Cation-? interactions of selected alkali metal ions with two benzene rings connected through linear chains, 2018

Quantum chemical calculations at M06-2X/6-311+G(2d,2p) level were employed to examine the structures, dissociation energies and vibrational spectra of complexes formed by Li+, Na+ and K+ with diphenylmethane, 1,2-diphenylethane, 1,3-diphenylpropane, [2.2]paracyclophane and [3.3]paracyclophane molecules. The effect of heteroatom substitution in the connecting chains of 1,3-diphenylpropane and [3.3]paracyclophane molecules on the binding affinity of cations with ligands was also included in this study. The complexes of [3.3] paracyclophane based molecules seem to have weak cation-pi interactions with metal ions Na+ and K+ when they were placed between two rings. The binding affinity of the metal ion varies from the ligands possessing single fusion to double fusion of alkyl chain (or hetero substituted alkyl chain) with two benzene rings. Vibrational frequencies related to metal-ligand stretching, C-H, N-H and P-H stretching are useful to characterize the complexes with different metal ions and their positional preference. KEY TERMS: Chemistry Science, Physical Chemistr

Density Functional Theory

Density Functional Theory (DFT) is a powerful technique for calculating and comprehending the molecular and electrical structure of atoms, molecules, clusters, and solids. Its use is based not only on the capacity to calculate the molecular characteristics of the species of interest but also on the provision of interesting concepts that aid in a better understanding of the chemical reactivity of the systems under study. This book presents examples of recent advances, new perspectives, and applications of DFT for the understanding of chemical reactivity through descriptors forming the basis of Conceptual DFT as well as the application of the theory and its related computational procedures in the determination of the molecular properties of different systems of academic, social, and industrial interest

Computational and Spectroscopic Investigations of Intermolecular Interactions in Clusters

In this thesis, the study of intermolecular interactions within cluster systems is presented. Covalently and non-covalently bound clusters possess oftentimes unique and unexpected properties which can be tuned by adjustment of size, composition, and geometry to target desired properties for use in nanotechnologies. Additionally, clusters present a computationally tractable model of bulk systems such as reactive sites on bulk heterogeneous catalysts. Infrared spectra have been collected of various clusters and theoretical computations have been conducted to interpret spectra and provide predictions for other properties to guide future works. Investigations of the forces binding cluster species together are conducted to provide insight into the fundamental underpinning of molecular properties with applications in the field of nanomaterial design. A variety of clusters have been studied here. Computational studies of size-dependency in nitrous oxide reactions with rhodium sulphide clusters have been conducted. Barriers to competing N2O desorption and decomposition have been ascertained and compared with and without thermal corrections. Inclusion of the sulphur atom is found to alter which reaction pathway is preferred, as seen by comparison with analogous studies on pure rhodium clusters. Infrared multiple photon dissociation (IRMPD) spectroscopy is utilized to probe the additional clusters; a series of palladium coordination complexes and a series of clusters containing icosahedral [B12X12]2─ (X = H, halogen) cages complexed with a cationic transition metal atom, a cationic amine, or a neutral polar cyclohexane-based compound. This IRMPD technique successfully produced infrared spectra for these species in the gas phase and unique properties were observed for each cluster upon IR induced dissociation. Density functional theory calculations determined geometries, dissociation thresholds, and interpreted IR spectra. Additional theoretical tools quantified molecular orbital interactions and topographical parameters of the electron density

Computational Mechanistic Studies in Gold(I) Catalysis and Design of New Chiral Ligands

