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A tridentate N,N,O-donor ligand, in the form of a Schiff base of aminoguanidine (LH) with salicylaldehyde, and its Cu(II) complex, [Cu2(LH)2](ClO4)2, have been synthesized. The single crystal X-ray structure of the complex is reported. The complex shows strong DNA binding affinity, with a binding constant value comparable to that of classical intercalators like ethidium bromide. Against the human colon cancer cell line HCT116, the complex shows significant in vitro cytotoxicity with a LD50 value of 20 μM. It is shown that the cytotoxicity of the complex follows the apoptosis mechanism. The complex can also be used for selective spectrophotometric or fluorometric determination of histidine. The binuclear Cu(II) complex shows strong intramolecular antiferromagnetic interaction between the Cu(II) atoms mediated by two bridging phenoxide ligands, with 2J = −656 cm−1. DFT calculations are used to explain the magnetic interaction. [ABSTRACT FROM AUTHOR]

In this manuscript, we report the synthesis and X-ray characterization of three N6-aminoacid/peptide–adenine-derivatives; the zwitterion N6GlyAde·0.5H2O (1), its corresponding protonated form N6GlyAde·2HCl·H2O (2) and N6GlyGlyAde·H2O (3). In the zwitterion complex (1), the adenine is protonated at N(3) and the anionic carboxylate interacts with the imidazole ring of the neighbouring purine molecule. It also interacts with the water molecule that connects it to another adenine ring through N(7)–H…O hydrogen bonds. The hydrochloride (compound 2) crystallizes forming a laminar structure and exhibits double protonation in the adenine ring (at N1 and N7). Moreover, energetically strong anion–π interactions are important for constructing the final solid state architecture in 2. Finally, compound 3, which presents a neutral adenine ring, crystallizes in a chiral point group and forms CH…O and CH…N H-bonding interactions in the solid state. We have also studied the noncovalent interactions energetically using DFT calculations and rationalized the interactions using Molecular Electrostatic Potential surfaces and Bader's theory of “Atoms-in-Molecules”. [ABSTRACT FROM AUTHOR]

Condensation of N-(2-hydroxyethyl)ethylenediamine and pyridine-2-carbaldehyde in the presence of ZnX2 salts (X = ClO4−, Cl−, Br−, I−) generates four complexes, namely, [ZnL1Cl](ClO4) (1), [ZnL1Cl][ZnCl3(H2O)]·2H2O (2), [ZnL1Br][ZnBr3(H2O)]·2H2O (3), and [Zn(L2)3]I2 (4), where L1 and L2 are aminal and hemiaminal ether derivatives, i.e., (E)-N-((pyridine-2-yl)methylene)-2-((2-pyridine-2-yl)oxazolidin-3-yl)ethanamine and 2-(2-pyridin-2-yl-imidazolidin-1-yl)-ethanol, respectively. No complex with the expected Schiff-base ligand (E)-2-(2-(pyridin-2-ylmethyleneamino)ethylamino)ethanol (L) or with 2-(2-pyridyl-3-(2-hydroxyethyl))oxazolidine (L3) was obtained. The structures of complexes 1, 3, and 4 have been elucidated by single crystal X-ray diffraction. All the complexes have been characterized by detailed NMR (1H, 13C and DEPT-135) and ESI-MS analyses, indicating retention of solid state structures in the solution phase. Complex 1 deserves special mention as during its formation, the ClO4− ion undergoes reduction to Cl− and thus, it forms a mixed anionic ligand complex. Thorough DFT calculations have been performed at the BP86-D3/def2-TZVP level of theory to rationalize the ligand and complex formation. The calculations suggest that the aminal form (L1) is the most favored species followed by the Schiff-base, whereas the hemiaminal ether form (L3) is the least preferred one. The role of halides during the formation of the monoanionic [ZnX3(H2O)]− species is crucial, and the achieved complex is highly favored when X = Cl and disfavored for X = I; this trend has been rationalized by the DFT calculations. The phosphatase activities of the complexes have been investigated, and their efficiencies follow the order 2 ＞ 1 ＞ 3 ＞ 4. [ABSTRACT FROM AUTHOR]

