Syntheses and structural characterisations of amidinates, diaminates and phenolates antimony (I and III) and aluminium (III) complexes

This thesis focuses on the synthesis and characterisation of antimony(III) and aluminium(III) amidates with an emphasis on structural characterisation, presenting the isolation of 22 new complexes. In addition, some chemistry of (2,6-di–tert-butyl-4-methyl) antimony and aluminium (III) complexes is added in the appendix of this thesis. Below is a general outline for each chapter of original research (2-4), showing the diverse range of compounds obtained from the following formamidinate and polyfluorophenylamidate ligands. Chapter 1 gives an overall introduction to antimony and aluminium (III) chemistry. This chapter describes the general aspects and overview of the relevant literature highlighting the most common synthetic methods used to synthesis antimony and aluminium compounds, particularly formamidinates, amidates, phenolates and their applications. Chapter 2 describes the metathesis reactions employed for the preparation of a range of mono- and bis-substituted formamidinato antimony (III) complexes. The bissubstituted complexes include [Sb(DippForm)₂Cl] (2.2), [Sb(DippForm)₂Br] (2.3) and [Sb(DippForm)₂I] (2.4) and mono-substituted products include [Sb(DippForm)Br₂] (2.5) and [Sb(DippForm)I₂] (2.6). Other complexes have been prepared as dimers [Sb(DippForm)(NSiMe₃)]₂ (2.8) and [Sb(DippForm)Cl(C₆F₅)]₂.(THF)₂ (2.12), also the formamidinato-bridged distibane [Sb₂{μ-(DippForm}₂].(THF)₈ (2.1) that represents an example of monovalent antimony. Fundamentally, the synthesis of antimony (I) and (III) formamidinate complexes was accomplished through deprotonation of N,N'-2,6-diisopropylphenylformamidine (DippFormH) by a metal alkyl/amide reagent (n-BuLi, LiN(SiMe₃)₂, NaN(SiMe₃)₂) in a donor solvent THF or in PhMe and then combined with SbX₃ in THF and/or PhMe. The unexpected [(DippForm)ClSb(μ-O)SbCl₂(Me₂NC₂H₄NMe₂)]₂.(C₆D₆) (2.11) was the only type of halogenated hetero dinuclear complex isolated in this study. Chapter 3 details the synthesis and characterisation of a series of heteroleptic and homoleptic N,N-dimethyl-N'-2,3,5,6-tetrafluorophenylethane-1,2-diaminate antimony (III) complexes. [Sb(p-HC₆F₄NC₂H₄NMe₂)₂Cl] (3.2) and [Sb(p-HC₆F₄NC₂H₄NMe₂)3] (3.3) complexes were isolated by metathesis reactions between SbCl3 and Li(p-HC₆F₄N(CH₂)₂NMe₂), a common synthetic route to antimony complexes; while the direct reaction between SbCl3 and p-HC₆F₄NH(CH₂)₂NMe₂ was used to synthesise [Sb(p-HC₆F₄NC₂H₄NMe₂)Cl₂] (3.1). Halo- and nonhalo-polyfluorophenylamido antimony (III) complexes were gained as monomers in the solid state. Chapter 4 Extending this chemistry to formamidinate aluminium resulted in the isolation of a group of new and interesting formamidinato aluminium (III) complexes ranging from mono- to bis-substituted, involving different bonding modes. Metathesis reactions between AlX₃ (X = Cl, Br, I) and two different deprotonated N,N'-chelating ligands (XylForm) and (DippForm) of varying steric bulk and functionality were used to increase the range of the haloorgano(formamidinato) aluminium (III) system. These complexes are [Al(XylForm)₂Cl] (4.1), [Al(XylForm)₂I].PhMe (4.2), [Al(XylFormH)Br₃] (4.3), [Al(DippFormH)Br₃] (4.5) and [Al(DippForm)₂Cl] (4.8). Using the bulkier formamidinate ligand (DippForm) allowed the isolation of [Al(DippForm)Cl₂(thf)] (4.6) and [Al(DippForm)ClBr(thf)] (4.7). The heteroleptic [Al₃(XylForm)₂(μ₃-O)(OH)Cl₄]₂.PhMe (4.4) was isolated as a monomer and represents a compound contained three aluminium atoms bridged by an oxygen atom. In a different approach, a chlorine/methyl exchange reaction was used for forming bimetallic Al/Sb (III) ionic complexes [Me₃Sb-SbMe₂][AlCl₄] (4.9) and [Br₃Sb-μBr-SbBr₃][AlCl₂(thf)₄] (4.10), showing relatively rare coordination modes. Overall, the knowledge regarding amidato antimony and aluminium (III) complexes has been enhanced and more information has been obtained regarding their structural motifs and bonding modes. The N,N'-bis(aryl)formamidinate ligands can form stable and structurally interesting mono/trivalent antimony and trivalent aluminium species using metathesis route, due to their ease of steric variability. In addition, this thesis demonstrates the ability of N,N-dimethyl-N'-2,3,5,6-tetrafluorophenylethane-1,2-diaminate ligand to stabilise antimony in its most common and stable oxidation state (III). Many of these compounds, particularly the compounds with M-X bonds, are now well set for potential reduction to low valent species. Reaction with KC₈ should form isolable low valent Sb or Al complexes and this work could be performed in future work. There are also many other formamidinate, guanidinate and amidinate ligands that could be used to extend this work

