New chiral Schiff base–zinc complexes and their esterolytic catalytic activity

Synthesis, characterization and crystal structure of 4-methoxybenzylidene-based zinc(II) complexes

Two novel zinc(II) complexes containing 4-methoxybenzylidene moieties namely, Zn(L)Cl2 (L = N, N′-bis(4-methoxybenzylidene)ethane-1, 2-diamine (1) or N-(4-methoxybenzylidene)-ethane-1, 2-diamine (2)) have been synthesized and characterized by infrared spectroscopy and single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P21/c with a = 9.2315(4); b = 12.0449(4); c = 18.2164(7) Å; β = 98.472(4)°, V = 1278.9(4) Å3 and Z = 4. Complex 2 crystallizes in the monoclinic space group P21/n with a = 6.5733 (2), b = 13.6595(5), c = 15.1615(5) Å; β = 101.846(4)°, V = 1332.33(8) Å3 and Z = 4. The environment of each Zn(II) atom is distorted tetrahedral with coordination of two terminal Cl atoms and two N atoms of the N,N′ – bis(4-methoxybenzylidene)ethane-1,2-diamine (1) or N-(4-methoxybenzylidene)ethane-1,2-diamine (2) ligand. The stability of the crystalline structure is ensured by the existence of intra- and intermolecular hydrogen bonds of the type C–H…Cl (1) and N–H…Cl (2) leading to supramolecular topologies.

Docking studies on an N4-donor Schiff base ligand and its Cu(II) complex supported by structural, spectral and theoretical studies

A new asymmetrical Schiff base ligand, N1-(3-((pyridin-2-ylmethylene)amino)propyl)ethane-1,2-diamine, and its copper(II) complex, [Cu(PPEA)Br]Br·H2O (1), have been prepared. The copper complex has an elongated square pyramidal geometry with a CuN4Br environment. The thermodynamic stability of the compounds and their charge distribution patterns were studied by Density Functional Theory and natural bond orbital analysis. The ability of the ligand and its copper complex to interact with 10 selected biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS, Top II and B-DNA) was investigated by docking studies and compared with that of doxorubicin.

Ligand libraries for high throughput screening of homogeneous catalysts

This review describes different approaches to construct ligand libraries towards high throughput screening of homogeneous metal catalysts.

Theoretical and experimental investigation of anticancer activities of an acyclic and symmetrical compartmental Schiff base ligand and its Co(ii), Cu(ii) and Zn(ii) complexes

A compartmental Schiff base ligand, 2,2′-((((((2-hydroxypropane-1,3-diyl)bis(oxy))bis(2,1-phenylene))bis(methylene))bis(azanylylidene))bis(methanylylidene))bis(4-bromophenol) (H₃L^Br) and its complexes with cobalt(ii), copper(ii) and zinc(ii) including, [Co(HL^Br)] (1), [Cu₂(L^Br)(μ-1,3-OAc)]·MeOH (2) and [Zn(HL^Br)] (3) were prepared using template synthesis and characterised by elemental analysis, FT-IR and ¹H NMR spectroscopies and single-crystal X-ray diffraction. In the structure of complexes 1 and 3 the metal atom has a MN₂O₂ environment with tetrahedral geometry while complex 2 has a binuclear structure with a MNO₄ environment and square planar geometry around the copper atom. The ability of all compounds to interact with the nine biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS and Top II) are investigated by docking calculations. For examination of the docking results, the in vitro activities of eight compounds against the human leukemia cell line K562 was investigated by evaluation of IC₅₀ values and mode of cell death (apoptosis).

A compartmental Schiff base ligand and its copper, cobalt and zinc complexes were prepared. The in vitro activities of all compounds against the human leukemia cell line K562 were investigated along with docking and DFT studies.

Selection of chiral zinc catalysts for the kinetic resolution of esters via dynamic templating

Dynamic combinatorial libraries of chiral tetradentate bis-imine zinc(II) complexes have been prepared and screened for (1) their discrimination of enantiomeric picolinate esters and pyridyl phosphonate transition state analogs (TSAs) and (2) their catalytic activity and selectivity for enantioselective methanolysis of racemic picolinate esters. The zinc complexes are in equilibrium with their imine ligands as well as with the aldehyde and amine building blocks that form them, enabling the composition of the library to adapt in response to the introduction of coordinating substrates or TSAs. Binary (L)Zn(OTf)(solv)(+) complexes are generated either individually or in libraries from chiral tartrate-derived diamines (2,3) and a set of N-heterocyclic aldehydes (4-12) and the distribution of complexes established by ESI-MS analysis. Binding studies of the (diimine)Zn(OTf)(2) complex libraries with enantiomeric R- and S-2-pyridyl phosphonate TSA 13 show chiral discrimination via formation of diastereomeric LZn(R/S-13)(+) complexes with low to moderate enatioselectivity ratios, k(R)/k(S) (α), ranging from 0.5 to 5.0; corresponding templating of selected binary complexes with the enantiomeric substrates, PyrCO(2)CH(OH)Ph (1), show negligible chiral recognition. The rate constants for methanolysis of the R- and S-esters, PyrCO(2)CH(OH)Ph (1) catalyzed by several L*Zn(OTf)(2) complexes range in value several fold depending on L and with enantioselectivity ratios, k(R)/k(S) (α), ranging from 0.76 to 2.8.