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Correlation of thermochemical measurements and quantum chemical calculations of thermally unduced structural transformations of polynuclear complexes [(en)(H2O)3Ni-(pyr)-Ni(H2O)3(en)] 4H2O and [Cd(N-Boc-gly)2(H2O)2]n.

dc.contributor.advisorMinić, Dragica
dc.contributor.otherJerosimić, Stanka
dc.contributor.otherPoleti, Dejan
dc.contributor.otherSimonović, Branislav
dc.creatorBegović, Nebojša N.
dc.date.accessioned2016-07-10T17:16:25Z
dc.date.available2016-07-10T17:16:25Z
dc.date.available2020-07-03T09:35:01Z
dc.date.issued2015-06-01
dc.identifier.urihttp://eteze.bg.ac.rs/application/showtheses?thesesId=3129
dc.identifier.urihttp://nardus.mpn.gov.rs/handle/123456789/5744
dc.identifier.urihttps://fedorabg.bg.ac.rs/fedora/get/o:11432/bdef:Content/download
dc.identifier.urihttp://vbs.rs/scripts/cobiss?command=DISPLAY&base=70036&RID=47565327
dc.description.abstractIspitana je termička stabilnost i mehanizam stupnjevitog razlaganja polinuklearnih kompleksa [(en)(H2O)3Ni - (pyr) - Ni(H2O)3(en)] 4H2O i [Cd(N - Boc - gly)2(H2O)2]n u temperaturskom intervalu od 320 do 760 K. Utvrđeno je da su svi stupnjevi termički aktivirani. Iz površine endotermnih pikova određene su entalpije procesa, a primenom Kissinger-ove metode određena je ukupna vrednost prividne energije aktivacije svakog stupnja razlaganja. Analiza izotermalnih merenja kompleksa nikla ukazala je na sve značajniji uticaj difuzije sa napredovanjem reakcije. Utvrđena je zavisnost reakcionog puta od brzine zagrevanja kompleksa. Analizom promene oblika zavisnosti efektivne energije aktivacije od stepena napredovanja utvrđeno je postojanje reverzibilnog stupnja u procesu dehidratacije kompleksa nikla i promena ograničavaju¢eg stupnja uz sve značajniji uticaj difuzije. Porast, a zatim pad prividne enrgije aktivacije tokom dehidratacije kompleksa kadmijuma i stupnja razgradnje kompleksa nikla ukazuje na promenu ograničavaju¢eg stupnja. Neprekidni porast energije aktivacije razlaganja kompleksa kadmijuma ukazuje da se tokom razlaganjana odvijaju dva paralelna procesa. Vibracione frekvencije izračunate za izokinetičke temperature odgovaraju vibracijama Ni - OH2, Cd - OH2 i Cd - O veza, što je kvantnohemijskim proračunima i određeno. Korelacijom eksperimentalno određenih i izra£unatih termodinamičkih i kinetičkih parametara definisani su mehanizami dehidratacionih i stupnjeva razlaganja oba kompleksa. Proračuni su pokazali da se tokom dehidratacije kompleksa nikla odvija polimerizacija. Pri malim brzinama, polimerizacija pospešuje izlazak vode iz sistema, dok se pri višim brzinama zagrevanja ovaj proces odvija znatno sporije. Ovo uzrokuje postojanje dva reakciona puta na različitim brzinama zagrevanja. Na osnovu proračuna izračunata je konstanta ravnoteže povratnog stupnja na različitim temperaturama tokom dehidratacije polaznog kompleksa. Na ovaj način je pokazano da gubitak kristalne vode pospešuje odlazak koordinovane vode iz sistema. Pokazano je da niža energija aktivacije razlaganja kompleksa kadmijuma na početku procesa odgovara premeštanju (N - Boc - gly) liganda iz unutrašnjosti sistema ka površini, dok viša odgovara njegovom otkidanju sa same površine.sr
dc.description.abstractThermal stability and degradation mechanism of [(en)(H2O)3Ni - (pyr) - Ni(H2O)3(en)] 4H2O and [Cd(N - Boc - gly)2(H2O)2]n coordination polymers was investigated in 320-760 K temperature range. It was determined that all of the individual steps are thermally activated. Overall enthalpies of these processes were determined from the area of corresponding endothermic peaks, while the overall average value of activation energies of individual degradation processes were determined using the Kissinger method. The thermal degradation starts with multi-step dehydration