Análisis filogenético y revisión sistemática de la subfamilia Allidiostomatinae (Coleoptera: Scarabaeidae)

Tesis presentada para optar al Grado de Doctor en Ciencias NaturalesFil: Neita Moreno, Jhon César. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentin

Reactions of Diiminopyridine Ligands with Chalcogen Halides

The reactions of the chalcogen halides (Ch = S, Se, Te) with a series of diiminopyridine (DIMPY) ligands were explored. It was determined through these studies that varying both the substitution on the α-carbon and the chalcogen halide reagent afforded different products. If methyl groups were present on the α-carbon, reactivity was observed through the eneamine tautomer to yield <i>N,N′,C</i>-bound neutral chalcogen complexes. In the cases where H and C₆H₅ groups were in the same position, <i>N,N′,N″</i>-chelated chalcogen cations or dications were produced. Many of the reactions resulted in complex mixtures postulated to occur by the release of halogen decomposing the product or, for reactions with the CH₃ substituted ligand, uncontrollable reactivity with the eneamine tautomer. This is the first report of reactions of sulfur and selenium halides with the ubiquitous diiminopyridine ligands and only the second example for a tellurium halide

An N-Heterocyclic Carbene Containing a Bithiophene Backbone: Synthesis and Coordination Chemistry

A new N-heterocyclic carbene (NHC) containing a fused bithiophene backbone has been synthesized along with its silver­(I) and BPh₃ complexes. The donor strength of this unique NHC has been determined from the IR stretching frequencies of the isolated NHC-Rh­(CO)₂Cl complex. The photophysical properties of all of the novel compounds have been investigated and are presented

Multifunctional Block Copolymer: Where Polymetallic and Polyelectrolyte Blocks Meet

Sequential reversible addition–fragmentation transfer (RAFT) polymerization of a mixed sandwich cobaltocene monomer (η⁵-cyclopentadienyl-cobalt-η⁴-cyclobutadiene (CpCoCb)) and a phosphonium salt functionalized styrene monomer resulted in the first example of a unique multifunctional block copolymer consisting of a metallopolymer block and a polyelectrolyte block. The polyelectrolyte block was decorated with a gold anion (AuCl₄^–) via salt metathesis, resulting in a heterobimetallic block copolymer with distinct gold and cobalt sections. Solution self-assembly behavior of this unique metallopolymer-<i>b</i>-polyelectrolyte copolymer before and after salt metathesis was studied. Heterobimetallic micelles with a gold containing core and a cobalt-containing corona were obtained, and then the core was reduced to form gold nanoparticles (AuNPs). Studies on the solid-state self-assembly of this unique block copolymer showed that it phase separated into hexagonally packed cylinders. Salt metathesis of the phase-separated block copolymers was utilized as the first example of a nonstandard selective staining method to exclusively stain the polyelectrolyte domains with the AuCl₄^– anion. Staining the metallopolymer domain by RuO₄ provided the complementary pattern. Pyrolysis of the self-assembled block copolymers resulted in magnetic cobalt-phosphate nanoparticles with 17% char yield

Synthesis of Zwitterionic Group 14 Centered Complexes: Traditional Coordination and Unusual Insertion Chemistry

Novel cationic E–Cl (E = Ge, Sn) fragments stabilized by a bis­(phosphino)­borate ligand (<b>2E</b>) were synthesized by a 1:1 stoichiometric addition of ECl₂ and [Tl]­[(Ph₂PCH₂)₂BPh₂]. The metrical parameters are consistent with dative bonds between the phosphorus atoms and the electron-deficient group 14 element, which is in contrast to the traditionally used aryl- and nitrogen-based ligands, which are always covalently bound. The reaction of a second equivalent of bis­(phosphino)­borate results in the unexpected insertion of the main group center into the aliphatic B–C bond of the ligand backbone to form <b>3E</b>, in addition to phosphine-borane dimer (Ph₂PCH₂BPh₂)₂ (<b>4</b>). The pendant phosphine on <b>3E</b> was shown to possess donor ability in the coordination of BH₃ (<b>5E</b>)

Trends in Hydrophilicity/Lipophilicity of Phosphonium Ionic Liquids As Determined by Ion-Transfer Electrochemistry

Ionic liquids (ILs) have become valuable new materials for a broad spectrum of applications including additives or components for new hydrophobic/hydrophilic polymer coatings. However, fundamental information surrounding IL molecular properties is still lacking. With this in mind, the microinterface between two immiscible electrolytic solutions (micro-ITIES), for example, water|1,2-dichloroethane, has been used to evaluate the hydrophobicity/lipophilicity of 10 alkylphosphonium ILs. By varying the architecture around the phosphonium core, chemical differences were induced, changing the lipophilicity/hydrophilicity of the cations. Ion transfer (IT) within the polarizable potential window (PPW) was measured to establish a structure–property relationship. The Gibbs free energy of IT and the solubility of their ILs were also calculated. For phosphonium cations bearing either three butyl or three hydroxypropyl groups with a tunable fourth arm, the latter displayed a wide variety of easily characterizable IT potentials. The tributylphosphonium ILs, however, were too hydrophobic to undergo IT within the PPW. Utilizing a micro-ITIES (25 μm diameter) housed at the tip of a capillary in a uniquely designed pipet holder, we were able to probe beyond the traditional potential window and observe ion transfer of these hydrophobic phosphonium ILs for the first time. A similar trend in lipophilicity was determined between the two subsets of ILs by means of derived solubility product constants. The above results serve as evidence of the validation of this technique for the evaluation of hydrophobic cations that appear beyond the conventional PPW and of the lipophilicity of their ILs

