Análisis comparativo del uso de las tecnologías de la información y comunicación (TIC), en la gestión empresarial de los hoteles ubicados en la ciudad de Estelí, Nicaragua entre los años 2008 y 2016

La presente investigación está dirigida al análisis de las Tecnologías de Información y Comunicación (TIC) en la gestión hotelera de los hoteles de la ciudad de Estelí, utilizando como referente un estudio realizado en 2008 y comparando resultados con el año 2016, es un estudio de tipo cuantitativo, se aplicaron 19 encuestas a gerentes, administradores de los hoteles y entrevistas para complementar los análisis estadísticos. Como resultado se encontró que hay cambios significativos en la implementación de nuevas tecnologías como: la incorporación de nuevos equipos tecnológicos (hardware), e incremento de programas (software) específicos para hoteles. El 30% de los encuestados afirmó que la principal limitante es la falta de capacitación y el 28% indica que los altos costos para incorporar las TIC, encontrando diferencia en las dificultades entre los dos años. La hipótesis planteada se acepta en un 84% las TIC han provocado cambios en la gestión empresarial y el uso de tecnología está dirigido al marketing de los hoteles a través del internet. Se proponen seis líneas estratégicas para la mejora del uso de las TIC

Silylium Ion/Phosphane Lewis Pairs

The reactivity of a series of silylium ion/phosphane Lewis pairs was studied. Triarylsilylium borates <b>4</b>[B­(C₆F₅)₄] form frustrated Lewis pairs (FLPs) of moderate stability with sterically hindered phosphanes <b>2</b>. Some of these FLPs are able to cleave dihydrogen under ambient conditions. The combination of bulky trialkylphosphanes with triarylsilylium ions can be used to sequester CO₂ in the form of silylacylphosphonium ions <b>12</b>. The ability to activate molecular hydrogen by reaction of silylium ion/phosphane Lewis pairs is dominated by thermodynamic and steric factors. For a given silylium ion increasing proton affinity and increasing steric hindrance of the phosphane proved to be beneficial. Nevertheless, excessive steric hindrance leads to a breakdown of the dihydrogen-splitting activity of a silylium/phosphane Lewis pair

Colorless Chlorophyll Catabolites in Senescent Florets of Broccoli (Brassica oleracea var. <i>italica</i>)

Typical postharvest storage of broccoli (Brassica oleracea var. <i>italica</i>) causes degreening of this common vegetable with visible loss of chlorophyll (Chl). As shown here, colorless Chl-catabolites are generated. In fresh extracts of degreening florets of broccoli, three colorless tetrapyrrolic Chl-catabolites accumulated and were detected by high performance liquid chromatography (HPLC): two “nonfluorescent” Chl-catabolites (NCCs), provisionally named <i>Bo</i>-NCC-1 and <i>Bo</i>-NCC-2, and a colorless 1,19-dioxobilin-type “nonfluorescent” Chl-catabolite (DNCC), named <i>Bo</i>-DNCC. Analysis by nuclear magnetic resonance spectroscopy and mass spectrometry of these three linear tetrapyrroles revealed their structures. In combination with a comparison of their HPL-chromatographic properties, this allowed their identification with three known catabolites from two other brassicacea, namely two NCCs from oil seed rape (Brassica napus) and a DNCC from degreened leaves of Arabidopsis thaliana

Quantitative Assessment of the Lewis Acidity of Silylium Ions

The Lewis acidity of several aryl-substituted tetrylium ions was classified experimentally by applying the Gutmann–Beckett method and computationally by calculation of fluoride ion affinities (FIA) (tetrel elements = Si, Ge). According to these measures, tetrylium ions are significantly more Lewis acidic than boranes, and aryl-substituted silylium borates are among the strongest isolable Lewis acids. A fine-tuning of the Lewis acidity of silylium ions is possible by taking advantage of electronic and/or steric substituent effects

Hafnocene-based Bicyclo[2.1.1]hexene Germylenes – Formation, Reactivity, and Structural Flexibility

2,5-Disilylsubstituted germole dianions <b>1</b> react with hafnocene dichloride to give hafnocene-based bicyclo[2.1.1]­hexene germylenes <b>3</b>. Their formation proceeds via hafnocene-germylene complexes <b>2</b> that were identified by NMR and UV spectroscopy. Germylenes <b>3</b> are stabilized by homoconjugation between the empty 4p­(Ge) orbital and the π-bond of the innercyclic C²C³ double bond. This interaction can be understood as σ², π-coordination of the butadiene part to the dicoordinated germanium atom that leaves the 16e^– hafnocene moiety electronically unsaturated. We demonstrate that this new class of germylenes might serve as ligand to a variety of low-valent transition-metal complexes. The structure of the germylene ligand in complexes with Fe(0), Ni(0), and Au­(I) and in reaction products with N-heterocyclic carbenes showed an intriguing structural flexibility that allows to accommodate different electronic situations at the ligating germanium atom. The origin of this structural adaptability is the interplay between the topological flexible unsaturated germanium ring and the hafnocene group

Dibenzosilanorbornadienyl Cations and Their Fragmentation into Silyliumylidenes

The terphenyl-substituted dibenzosilanorbornadienyl cation <b>11</b> was synthesized and isolated in the form of its [B­(C₆F₅)₄]⁻ salt. The salt was characterized by NMR spectroscopy supported by quantum mechanical computations and by an XRD analysis of a corresponding acetonitrilium salt. The thermal fragmentation of <b>11</b>[B­(C₆F₅)₄] in benzene results in the high-yield formation of diphenylterphenylsilylium borate <b>17</b>[B­(C₆F₅)₄]. High-lying intermediates in this process are solvent-complexed terphenylsilyliumylidene <b>8</b> and the hydrogen- and phenyl-substituted silylium ion <b>20</b>. The formation of silylium ion <b>20</b> by reaction of silyliumylidene <b>8</b> with the solvent benzene demonstrates the high potential of this four valence electron species in C–H bond activation reactions. In addition, the instability of the hydrogen-substituted silylium ion <b>20</b> in benzene opens new mechanistic perspectives particular for dihydrogen activation by silyl cationic frustrated Lewis pairs and in general for the dihydrogen activation by strong Lewis acids

