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Binuclear double end-on azido bridged Ni(II) complex (1) with composition [Ni2L2(?-1,1-N3)2(N3)2]?6H2O, (L = (E)-N,N,N-trimethyl-2-oxo-2-(2- -(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-amin) was synthesized and characterized by single-crystal X-ray diffraction method. Ni(II) ions are hexacoordinated with the tridentate heteroaromatic hydrazone-based ligand and three azido ligands (one terminal and two are end-on bridges). DFT calculations revealed that coupling between two Ni(II) centers is ferromagnetic in agreement with binuclear Ni(II) complexes with similar structures.

In this work we present the synthesis, and experimental and theoretical analysis of a binuclear nickel(II) complex coordinated to a new phthalazine dihydrazone-based ligand. Single-crystal X-ray diffraction analysis of the metal complex shows that the coordination geometry around each nickel(II) atom is distorted octahedral. DFT calculations predict that the magnetic exchange coupling constant of the binuclear nickel(II) complex is predominantly anti-ferromagnetic. Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3317]

To improve the description of interactions among the localized d, f electrons in transition metals, we have introduced a ligand-field motivated contribution into the Density Functional Tight Binding (DFTB) model. Referred to as DFTB3+U, the approach treats the d, f electron repulsions with rotationally invariant orbital–orbital interactions and a Hartree–Fock model; this represents a major conceptual improvement over the original DFTB3 approach, which treats the d, f-shell interactions in a highly averaged fashion without orbital level of description. The DFTB3+U approach is tested using a series of nickel compounds that feature Ni(II) and Ni(III) oxidation states. By using parameters developed with the original DFTB3 Hamiltonian and empirical +U parameters (F0/2/4 Slater integrals), we observe that the DFTB3+U model indeed provides substantial improvements over the original DFTB3 model for a number of properties of the nickel compounds, including the population and spin polarization of the d-shell, nature of the frontier orbitals, ligand field splitting and the energy different between low and high spin states at OPBE optimized structures. This proof-of-concept study suggests that with self-consistent parameterization of the electronic and +U parameters, the DFTB3+U model can develop into a promising model that can be used to efficiently study reactive events involving transition metals ion condensed phase systems. The methodology can be integrated with other approximate QM methods as well, such as the extended tight binding (xTB) approach.

Two binuclear double end-on azido bridged Ni(II) complexes, [Ni2L2(μ-1,1-N3)2(N3)2]⋅2H2O (1a), and [Ni2L2(μ-1,1-N3)2(N3)2]⋅4H2O (1b) having the same inner sphere, where L=((E)-N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)hydrazinyl)ethan-1-aminium, were synthesized from the same solution and characterized by single-crystal X-ray diffraction methods. Variable‐temperature magnetic susceptibility measurements showed intra-dimer ferromagnetic coupling between Ni(II) ions. The ferromagnetic coupling is supported by the broken-symmetry DFT calculations, with the level of theory chosen based on a benchmark study on 19 additional structurally related binuclear Ni(II) complexes. The role of water molecules in crystals of 1a and 1b is explained by DFT based energy decomposition analysis. This is the peer-reviewed, authors’ version of the article: Keškić, T.; Jagličić, Z.; Pevec, A.; Čobeljić, B.; Radanović, D.; Gruden, M.; Turel, I.; Anđelković, K.; Brčeski, I.; Zlatar, M. Synthesis, X-Ray Structures and Magnetic Properties of Ni(II) Complexes of Heteroaromatic Hydrazone. Polyhedron 2020, 191, 114802. [https://doi.org/10.1016/j.poly.2020.114802] Published version: [http://cer.ihtm.bg.ac.rs/handle/123456789/3684] Supplementary data: [https://cer.ihtm.bg.ac.rs/handle/123456789/4439] Crystallographic data (CCDC 2009327): [https://cer.ihtm.bg.ac.rs/handle/123456789/4441] Crystallographic data (CCDC 2009328): [https://cer.ihtm.bg.ac.rs/handle/123456789/4440]

The reaction of (E)-N,N,N-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium-chloride (HLCl) with copper(II) perchlorate led to mononuclear [CuLCl]ClO4 complex (1). The same reaction with excess of sodium azide gives dinuclear azido double end-on bridged Cu(II) complex [Cu2L2(μ-1,1-N3)2](ClO4)2 (2). In both complexes hydrazone ligand is NNO coordinated in monodeprotonated formally neutral zwitter-ionic form. Complexes were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray crystallography. Variable‐temperature magnetic susceptibility measurements for dinuclear Cu(II) complex showed intra-dimer ferromagnetic coupling between Cu(II) ions (J = 7.4 cm−1). DFT-BS calculations provided explanation for magnetic properties of dinuclear Cu(II) complex. Both complexes were shown to highly efficiently catalyze the N-arylation of imidazole and benzimidazole with electron-poor or electron-rich aryl iodides, under user-friendly and sustainable conditions. © 2019 Elsevier Ltd

The structures of nine iron complexes that show a diversity of experimentally observed spin ground states are optimized and analyzed with Density Functional Theory (DFT). An extensive validation study of the new S12g functional is performed, with the discussion concerning the influence of the environment, geometry and its overall performance based on the comparison with the well proven OPBE functional. The OPBE and S12g functionals give the correct spin ground state for all investigated iron complexes. Since S12g performs remarkably well it can be considered a reliable tool for studying spin state energetics in complicated transition metal systems. [Ministerio de Ciencia e Innovación (MICINN, project CTQ2011-25086/BQU), the Ministerio de Economia y Competitividad (MINECO, project CTQ2014-59212/BQU) and the DIUE of the Generalitat de Catalunya (project 2014SGR1202, and Xarxa de Referència en Química Teòrica i Computacional); MICINN and the FEDER fund (European Fund for Regional Development) under grant UNGI10-4E-801, and the Serbian Ministry of Education and Science (Grant No. 172035). This work was performed in the framework of the COST action CM1305 "Explicit Control Over Spin-states in Technology and Biochemistry (ECOSTBio)" (STSM reference: ECOST-STSM-CM1305-27360).]

