Modeling and analysis of fundamental properties of sumanene

U  disertaciji  je  sprovedeno  teorijsko  istraživanje  fizičko-hemijskih  svojstava elektronskog podsistema molekula sumanena. Proračuni su sprovedeni u okvirima DFT i TDDFT  teorije  sa  B3LYP  funkcionalom  i  6-31Gd,  6-31Gdp i  6-31++Gdp  bazisom.  Za  sve proračune  u  okvirima  navedenog  nivoa  teorije,  korišćen  je  softverski  paket  Gaussian03. Ispitana  su:  strukturna  i  optička  (zajedno  sa  nelinearnim)  svojstva  sumanena  i  njegovih derivata dobijenih modifikovanjem sa atomima bora iazota, aromatična i inverziona svojstva svojstva  sumanena  i  njegovih  derivata,  adsorpciona  svojstva  sumanena  prema  molekulima H2, CO, CO2 i NH3 i uticaj spoljašnjeg električnog polja na svojstva sumanena. Prema  dobijenim  rezultatima,  fundamentalna  fizičko-hemijska  svojstva  molekula  sumanena mogu se efikasno i fino podešavati supstitucijom i disupstitucijom hetero-atomima bora  i  azota.  Dubina  i  inverziona  barijera  sumanena se  na  ovaj  način  može  menjati  u  oba smera.  Pokazalo  se  da  su  ova  dva  parametra  u  korelaciji,  s  obzirom  da inverziona  barijera skoro potpuno zavisi od dubine sumanena. Slično je i sa aromatičnim svojstvima prstenova, koja se u zavisnosti od broja uvedenih hetero-atomamenja od aromatične preko nearomatične do antiaromatične prirode. Optička svojstva su, pomenutim modifikacijama, takođe značajno poboljšana: apsorpcioni pikovi kod UV/Vis spektra se pomeraju ka vidljivoj oblasti, dok je hiperpolarizibilnost  sumanena  i  derivata  sa  jednim  atomom  bora  viša  od  referentnog molekula uree, respektivno, 9 i 49 puta. Prema dobijenim rezultatima, adsorpciona svojstva sumanena su veoma kompetitivna sa  ostalim  organskim  molekulima  kao  što  su  ugljenične  nanotube  i  fuleren  C60,  usled postojanja  značajnog  dipolnog  momenta  zbog  specifične  geometrije.  Posebno  se  ističu pozitivna adsorpciona svojstva prema molekulima H2  i CO. Dok je prvo pomenuti bitan sa energetskog  aspekta,  specifičnost  drugog  molekula  se  ogleda  u  činjenici  da  ne  može  biti adsorbovan od strane ugljeničnih nanotuba.  Potencijal sumanena, posebno u oblasti organske elektronike, dodatno ističu i rezultati ispitivanja  uticaja  spoljašnjeg  električnog  polja.  Naime,  dobijeni  rezultati  ukazuju  da  se specifična  (posebno  adsorpciona)  svojstva  sumanena  mogu  dodatno  poboljšati  primenom slabog, i eksperimentalno lako ostvarljivog, električnog  polja, jer se intenzivira razdvajanje naelektrisanja.Theoretical  investigation  of  physicochemical  properties  of  electron  subsystem  of sumanene  molecule  has  been  conducted  in  this  doctoral  work.  Calculations  are  performed within DFT and TD-DFT with B3LYP functional and 6-31Gd, 6-31Gdp i   6-31++Gdp basis sets. For all calculations, on the mentioned level of theory, Gaussian03software package was used.  Investigation  encompassed:  structural   and  optical  (including  nonlinear)  properties  of sumanene  and  its  derivatives  obtained  by  modification  with  boron  and  nitrogen  atoms, aromatic and bowl to bowl inversion properties of sumanene and its derivatives, adsorption properties of sumanene towards H2, CO, CO2 i NH3 molecules and the influence of external electric field to the properties of sumanene. According to obtained results, fundamental physicochemical properties of sumanene molecule could be efficiently and finely adjusted with the monosubstitution and disubstitution with  hetero-atoms  of  boron  and  nitrogen.  Bowl  depth and  bowl  to  bowl  inversion  barrier could  be  tuned  in  both  directions.  It  was  demonstrated  that  these  two  parameters  are correlated, since bowl to bowl inversion barrier principally depends on the fourth power of bowl  depth.  Similar  situation  is  with  aromatic  nature  of  sumanene  rings,  which  change, depending  on  the  number  of  introduced  boron  and  nitrogen  atoms,  from  aromatic  through non-aromatic  towards  anti-aromatic  nature.  Thanks  to  mentioned  modifications,  optical properties  are  improved  as  well:  absorption  peaks  in  UV/Vis  spectra  shift  towards  visible area,  while  hyperpolarizabilities  of  sumanene  and  its  derivative  containing  one  boron  atom are higher than hyperpolarizability of referent molecule of urea, respectively, 9 and 49 times.  Thanks  to  significant  dipole  moment  due  to  the  specific  geometry,  nvestigated  adsorption properties of sumanene are very competitive to the other  organic molecules such as carbon nanotubes and fullerene C60. Positive adsorption properties of sumanene towards H2 and CO molecules are distinguished. While the H2 molecule is important from the energetic aspects, specificity of CO molecules is that it can’t be adsorbed by carbon nanotubes. Potential  of  sumanene,  especially  in  the  field  of  organic  electronics,  is  emphasized through the obtained results related to the investigation of the influence of external electric field.  Obtained  results  indicate  that  specific  (especially  adsorption)  properties  of  sumanene could be additionally improved by application of  weak, and experimentally easily achievable, external electric field, due to the higher charge separation.