Overcoming a Tight Coil To Give a Random “Co” Polymer Derived from a Mixed Sandwich Cobaltocene

Reversible addition–fragmentation transfer (RAFT) polymerization of a η⁵-cyclopentadienylcobalt-η⁴-cyclobutadiene (CpCoCb) containing monomer under a wide variety of experimental conditions (e.g., different solvents, temperatures, RAFT agents, concentrations, and [RAFT agent]/[initiator]) was examined. In all cases the results revealed that although the monomer was being consumed over the course of the reaction, there was no significant increase in the molecular weight of the resulting polymer. It was determined that as the polymer chain grows (DP ≈ 10), a tight coil morphology was adopted, which hinders the approach of an additional, sterically demanding CpCoCb-containing monomer. This resulted in premature termination/chain transfer reactions rather than an increase in the polymer chain length. To address this problem, methyl acrylate (MA) with its lower steric demand was copolymerized with the bulky CpCoCb-containing monomer to act as a spacer. This provided the necessary steric relief and an opportunity for the metallopolymer to grow. This copolymerization resulted in dramatic improvements in the polydispersity and molecular weight of the end material. In subsequent experiments, the random copolymer was used as a macro-RAFT agent to prepare diblock copolymers, with good control over the molecular weight, allowing for an examination of the self-assembly behavior of the block copolymer in the solid state

A Novel Diiminopyridine Ligand Containing Redox Active Co(III) Mixed Sandwich Complexes

The synthesis of a diiminopyridine (DIMPY) ligand containing pendant mixed sandwich cobaltocene functionalities on the imine nitrogens was prepared and characterized (<b>18</b>). Its reactivity with 2 equiv of GeCl₂·dioxane and SnCl₂ in THF yields the respective Lewis base mediated autoionization products (<b>18Ge</b> and <b>18Sn</b>). Analogous low-valent complexes utilizing an <i>N</i>,<i>N</i>′- differocenyl diiminopyridine support were also prepared (<b>15Ge</b> and <b>15Sn</b>). All compounds were characterized by spectroscopic and X-ray crystallographic methods. Electrochemical studies were conducted for both <b>15Sn</b> and the precursor of <b>18</b>

Anion-Exchange Reactions on a Robust Phosphonium Photopolymer for the Controlled Deposition of Ionic Gold Nanoclusters

UV curing (photopolymerization) is ubiquitous in many facets of industry ranging from the application of paints, pigments, and barrier coatings all the way to fiber optic cable production. To date no reports have focused on polymerizable phosphonium salts under UV irradiation, and despite this dearth of examples, they potentially offer numerous substantial advantages to traditional UV formulation components. We have generated a highly novel coating based on UV-curable trialkylacryloylphosphonium salts that allow for the fast (seconds) and straightforward preparation of ion-exchange surfaces amenable to a roll-to-roll process. We have quantified the surface charges and exploited their accessibility by employing these surfaces in an anion exchange experiment by which [Au₂₅L₁₈]⁻ (<i>L</i> = SCH₂CH₂Ph) nanocrystals can be assembled into the solid state. This unprecedented application of such surfaces offers a paradigm shift in the emerging chemistry of Au₂₅ research where the nanocrystals remain single and intact and where the integrity of the cluster and its solution photophysical properties are resilient in the solid state. The specific loading of [Au₂₅L₁₈]⁻ on the substrates has been determined and the completely reversible loading and unloading of intact nanocrystals to and from the surface has been established. In the solid state, the assembly has an incredible mechanical resiliency, where the surface remains undamaged even when subjected to repeated Scotch tests

Addressing the Chemical Sorcery of “GaI”: Benefits of Solid-State Analysis Aiding in the Synthesis of P→Ga Coordination Compounds

The differing structures and reactivities of “GaI” samples prepared with different reaction times have been investigated in detail. Analysis by FT-Raman spectroscopy, powder X-ray diffraction, ⁷¹Ga solid-state NMR spectroscopy, and ¹²⁷I nuclear quadrupole resonance (NQR) provides concrete evidence for the structure of each “GaI” sample prepared. These techniques are widely accessible and can be implemented quickly and easily to identify the nature of the “GaI” in hand. The “GaI” prepared from exhaustive reaction times (100 min) is shown to possess Ga₂I₃ and an overall formula of [Ga⁰]₂[Ga⁺]₂[Ga₂I₆^2–], while the “GaI” prepared with the shortest reaction time (40 min) contains GaI₂ and has the overall formula [Ga⁰]₂[Ga⁺]­[GaI₄^–]. Intermediate “GaI” samples were consistently shown to be fractionally composed of each of these two preceding formulations and no other distinguishable phases. These “GaI” phases were then shown to give unique products upon reactions with the anionic bis­(phosphino)­borate ligand class. The reaction of the early-phase “GaI” gives rise to a unique phosphine Ga­(II) dimeric coordination compound (<b>3</b>), which was isolated reproducibly in 48% yield and convincingly characterized. A base-stabilized GaI→GaI₃ fragment (<b>4</b>) was also isolated using the late-phase “GaI” and characterized by multinuclear NMR spectroscopy and X-ray crystallography. These compounds can be considered unique examples of low-oxidation-state P→Ga coordination compounds and possess relatively long Ga–P bond lengths in the solid-state structures. The anionic borate backbone therefore results in interesting architectures about gallium that have not been observed with neutral phosphines