The effect of two types of dibenzoannulation of pentalene on molecular energies and magnetically induced currents

The effect of two types of dibenzo-fusion of pentalene in the singlet and triplet states on its molecular energies and magnetically induced ring currents was examined via density functional calculations. The isomerization energy decomposition analysis (IEDA) together with the calculated aromaticity indices (NICS(1) zz , HOMA and FLU π ), estimation of resonance energies (RE) and extra cyclic resonance energies (ECRE) via the NBO method, and the NICS-XY-scans revealed that the π-electronic system is the most important factor controlling the molecular energies. The [a,f] topology features greater delocalization, which results in two opposing effects: larger ECRE, but weaker π-bonding. The latter is mainly responsible for the higher energy of [a,f]-dibenzopentalene (DBP) (ΔE iso = 21.7 kcal mol -1 ), with the other effects being σ-orbital and electrostatic interactions. The reversal of energetic stability in the triplet states (ΔE iso = -10.8 kcal mol -1 ) mainly comes from the reduced Pauli repulsion in [a,f]-DBP, which stabilizes the unpaired spin density over the central trimethylenemethane subunit vs. the central pentalene subunit in [a,e]-DBP. Although the [a,e] topology only reduces the diatropic and paratropic currents of the elementary subunits, benzene and pentalene, the [a,f] topology also creates strong global paratropicity involving the benzene rings. Both DBP isomers are characterized by global and smaller semi-global and local diatropic currents in the triplet state.This is the peer-reviewed version of the following article: Baranac-Stojanović, M.; Stojanović, M. The Effect of Two Types of Dibenzoannulation of Pentalene on Molecular Energies and Magnetically Induced Currents. Physical Chemistry Chemical Physics 2019, 21 (6), 3250–3263. [https://doi.org/10.1039/c8cp07875k

The study of influence of biostimulation factors on microbiological degradation of main components in petroleum-type pollutant

Cilj ove teze bio je ispitivanje uticaja biostimulacionih faktora na degradaciju glavnih komponenti naftnog zagadjivača. Kao najznačajnije komponente, sa stanovišta hemije životne sredine, odabrani su aromatični ugljvodonici u naftnom zagadjivaču. Zemljište zagađeno mazutom je iskopano zagađeno zemljište iz kruga jedne termoelektrane. Usled kvara objekata termoelektrane zemljište je bilo zagađeno mazutom i sedimentom iz rezervoara za mazut tokom godinu dana. Zemljište zagađeno mazutom je ravnomerno raspoređeno preko neispranog i nesortiranog peska iz reke Save. Rečni pesak je dodat kao materijal za povećanje zapremine i poroznosti. Piljevina od topole, bukve i hrasta je dodata kao materijal za povećanje retencionog kapaciteta vode ali i kao dodatni izvor ugljenika. U cilju homogenizacije komponente su promešane. Čitav homogenizovan materijal je zatim formiran u oblik halde. Konzorcijum mikroorganizama je izolovan iz zagađenog zemljišta. „Analytical profile index“ testovi su korišćeni za identifikaciju mikroorganizama. Broj mikroorganizama je određivan zasejavanjem odgovarajućih serijskih razblaženja na agrne ploče inkubirane na 28 °C. Nakon formiranja halda je jednom mesečno prskana biomasom mikrobiološkog konzorcijuma izolovanog iz zemljišta kontaminiranog mazutom (reinokulacija) i hranljivim supstancama (biostimulacija). Biosurfaktant tipa „biosolve“ je dodat haldi radi rastvaranja naftnog zagađivača. Tokom bioremedijacije halda je kvašena, okretana i mešana svake dve sedmice radi održavanja potrebne vlage i aerisanosti. Na početku ispitivanja, odmah nakon mešanja ali pre dodatka piljevine, biomase, hranljivih supstanci i biosurfaktanta, približno 10 m3 smeše sa halde je odvojeno sa strane za potrebe korišćenja kao kontrolna halda. Celokupana analitički postupak koji je primenjen na uzorke halde primenjen je i na kontrolne uzorke tokom nezavisnog paralelnog eksperimenta nebiostimulisane biodegradacije. Tokom perioda od šest meseci, uzorci su prikupljeni pet puta...The aim of this thesis was the investigation of the influence of biostimulation factors on degradation of the main components of petroleum pollutant. As the most significant component, from the environmental chemistry point of view, the aromatic hydrocarbons in oil pollutant were chosen. The heavy fuel oil polluted soil was excavated contaminated soil from an energy power plant. Due to a breakdown of the energy power plant facilities, the soil had been polluted with heavy fuel oil (mazut) and sediment from a heavy fuel oil reservoir for a year. The mazut polluted soil was uniformly distributed over not rinsed ungraded sand from the Sava River. River sand was added as a bulking and porosity increasing material. The sawdust from poplar, beech, and oak was added in order to increase the retention water capacity, but as alternative additional carbon source as well. To ensure homogeneity, the components were mixed. The entire homogenized material was then formed into a biopile shape. A consortium of microorganisms was isolated from the polluted soil. Analytical profile index tests were used for identification of microorganisms. The number of microorganisms was determined by plating appropriate serial dilutions on agar plates incubated at 28 °C. After formation the biopile was sprayed once a month with the biomass of microbial consortia isolated from the heavy fuel oil – contaminated soil (re-inoculation) and nutritive substances (biostimulation). Biosurfactant of biosolve type was applied on the biopile to solubilize the oil pollutant. During bioremediation, the biopile was watered, turned and mixed each 2 weeks to maintain the required moisture and aeration levels. At the beginning of the study, immediately after mixing, but before the addition of sawdust, biomass, nutrient substances, and biosurfactant, approximately 10 m3 of the biopile mixture was set aside on the same waterproof asphalt surface, to be used as a control pile. The complete analytical procedure that was applied to the samples was also applied to the control samples during an independent parallel non-biostimulated biodegradation experiment..