Computational study of amiloride – a WADA banned molecule

Amiloride (AMI) is a representative of diuretics. Among other purposes, it is utilized for high blood pressure or swelling induced by heart failure. While it is identified as one of the safest medicines available, it is also listed in the World Anti-doping Agency’s list of substances banned in sport, because it is considered a masking agent. Since it has been abused in sports, methods have been developed to be able to detect it during doping controls. We have computationally investigated selected structural and reactive properties of the AMI molecule in this work, employing density functional theory calculations

Structural and computational study of quinoline-based chalcogensemicarbazones

Chalcogensemicarbazones are condensation products between semicarbazide and its sulphur and selenium isosters with carbonyl compounds with a broad spectrum of biological activities [1-3]. In this work the X-ray structural investigation of library of six chalcogensemicarbazones has been complemented with computational study of their global and local reactive properties, within the framework of density functional theory (DFT). Among other information, DFT calculations helped us to locate the most reactive sites of studied molecules and to identify their sensitivity towards the oxidation. Investigated compounds have been also checked for their optoelectronic properties, due to the fact that they share certain structural similarity with molecules that have exhibited potentially important properties for the area of organic electronics. Pharmacokinetic properties have been assessed by the analysis of frequently employed drug likeness parameters

Titanium Dioxide as the Most Used Photocatalyst for Water Purification: An Overview

Titanium dioxide (TiO2), one of the most frequently used materials in general, has emerged as an excellent photocatalytic material for environmental applications. In this review, principles and mechanisms of the photocatalytic activity of TiO2 have been analyzed. Structural and physical specificities of TiO2 nanoparticles, such as morphology, crystal structure, and electronic and optical properties, have been considered in the context of photocatalytic applications. A review of the influence of several factors, such as the type and dimensions of photocatalyst particles, pH of the solution, the influence of oxidants/electron acceptors, and light intensity on photocatalytic properties of TiO2, has been provided. Superhydrophilicity as an intrinsic property of the TiO2 surface was discussed through surface reconstruction on TiO2 during the reversible hydrophilic changes. Additionally, attention was paid to improving the photocatalytic properties of TiO2 particles through aggregation and agglomeration

TRANSPORT PROPERTIES OF PENTACENE, HEXACENE AND THEIR BN ANALOGUES

We have investigated transport properties of higher acenes pentacene and hexacene and compared it with the transport properties of their BN analogues. Charge hopping from one structure to another was investigated through calculations of reorganization energies based on DFT and Marcus semiempiric approach, while the investigation of charge transport along the investigated structures was based on DFT calculations and non-equilibrium Green's function (NEGF) method. Attention was also paid to the energy separation between the lowest excited singlet (S1) and triplet (T1) state, which is quantity that is important for the field of thermally activated delayed fluorescence (TADF). The obtained results indicate that both groups of investigated structures have certain advantages and drawbacks. According to the reorganization energies and I-V characteristics, pentacene and hexacene have better properties, while from the aspect of TADF, BN analogues of pentacene and hexacene have better properties

