Sharif Digital Repository

The first part of this thesis describes the synthesis and characterization of several Mn, Fe and Mo complexes containing tridentate Schiff base and oxazoline ligands and their reactivities as catalysts in the oxidation of organic compounds like olefins and sulfides, as well. The crystal structures of newly prepared cis-dioxo-bis[2-(2′-hydroxyphenyl)-oxazolinato]molybdenum(VI), cis-[MoO2(phox)2] and (N-hydroxyphenyl-salicylidenamine)(acetylacetonato)ethanol iron(III), [FeIII(N-OPh-sal)(acac)EtOH] complexes have been described by X-ray crystallography. Due to the difficulties in the preparation of suitable single crystals of novel... 

Quantum calculation based on the density functional theory (DFT) level and 6-311++G (d,p) basis set was employed to study the relation between the structure and radical scavenging activity of a series of hydroxybenzohydroxamic acid derivatives, namely: [HU]; hyroxyurea, [TX]; 3,4,5-trihydroxybenzamidoxime, [DX]; 3,4-dihydroxybenzohydroxamic acid, [4-HBA]; 4-hydroxybenzohydroxamic acid, [2,3-DHBA]; 2,3-Dihydroxybenzohydroxamic acid, [3,5-DHBA]; 3,5-Dihydroxybenzohydroxamic acid and [2-HBA]; 2-hydroxybenzohydroxamic acid in the gas phase, water and benzene environments. The hydrogen bond property of the studied structures and their radicals as well as radical cations was investigated using... 

Hydrogen bond is a type of molecular bond which occurs between hydrogen and a highly electronegative atom (usually F, N and O) and results in special properties.Alkyl phosphonic acids and their derivatives have several applications as pesticides, antibiotics and anti-viruses. Furthermore, some chemicals in human nervous system hydrolyze to alkyl phosphonates and finally to methyl phosphonic acid. Linear alkyl phosphonic acids and their saults have both organic nonpolar hydrophobic groups and inorganic hydrophilic groups and used as surfactants.Different substituents can affect the acidity of alkyl phosphonic acids. Investigation have shown that hydroxyl functional group can increase the... 

Recently, The interest of using the coherent and incoherent photons in chemical synthesis have been raised considerably. In this project, theoretical calculations due to investigation of irradiation’s effects on Fischer- Tropsch synthesis have done. Fischer – Tropsch synthesis is the process that converts synthesis gas, i.e. a mixture of carbon monoxide and hydrogen, in to a wide range of long chain hydrocarbons and oxygenates. We invest the first chapter of this project to introduce of Fischer- Tropsch synthesis and its importance. Following in the next chapter we have analyzed the photocatalyst in microscopic scale. In third chapter, we have claimed the necessary theories which are useful... 

Entropy is one of the important quantities in thermodynamics. In this project has tried to make this quantity as a bridge between quantum and thermodynamics. Entropy has many definitions that the Shannon entropy is chosen in this work. By this definition of entropy, we are able to define the entropy for a electronic system in molecules. By this definition, we are seeking an answer for this question,”whether entropy has a similar application in quantum like thermodynamics or not?”. To elucidate this hypothesis, simple diatomic molecules are computed. In fact, displacement of the Shannon entropy has investigated in bond making process. The question is that whether we can use this quantity to... 

In Li batteries, lithium ions are exchanged between two electrodes, along with the accompaning electron transfer to maintain riability good ionic conductivities and electrolytes stability are achived through additives to the electrolyte. Such matrial should possess good anions acceptability. This work investigates the potential of aza-ethers in this regard. The softness criteris is basically employed. DFT calculation for selected molecules of different size, substituents and interacting atoms are used to correlate softness, electrophilicity, Fukui no, etc to the usefulness of the corresponding matrials  

It is believed that intramolecular hydrogen bonding and also conjugation can affect the acidity power of organic molecules. But simultaneous effects of intramolecular hydrogen bonding and conjugation have not investigated systematically yet. In this project, we choose Ascorbic acid as a basic structure. Then we have changed its structure conveniently, and have explored the roles of hydrogen bonding and conjugation on the acidity of this molecule by using B3LYP functional with the 6-311++G(d,p) basis set. After that we similarly investigate these effects on the acidity of three different systems, including enols, enamines and alcohols. In this project we probe the effect of different hydrogen... 

In this project, the ionization and dissociation of methane molecule by intense femto-second lasers has been studied. Dissociation probability is calculated for interacting CH4 molecule under Ti: Sapphire laser pulse with pulse durations of 10- 40fs in intensities at the range of 1014-1016 Wcm-2. Calculations are carried out with time-dependent density functional theory using Gaussian03 and Octopus packages as powerful computational chemical physics programs. Due to importance of the dependence of interaction dynamics to laser parameters, the effect of these parameters including different intensities, polarization, various pulse durations and pulse envelopes are investigated. The optimal... 

Many of the significant reactions in chemistry and biology are related to bimolecular nucleophilic substitution (SN2) reactions which have been studied first by Hughes and Ingold in the 1930s. Afterward, many organic chemists have continued this work. Up to now, numerous experimental kinetic and theoretical researches have studied the mechanism of these reactions. Since most SN2 reactions occur in solution, a large number of these studies have been devoted to the solvent effects. One of these effects that has been examined extremely is H-bonding via protic solvents that lowers the energy of an anionic nucleophile relative to the transition state, in which the charge is more diffuse, and... 

Iron based superconductors that are studied more in recent years, have the same and different features with copper oxide high temperature superconductors which they can help in solving problems related to high temperature superconductors. In addition, these compounds have attractive physical characteristics such as superconductivity despite of presence of magnetic Iron element or other magnetic elements like nickel and cobalt (In other superconductivity groups, low doping of magnetic elements destroys superconductivity) and also concurrent presence of magnetic and superconductivity phases. The most reported transition temperature in these compounds is 56.3K in Gd0.8Th 0.2FeAsO compound.... 

The ternary 122-type AeFe2As2 (Ae=Ba,Sr,Ca) compounds are antiferromagnetic metals with the orthorhombic lattice structure at ambient pressure and low temperature. By applying mechanical pressure, structural, magnetic and superconducting transitions occur in these compounds. The isovalent doping of Ba with Sr and Ca elements induces chemical pressure and reduces the onset pressure of these transitions. The main purpose of this thesis is to investigate and compare the effects of mechanical and chemical pressures on the structural and magnetic phase transition in the 122 compounds. To achieve this purpose, we have done first-principle calculations for many properties such as the structural...