process, which exhibits increased influence of diffusion on the reaction mechanism during the progress of the reaction, and its reaction path depends on the heating rate. Analysis of dependence of the value of the effective apparent activation energy on the reaction conversion degree indicates the existence of a reversible step in the dehydration process of Ni-coordination polymer and a change of rate-limiting step of this reaction, probably due to diffusion. Increase and then decrease in the value of the effective apparent activation energy for dehydration reaction of Cd-coordination polymer and degradation reaction of Ni-coordination polymer indicates a change of rate-limiting step, likely due to diffusion of released products. Continuous increase in the value of the effective apparent activation energy for degradation reaction of Cd-coordination polymer indicates that the reaction mechanism consists of two parallel processes. Vibrational frequencies corresponding to the determined values of isokinetic temperatures correspond to Ni - OH2,Cd - OH2 and Cd - O bonds, respectively, and this was confirmed using quantum-chemical calculations. Correlation of experimental and calculated thermodynamic and kinetic parameters has allowed the formulation of the corresponding mechanisms of thermal dehydration and degradation for both of these coordination polymers. DFT calculations indicate that Ni-coordination polymer undergoes polymerization during the dehydration process. At low heating rates, polymerization promotes release of water, while at higher heating rates the polymerization is much slower, resulting in two distinct reaction paths at different heating rates. DFT calculations were used to calculate the equilibrium constant of the reversible step of dehydration of Ni-coordination polymer, indicating that the release of uncoordinated water molecules promotes subsequent release of coordinated water molecules. The lower value of activation energy of thermal degradation of Cd-coordination polymer at the beginning of the process corresponds to the transfer of (N - Boc - gly) ligand from the bulk to the surface, while the higher value of activation energy at the end of process corresponds to release of (N - Boc - gl) ligand from the surface.en
dc.formatapplication/pdf
dc.languagesr
dc.publisherУниверзитет у Београду, Факултет за физичку хемијуsr
dc.rightsopenAccessen
dc.sourceУниверзитет у Београдуsr
dc.subjectkoordinacioni polimersr
dc.subjectcoordination polymeren
dc.subjectthermal analysisen
dc.subjectDSCen
dc.subjectTGen
dc.subjectapperent activation energyen
dc.subjectenthalpyen
dc.subjectreaction mechanismen
dc.subjectDFT calculationen
dc.subjecthydrogen bonden
dc.subjectpolynuclear complexesen
dc.subjecttermalna analizasr
dc.subjectDSCsr
dc.subjectTGsr
dc.subjectprividna energija aktivacijesr
dc.subjectentalpijasr
dc.subjectreakcioni mehanizamsr
dc.subjectDFT proračunsr
dc.subjectvodonična vezasr
dc.subjectpolinuklearni kompleksisr
dc.titleKorelacija termohemijskih merenja i kvantnohemijskih izračunavanja termički indukovanih strukturnih transformacija polinuklearnih kompleksa [(en)(H2O)3Ni-(pyr)-Ni(H2O)3(en)] 4H2O i [Cd(N-Boc-gly)2(H2O)2]nsr
dc.titleCorrelation of thermochemical measurements and quantum chemical calculations of thermally unduced structural transformations of polynuclear complexes [(en)(H2O)3Ni-(pyr)-Ni(H2O)3(en)] 4H2O and [Cd(N-Boc-gly)2(H2O)2]n.en
dc.typedoctoralThesis
dc.rights.licenseBY-NC-ND
dcterms.abstractМинић, Драгица; Симоновић, Бранислав; Јеросимић, Станка; Полети, Дејан; Беговић, Небојша Н.;
dc.identifier.fulltexthttp://nardus.mpn.gov.rs/bitstream/id/21170/Disertacija3669.pdf
dc.identifier.fulltexthttp://nardus.mpn.gov.rs/bitstream/id/21171/Begovic_Nebojsa.pdf


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