La recerca en catàlisi homogènia amb or ha proporcionat una eina única per la construcció l'eficient de molècules complexes mitjançant l'activació selectiva d'alquins. Malgrat això, la naturalesa dels intermedis de les reaccions de cicloisomerització catalitzades per or(I) continua sent desconcertant. Per tal d'entendre millor el mecanisme d'aquestes reaccions, s'han dut a terme estudis computacionals. S'ha investigat la naturalesa dels ciclopropil carbens d'or(I) i les seves possibles formes canòniques. Un estudi comparatiu dels mètodes DFT juntament amb la teoria QTAIM i l'anàlisi NBO van confirmar la presència de diferents intermedis en les cicloisomeritzacions d'enins. En aquest context, també es va calcular la formació selectiva de ciclopropans fusionats en trans mitjançant una reacció de ciclació en cascada, catalitzada per or(I). S'ha descobert un sistema catalític amb or que permet incorporar acetilè gas per formar sistemes complexes. La formació diastereoselectiva de bisciclopropà s'ha estudiat computacionalment. Malgrat l'èxit assolit per l'or(I) en catàlisi homogènia, les reaccions enantioselectives són encara escasses, particularment en el context de les reaccions intermoleculars. Per aquest motiu, es van preparar una sèrie de nous complexos d'or emprant fosfits quirals i es va assajar la seva activitat. També, es va desenvolupar la cicloadició enantioselectiva intermolecular d'alquins terminals i alquens utilitzant complexes dinuclears d'or(I) amb fosfines Josiphos. Els nostres estudis mecanístics indiquen que només un dels centres d'or(I) està directament implicat en l'activació de l'aquí, tot i que el segon és necessari per induir enantioselectivitat. Per tal de fer front a les limitacions de la catàlisi enantioselectiva, el nostre grup ha dissenyat una nova classe de catalitzadors d'or(I) que contenen pirrolidines 2,5-disubstituides C2 simètriques. Tal com revelen els NCI plots, el catalitzador exerceix l'estereocontrol mitjançant interaccions no covalents. A més, s'ha investigat la segona generació de lligands quirals a fi determinar el paper de cada component i predir enantioselectivitats més elevades.La investigación en catálisis homogénea con oro ha proporcionado una herramienta única para la construcción de moléculas complejas mediante la activación selectiva de alquinos. Sin embargo, la naturaleza de los intermedios de las reacciones de cicloisomerización catalizadas por oro(I) sigue siendo desconcertante. Para entender mejor el mecanismo de estas reacciones, se han llevado a cabo estudios computacionales. Se ha investigado la naturaleza de los ciclopropil carbenos de oro(I) y sus posibles formas canónicas. Un estudio comparativo de los métodos DFT junto con la teoría QTAIM y el análisis NBO confirmaron la presencia de diferentes intermedios en las cicloisomeritzaciones de eninos. En este contexto, también se calculó la formación selectiva de ciclopropanos fusionados en trans mediante una reacción de ciclación en cascada, catalizada por oro(I). Se ha descubierto un sistema catalítico con oro que permite incorporar acetileno gas para formar sistemas complejos. La formación diastereoselectiva de bisciclopropano se ha estudiado computacionalmente. A pesar del éxito alcanzado por el oro(I) en catálisis homogénea, las reacciones enantioselectivas son aún escasas, particularmente las intermoleculares. Por este motivo, se prepararon una serie de nuevos complejos de oro empleando fosfitos quirales y se ensayó su actividad. También, se desarrolló la cicloadición enantioselectiva intermolecular de alquinos y alquenos utilizando complejos dinucleares de oro(I) con fosfinas Josiphos. Nuestros estudios mecanísticos indican que sólo uno de los centros de oro está directamente implicado en la activación del aquino, aunque el segundo es necesario para inducir enantioselectividad. Para hacer frente a las limitaciones de la catálisis enantioselectiva, nuestro grupo ha diseñado una nueva clase de catalizadores de oro(I) que contienen pirrolidinas 2,5-disubstituidas. Tal como revelan los NCI plots, el catalizador ejerce la estereocontrol mediante interacciones no covalentes. Además, se ha investigado la segunda generación de ligandos quirales a fin determinar el papel de cada componente y predecir enantioselectividades más elevadas.Research in homogeneous gold catalysis has provided unique tool for the ready construction of molecular complexity through the selective activation of alkynes. However, the nature of intermediates in gold(I)-catalyzed cycloisomerization reactions was still puzzling. In order to shed light on the mechanism of these transformations, we performed computational studies. We investigated the nature of cyclopropyl gold(I) carbenes and their different canonical possible forms. Benchmark of DFT methods together with QTAIM theory and NBO analysis confirmed the presence of different intermediates in cycloisomerizations of enynes. In this context, we also computed the selective formation of trans-fused cyclopropanes by gold(I)-catalyzed cyclization cascade of functionalized dienynes. We discovered a Au(I)-catalyzed system for the incorporation of acetylene gas into complex frameworks. Formation of only one diastereomer of biscyclopropanes when mixing trans-stilbene with acetylene, has been rationalized by means of DFT calculations. Despite the success of gold(I) in homogeneous catalysis, highly enantioselective reactions are still relatively scarce, particularly in the context of intermolecular transformations. We prepared a series of novel chiral phosphite gold(I) complexes and tested their activity. Moreover, we developed the enantioselective intermolecular gold(I)-catalyzed [2+2] cycloaddition of terminal alkynes and alkenes using non C2-chiral Josiphos digold(I) complexes as catalysts. Our mechanistic studies indicate that only one of the gold(I) centers is directly involved in the activation of the alkyne, although the second one is required to induce the enantioselectivity. To address the limitations on enantioselective catalysis, our group have designed a new class of gold(I) catalysts containing remote C2-symmetric 2,5-disubstituted pyrrolidines. As revealed by NCI Plots, we proposed that the catalyst exerts the stereocontrol by non-covalent interactions. In addition, 2nd generation of chiral ligands have been investigated in order to determine the role of each component and predict the higher enantioselectivities