Crystal structures of aminopyridine–succinate salts (1–3) were solved by single crystal X-ray diffraction where salt bridge (SB) interactions between the succinate and protonated aminopyridine dominated their supramolecular architecture. X-ray crystallography reveals that compounds 1 (hydrogensuccinate 2-amino-5-methylpyridinium salt) and 2 (hydrogensuccinate 2-amino-4-methylpyridinium salt) exhibit C–H…SB…π+ assemblies, while compound 3 (succinato-aminopyridinium salt) displays unique N–H…SB…lone pair (l)p networks in the solid state. These unexplored extended networks are described and investigated for the first time in crystalline structures. Our study also describes the duality of the salt bridge in establishing π-facial interactions with electron rich and/or electron poor moieties depending on the positive or negative nature of the SB counterpart that interacts with the SB surface. The theoretical study combines an energetic investigation of the noncovalent forces that contribute to the extended supramolecular network and the characterization of the diverse interactions by means of Bader's theory of “atoms in molecules” (AIM) and the NCIplot index. [ABSTRACT FROM AUTHOR]

Two novel Cu(ii) complexes, [Cu2L2(μ1.1-N3)2] (1) and [Cu2L2(μ1.1-CH3COO−)2]·2H2O (2), have been synthesized using a tridentate NNO donor Schiff base ligand, 2-[(piperidin-2-ylmethylimino)-methyl]-phenol (HL) and azide or acetate as the co-ligand. Both the structures exhibit elongated (4 + 1) square pyramidal geometries and are centrosymmetric dimers, in which the metal centers are connected by the double μ1.1-azido and acetate bridges. Both complexes exhibit unconventional C–H…π(chelate) interaction along with conventional C–H…π(aryl) supramolecular interactions in the solid-state assembly. A detailed analysis of Hirshfeld surfaces and fingerprint plots elegantly quantifies the interactions within the crystal structures, revealing significant similarities and differences in the interactions experienced by the complexes. The intricate combinations of C–H…π(chelate) and C–H…π(aryl) interactions are fully described along with the computational studies. The binding energies associated with the noncovalent interactions observed in the crystal structures and the interplay between them have been calculated using theoretical DFT calculations. Moreover, the interactions have been characterized by using both Bader's theory of “atoms-in-molecules” and the noncovalent interaction plot (NCI plot). [ABSTRACT FROM AUTHOR]

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]

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]

A theoretical study of nitryl halide heterodimers has been carried out using SCS-RI-MP2 and CCSD(T) at the complete basis set (CBS) calculations. For this purpose, 66 heterodimers have been characterized as minima and arranged in six groups depending on the interactions involved and their geometrical arrangements. The CCSD(T)/CBS interaction energies vary between −0.6 and −11.1 kJ mol−1. The heavier the halogen atoms, the larger the interaction energies. Natural bond orbital (NBO) and “atoms-in-molecules” (AIM) theories were then used to analyze the complexes, confirming the presence of halogen, chalcogen, and π-hole interaction bonds. The largest charge-transfer energy contributions were found for halogen bonded complexes (up to 29.1 kJ mol−1). Furthermore, the physical nature of the interactions was studied using symmetry-adapted perturbation theory (SAPT) calculations, and it was concluded that dispersion was the major source of attraction, although electrostatics is important in halogen bonded complexes. [ABSTRACT FROM AUTHOR]

In 1996 J. Derek Woollins reported “π-facial” interactions between the chloride anion and the seven-membered aromatic [S4N3]+ and inorganic ring (Polyhedron, 1996, 15, 4603–4605). In spite of this manuscript has not been highlighted before (only 5 citations so far), it can be considered as a pioneering work in the field of noncovalent interactions involving anions, since unprecedented anion–π contacts were described as “π-facial” interactions. In this manuscript several complexes of [S4N3]+ with anions were optimized at the BP86-D3/def2-TZVPD level of theory and compared to X-ray structures retrieved from the CSD. We have evaluated the interaction energies between the chloride and nitrate anions and the [S4N3]+ ring. The anion–π complexes are energetically favourable and the complexation has been characterized by means of Bader's theory of “atoms in molecules”. Moreover, the π-orbitals of the [S4N3]+ ring have been computed and the aromaticity of the 10-π electron seven membered ring was analysed. [ABSTRACT FROM AUTHOR]