Teorijsko proučavanje Jahn-Teller-ovog efekta i njegovog uticaja na osobine hemijskih sistema

Quantum mechanical description of the changes in electronic structure due to distortions in molecular shape and vice versa is given in the form of the vibronic coupling theory. Probably, the most famous concept based on this theory is the Jahn−Teller (JT) effect. The JT theorem states that a molecule with a degenerate electronic state spontaneously distorts along a non-totally symmetric vibrational coordinates. This removes the degeneracy and lowers the energy. In fact, the vibronic coupling, correlation between electronic states and vibrational motion of nuclei, describes all spontaneous symmetry breaking distortions, attributed to the JT, Renner-Teller and pseudo JT effects. The consequences of the JT effect are far-reaching. JT effect affects the high magneto-resistance in manganites, superconductivity in fullerides, aromaticity, molecular stereochemistry, reactivity, magnetic properties of molecules, as well as many other properties. It should be emphasized that the JT effect has inspired very significant scientific discoveries, e.g. the concept of high-temperature superconductivity. The significance of the JT effect is increasingly recognized, hence, quantifying the distortion and getting insight into the mechanism lies at the heart of modern investigations. In this thesis, the JT effect and its consequences on the structure and properties of organic and inorganic molecules, aromaticity, excitonic coupling and excitation energy transfer are studied. The JT effect was analyzed and the JT parameters were determined for the JT active cyclobutadienyl radical cation (C4H4+•), cyclopentadienyl radical (C5H5•), benzene cation (C6H6+), benzene anion (C6H6-), tropyl radical (C7H7•), anions and cations of corannulene and coronene (C20H10- , C20H10+, C24H12- and C24H12+), small metal and metalloid clusters (Na3, Ag3, As4− , Sb4−), hexaflurocuprat(II) ion ([CuF6]4-), manganese chelate complex ([Mn(acac)3]) and the organometallic compound cobaltocene (CoCp2) by the means of...Kvantno-mehanički opis promena u elektronskoj strukturi kao posledica distorzije molekula i obrnuto dat je u formi teorije vibronske sprege. Jahn-Teller-ov (JT) efekat je verovatno najpoznatiji koncept zasnovan na ovoj teoriji. Po JT teoremi svi nelinearni molekuli sa degenerisanim elektronskim stanjem spontano se distorguju duž vibracija koje nisu totalno simetrične, pri čemu dolazi do uklanjanja degeneracije uz sniženje energije.U stvari, vibronska sprega, korelacija između elektronskih stanja i pomeraja jezgara, opisuje sve spontane distorzije molekulskih sistema i odnosi se na JT efekat, Renner-Teller-ov efekat i pseudo JT efekat. Posledice JT efekta su dalekosežne. JT efekat utiče na visoku magneto-otpornost manganita, superprovodljivost fulerida, aromatičnost, stereohemiju molekula, reaktivnost, magnetne osobine molekula, kao i mnoge druge osobine. Treba istaći da je JT efekat inspirisao veoma značajna naučna otkrića, na primer, koncept visoko-temperaturne superprovodljivosti. Značaj JT efekta se sve više prepoznaje, stoga, kvantifikovanje distorzije i dobijanje uvida u njen mehanizam se nalazi u centru modernih istraživanja. U okviru ove teze, analiziran je JT efekat i njegove posledice na strukturu i osobine organskih i neorganskih molekula, aromatičnost, ekscitonsku spregu i prenos energije ekscitacije. JT efekat je analiziran i izračunati su JT parametri za ciklobutadienil radikal katjon (C4H4+•), ciklopentadienil radikal (C5H5•), benzen katjon (C6H6+), benzen anjon (C6H6-), tropil radikal (C7H7•), anjone i katjone koranulena i koronena (C20H10- , C20H10+, C24H12- and C24H12+), male metalne i metaloidne klastere (Na3, Ag3, As4− , Sb4−), heksafluorokuprat(II) jon ([CuF6]4-), helatni kompleks mangana ([Mn(acac)3]) i organometalno jedinjenje kobaltocen (CoCp2) primenom multideterminantne teorije funkcionala gustine (eng. Density Functional Theory, DFT). Validacija multideterminantnog DFT metoda je izvedena uz sistematsko ispitivanje uticaja različitih..