Cornerstones in Contemporary Inorganic Chemistry

A collection of essential research articles and scientific reviews covering some of the most pertinent and topical areas of study that currently constitute Inorganic Chemistry in the early 21st century

Organophosphorus Chemistry 2018

Organophosphorus chemistry is an important discipline within organic chemistry. Phosphorus compounds, such as phosphines, trialkyl phosphites, phosphine oxides (chalcogenides), phosphonates, phosphinates and >P(O)H species, etc., may be important starting materials or intermediates in syntheses. Let us mention the Wittig reaction and the related transformations, the Arbuzov- and the Pudovik reactions, the Kabachnik–Fields condensation, the Hirao reaction, the Mitsunobu reaction, etc. Other reactions, e.g., homogeneous catalytic transformations or C-C coupling reactions involve P-ligands in transition metal (Pt, Pd, etc.) complex catalysts. The synthesis of chiral organophosphorus compounds means a continuous challenge. Methods have been elaborated for the resolution of tertiary phosphine oxides and for stereoselective organophosphorus transformations. P-heterocyclic compounds, including aromatic and bridged derivatives, P-functionalized macrocycles, dendrimers and low coordinated P-fragments, are also of interest. An important segment of organophosphorus chemistry is the pool of biologically-active compounds that are searched and used as drugs, or as plant-protecting agents. The natural analogue of P-compounds may also be mentioned. Many new phosphine oxides, phosphinates, phosphonates and phosphoric esters have been described, which may find application on a broad scale. Phase transfer catalysis, ionic liquids and detergents also have connections to phosphorus chemistry. Green chemical aspects of organophosphorus chemistry (e.g., microwave-assisted syntheses, solvent-free accomplishments, optimizations, and atom-efficient syntheses) represent a dynamically developing field. Last, but not least, theoretical approaches and computational chemistry are also a strong sub-discipline within organophosphorus chemistry

Non-covalent interactions in organotin(IV) derivatives of 5,7-ditertbutyl- and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine as recognition motifs in crystalline self- assembly and their in vitro antistaphylococcal activity

Non-covalent interactions are known to play a key role in biological compounds due to their stabilization of the tertiary and quaternary structure of proteins [1]. Ligands similar to purine rings, such as triazolo pyrimidine ones, are very versatile in their interactions with metals and can act as model systems for natural bio-inorganic compounds [2]. A considerable series (twelve novel compounds are reported) of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) and 5,7-diphenyl- 1,2,4-triazolo[1,5-a]pyrimidine (dptp) were synthesized and investigated by FT-IR and 119Sn M\uf6ssbauer in the solid state and by 1H and 13C NMR spectroscopy, in solution [3]. The X-ray crystal and molecular structures of Et2SnCl2(dbtp)2 and Ph2SnCl2(EtOH)2(dptp)2 were described, in this latter pyrimidine molecules are not directly bound to the metal center but strictly H-bonded, through N(3), to the -OH group of the ethanol moieties. The network of hydrogen bonding and aromatic interactions involving pyrimidine and phenyl rings in both complexes drives their self-assembly. Noncovalent interactions involving aromatic rings are key processes in both chemical and biological recognition, contributing to overall complex stability and forming recognition motifs. It is noteworthy that in Ph2SnCl2(EtOH)2(dptp)2 \u3c0\u2013\u3c0 stacking interactions between pairs of antiparallel triazolopyrimidine rings mimick basepair interactions physiologically occurring in DNA (Fig.1). M\uf6ssbauer spectra suggest for Et2SnCl2(dbtp)2 a distorted octahedral structure, with C-Sn-C bond angles lower than 180\ub0. The estimated angle for Et2SnCl2(dbtp)2 is virtually identical to that determined by X-ray diffraction. Ph2SnCl2(EtOH)2(dptp)2 is characterized by an essentially linear C-Sn-C fragment according to the X-ray all-trans structure. The compounds were screened for their in vitro antibacterial activity on a group of reference staphylococcal strains susceptible or resistant to methicillin and against two reference Gramnegative pathogens [4] . We tested the biological activity of all the specimen against a group of staphylococcal reference strains (S. aureus ATCC 25923, S. aureus ATCC 29213, methicillin resistant S. aureus 43866 and S. epidermidis RP62A) along with Gram-negative pathogens (P. aeruginosa ATCC9027 and E. coli ATCC25922). Ph2SnCl2(EtOH)2(dptp)2 showed good antibacterial activity with a MIC value of 5 \u3bcg mL-1 against S. aureus ATCC29213 and also resulted active against methicillin resistant S. epidermidis RP62A

