A novel 3D double helix cobalt(II) coordination polymer: Synthesis, crystal structures and third-order non-linear optical properties

Nonlinear optical properties, upconversion and lasing in metal–organic frameworks

The building block modular approach that lies behind coordination polymers (CPs) and metal–organic frameworks (MOFs) results not only in a plethora of materials that can be obtained but also in a vast array of nonlinear optical properties that could be aimed at.

Magnetic order in a novel 3D oxalate-based coordination polymer {[Cu(bpy)3][Mn2(C2O4)3]·H2O}n

A heterometallic coordination polymer {[Cu(bpy)3][Mn2(C2O4)3]·H2O}n (1; bpy = 2,2'-bipyridine) was synthesized using a building-block approach and characterized by IR spectroscopy, single-crystal X-ray diffraction, magnetization measurement, and X-band ESR spectroscopy both on a single crystal and a polycrystalline sample. The molecular structure of 1 is made of a three-dimensional (3D) anionic network [Mn2(C2O4)3]n(2n-) and tris-chelated cations [Cu(bpy)3](2+) occupying the vacancies of the framework. In compound 1 magnetic order is confirmed below 12.8 K - magnetization measurements reveal an antiferromagnetic-like network of canted Mn(2+) spins with incorporated paramagnetic Cu(2+) centres. The ESR spectroscopy distinctly shows the phase transition; above T≈ 13 K, single isotropic Lorentzian lines of Mn(2+) ions in the high spin state S = 5/2 were observed, while below this temperature, only characteristic Cu(2+) signals from cations were detected. Thermal decomposition residues of 1 at different temperatures (800-1000 °C) were analyzed by powder X-ray diffraction; by heating the sample up to 1000 °C the spinel oxide CuMn2O4 [94.1(2) wt%] was formed. From the refined structural parameters, it could be seen that the obtained spinel is characterized by the inversion parameter δ∼ 0.8, and therefore the structural formula at room temperature can be written as (tet)[Cu0.17Mn0.83](oct)[Mn1.17Cu0.83]O4.

A 3D oxalate-based network as a precursor for the CoMn₂O₄ spinel: synthesis and structural and magnetic studies

A novel heterometallic oxalate-based compound of the formula {[Co(bpy)3][Mn2(C2O4)3]·H2O}n (1; bpy = 2,2'-bipyridine) was synthesized and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction (XRD), and magnetization measurement. The molecular structure of 1 is made of a three-dimensional (3D) anionic network, [Mn2(C2O4)3]n(2n-), and tris-chelated cations [Co(bpy)3](2+) occupying the vacancies of the framework. Splitting between the zero-field-cooled (ZFC) and field-cooled (FC) branches of susceptibility below the small peak at 13 K indicates magnetic ordering. Compound 1 was used as a single-source precursor for the formation of the mixed-metal oxide CoMn2O4. This conversion via thermal decomposition was explored by thermal analysis (TGA and DTA), IR spectroscopy, powder XRD, and magnetic susceptibility measurement. From refined structural parameters, it could be seen that the spinel obtained by the thermal treatment of 1 at 800 °C is characterized by the inversion parameter δ = 21%, and therefore the structural formula at room temperature can be written as (tet)[Co(0.79)Mn(0.21)](oct)[Co(0.105)Mn(0.895)]2O4. The temperature dependence of magnetization for CoMn2O4 points to at least three magnetic phases: the ferrimagnetic state is observed below 83 K, and up to 180 K blocking of the magnetic moments of nanocrystallites of 31 nm appears, transforming to paramagnetic-like behavior above 180 K. Microstructural characterization of the CoMn2O4 sample was carried out by means of XRD line-broadening analysis.

Some new nano-structure zinc(II) coordination compounds of an imidazolidine Schiff base: spectral, thermal, antimicrobial properties and DNA interaction

Some novel nano-sized structure zinc complexes of a new Schiff base ligand entitled as (3-nitro-benzylidene)-{2-[2-(3-nitro-phenyl)-imidazolidine-1-yl]-ethyl}-amine(L) with general formula of ZnLX2 wherein X=Cl(-), Br(-), I(-), SCN(-) and N3(-) have been synthesized under ultrasonic conditions. The ligand and its complexes have been characterized by elemental analysis, molar conductance measurements, FT-IR, (1)H and (13)C NMR and UV-Visible spectroscopy. The resulting data from spectral investigation especially (1)H and (13)C NMR well confirmed formation of an imidazolidine ring in the ligand structure. Transmission electron microscopy (TEM) showed nano-size structures with average particle sizes of 21.80-78.10nm for the zinc(II) Schiff base complexes. The free Schiff base and its Zn(II) complexes have been screened in vitro both for antibacterial activity against some gram-positive and gram-negative bacteria and also for antifungal activity. The metal complexes were found to be more active than the free Schiff base ligand. The results showed that ZnL(N3)2 is the most effective inhibitor against Escherichia coli, Pseudomonas aereuguinosa, Staphylococcus aureus and Candida albicans while ZnLBr2 was found to be more effective against Bacillus subtillis than other compounds. Moreover, DNA cleavage potential of all compounds with plasmid DNA was investigated. The results showed that the ligand and ZnLCl2 complex cleave DNA more efficiently than others. In final, thermal analysis of ligand and its complexes revealed that they are decomposed via 2-3 thermal steps in the range of room temperature to 1000°C. Furthermore some activation kinetic parameters such as A, E(*), ΔH(*), ΔS(*) and ΔG(*) were calculated based on TG/DTA plots by use of coats - Redfern relation. Positive values of activation energy evaluated for the compounds confirmed the thermal stability of them. In addition to, the positive ΔH(*), and ΔG(*) values suggested endothermic character for the thermal decomposition steps.