nitrogen (donor atom) in the Gemcitabine to the $$ \sigma^{ * } $$ orbital of the carbon atoms (acceptor atoms) in single-walled carbon nanotube. As well as the data of the atoms in a molecule (AIM) theory showed which the N17–C61 bond is a partial covalent bond.

Crystallographic Analysis of a Copper(II) Complex with bis(4,4′-Ethane-1,2-Diylbis(Azanediyl))-bis(3-(2-(4-Flurophenyl)Hydrazinyl)Pentan-2-One)

A new copper(II) complex with bis(4,4′-(ethane-1,2-diylbis(azanediyl))bis(3-(2-(4-fluorophenyl) hydrazinyl)pentan-2-one) (1) is synthesized and analyzed by single crystal X-ray diffraction. The crystals are monoclinic: a = 11.1340(9) A, b = 11.6716(10) A, c = 18.7797(16) A, β = 94.792(2)°, V = 2431.9(4) A3, space group P21/n, Z = 4, ρcalc = 1.713 mg/m3, R = 0.0695. The environment of the copper atom is formed by four donor nitrogen atoms (N1, N3, N4, N6). These atoms are at the equatorial position. The N6 atom slightly deviates from the middle plane. Phenyl rings are not involved in the coordination. Additional crystallographic data are available from the Cambridge Crystallography Data Center under number CCDC 1907359.

DFT Quantum-Chemical Calculations of Molecular Structures for Heteroligand M(III) Complexes of 3d Elements with Porphyrazine and Fluoride Ion

The molecular structures of heteroligand (6666)macrotetracyclic chelates of M(III) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Cu) with porphyrazine (an (NNNN)-donating ligand) and F– ion are calculated by the DFT OPBE/TZVP method. The key bond lengths, bond angles, and nonbonded angles in these complexes are reported. The standard enthalpies, entropies, and Gibbs free energies of formation are calculated for the complexes. All complexes have a slightly distorted tetragonal-pyramidal geometry, where the complex former M(III) is to some degree raised above the pyramid base made up of the donor nitrogen atoms. Characteristically, all 6-membered metal chelate rings in these metal chelates are identical to one another both in terms of the sum of bond angles and in their varieties.

Stabilization of unusual metal oxidation state +4 in the iron, cobalt, nickel, and copper complexes with trans-di[benzo]porphyrazine and two fluoride anions: a DFT quantum chemical analysis

Molecular structure calculations of heteroligand (6666)macrotetracyclic metal (MIV) chelates (M = Fe, Co, Ni, Cu) with trans-di[benzo]porphyrazine as the (N,N,N,N)-donor ligand and two F− anions were carried out at the OPBE/TZVP level of density functional theory. The key bond lengths, bond angles, and non-bond angles in the complexes were determined and corresponding standard enthalpies, entropies, and Gibbs energies of formation were calculated. All complexes have slightly distorted tetrahedral structures. The complex-forming agent MIV lies in the plane formed by the donor nitrogen atoms. The metal—nitrogen bonds are usually pair-wise equal. The six-membered metal chelate rings in the complexes are identical to one another from the standpoint of both the sum and set of the bond angles.

Urea formaldehyde modified alginate beads with improved stability and enhanced removal of Pb2+, Cd2+, and Cu2+

Urea formaldehyde (UF) was grafted onto the backbone of alginate to prepare microbeads as an adsorbent for the removal of heavy metal ions from aqueous solutions. The expensive alginate was crosslinked with cheaper UF at different ratios (1: 2.5∼1: 12.5) to produce sturdy alginate-UF beads at lower cost. Characterization results showed that UF modification enhanced the pore network and structural stability of the beads, which can be attributed to the reduced intermolecular forces and plentiful of nitrogen and oxygen donor atoms of the beads. The swelling of air-dried alginate-UF beads in different solutions was much lower than that of the unmodified alginate beads, confirming the improved stability. The replacement of alginate with UF at different ratios either did not affect or increased the adsorption of heavy metal ions (Pb2+, Cd2+, and Cu2+) on the beads. For example, the adsorption capacities of Pb2+, Cd2+, and Cu2+ on air-dried alginate-UF (1: 2.5) beads were 1.66, 0.61, and 0.80 mmol/g, which were 39.88%, 9.29%, and 9.52% higher than those of the corresponding unmodified alginate beads, respectively. The adsorption of heavy metals on the alginate-UF beads was mainly controlled by ion exchange, complexation, and electrostatic interaction mechanisms.

Carboxylation of the Ni–Me Bond in an Electron-Rich Unsymmetrical PCN Pincer Nickel Complex

The synthesis of a new unsymmetrical PCN ligand bearing tert-butyl groups on the phosphorus atom and isopropyl groups on the nitrogen donor atom is presented. It reacts with the commercially availa...