Novel Heterobimetallic Manganese-Chromium and Rhenium-Chromium Complexes : Coordination, Cyclometallation, Benzannulation and Haptotropic Metal Migration

A characteristic property of transition metal π-complexes with polycyclic aromatic ligands is their ability to undergo haptotropic rearrangements; the metal fragment is considered as the moveable functional group that is shifted between two non-equivalent rings of an oligocyclic ligand. We decided to add second different metal units coordinated to the (polyarene)Cr(CO)3 complexes in order to study their influences on the migration of the chromium moiety. In this context, we synthesized the first syn and anti heterobimetallic Cr(CO)3-Mn(CO)3 and Cr(CO)3-Re(CO)3 oligocyclic fused-arene complexes. Moreover, we investigated a novel synthesis of (N-heterocyclic polyarene)Cr(CO)3 and cyclomanganated (N-heterocyclic polyarene)Cr(CO)3 complexes. In all binuclear cases, the chromium-templated-[3+2+1] benzannulation of Fischer arylcarbenes bearing an additional metal label was employed to introduce the chromium moiety. The thermo-induced haptotropic chromium migrations along the π-face of the platforms were performed with all these complexes and yielded in most case to the desired thermodynamic haptotropomers. The intramolecular courses of the chromium fragment were confirmed by NMR-studies which revealed first order kinetics. Besides, all the heterobimetallic structures were determined by X-ray analyses

From phosphinoboranes to mercaptopyridines : a journey into the reactivity of not so frustrated Lewis pairs

La catalyse est une des pierres d’assise de la chimie moderne. Elle permet de faire des transformations difficiles d’une manière efficace et sélective, rendant possible des voies de synthèse plus courtes qui permettent ainsi à l’industrie chimique des économies de temps et d’argent. Par conséquent, le développement de la catalyse est d’une grande importance. Dans les dernières décennies, la plupart des efforts ont été orientés vers l’utilisation de métaux de transition de la seconde et troisième rangée, une approche couronnée de succès. Cependant, la maturité de ce sous-domaine et les améliorations des méthodes de caractérisation et de modélisation ont encouragé les chercheurs académiques à explorer le potentiel d’autres éléments du tableau périodique pour la catalyse. Cette thèse explore la catalyse sans métal, ou comme nous aimons l’appeler, la chimie organométallique sans métal. Elle présente des avancées dans le domaine des paires de Lewis frustrées (PLFs), qui utilisent des molécules comportant des fonctions acide de Lewis et base de Lewis pour rendre possible des transformations qui ne le seraient pas en utilisant seulement l’une ou l’autre des fonctions. Le focus particulier du travail est de comprendre et d’exploiter la chimie des PLFs. Par conséquent, nous ne nous sommes pas limités à seulement une sous-classe de PLFs ni à une seule transformation chimique. Les sujets contenus dans la thèse sont diversifiés et incluent la réduction du CO2, la fonctionnalisation de liens C-H, la chimie des liens B-B, la chimie des liens B-S ainsi que des discussions plus fondamentales sur le futur de la catalyse utilisant les PLFs.Catalysis is one of the cornerstones of modern chemistry. It allows difficult transformations to take place in an efficient and selective manner, making possible the design of shorter synthetic pathways and saving the chemical industry time and money. Thus, the improvement of catalysis is of great importance. In the past decades, most efforts have been oriented toward the use of second and third row transition metals, an approach that has been very successful. However, the maturity of that subfield and the improvement of characterization and modelization techniques have been leading academic researchers in exploring catalysis with other elements of the periodic table. This thesis explores metal-free catalysis, or as we like to call it metal-free organometallic chemistry. It presents advances in frustrated Lewis pair (FLP) chemistry, which uses molecules containing Lewis basic and Lewis acidic functions to access transformations that would not be possible using only one or the other. The focus of the work is mostly on understanding and exploiting FLP chemistry. Thus, we did not limit ourselves to some sub-class of FLP nor to only one transformation. The subjects contained in the thesis are quite diverse and include CO2 reduction, C-H bond functionalization, B-B bond chemistry, B-S bond chemistry as well as more fundamental discussions on future FLP catalysis development