Radical cyclisations onto imidazoles

This thesis describes the development of new pathways towards the synthesis of novel antimicrobial (and anticancer) agents. Two synthetic protocols based on free radical chemistry are studied, which are used to access polycyclic heterocyclic compounds of potential biological importance. Both these procedures involve the generation of radicals using Bu3SnH and AIBN initiators, and the subsequent intramolecular radical cyclisation onto the imidazole ring. Radical cyclisations onto benzimidazoles and pyrroles are also described. [Continues.

Inductanceless high order low frequency filters for medical applications

In this paper, a designed circuit used for low-frequency filters is implemented and realized the filter is based on frequency-dependent negative resistance (FDNR) as an inductor simulator to substitute the traditional inductance, which is heavy and high cost due to the coil material manufacturing and size area. The simulator is based on an active operation amplifier or operation transconductance amplifier (OTA) that is easy to build in an integrated circuit with a minimum number of components. The third and higher-order Butterworth filter is simulated at low frequency for low pass filter to use in medical instruments and low-frequency applications. The designed circuit is compared with the traditional proportional integral controller enhanced (PIE) and T section ordinary filter. The results with magnitude and phase response were compared and an acceptable result is obtained. The filter can be used for general applications such as medical and other low-frequency filters needed

1-Fluoro-2,5-dimethoxy-4-nitrobenzene

1-Fluoro-2,5-dimethoxy-4-nitrobenzene was synthesized in 90% yield by the reaction of commercial 2-fluoro-1,4-dimethoxybenzene with nitric acid. The structure was confirmed by X-ray crystallography. The new title compound was characterized by 1H and 13C-NMR, elemental analysis, EI-MS and FT-IR

A Survey of Artificial Intelligence Techniques Employed for Adaptive Educational Systems within E-Learning Platforms

Abstract The adaptive educational systems within e-learning platforms are built in response to the fact that the learning process is different for each and every learner. In order to provide adaptive e-learning services and study materials that are tailor-made for adaptive learning, this type of educational approach seeks to combine the ability to comprehend and detect a person’s specific needs in the context of learning with the expertise required to use appropriate learning pedagogy and enhance the learning process. Thus, it is critical to create accurate student profiles and models based upon analysis of their affective states, knowledge level, and their individual personality traits and skills. The acquired data can then be efficiently used and exploited to develop an adaptive learning environment. Once acquired, these learner models can be used in two ways. The first is to inform the pedagogy proposed by the experts and designers of the adaptive educational system. The second is to give the system dynamic self-learning capabilities from the behaviors exhibited by the teachers and students to create the appropriate pedagogy and automatically adjust the e-learning environments to suit the pedagogies. In this respect, artificial intelligence techniques may be useful for several reasons, including their ability to develop and imitate human reasoning and decision-making processes (learning-teaching model) and minimize the sources of uncertainty to achieve an effective learning-teaching context. These learning capabilities ensure both learner and system improvement over the lifelong learning mechanism. In this paper, we present a survey of raised and related topics to the field of artificial intelligence techniques employed for adaptive educational systems within e-learning, their advantages and disadvantages, and a discussion of the importance of using those techniques to achieve more intelligent and adaptive e-learning environments.</jats:p

Improving the security of LBlock lightweight algorithm using bit permutation

Lightweight block cipher algorithms are important for constrained environment. LBlock uses word permutation to do the diffusion while this research uses bit permutation to increase the number of active Substitution box (S-box). The number of active S-box is a regular method to evaluate the security against linear and differential attacks. The bit permutation method is described in this research with analysis and discussion. The preliminary results show that the proposed algorithm has 32 active S-box for 13 rounds which is higher than 32 active S-box for 15 rounds of LBlock algorithm. Also, we can conclude that the proposed algorithm is better than LBlock algorithm in the perspective of security

2-(Fluoromethyl)-4,7-dimethoxy-1-methyl-1H -benzimidazole

Selectfluor (1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)) substitutes the TEMPO free radical with fluorine on 4,7-dimethoxy-1-methyl-2-{[(2,2,6,6-tetramethylpiperidin-1-yl)oxy]methyl}-1H-benzimidazole to give the title compound in a 77% yield. A mechanism is proposed for the formation of this novel methylene fluoride