Bioaccumulation potential of 'Meeker' and 'Willamette' raspberry (Rubus idaeus L.) fruits towards macro- and microelements and their nutritional evaluation

Raspberry (Rubus idaeus L.) is the most important type of berry fruit in the Republic of Serbia. The bioaccumulation factor (BF) for the elements detected in the fruits of the raspberry cultivars 'Willamette' and 'Meeker' was calculated to determine their bioaccumulation potential. In addition, the nutritional quality of fruits in relation to nutritionally essential elements was evaluated and compared with the recommended daily intake. For determining the concentrations of 19 macro- and microelements in fruits and the soil, the analytical technique of optical emission spectrometry with inductively coupled plasma was used. Among the analyzed elements, As, Cd, Co, Cr, Li and Mo were below the limit of detection in the fruits of both raspberry cultivars, whereas Na and Ni were detected only in fruits of the 'Meeker' cultivar. All analyzed elements were detected in the soil. The results of the work indicated the high potential of the studied cultivars to accumulate nutritional elements K and Ca. In both raspberry cultivars, there were no substantial differences in the bioaccumulation of most elements. However, two elements (B and Mn) can be singled out; the BF for B in the 'Willamette' fruit was 3 times lower compared to the BF in the 'Meeker' fruit, whereas, the BF value for Mn in the 'Willamette' fruit was almost 8 times higher compared to the BF value for the 'Meeker' fruit. Furthermore, the cultivars did not tend to accumulate potentially toxic elements such as Ba, Co, Cu and Ni. The nutritional evaluation revealed that the studied raspberry fruits are a good source of K, Ca, Mg, Fe, Mn and Cu. Based on the BF values, differences observed in the accumulation of B, Ba, Na, Ni and Mn may be attributed to the characteristics of the cultivars

Light-induced dynamics in photoactive metal complexes with secondary chromophores

The present thesis is concerned with the photophysical characterization of mono- and multimetallic photoactive transition metal complexes and corresponding dyads and triads with functional organic chromophores. In particular, electronic interactions in ground and excited states between the constituents in multichromophoric compounds are analyzed. Light-induced dynamics in the given systems are probed using femtosecond transient absorption spectroscopy in order to identify and detail energy and electron transfer processes. The major portion of this thesis treats bis(tridentate) complexes based on 4-substituted 2,2 :6 ,2 -terpyridines and Fe(II), Ru(II), Os(II) and Ir(III) central ions. Such compounds are studied as potential building blocks for hierarchic coordination oligomers. In this context, dyads with Ru(II) central ions and fullerene units are analyzed in dependence of the size of bridging chromophore and linker units. With respect to multimetallic complexes, energy transfer processes between Ru(II) and Os(II) and Fe(II) complex fragments are studied. In a trinuclear Ru(II)-Fe(II)-Ru(II) complex exposed to high excitation fluence kinetically hindered energy transfer is observed. Keywords: Ruthenium(II), Iron(II), Osmium(II), Iridium(III), transition metal complexes, 2,2 :6 ,2 -terpyridine, 2,6-di(quinolin-8-yl)pyridine, time-resolved spectroscopy, transient absorption, multichromophoric compounds, dual emission, excitation energy transfer