Sumanene and its adsorption properties towards CO, CO2 and NH3 molecules

Density functional theory calculations were used in the theoretical investigation of the adsorption properties of sumanene towards molecules considered as common air pollutants: CO, CO2 and NH3. The insignificant perturbation of sumanene after adsorption and the adsorption energies obtained indicate a physisorption mechanism. It was shown that, contrary to carbon nanotubes, sumanene is able to adsorb CO molecules, and that adsorption of CO2 by sumanene is stronger than adsorption of CO2 by C-60. To better understand the adsorption characteristics of sumanene, density of states and natural bond order analyses were performed, which showed that chemical interactions exist and that these are more important mostly on the convex side. Better adsorption properties were obtained for the concave side as adsorption is dictated by physisorption mechanisms due to the specific bowl-shaped geometry of sumanene, because of which more negative charge is located precisely on the concave side. Molecular electrostatic potential surfaces were also used in order to better locate the adsorption sites and gain additional details about adsorption

Remarkable Sensing Behavior of Pyrazole-based Chemosensor Towards Cu(II) Ion Detection: Synthesis, Characterization and Theoretical Investigations

We report the synthesis of a new imine based ligand, 3-((3-methoxybenzylidene)amino)-1H-pyrazol-5-ol (HL) and its Cu(II) complexes in 2:1 (HL:metal) and 1:1:1 (HL:metal:HQ) stoichiometric ratio using 8-hyroxyquinoline (HQ) as an additional bidentate ligand. The synthesized ligand (HL) and its Cu(II) complexes (1 and 2) are structurally characterized using FT-IR, electronic absorption and emission, NMR, MS and TGA techniques. Furthermore, the complexation of Cu2+ with HL leads to the immediate formation of brown colored solution which indicates that HL can act as simple colorimetric sensor for Cu2+ ions. We further investigated that the sensor could selectively bind to the Cu2+ ions even in the presence of competitive ions such as Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Ag+ and Na+ ions in aqueous solutions which was studied by electronic absorption spectroscopy. The HL ligand and corresponding Cu(II) complexes have been investigated for their reactive properties by density functional theory (DFT) calculations. Quantum molecular descriptors describing local reactive properties have been calculated in order to identify the most reactive molecule sites of title compounds. DFT calculations encompassed molecular electrostatic potential (MEP), local average ionization energies (ALIE), Fukui functions and bond dissociation energies for hydrogen abstraction (H-BDE)

Particularities in physical characteristics of molecular crystalline nanofilms

In this paper, the alterations and changes in dielectrical properties of different nanofilm molecular crystals, caused by the presence of boundaries were theoretically investigated and analyzed. By combined analytical and numerical calculations, allowed exciton states were found, and their spatial distribution along the axis limit (by layers of film) and the surface localization was examined. The relative permittivity of the observed ultrathin film was determined, and the impact of (five) boundary parameters on resonant absorption phenomenon: discrete (by frequencies) and selective (by layers of film) was examined. The conditions for the emergence of single-resonant absorption lines were found

Zeolites as Adsorbents and Photocatalysts for Removal of Dyes from the Aqueous Environment

This study investigated the potential of zeolites (NH4BETA, NH4ZSM-5, and NaY) to remove two frequently used dyes, methylene blue (MB) and rhodamine B (RB), from an aqueous environment. The removal of dyes with zeolites was performed via two mechanisms: adsorption and photocatalysis. Removal of dyes through adsorption was achieved by studying the Freundlich adsorption isotherms, while photocatalytic removal of dyes was performed under UV irradiation. In both cases, the removal experiments were conducted for 180 min at two temperatures (283 K and 293 K), and dye concentrations were determined spectrophotometrically. Additionally, after photodegradation, mineralization was analyzed as chemical oxygen demand. A computational analysis of the structures of MB and RB was performed to gain a deeper understanding of the obtained results. The computational analysis encompassed density functional theory (DFT) calculations and analysis of two quantum-molecular descriptors addressing the local reactivity of molecules. Experimental results have indicated that the considered zeolites effectively remove both dyes through both mechanisms, especially NH4BETA and NH4ZSM-5, due to the presence of active acidic centers on the outer and inner surfaces of the zeolite. The lowest efficiency of dye removal was achieved in the presence of NaY zeolite, which has a lower SiO2/Al2O3 ratio. A more efficient reduction was completed for RB dye, which agrees with the computationally obtained information about reactivity