Evaluation of 1‐arylpiperazine derivative of hydroxybenzamides as 5‐HT1A and 5‐HT7 serotonin receptor ligands: An experimental and molecular modeling approach

The synthesis and evaluation as 5‐HT_1A and 5‐HT₇ serotonin receptor ligands of the two sets of O‐substituted hydroxybenzamides, structurally related to 2‐{3‐[4‐(2‐methoxyphenyl)piperazin‐1‐yl]propoxy}benzamide ( 1 ), (K_i 5‐HT_1A = 21 nM, 5‐HT₇ = 234 nM) are reported. To affect the affinity for 5‐HT_1A and 5‐HT₇ receptors, an amide moiety ( 2 , 3 , 4 , 5 , 6 ) and a hydrocarbon chain length ( 7 , 8 , 9 , 10 ) were modified. The serotonergic activity of compounds 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 was generally higher in the case of 5‐HT_1A receptors compared with 5‐HT₇ ones; the most active 5‐HT_1A ligands being meta‐isomer 2 (K_i = 7 nM) and both analogs of 1 with the longest spacer, i.e., penta‐ and hexa‐methylene derivatives 9 and 10 (K_i = 4 and 3 nM, respectively). The observed biological properties of compounds 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 were elucidated using molecular modeling procedures. J. Heterocyclic Chem., (2010).     

Synthesis, antimicrobial and antiproliferative activity of novel silver(I) tris(pyrazolyl)methanesulfonate and 1,3,5-triaza-7-phosphadamantane complexes

Five new silver(I) complexes of formulas [Ag(Tpms)] (1), [Ag(Tpms)(PPh(3))] (2), [Ag(Tpms)(PCy(3))] (3), [Ag(PTA)][BF(4)] (4), and [Ag(Tpms)(PTA)] (5) {Tpms = tris(pyrazol-1-yl)methanesulfonate, PPh(3) = triphenylphosphane, PCy(3) = tricyclohexylphosphane, PTA = 1,3,5-triaza-7-phosphaadamantane} have been synthesized and fully characterized by elemental analyses, (1)H, (13)C, and (31)P NMR, electrospray ionization mass spectrometry (ESI-MS), and IR spectroscopic techniques. The single crystal X-ray diffraction study of 3 shows the Tpms ligand acting in the N(3)-facially coordinating mode, while in 2 and 5 a N(2)O-coordination is found, with the SO(3) group bonded to silver and a pendant free pyrazolyl ring. Features of the tilting in the coordinated pyrazolyl rings in these cases suggest that this inequivalence is related with the cone angles of the phosphanes. A detailed study of antimycobacterial and antiproliferative properties of all compounds has been carried out. They were screened for their in vitro antimicrobial activities against the standard strains Enterococcus faecalis (ATCC 29922), Staphylococcus aureus (ATCC 25923), Streptococcus pneumoniae (ATCC 49619), Streptococcus pyogenes (SF37), Streptococcus sanguinis (SK36), Streptococcus mutans (UA159), Escherichia coli (ATCC 25922), and the fungus Candida albicans (ATCC 24443). Complexes 1-5 have been found to display effective antimicrobial activity against the series of bacteria and fungi, and some of them are potential candidates for antiseptic or disinfectant drugs. Interaction of Ag complexes with deoxyribonucleic acid (DNA) has been studied by fluorescence spectroscopic techniques, using ethidium bromide (EB) as a fluorescence probe of DNA. The decrease in the fluorescence of DNA-EB system on addition of Ag complexes shows that the fluorescence quenching of DNA-EB complex occurs and compound 3 is particularly active. Complexes 1-5 exhibit pronounced antiproliferative activity against human malignant melanoma (A375) with an activity often higher than that of AgNO(3), which has been used as a control, following the same order of activity inhibition on DNA, i.e., 3 > 2 > 1 > 5 > AgNO(3)? 4.     

Crystal structure and morphology evolution in the LaXO3, X = Al, Ga, In nano-oxide series. Consequences for the synthesis of luminescent phosphors

The LaXO(3):Tb(3+) (X = Al(3+), Ga(3+), In(3+)) perovskite nanoparticles were obtained using the nonhydrolytic treatment (Bradley reaction) of the molecular precursors of the La(O(i)Pr)(3), Al(O(i)Pr)(3), Ga(O(i)Pr)(3), In(5)O(O(i)Pr)(13), and Tb(acac)(3), respectively. It was shown that crystal structure and morphology evolution in the LaXO(3), X = Al, Ga, In nano-oxide series depended on the size and chemical properties of the X-metal atom. Formation of the LaInO(3):Tb(3+) nanoparticles is distinctly less thermodynamically demanding on contrary to the LaAlO(3):Tb(3+) and LaGaO(3):Tb(3+) since it provided crystalline product directly in the solution synthesis at 202 °C, which is the lowest reported synthesis temperature for this compound up-to-date. This behavior was ascribed to the effects directly connected with the dopant substitution (exchange of bigger La(3+) cation with smaller Tb(3+)) as well as reduction of the particle size. The size effects are mostly reflected in the expansion of the cell volume, changes of the cell parameters as well as shifting and broadening of the Raman bands. Indirectly, size reduction has also an effect on the luminescence properties through the higher probability of presence of surface and net defects as well as heterogeneous distribution of the Tb(3+) ions caused by high surface-to-volume ratio. The prepared nanophosphors show basically green emission with exception of white-green in case of the LaInO(3):Tb(3+). Strong emission quenching was found in the latter case being most likely a consequence of the nonradiative energy transfer between Tb(3+) and In(3+) as well as the presence of defects. In comparison to the Pechini's method, the LaXO(3) nanoparticles required significantly lower annealing temperature (700 °C) necessary for complete crystallization. Generally the resulting particles are distinctly smaller (5 to 25 nm) and less agglomerated (50-100 nm) depending on the reaction conditions as well as thermal treatment. For the first time, it was shown that the LaGaO(3):Tb(3+) nanopowder has crystallized in the high-temperature rhombohedral R3c phase.     

