Synthesis, structural characterization and conformational aspects of nostoclide analogues

The synthesis and structural analysis of a set of nostoclide analogues with potential herbicide activity is described. The influence of intra- and intermolecular hydrogen bonding, as well as other interactions on the conformation and packing of the compounds is thoroughly described using DFT calculations and single crystal X-ray diffraction analyses. All lactones exhibited the Z configuration as confirmed by NOESY experiments and by single crystal X-ray diffraction measurementsCNPQFAPEMI

Methyl 4-(piperidin-1-ylcarbon­yl)benzoate

In the title compound, C14H17NO3, the piperidine ring has a chair conformation and an intra­molecular C—H⋯O inter­action stabilizes the mol­ecular conformation. In the crystal, weak inter­molecular C—H⋯O inter­actions occur

Magneto-structural versatility of copper(ii)-3-phenylpropionate coordination polymers with N-donor coligands

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)A novel series of copper(II) coordination polymers [Cu-2(O2CC8H9)(4)(pyz)](n) (1), [Cu-2(O2CC8H9)(4)(dps)](n) (2), {[Cu(O2CC8H9)(2)(dps)(H2O)]center dot H2O}(n) (3), {[NaCu(O2CC8H9)(2)(bpm)(NO3)]center dot H2O}(n) (4), and [Cu-4(O2CC8H9)(6)-(OH)(2)(bpp)(2)](n) (5) [O2CC8H9- = 3-phenylpropionate anion, pyz = pyrazine, dps = di(4-pyridyl)sulfide, bpm = 2,2'-bipyrimidine, and bpp = 1,3-bis(4-pyridyl)propane] have been synthesized and magneto-structurally investigated. Compounds 1 and 2 belong to a large group of copper(II) carboxylates where bis-monodentate pyz (1) and dps (2) ligands connect the paddle-wheel [Cu-2(II)(mu-O2CC8H9)(4)] units leading to alternating copper(II) chains. The structure of 3 consists of uniform chains of trans-[Cu-II(O2CC8H9)(2)] units linked by the bis-monodentate dps ligand. Compound 4 consists of heterobimetallic chains where [(Na2Cu2II)-Cu-I(mu-O2CC8H9)(4)(NO3)(2)] units are doubly bridged by bis-bidentate bpm ligands. Compound 5 is also a chain compound whose structure is made up by tetranuclear [Cu-4(II)(mu(3)-OH)(2)(mu-O2CC8H9)(4)(O2CC8H9)(2)] units which are doubly bridged by bis-monodentate bpp ligands. The magnetic properties were investigated in the temperature range 1.8-300 K. Strong antiferromagnetic interactions across the quadruple syn-syn carboxylate are observed in 1 and 2 [J = -378 (1) and -348 cm(-1) (2)] whereas a weak ferromagnetic coupling through the double out-of-plane oxo(carboxylate) bridge occurs in 4 [J = +2.66 cm(-1)], the spin Hamiltonian being defined as H = -JS(1).S-2 with S-1 = S-2 = S-Cu = 1/2. A quasi Curie law is observed for 3 (theta = -0.36 cm(-1)), the bis-monodentate dps ligand being a very poor mediator of magnetic interactions. The analysis of the magnetic properties of 5 is quite complex because of the presence of two crystallographically independent tetracopper(II) units with single-mu-hydroxo, di-mu-hydroxo, mu(3)-hydroxo and single-mu-hydroxo plus double syn, syn carboxylate bridges in each one. The nature and values of the magnetic couplings for 5 obtained by fitting (intermediate, strong and weak antiferromagnetic interactions for the three former exchange pathways respectively, and intermediate ferromagnetic interactions for the latter one) were substantiated by DFT type calculations.A novel series of copper(II) coordination polymers [Cu2(O2CC8H9)4(pyz)]n (1), [Cu2(O2CC8H9)4(dps)]n (2), {[Cu(O2CC8H9)2(dps)(H2O)]·H2O}n (3), {[NaCu(O2CC8H9)2(bpm)(NO3)]·H2O}n (4), and [Cu4(O2CC8H9)6(OH)2(bpp)2]n (5) [O2CC8H9− = 3-phenylpropionate anion,451172189CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIGCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)sem informaçãosem informaçãosem informaçãoThe authors thank the Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq), the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), FINEP (ref. 134/08

Influence of hydrogen bonds on the molecular structure and conformations of two ('C IND. 30''H IND. 48''O IND. 2') pentacyclic triterpene isomers