The aromatic/antiaromatic behavior of the cyclopentadienyl anion (Cp-), bis(η5-cyclopentadienyl)iron(II) (Fe(Cp)2), as well as of the Jahn-Teller (JT) active cyclopentadienyl radical (Cp∙) and bis(η5-cyclopentadienyl)cobalt(II) (Co(Cp)2) has been investigated using Density Functional Theory (DFT) calculations of the Nuclear Independent Chemical Shifts (NICS). According to the NICS values, pentagon ring in Fe(Cp)2 is more aromatic than isolated Cp-. The NICS parameters have been scanned along the Intrinsic Distortion Path (IDP) for Cp∙ and Co(Cp)2 showing antiaromaticity, which decreases with increasing deviation from high symmetry D5h to low symmetry (LS) C2v. Changes in the NICS values along the IDP revealed that Co(Cp)2 in the LS nuclear arrangement has aromatic character, in contrast to the case of Cp∙ [Projekat Ministarstva nauke Republike Srbije, br. 172035]

In this work, the syntheses and characterization of two novel compounds of adamantane-1-sulfonic acid (1-AdSO(3)H) with cobalt(II) and cadmium(II) are reported. The results of single crystal X-ray analysis of the compounds revealed that adamantane-1-sulfonate (1-AdSO(3)(-)) in the monoanionic form plays different roles in the investigated compounds. Namely, while in compound [Co(H2O)(6)](1-AdSO(3))(2), six water molecules are coordinated to the cobalt(II) ion and 1-AdSO(3)(-) serves as a counter ion, in compound [Cd(H2O)(4)(1-AdSO(3))(2)], two molecules of 1-AdSO(3)(-) are trans-coordinated to the cadmium(II) ion as a monodentate (O)-ligand and the other coordination sites are occupied by water molecules. The obtained compounds showed moderate activity against Artemia salina. U ovom radu prikazana je sinteza i karakterizacija dva nova jedinjenja adamantan-1-sulfonske kiseline (1-AdSO3H) sa kobaltom(II) i kadmijumom(II). Rezultati rend- genske strukturne analize datih jedinjenja ukazuju da monoanjon adamantan-1-sulfonata (1-AdSO3 pokazuje različit afinitet prema Co(II) i Cd(II) jonima). U kompleksu [Co(H2O)6](1-AdSO3)2, šest molekula vode se koordinuje za Co(II) jon, dok 1-AdSO3 ima ulogu kontrajona. U kompleksu [Cd(H2O)4(1-AdSO3)2] dva jona 1-AdSO3 su koordinovana za Cd(II) jon kao monodentati u trans položaju preko kiseonikovih atoma, dok su ostala koordinaciona mesta zauzeta molekulima vode. Dobijena jedinjenja su pokazala umerenu aktivnost na Artemia salina.

The aromatic/antiaromatic behavior of the Jahn–Teller (JT) active benzene cation and anion has been investigated using Density Functional Theory (DFT) calculations of Nuclear Independent Chemical Shifts (NICS) and magnetic susceptibility. NICS parameters have been scanned along the Intrinsic Distortion Path (IDP) for the benzene cation showing antiaromaticity which decreases with increasing deviation from D6h to D2h symmetry. Changes in NICS values along the IDP from D6h to C2v in the benzene anion revealed non-aromatic character.

Density functional theory (DFT) in conjunction with the intrinsic distortion path (IDP) is employed to study the Jahn–Teller (JT) effect in all four diastereoisomers of tris(ethylenediamine)copper(II) ( [ Cu ( en ) 3 ] 2 + ) and tris(ethyleneglycol)copper(II) ( [ Cu ( eg ) 3 ] 2 + ) complexes. As a consequence of the JT effect all the isomers tetragonally elongate to the C 2 configurations. Although there are energy differences between the isomers of [ Cu ( en ) 3 ] 2 + , almost equal JT parameters suggest that chelate ring conformation does not have affect on the JT distortion. In a case of [ Cu ( eg ) 3 ] 2 + JT effect causes additional hydrogen bond formation and these two effects define the overall geometry of isomers.

The effects of adsorption on the graphite(0001) surface on the nonplanar distortions of nickel(II) octaethylporphyrin were studied by molecular mechanics (MM) approach. Using the Consistent Force Field (CFF) program with previously developed parameters for metalloporphyrins and supplemented to treat intermolecular interactions geometry optimizations were carried out for 43 conformations of 28 distinct conformers of nickel(II) octaethylporphyrin. The stable energy-minimized conformers were stereochemically characterized, analyzed by the Normal-coordinate Structural Decomposition (NSD) method and compared with the available theoretical and experimental data for the isolated nickel(II) octaethylporphyrin structures.