Part 1: Towards the Synthesis of Pyrene Zigzag Cyclacenes, Part 2: New Methods for the Synthesis of Conjugated Polymers

Part 1: Carbon nanotubes (CNTs) are allotropes of carbon that have emerged as candidates for implementation in electronic devices ranging from transistors to solar cells. Unfortunately, the behavior of CNTs is highly dependent on their structure and modern synthetic methods for generating CNTs are not able to provide uniform samples for electronic applications. Recently, the synthesis of cycloparaphenylenes (CPPs), which closely resemble metallic CNTs, has been elucidated and has since been further expanded to allow for the CPPs of varying diameters and subunits. More importantly, CPPs were also shown to allow for the controlled bottom-up synthesis of CNTs, opening the door towards the concise synthesis of CNTs. Herein, we will outline our synthetic attempts towards the synthesis of zigzag cyclacenes and how the creation of a zigzag nanobelt could bring forth the defined synthesis of semiconducting zigzag nanotubes. Drawing inspiration from previous attempts at cyclacenes and the successful synthesis of CPPs, we set out to construct a zigzag macrocycle using a Diels-Alder approach with pyrene as the backbone of the cycle. We were able to successfully construct the cyclic precursor to the cyclacene following numerous attempts; however, isolation of the fully aromatized product was not accomplished because the strain exhibited by the cycle led to an over reduction. Our search to create cyclacenes led us towards phosphonium salts as a new method for the mild creation of benzyne. Unfortunately, the phosphonium benzyne performed poorly due to regioselectivity issues, but in trying to create the aryl phosphonium salts, we created a new route towards these compounds. Herein, we will describe our development of a metal free synthesis of aryl phosphonium salts. When aryl halides are irradiated with UV light in the presence of a phosphine, the two species can couple leading to the formation of the phosphonium salt. The reaction is amenable to a variety of phosphines and can proceed with aryl chlorides, iodides, bromides, and pseudohalides. Part 2: Conjugated polymers have gained a great deal of interest as these compounds can be used as active materials and enable the creation of lightweight, flexible, and low-cost electronic devices. Critical to the advancement of these technologies is the creation of new synthetic methods and facile access to material. Herein, we will outline the development of new synthetic techniques for the creating conjugated polymers. First, we will discuss the development of a new metal free dehydrative polymerization of thiazole N-oxides. Drawing inspiration from nature and from the industrial synthesis of commodity polymers, such as PET and nylon-6,6, we developed a new transformation that can dimerize thiazole N-oxides in the absence of a metal with the formal loss of water being the sole byproduct. This methodology was later extended onto bifunctional monomers and allowed for the synthesis of conjugated polymers in quantitative yield and good molecular weights. Secondly, we will discuss the design and synthesis of a new palladium precatalyst for the synthesis of conjugated polymers through direct arylation polymerization. Conjugated polymers are mostly synthesized using transition metal couplings such as Stille or Suzuki couplings; however, these methods require pre- functionalization and can leave behind toxic byproducts. Direct arylation polymerization has recently emerged as a new technique for synthesizing conjugated polymers; however, the nature of the propagating species means that conjugated polymers created this way are more prone to branching/crosslinking defects. We designed a palladium precatalyst specifically for direct arylation polymerization that can reduce unwanted functionalization while providing good molecular weights, high yields, lower loadings, and improved thermal properties

Synthesis of different series of small molecules targeting HIV-1 RT, Candida albicans, MAO and G-Quadruplex

My PhD work has been focused towards four different targets: HIV-1 RT, Candida albicans, Monoamine oxidase, and G-Quadruplex. Thus in order to give the reader a clearer exposition this report has been divided in four different chapters. Each of the chapters has his own figures, schemes, tables and references. The main part of my work has been dedicated to HIV-1 RT, thus this chapter is the major and first one

Synthesis of different series of small molecules targeting HIV-1 RT, Candida albicans, MAO and G-Quadruplex

My PhD work has been focused towards four different targets: HIV-1 RT, Candida albicans, Monoamine oxidase, and G-Quadruplex. Thus in order to give the reader a clearer exposition this report has been divided in four different chapters. Each of the chapters has his own figures, schemes, tables and references. The main part of my work has been dedicated to HIV-1 RT, thus this chapter is the major and first one