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Four hetero-dinuclear nickel(ii)/lead(ii) complexes have been synthesized and characterized. Their structures have been confirmed by single crystal X-ray diffraction studies. In each complex, nickel(ii) is placed in the inner N2O2 compartment and lead(ii) in the outer O2O2′ compartment of the respective Schiff base. In complexes 1, 3 and 4, lead(ii) centres are hemidirectionally coordinated, and thus are well suited for establishing tetrel bonding interactions which have been investigated thoroughly by means of DFT calculations. [ABSTRACT FROM AUTHOR]

Three heteronuclear cobalt(iii)/sodium Schiff base complexes have been synthesized and characterized by elemental and spectral analysis. The structures of all three complexes have been confirmed by single crystal X-ray analyses. Each of these three complexes crystallizes in monoclinic space group P21/c. In each complex, cobalt(iii) is placed in the inner N2O2 compartment and sodium is placed in the outer O2O′2 compartment (O and O′ denote the phenolic and ethoxy/methoxy oxygen atoms, respectively) of the Schiff bases. With decrease in steric hindrance around the O2O′2 compartment by the replacement of ethyl groups with methyl groups, tetranuclear complexes resulted instead of dinuclear ones. Interesting carbon bonding interactions in the solid state of the complexes have been studied by means of DFT calculations using several computational tools such as “atoms-in-molecules” (AIM) and natural bond orbital (NBO) analyses. [ABSTRACT FROM AUTHOR]

Variable temperature magnetic measurements of a novel tetranuclear nickel(ii) complex, consisting of two pseudo-dinuclear entities bridged by an end-to-end azide, indicate the presence of both intra- and inter-dinuclear ferromagnetic interactions (J1 = 16.48 cm−1 and J2 = 24.17 cm−1, respectively), as also corroborated by DFT calculations (J1 = 12.0 cm−1 and J2 = 29.2 cm−1). [ABSTRACT FROM AUTHOR]

A novel mononuclear Mn(iii) complex, [MnIII(L1)Cl(H2O)]·H2O (1), and a tetranuclear Zn(ii)–Mn(ii) complex, [{ZnII2(L2)2Cl2}MnII2(μ1,1-N3)2(H2O)2]·2H2O (2), have been synthesized involving azo Schiff base ligands, viz. H2L1 = (E)-6,6′-((1E,1′E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(2-methoxy-4-((E)-p-tolyldiazenyl)phenol) and H2L2 = (E)-6,6′-((1E,1′E)-((2,2-dimethylpropane-1,3-diyl)bis(azanylylidene))bis(methanylylidene))bis(2-methoxy-4-((E)-p-tolyldiazenyl)phenol), respectively. The solid-state structures were determined by single crystal X-ray crystallography. In complex 1, the Mn(iii) centre adopts slightly distorted octahedral geometry, while in complex 2 the Mn(ii) centre residing in the outer core of the ligand adopts a distorted pentagonal bipyramidal geometry. In complex 1, the chloride ion simply acts as a terminal coligand, while in complex 2, azide ions bind the metal centres in an end-on bridging fashion to produce a tetranuclear complex. The phenoxazinone synthase-like activity of both complexes has been examined and a detailed investigation of the structure–property correlation has been performed. Whereas the mononuclear complex 1 exhibits significant phenoxazinone activity, complex 2 is almost inactive, although in both complexes labile sites are available at manganese centres for substrate binding. The present work therefore highlights the importance of higher oxidation states of manganese over nuclearity for the development of better in vitro catalysts. In addition, extensive efforts have been made to visualize and quantify all supramolecular interactions present in 1 and 2. [ABSTRACT FROM AUTHOR]

Reaction of tetrameric trimethylplatinum(iv) iodide with an excess of 3-substituted pyridines in chloroform afforded mononuclear complexes, [PtMe3L2I] (L = 3-CNpy, 3-Brpy, 3-MeOpy, 3-Mepy and 3-Etpy). The complexes were characterized by 1H NMR, CHN analysis and X-ray single crystal structure analysis. The mononuclear complexes undergo reaction with trimethylplatinum(iv) iodide in chloroform to form the corresponding dinuclear forms (both syn and anti). A comparison of both the mononuclear and dinuclear forms in solution for a particular pyridine substituent has been studied in detail with the help of 1H NMR spectroscopy, ably supported by DFT computational studies. The investigation further shows the influence of the pyridine substituent on controlling the mode of the reaction. The crystal structures of two dinuclear complexes, syn-[PtMe3(3-CNpy)I]2 and anti-[PtMe3(3-Brpy)I]2, have also been described here. [ABSTRACT FROM AUTHOR]

Three new heteronuclear nickel(ii)/cadmium(ii) complexes, [(SCN)(Cl)Cd(L)Ni(DMF)2] (1), [(SCN)(CH3CO2)Cd(L)Ni(CH3OH)2] (2) and [(SCN)(Cl)Cd(L)Ni(NH2CH2CH2CH2NH2)]n (3) {where H2L = N,N′-bis(3-ethoxy-salicylidene)propane-1,3-diamine is a N2O4 compartmental Schiff base}, have been synthesized and characterized. The structures of the complexes have been confirmed by single crystal X-ray diffraction studies. In each complex, nickel(ii) is placed in the inner N2O2 environment and cadmium(ii) is placed in the outer O4 compartment of the compartmental Schiff base. Furthermore, the importance of unconventional C–H…π (chelate) interactions in the solid state of both complexes and C–H…π (thiocyanate) interaction in complex 2 has been described by means of DFT and MEP calculations and characterized using NCI plots. All complexes show photoluminescence at room temperature upon irradiation by ultraviolet light. The lifetimes of excited states are in the range of 2–6 ns. [ABSTRACT FROM AUTHOR]