Weak intermolecular interactions in gas-phase nuclear magnetic resonance

Gas-phase nuclear magnetic resonance (NMR) spectra demonstrating the effect of weak intermolecular forces on the NMR shielding constants of the interacting species are reported. We analyse the interaction of the molecular hydrogen isotopomers with He, Ne, and Ar, and the interaction in the He-CO(2) dimer. The same effects are studied for all these systems in the ab initio calculations. The comparison of the experimental and computed shielding constants is shown to depend strongly on the treatment of the bulk susceptibility effects, which determine in practice the pressure dependence of the experimental values. Best agreement of the results is obtained when the bulk susceptibility correction in rare gas solvents is evaluated from the analysis of the He-rare gas interactions, and when the shielding of deuterium in D(2)-rare gas systems is considered.     

Geometric and magnetic properties of Pt clusters supported on graphene: relativistic density-functional calculations

The geometric and magnetic structures of small Pt(n) clusters (n = 1 - 5) supported on a graphene layer have been investigated using ab initio density functional calculations including spin-orbit coupling. Pt-Pt interactions were found to be much stronger than the Pt-C interactions promoting the binding to the support. As a consequence, the equilibrium structure of the gas-phase clusters is preserved if they are deposited on graphene. However, the clusters bind to graphene only via at most two Pt-C bonds: A Pt(2) dumbbell prefers an upright position, the larger clusters are bound to graphene only via one edge of the planar cluster (Pt(3) and Pt(5)) or via two terminal Pt atoms of a bent Pt(4) rhombus. Evidently, the strong buckling of the graphene layer induced by the Pt-C bonds prevents the formation of a larger number of cluster-support bonds. As the local spin and orbital magnetic moments are quenched on the Pt atoms forming Pt-C bonds, the magnetic structure of the supported clusters is much more inhomogeneous as in the gas-phase. This leads to noncollinear magnetic structures and a strongly reduced magnetic anisotropy energy.     

Polarization justified Fukui functions: the theory and applications for molecules

The Fukui functions based on the computable local polarizability vector have been presented for a group of simple molecules. The necessary approximation for the density functional theory softness kernel has been supported by a theoretical analysis unifying and generalizing early concepts produced by the several authors. The exact relation between local polarizability vector and the derivative of the nonlocal part of the electronic potential over the electric field has been demonstrated. The resulting Fukui functions are unique and represent a reasonable refinement when compared to the classical ones that are calculated as the finite difference of the density in molecular ions. The new Fukui functions are strongly validated by their direct link to electron dipole polarizabilities that are reported experimentally and by other computational methods.     

Strong spin-orbit effects in small Pt clusters: geometric structure, magnetic isomers and anisotropy

Ab initio density functional calculations including spin-orbit coupling (SOC) have been performed for Pt(n), n = 2-6 clusters. The strong SOC tends to stabilize planar structures for n = 2-5, whereas for clusters consisting of six atoms, three-dimensional structures remain preferred. SOC leads to the formation of large orbital magnetic moments and to a mixing of different spin states. Due to the spin-mixing the total magnetic moment may be larger or smaller than the spin moment in the absence of SOC. Both spin and orbital moments are found to be anisotropic. Because of the strong SOC the energy differences between coexisting magnetic isomers can be comparable to or even smaller than their magnetic anisotropy energies. In this case the lowest barrier for magnetization reversal can be determined by a magnetic isomer which is different from the ground state configuration.     

Common origin, common fate: regular porphyrin and N-confused porphyrin yield an identical tetrapyrrolic degradation product

The formation of an identical linear tetrapyrrole observed in the course of photooxidation of meso-tetraarylporphyrin and its N-confused isomer can be explained as a result of 1,2- and 1,3-dioxygen addition, respectively, as substantiated by DFT calculations.     

Oxidation of annelated diarylamines: analysis of reaction pathways to nitroxide diradical and spirocyclic products

Oxidation of diaryldiamine 2, a tetrahydrodiazapentacene derivative, provides diarylnitroxide diradical 1 accompanied by an intermediate nitroxide monoradical and a multitude of isolable diamagnetic products. DFT-computed tensors for EPR spectra and paramagnetic (1)H NMR isotropic shifts for nitroxide diradical 1 show good agreement with the experimental EPR spectra in rigid matrices and paramagnetic (1)H NMR spectra in solution, respectively. Examination of the diamagnetic products elucidates their formation via distinct pathways involving C-O bond-forming reactions, including Baeyer-Villiger-type oxidations. An unusual diiminoketone structure and two spirocyclic structures of the predominant diamagnetic products are confirmed by either X-ray crystallography or correlations between DFT-computed and experimental spectroscopic data such as (1)H, (13)C, and (15)N NMR chemical shifts and electronic absorption spectra.     

Magnetocaloric effect in the ternary DyCo3B2 compound

A large magnetocaloric (MCE) effect has been observed for the ternary compound DyCo₃B₂. This material shows the magnetic ordering below T_C = 22 K for H = 0 T. MCE has been determined based on the isothermal magnetization curves measurements and the isomagnetic heat capacity dependence on temperature. The maximum magnetic entropy change −ΔS_M = 17.5 J kg⁻¹K⁻¹ and the adiabatic temperature change ΔT_ad = 14 K have been observed in the neighborhood of the magnetic phase transition at the magnetic field change of 9 T. The analysis of the magnetic contribution to the specific heat indicates on the important role of the crystal electric field and the anisotropy for the properties of the DyCo₃B₂ compound.