Rice field flora and vegetation in the provinces of Valencia and Tarragona

Twenty nine emergent and twenty floating or submerged taxa , were found in the rice fields in Valencia and Tarragona provinces. Eleven of the se taxa, all them emergent, are alien Of introduced ones. Echinochloa oryzoides and E. oryzicola are the most important in both areas, together with Cyperus difformis and Echinochloa hispidula in Valencia. The remaining thirty eight taxa belong to the native flora. There are predominantly the emergent Scirpus maritimus, Alisma plantago-aquatica. Echinochloa crus-galli and Paspalum distichum; the floating Lemna minor and L. gibba; the submersed Potamogeton nodosus; Zannichellia palustris and Najas minor; and the macroscopical algae Chara vulgaris, Cladophora glomerata, Oedogonium capilliforme, Spirogyra spp., Pithophora oedogania and Hydrodictyon reticulatum. The flora evolution during the last years is analyzed and the present weed communities are studied. The contribution of the different phytosociological classes to the rice field weed flora is presented.De los 49 táxones registrados (29 emergentes y 20 flotantes o sumergidos) 11 son exóticos introducidos, de los cuales los más importantes son Echinochloa oryzoides y E. oryzicolaen ambas zonas, además de Cyperus difformis y Echinochloa hispidula en Valencia, y el resto propios de la flora autóctona, predominando Scirpus maritimus, Alisma plantago-aquatica. Echinochloa crus-galli y Paspalum distichum como emergentes, Lemna minor y L. gibba como flotantes, Potamogeton nodosus, Zannichellia palustris y Najas minor como sumergidos y Chara vulgaris, Cladophora glomerata, Oedogonium capilliforme. Spirogyra spp., Pirhophora oedogonia e Hydrodictyon reticulatum como algas macroscópicas. Se analiza la evolución experimentada por la flora en los últimos años, además de estudiar las comunidades vegetales presentes y de indicar la importancia de las distintas clases fitosociológicas en su contribución a la flora arvense del cultivo

Light-Induced Charge Separation in Densely Packed Donor–Acceptor Coordination Cages

Photon-powered charge separation is achieved in a supramolecular architecture based on the dense packing of functional building blocks. Therefore, self-assembled dimers of interpenetrated coordination cages consisting of redoxactive chromophors were synthesized in a single assembly step starting from easily accessible ligands and Pd­(II) cations. Two backbones consisting of electron rich phenothiazine (PTZ) and electron deficient anthraquinone (ANQ) were used to assemble either homo-octameric or mixed-ligand double cages. The electrochemical and spectroscopic properties of the pure cages, mixtures of donor and acceptor cages and the mixed-ligand cages were compared by steady-state UV–vis and transient absorption spectroscopy, supported by cyclic voltammetry and spectroelectrochemistry. Only the mixed-ligand cages, allowing close intra-assembly communication between the donors and acceptors, showed the evolution of characteristic PTZ radical cation and ANQ radical anion features upon excitation in the transient spectra. In contrast, excitation of the mixtures of the homo-octameric donor and acceptor cages in solution did not lead to any signs of electron transfer. Densely packed photo- and redox-functional self-assemblies promise molecular-level control over the morphology of the charge separation layer in future photovoltaic applications

Triggered Exchange of Anionic for Neutral Guests inside a Cationic Coordination Cage

Molecular encapsulation processes under the control of an external trigger play a major role in biological signal transduction processes and enzyme catalysis. Here, we present an artificial mimic of a controllable host system that forms via self-assembly from a simple bis-monodentate ligand and Pd­(II) cations. The resulting interpenetrated double cage features three consecutive pockets which initially contain one tetrafluoroborate anion, each. Activation of this host system with two halide anions triggers a conformational change that renders the central pocket susceptible to the uptake of small neutral guest molecules. Thereby, the pentacationic cage expels the central anion and replaces it with a neutral molecule to give a hexacationic species. The cage structures prior and after the halide triggered binding of benzene were examined by X-ray crystallography, ESI MS, and NMR techniques. The kinetics and thermodynamics of the encapsulation of benzene, cyclohexane, and norbornadiene are compared

Triggered Exchange of Anionic for Neutral Guests inside a Cationic Coordination Cage