In this manuscript we report for the first time the concurrent agostic and tetrel bonding interactions involving the heaviest tetrel atom (Pb) in N′-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide–PbX complexes (X = Cl, I, NCS, NO2). [ABSTRACT FROM AUTHOR]

Two new pyridine-based heterocyclic thiosemicarbazone ligands and their Ni(ii), Cd(ii), Mn(ii), Co(iii) and Cu(ii) complexes have been synthesized and characterized by structural, analytical and spectroscopic methods. The monodeprotonated anionic forms of the ligands coordinate in a tridentate fashion via two nitrogen and one sulphur donor atoms to yield seven complexes in which metal centres vary from four-coordinated square planar to six-coordinated distorted octahedral geometries. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending on the anion coordinated to the metal centre. We have analysed the interesting supramolecular assemblies observed in the solid state of some complexes by means of DFT calculations. These assemblies are formed by a combination of several noncovalent interactions, including chelate ring–π, π–π, and chalcogen bonding interactions, that have been characterized using Bader's Theory of “atoms-in-molecules”. [ABSTRACT FROM AUTHOR]

In this manuscript we report the synthesis and X-ray characterization of several complexes of Cu(ii), Co(ii) and Ni(ii) with 2-(N-benzimidazolyl)-pyrimidine (L) and nitrate co-ligands. Complexes 1 and 2 are trans and cis isomers, respectively, with formula [CuL2(NO3)2]. Furthermore, complexes 2, [CoL2(NO3)2] (3) and [NiL2(NO3)2] (4) are essentially isostructural with a cis-disposition of the nitrate ligands. In compounds 1–4, the coordination mode of nitrate is terminal bidentate. Finally, during the synthesis of compound 1, a few crystals of a different complex were found and separated manually from the bulk sample and characterized by X-ray diffraction. In this compound (5), the benzimidazole ring of the ligand is oxidized to benzimidazolone (L′) and the formula of this unexpected compound is [CuL′2(H2O)2](NO3)2. Complexes 1 and 5 are characterized by the presence of anion–π interactions that are relevant to the final 3D architecture and packing. In the crystal structures of the five compounds, C–H…O hydrogen bonds, anion–π and π-stacking interactions are described and analysed by means of density functional theory (DFT) calculations since they play an important role in the construction of three-dimensional supramolecular frameworks. Moreover, some unconventional interactions have been characterized using Bader's theory of atoms-in-molecules. [ABSTRACT FROM AUTHOR]

A series of four mononuclear Schiff-base complexes, namely, [Zn(L)(NCS)2] (1), [Zn(L)(N3)2] (2), [Cu(L)(NCS)2] (3) and [Ni (L)(2bpy)(NCS)](ClO4) (4), [where L = N,N-dimethyl-N′-(phenyl-pyridin-2-yl-methylene)-ethane-1,2-diamine and 2bpy = 2-benzoylpyridine] were synthesized with the aim of investigating the role of different non-covalent weak interactions responsible for the crystal packing of the complexes. All of them were structurally characterised by X-ray diffraction analysis. In addition to conventional CH3…π and π…π interactions, the importance of unconventional C–H…π interactions in the crystal packing of compounds 1–4 was investigated by means of Hirshfeld surface analysis and DFT calculations. In these unconventional C–H…π interactions, the π-system (electron donor) is provided by the pseudohalide coligands. The interactions formed by the π-system depend on the nature of the pseudohalide (N3, NCO, NCS or NCSe) as demonstrated by molecular electrostatic potential calculations. Additionally, we have explored the photophysical properties of these complexes. Finally, we have combined a search in the Cambridge Structural Database and DFT energy calculations to analyse the rare ambidentate behaviour of SCN within the same complex. [ABSTRACT FROM AUTHOR]

Two new trinuclear hetero-metallic copper(II)-cadmium(II) complexes [(CuL)2Cd(NCS)2] (1) and [(CuLR)2Cd(SCN)2] (2) have been synthesized using [CuL] and [CuLR] as ''metalloligands'' (where H2L = N,N'-bis(salicylidene)-1,4-butanediamine and H2LR = N,N'-bis(2-hydroxybenzyl)-1,4-butanediamine) respectively. Both the complexes were characterized by elemental analysis, various spectroscopic methods and single crystal XRD. Complex 1 is an angular trinuclear species, in which two terminal four-coordinate square planar ''metalloligands'' [CuL] are coordinated to a central Cd(II) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal thiocyanate ions. In complex 2, which is linear, in addition to the double phenoxido bridge, two SCN- coordinate to the trans positions of the central octahedral Cd(II) via S atoms. Theoretical calculations on the energetic difference between the two possible coordination modes of the thiocyanate anion to the Cd atom reveal that N-coordination is preferred over S-coordination in agreement with the much greater abundance of the reported N-bonded structures. In 2, there is a strong N-H . . . NCS-Cd H-bonding interaction, the binding energy of which is computed to be approximately -9.3 kcal mol-1, which is sufficient to compensate the 9.0 kcal mol-1 of energetic cost due to the unusual Cd-SCN coordination mode. [ABSTRACT FROM AUTHOR]