Modelovanje i analiza fundamentalnih svojstava sumanena

Abstract

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.