The technetium-99m complex of the L,L-ethylenedicysteine diethylester (EC), of the brain imaging agent, was reported as a good choice for replacement of the renal nuclear medicines like OIH radiopharmaceutical. This present research work studies the structural, electronic and spectral properties of the EC compound and its complex with technetium-99m radionuclide from theoretical insight. All computations were done by Gaussian 03 package at B3LYP/6-31+G(d,p) level of theory. The frontier molecular orbital (FMO) computations show the stability of 99mTc-EC structure is lower than the EC molecule. In contrast, the highest reactivity is related to the 99mTc-EC complex. From the nuclear magnetic resonance (NMR) calculations, the comparison between chemical shifts of carbon atoms of 99mTc-EC to EC molecule shows the carbon atoms of technetium-99m-EC complex are more shielded. Also, the natural bond orbital (NBO) analysis shows more d orbitals of technetium atom and more p orbitals of sulfur, nitrogen and oxygen atoms are used for Tc-S, Tc-N and Tc-O molecular orbital hybrids. Manuscript profile

During recent years, the silicon organic-inorganic compounds play the key role in medicinal chemistry and pharmaceutical industry. This is because of their similar chemical properties with carbon compounds. The second reason is related to their easy transfer from the cell membranes. So, molecular simulation and study the properties of novel organosilicon compounds can be more important. From this sight of view, we designed and investigated silicon analogs of benzene ring before. Here, the various derivatives of hexasiline molecule will be discussed in the following. Our investigations are based on the density functional theory (DFT) computations. The present research work was focused on investigation of the structural and spectral properties and reactivity of hexasiline using B3LYP/cc-pVDZ level of theory. The Fukui indices (local reactivity) showed that the electrophilic attacks happen on the Si4 atoms of the molecules. On the other hand, the molecules containing electron-donating and electron-withdrawing substituents prefer do nucleophilic reactions on their Si4 and Si3 positions, respectively. Manuscript profile

The main purpose of the present investigation is the study of therapeutically effect of Zotepine in schizophrenia disease treatment. In first step, the molecular structure of the said compound is optimized using density functional theory (DFT) technique by B3LYP functional method at 6-311++G(d,p) level of theory. Then the electronic properties of the title molecule are calculated using frontier molecular orbitals (FMOs) theory. The global reactivity indices show the molecule has high stability and can react with both nucleophiles and electrophiles. In overall, Zotepine shows low reactivity against the biomolecules. Finally, the molecular docking studies indicate the Zotepine-D2R complex formation is mainly carried out by the residues Phe 437, His 442, Ser 433, Phe 433 and Leu 441 using steric interactions. Manuscript profile

Breast cancer is a complicated disease that it is accompanied by different symptoms. Diagnosis of this disease is performed by various techniques. Using Radiopharmaceuticals is a new method to diagnose the said tumors. [18F]-FPTT is one of these nuclear medicines for detection of breast cancer. It seems that the binding of the title radiopharmaceutical to the progesterone receptor is the main cause of the breast cancer diagnosis. Studying the electronic properties, stability, reactivity and binding of the title compound to the progesterone receptor are the main purposes of the present research work. In first step, [18F]-FPTT molecular structure is optimized at B3LYP/6-311++G(d,p) level of theory at room temperature. Then, its stability and reactivity properties are calculated by frontier molecular orbitals (FMOs) energies. The global reactivity indices show this medicinal molecule may be interacted with active reagents into the cell such as free radicals. Also, this radiopharmaceutical has a molecular structure with high reactivity and it prefers to interact with nucleophile agents or residues. Analyzing the molecular electrostatic potential (MEP) graph of the compound indicates it prefers to interact with the residues of a receptor by its oxygen atoms. On the other hand, the docking analysis of the ligand-receptor complex shows the steric interactions play the main role in this complex formation. The docking analysis data shows the progesterone receptor (PR) residues containing Arg 899 [B], Phe 895 [A], Phe 895 [B], Ser 898 [B], Ser 910 [A], Ile 896 [A], Ser 898 [A], Ile 896 [B], Val 903 [B], Glu 911 [A], Ser 902 [B], Arg 899 [A] and Glu 904 [B] are the major amino acids participating in the ligand-receptor complex formation. Manuscript profile