Molecular encapsulation processes under the control of an external trigger play a major role in biological signal transduction processes and enzyme catalysis. Here, we present an artificial mimic of a controllable host system that forms via self-assembly from a simple bis-monodentate ligand and Pd­(II) cations. The resulting interpenetrated double cage features three consecutive pockets which initially contain one tetrafluoroborate anion, each. Activation of this host system with two halide anions triggers a conformational change that renders the central pocket susceptible to the uptake of small neutral guest molecules. Thereby, the pentacationic cage expels the central anion and replaces it with a neutral molecule to give a hexacationic species. The cage structures prior and after the halide triggered binding of benzene were examined by X-ray crystallography, ESI MS, and NMR techniques. The kinetics and thermodynamics of the encapsulation of benzene, cyclohexane, and norbornadiene are compared

Template Control over Dimerization and Guest Selectivity of Interpenetrated Coordination Cages

We have previously shown that the self-assembly of dibenzosuberone-based bis-monodentate pyridyl ligands <b>L</b>^<b>1</b> with Pd^II cations leads to the quantitative formation of interpenetrated coordination cages [BF₄@Pd₄<b>L</b>^<b>1</b>₈]. The BF₄^– anion inside the central cavity serves as a template, causing the outer two pockets to show a tremendous affinity for allosteric binding of two small chloride anions. Here we show that derivatization of the ligand backbone with a bulky aryl substituent allows us to control the dimerization and hence the guest-binding ability of the cage by the choice of the templating anion. Steric constraints imposed by <b>L</b>^<b>2</b> prevent the large BF₄^– anion from serving as a template for the formation of interpenetrated double cages. Instead, a single isomer of the monomeric cage [Pd₂<b>L</b>^<b>2</b>₄] is formed. Addition of the small anionic template Cl^– permits dimerization, yielding the interpenetrated double cage [Cl@Pd₄<b>L</b>^<b>2</b>₈], whose enlarged outer pockets show a preference for the binding of large anions such as ReO₄^–

Geometric Complementarity in Assembly and Guest Recognition of a Bent Heteroleptic <i>cis</i>-[Pd₂<b>L</b>^<b>A</b>₂<b>L</b>^<b>B</b>₂] Coordination Cage

Due to the inherent difficulties in achieving a defined and exclusive formation of multicomponent assemblies against entropic predisposition, we present the rational assembly of a heteroleptic [Pd₂<b>L</b>^<b>A</b>₂<b>L</b>^<b>B</b>₂]⁴⁺ coordination cage achieved through the geometric complementarity of two carefully designed ligands, <b>L</b>^<b>A</b> and <b>L</b>^<b>B</b>. With Pd­(II) cations as rigid nodes, the pure distinctly angular components readily form homoleptic cages, a [Pd₂<b>L</b>^<b>A</b>₄]⁴⁺ strained helical assembly and a [Pd₄<b>L</b>^<b>B</b>₈]⁸⁺ box-like structure, both of which were characterized by X-ray analysis. Combined, however, the two ligands could be used to cleanly assemble a <i>cis</i>-[Pd₂<b>L</b>^<b>A</b>₂<b>L</b>^<b>B</b>₂]⁴⁺ cage with a bent architecture. The same self-sorted product was also obtained by a quantitative cage-to-cage transformation upon mixing of the two homoleptic cages revealing the [Pd₂<b>L</b>^<b>A</b>₂<b>L</b>^<b>B</b>₂]⁴⁺ assembly as the thermodynamic minimum. The structure of the heteroleptic cage was examined by ESI-MS, COSY, DOSY, and NOESY methods, the latter of which pointed toward a <i>cis</i>-conformation of ligands in the assembly. Indeed, DFT calculations revealed that the angular ligands and strict Pd­(II) geometry strongly favor the <i>cis</i>-[Pd₂<b>L</b>^<b>A</b>₂<b>L</b>^<b>B</b>₂]⁴⁺ species. The robust nature of the <i>cis</i>-[Pd₂<b>L</b>^<b>A</b>₂<b>L</b>^<b>B</b>₂]⁴⁺ cage allowed us to probe the accessibility of its cavity, which could be utilized for shape recognition toward stereoisomeric guests. The ability to directly combine two different backbones in a controlled manner provides a powerful strategy for increasing complexity in the family of [Pd₂<b>L</b>₄] cages and opens up possibilities of introducing multiple functionalities into a single self-assembled architecture