A pair of stereoisomers of nickel Schiff base complexes, namely [Ni(C17H15N4O2)2·2CH3OH]n (1) (C17H15N4O2 = 2-acetylpyrazine-l-tryptophan) and [Ni(C17H15N4O2)2·2CH3OH]n (2) (C17H15N4O2 = 2-acetylpyrazine-d-tryptophan), were synthesized and characterized by physico-chemical and spectroscopic methods. The X-ray diffraction single-crystal analyses indicate that the structure of 2 is essentially 0D monomeric, while a 2D layer structure is formed through N–H…O intermolecular hydrogen bonds for 1. The interactions between complex 1 and calf thymus DNA were investigated by spectroscopic and viscometric methods. The results indicate that complex 1 interacts with DNA very strongly (K
 b = 1.01 × 107 mol−1 L and K
 sq = 1.11). The nature of the binding seems to be mainly an electrostatic interaction between DNA and the complex. However, other binding modes, such as hydrogen bonding, may also be present in this system.

Nickel(II) complexes with Schiff bases derived from 2-acetylpyrazine and tryptophan: synthesis, crystal structures and DNA interactions

Two dinuclear succinato-bridged nickel(II) complexes [Ni(RR-L)]2(μ-SA)(ClO4)2 (1) and [Ni(SS-L)]2(μ-SA)(ClO4)2 (2) (L = 5, 5, 7, 12, 12, 14-hexamethyl-1, 4, 8, 11-tetraazacyclotetradecane, SA = succinic acid) were synthesized and characterized by EA, Circular dichroism (CD), as well as IR and UV/Vis spectroscopy Single crystal X-ray diffraction analyses revealed that the NiII atoms display a distorted octahedral coordination arrangement, and the succinato ligand bridges two central NiII atoms in a bis bidentate fashion to form dimers in 1 and 2 The monomers of {[Ni(RR-L)]2(μ-SA)}2+ and {[Ni(SS-L)]2(μ-SA)}2+ are connected by O–H···O and N–H···O hydrogen bonds into a 1D right-handed and left-handed helical chain along the b axis, respectively The homochiral natures of 1 and 2 are confirmed by the results of CD spectroscopy

Synthesis and Crystal Structure of Two Succinato-Bridged Macrocyclic Nickel(II) Complexes

Vascular endothelial growth factor receptor-2, (VEGFR-2), is a key element in angiogenesis, the process by which new blood vessels are formed, and is thus an important pharmaceutical target. Here, 3-D quantitative structure-activity relationship (3-D QSAR) were used to build a quantitative screening and pharmacophore model of the VEGFR-2 receptors for design of inhibitors with improved activities. Most of available experimental data information has been used as training set to derive optimized and fully cross-validated eight mono-probe and a multi-probe quantitative models. Notable is the use of 262 molecules, aligned following both structure-based and ligand-based protocols, as external test set confirming the 3-D QSAR models' predictive capability and their usefulness in design new VEGFR-2 inhibitors. From a survey on literature, this is the first generation of a wide-ranging computational medicinal chemistry application on VEGFR2 inhibitors.

Vascular endothelial growth factor receptor-2 (VEGFR-2) inhibitors: development and validation of predictive 3-D QSAR models through extensive ligand- and structure-based approaches.

The reactions of a racemic four-coordinate Ni(II) complex [Ni(rac-L)](ClO4)2 with l- and d-alanine in acetonitrile/water gave two six-coordinate enantiomers formulated as [Ni(RR-L)(l-Ala)](ClO4)·2CH3CN (1) and [Ni(SS-L)(d-Ala)](ClO4) (2) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclo-tetradecane, Ala− = alanine anion), respectively. Evaporation from the remaining solutions gave two four-coordinate enantiomers characterized as [Ni(SS-L)](ClO4)2 (S-3) and [Ni(RR-L)](ClO4)2 (R-3), respectively. Single-crystal X-ray diffraction analyses of complexes 1 and 2 revealed that the Ni(II) atom has a distorted octahedral coordination geometry, being coordinated by four nitrogen atoms of L in a folded configuration, plus one carboxylate oxygen atom and one nitrogen atom of l- or d-Ala− in mutually cis-positions. Complexes 1 and 2 are supramolecular stereoisomers, constructed via hydrogen bonding between [Ni(RR-L)(l-Ala)]+ or [Ni(SS-L)(d-Ala)]+ monomers to form 1D hydrogen-bonded zigzag chains. The homochiral natures of complexes 1 and 2 have been confirmed by CD spectroscopy.

Chiral resolution of l- and d-alanine and a racemic macrocyclic nickel(II) complex: synthesis and crystal structures

A nickel(II) coordination polymer of succinic acid (1,4-butanedioic acid, H2succ), [Ni(succ)(H2O)4]n (1), was prepared and characterized in depth using IR and Raman spectroscopic methods and theore...

IR and Raman spectroscopic analysis, DFT modeling, and magnetic properties of a nickel(II) complex, [Ni(succ)(H2O)4]n

Three dinuclear terephthalato-bridged nickel(II) complexes [Ni(rac-L)]2(μ-TPA)(ClO4)2 (1), [Ni(RR-L)]2(μ-TPA)(ClO4)2 (2), and [Ni(SS-L)]2(μ-TPA)(ClO4)2 (3) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, TPA = terephthalic acid) have been synthesized and characterized. Single-crystal X-ray diffraction analyses revealed that the Ni(II) atoms have six-coordinated distorted octahedral environments, and the terephthalato ligand bridges two Ni(II) centres in a bis bidentate fashion to form dimers in all three complexes. The monomers of {[Ni(RR-L)]2(μ-TPA)}2+ and {[Ni(SS-L)]2(μ-TPA)}2+ are connected through intermolecular hydrogen bonds to generate 1D right-handed and left-handed helical chains, respectively. The racemic character of 1 and the homochiral natures of 2 and 3 are confirmed by the results of CD spectroscopy.

Xiao-Ping Jiang

Papers

Synthesis and crystal structures of terephthalato-bridged macrocyclic nickel(II) complexes with cis configurations

3D-QSAR Studies of VEGFR-2 Kinase Inhibitors Based on Docking