Tetrazole-containing compounds have been the subject of much recent research because of theirpotential as high energy density materials (HEDMs). In this work, theoretical studies on the 1Htetrazolylderivatives of tetrahedrane were done at the density functional theory (DFT) method withthe 6-31G(d) basis set without any symmetrical restrictions in order to find the structural andenergetically properties. Geometric and electronic structures, natural bond orbitals (NBOs)population, aromaticity of tetrazole rings, thermodynamic properties and detonation performances ofthese molecules have been studied using mentioned level of theory. Nucleus independent chemicalshift (NICS) calculations show the tetrazole rings on the tetrahedrane system are aromatic. The heatof formation (HOF) values of all structures has been calculated by a proper isodesmic reaction. TheHOFs are found to be correlative with the number of tetrazole groups. According to the results of thecalculations, only tri-substituted derivative of tetrahedrane can be a viable candidate of high energymaterials. Manuscript profile

Tetrahedrane is most strained and the smallest cage compound. It attracts organic chemists because ofits unusual bonding nature and highly symmetrical structure. However, many efforts to isolate theparent tetrahedrane have been unsuccessful because of the high reactivity and very short lifetimecaused by the strain in this molecule. Modeling of molecules for determination of structuralproperties of them prior to synthesizing molecule in the laboratory is an important method. Thecomputational chemistry is more completely in understanding a problem. In present study, the densityfunctional theory (DFT-B3LYP) method with 6-31G (d) basis set was used for optimizing andstudying the electronic structural and detonation properties of tetrahedrane derivatives at 298.15 Ktemperature and 1 atmosphere pressure. The results show the tetrahedrane system with more electronwithdrawing groups will be deviated from standard and stable state. And also, the NHNH2, -NHNO2, -NO2 and -ONO2 groups give the detonation property to the tetrahedrane system. Manuscript profile

In present study, the density functional theory (DFT-B3LYP) method with SVP basis set was used for optimizing and studying the electronic structural properties of cis and trans isomers of bis-(5-nitro-2H-tetrazolato-N2) tetraammine cobalt (III) perchlorate (BNCP) as powerful explosives at 298.15 K temperature and 1 atmosphere pressure. And also, Natural Bond Orbital (NBO) population analysis and the molecular electrostatic potential (MEP) surface of the structures were studied by mentioned level of theory. The effect of ligands sites attached to the transition metal (cobalt) at the BNCP isomers was studied on the HOMO-LUMO energies, the electronic chemical potential, the absolute hardness and electrophilicity index. The geometry optimization of the structures shows the octahedral environment around cobalt. The tetrazole nitrogen atoms have large negative charge. The three-dimensional electrostatic potential maps of the isomers show that the negative charge is located on the nitro and perchlorate groups. The NBO analysis shows that the Co-ligand bonds in the near of perchlorate ion are formed from short, strong and sigma bonds. Manuscript profile

The present work reports the detailed B3LYP/6-311++G(d,p) study of most stable transand cisconfigurations photoisomerization in the core system of computational photochemistry-the 5,5'-disubstituted-1,1'-azobis (tetrazole) molecules. All computations were carried out in gas phase attemperature 293.15 K and pressure 1 atm. Firstly; the potential energy surface (PES) of the groundstate of the molecules has been directly optimized and scanned using a multistate multiconfigurationsecond-order perturbation theory. We characterize the cis and trans molecules geometric domains ofthe ground states. The imaginary frequencies were not shown in frequency computation analysis ofthe optimized molecules. Also we calculate the electronic and thermal energy, polarizability,equilibrium constant, HOMO-LUMO energies gap and chemical hardness of the configurations in theground state. In general, the DFT results confirm the stability of the trans configurations among allstructures. In the last section of this study, the detonation parameters of the compounds are calculated. Manuscript profile