The structural study of two (C30H48O2) pentacyclic triterpene (PCTT) isomers is presented. These terpenes, known as 30-hydroxy-lup-20(29)-en-3-one (1) and (11α)-11-hydroxy-lup-20(29)-en-3-one (2), were isolated from Maytenus imbricata Mart. Ex Reissek (Celastraceae). The molecular structure of 1 and 2 differs in the position of the hydroxyl group. Both compounds crystallize in non-centrosymmetric space groups with two molecules in the asymmetric unit. The crystal structure of 1 shows a triclinic P1 space group (a = 9.5518(1) Å, b = 9.7083(1) Å, c = 14.4696(2) Å, α = 93.832(1)°, β = 102.833(1)°, and γ = 103.307(1)°), while compound 2 crystallizes in a monoclinic P21 one (a = 13.4439(16) Å, b = 14.4463(14) Å, c = 13.5224(9) Å and β = 99.703(8)°). The two molecules independent by symmetry of 1 differ slightly due to the presence of static disorder in oxygen atoms. In addition, the intermolecular geometries of 1 and 2 were analysed, and in each isomer the crystal packing is stabilized by O-H…O intermolecular hydrogen bonds and van der Waals forces.FAPEMIG (APQ-02685-09 and APQ-01093-10)FINEP (0134/08 and 0336/09)CAPES (PNPD-2007)CNPq (PIBIC-CNPq-Unifal-MG

The foliar application of a mixture of semisynthetic chitosan derivatives induces tolerance to water deficit in maize, improving the antioxidant system and increasing photosynthesis and grain yield.

Research has shown that chitosan induces plant stress tolerance and protection, but few studies have explored chemical modifications of chitosan and their effects on plants under water stress. Chitosan and its derivatives were applied (isolated or in mixture) to maize hybrids sensitive to water deficit under greenhouse conditions through foliar spraying at the pre-flowering stage. After the application, water deficit was induced for 15 days. Analyses of leaves and biochemical gas exchange in the ear leaf were performed on the first and fifteenth days of the stress period. Production attributes were also analysed at the end of the experiment. In general, the application of the two chitosan derivatives or their mixture potentiated the activities of the antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and guaiacol peroxidase at the beginning of the stress period, in addition to reducing lipid peroxidation (malonaldehyde content) and increasing gas exchange and proline contents at the end of the stress period. The derivatives also increased the content of phenolic compounds and the activity of enzymes involved in their production (phenylalanine ammonia lyase and tyrosine ammonia lyase). Dehydroascorbate reductase and compounds such as total soluble sugars, total amino acids, starch, grain yield and harvest index increased for both the derivatives and chitosan. However, the mixture of derivatives was the treatment that led to the higher increase in grain yield and harvest index compared to the other treatments. The application of semisynthetic molecules derived from chitosan yielded greater leaf gas exchange and a higher incidence of the biochemical conditions that relieve plant stress

Multifunctional nanostructured Co-doped ZnO: Co spatial distribution and correlated magnetic properties

In this report we present a systematic structural and magnetic analysis of Co-doped ZnO nanoparticles prepared via a microwave-assisted hydrothermal route. The structural data confirm the incorporation of Co ions into the wurtzite ZnO lattice and a Co concentration mainly near/at the surface of the nanoparticles. This Co spatial distribution is set to passivate the surface of the ZnO nanoparticles, inhibiting the nanoparticle growth and suppressing the observation of a ferromagnetic phase. Based on experimental and theoretical results we propose a kinetic-thermodynamic model for the processes of nucleation and growth of the Co-doped ZnO nanoparticles, and attribute the observed ferromagnetic order to a ferromagnetism associated with specific defects and adsorbed elements at the surface of the nanoparticle. Our findings give valuable contribution to the understanding of both the doping process at the nanoscale and the nature of the magnetic properties of the Co-doped ZnO system.Support from agencies FAPEMIG (PPM-00533-16; APQ-00273-14; RED-00010-14), CNPq (470069/2013-9; 448723/2014-0; 308162/2015-3, 306065/2015-0), FAPESP (2013/07909-4; 2015/16191-5) and CAPES (PNPD-2011) is gratefully acknowledged. We also thank CNPq (WAAM, MIBB and ACD) and CAPES (NCM, AOZ) for research fellowships. We thank Red Española de Supercomputación (Proyect ID: QCM-2014-1-0036) and CENAPAD/SP (Brazil) for computing facilities.Peer reviewe