Dibenzosilanorbornadienyl Cations and Their Fragmentation into Silyliumylidenes

The terphenyl-substituted dibenzosilanorbornadienyl cation <b>11</b> was synthesized and isolated in the form of its [B­(C₆F₅)₄]⁻ salt. The salt was characterized by NMR spectroscopy supported by quantum mechanical computations and by an XRD analysis of a corresponding acetonitrilium salt. The thermal fragmentation of <b>11</b>[B­(C₆F₅)₄] in benzene results in the high-yield formation of diphenylterphenylsilylium borate <b>17</b>[B­(C₆F₅)₄]. High-lying intermediates in this process are solvent-complexed terphenylsilyliumylidene <b>8</b> and the hydrogen- and phenyl-substituted silylium ion <b>20</b>. The formation of silylium ion <b>20</b> by reaction of silyliumylidene <b>8</b> with the solvent benzene demonstrates the high potential of this four valence electron species in C–H bond activation reactions. In addition, the instability of the hydrogen-substituted silylium ion <b>20</b> in benzene opens new mechanistic perspectives particular for dihydrogen activation by silyl cationic frustrated Lewis pairs and in general for the dihydrogen activation by strong Lewis acids

Activation of 7‑Silanorbornadienes by N‑Heterocyclic Carbenes: A Selective Way to N‑Heterocyclic-Carbene-Stabilized Silylenes

The synthesis of hydridosilylenes Ter­(H)­Si: <b>3a</b> (Ter: 2,6-bis­(2,4,6-trimethylphenyl)­phenyl) and Ter*­(H)­Si: <b>3b</b> (Ter*: 2,6-bis­(2,4,6-tri<i>iso-</i>propylphenyl)­phenyl) stabilized by the N-heterocyclic carbene (NHC) ImMe₄ is reported. The synthesis of stabilized hydridosilylenes <b>3</b> was accomplished by a previously unknown NHC-induced fragmentation of silanorbornadiene derivatives. Structural studies of the stabilized silylenes <b>3</b> and of its Fe­(CO)₄ complex <b>12</b> accompanied by a theoretical analysis of their bonding situation indicate that stabilized silylenes such as <b>3</b> can be regarded as neutral silyl anion equivalents. A computational investigation of the reaction course indicate a virtual one-step reaction between the NHC and the silanorbornadiene. A theoretical assessment of the scope and limitations of this reaction suggests that it is general and can be used also for the synthesis of other carbene analogues such as germylenes and phosphinidenes

Activation of 7‑Silanorbornadienes by N‑Heterocyclic Carbenes: A Selective Way to N‑Heterocyclic-Carbene-Stabilized Silylenes

The synthesis of hydridosilylenes Ter­(H)­Si: <b>3a</b> (Ter: 2,6-bis­(2,4,6-trimethylphenyl)­phenyl) and Ter*­(H)­Si: <b>3b</b> (Ter*: 2,6-bis­(2,4,6-tri<i>iso-</i>propylphenyl)­phenyl) stabilized by the N-heterocyclic carbene (NHC) ImMe₄ is reported. The synthesis of stabilized hydridosilylenes <b>3</b> was accomplished by a previously unknown NHC-induced fragmentation of silanorbornadiene derivatives. Structural studies of the stabilized silylenes <b>3</b> and of its Fe­(CO)₄ complex <b>12</b> accompanied by a theoretical analysis of their bonding situation indicate that stabilized silylenes such as <b>3</b> can be regarded as neutral silyl anion equivalents. A computational investigation of the reaction course indicate a virtual one-step reaction between the NHC and the silanorbornadiene. A theoretical assessment of the scope and limitations of this reaction suggests that it is general and can be used also for the synthesis of other carbene analogues such as germylenes and phosphinidenes

Polyradical Character of Triangular Non-Kekulé Structures, Zethrenes, <i>p</i>‑Quinodimethane-Linked Bisphenalenyl, and the Clar Goblet in Comparison: An Extended Multireference Study

In this work, two different classes of polyaromatic hydrocarbon (PAH) systems have been investigated in order to characterize the amount of polyradical character and to localize the specific regions of chemical reactivity: (a) the non-Kekulé triangular structures phenalenyl, triangulene and a π-extended triangulene system with high-spin ground state and (b) PAHs based on zethrenes, <i>p</i>-quinodimethane-linked bisphenalenyl, and the Clar goblet containing varying polyradical character in their singlet ground state. The first class of structures already have open-shell character because of their high-spin ground state, which follows from the bonding pattern, whereas for the second class the open-shell character is generated either because of the competition between the closed-shell quinoid Kekulé and the open-shell singlet biradical resonance structures or the topology of the π-electron arrangement of the non-Kekulé form. High-level ab initio calculations based on multireference theory have been carried out to compute singlet–triplet splitting for the above-listed compounds and to provide insight into their chemical reactivity based on the polyradical character by means of unpaired densities. Unrestricted density functional theory and Hartree–Fock calculations have been performed for comparison also in order to obtain better insight into their applicability to these types of complicated radical systems