Preparation Of Perylene Tetracarboxylic Diimides With Polyhedraloligosilsesquioxane Side Chain And Its Aggregation And Research On Their Structures

Perylene diimide dye has planar structure with two imines of perylene ring having strong π-conjugation,which have very strong photonics and fluorescence properties.In dilute solution,perylene diimide has high fluorescence quantum yield(near 100%),however,the fluorescence is highly quenching due to attraction of dipole-dipole interaction,and π-π stacking between molecules.POSS is an inorganic nanoparticle with silica skeleton structure and cage like shape.Its diameter is about 0.78nm which is greater than π-π stacking distance.When this nanoparticle is covalently attached to PDI core,it can help PDI become more soluble in most organic solvents by increasing the π-π stacking distance of the molecules.In this thesis,a series of symmetric and asymmetric PDI molecular with nanoparticle POSS as a side group were designed and synthesized.Their solution self-assembly behavior and optical properties were examined.The main results are as follows:1.Octyl-POSS-PDI-POSS and Octyl-POSS-PDI-OH has been synthesized and modified by one pot procedure.FTIR,NMR,and MALDI-TOF showed that both products had the target molecular structures.The yields were 57%and 30%,respectively.TGA and DSC curve analysis showed good thermal stability,and there was no thermal degradation observed up to 400℃ and 450℃.2.The solution self-assembly behavior of Octyl-POSS-PDI-POSS was examined by UV-Vis absorption spectroscopy(UV-Vis),fluorescence emission spectrum(FP)and Traveling Wave Ion Mobility-Molecular Spectra(TWIM-MS).Results showed that,the absorption spectrum of Octyl-POSS-PDI-POSS in single solvent chloroform had a typical monomeric peaks transition band with three resolved peaks at 456nm,488nm and 525nm,usually marked as 0-0,0-1,and 0-2 electronic transitions.There was a clear relationship between molar excinction coefficient and concentration under dilute concentration(10-6 mol/L).The increase of concentration linearly decreased the 0-1 and 0-0 peaks at ε488/ε524 extinction coefficient.This was a clear demonstration of aggregation in solution system.The fluorescence spectrum and UV-Vis absorption spectrum of dilute solutions were mirror symmetry.The fluorescence intensity increased with the increase of concentration and a red shift happened.However when the concentration was greater than 1×10-6 mol/L,the fluorescence intensity did not increase with the increase of concentration and a large red shift occured.This could be due to the formation of aggregations of Octyl-POSS-PDI-POSS under high solution concentration,which caused decrease of fluorescence intensity.In bisolvent system(good solvent and poor solvent of chloroform/methanol volume ratio is 1:1),the π-πstacking of Octyl-POSS-PDI-POSS was observed.The aggregation rate was calculated by using monomer-dimer model and the data was from concentration dependant UV-Vis absorption spectrum.The results showed that the aggregation rate increased and tended to become constant due to monomer-dimer equilibrium when concentration was higher than 1×10-4 mol/L.ESI-TWIM-MS-TOF was used to further analyse the aggregations of different types.The results indicated that the aggregations in the system mainly existed as dimers and tracely existed as trimers.The drift time of dimer is 4.49 ms,7.05 ms and 9.75 ms,respectively.The dimer with drift time 9.75 ms was dominat.So it could be speculated that dimer had three different stacking mode.3.The solution self-assembly behavior of Isooctyl-POSS-PDI-OH was investigated.The results showed that the component had the highest molar extinction coefficient(ε)in dilute solution(c=1×10-6 mol/L)and there were three characteristic peaks,460nm,490nm and 527nm.With the increase of concentration,the ratio of ε490 to ε527 tended to become unity,which meant there was a balance between monomer and dimer in the solution.From the fluorescence emission spectrum,it was found that the fluorescence intensity in dilute solution(10-6 mol/L)increased with increasing concentration and the highest fluorescence emission wavelength showed red shift character.When the concentration was higher than 1×10-5 mol/L,the dimers of Isooctyl-POSS-PDI-OH generated in the solution due to the increase of concentration decreased the intensity of fluorescence.Also the highest fluorescence emission peak showed red shift to 548nm.When the volume ratio of chloroform to methanol was 1:4 and the concentration was higher than 1×10-4 mol/L,a balance between monomers and dimers existed in solution.TWIM-MS spectrum indicated that dimmers with three different stacking modes were dominant in the aggregations.4.Two typical solid samples with quite different condensed state,lower ordered powder and perfectly ordered crystal,were prepared by precipitation and phase separation.Their optical properties were examined by solid-state UV-Vis spectrum and solid-state fluorescence emission spectrum with integrating sphere and compared with those as single molecular in solution.The results showed that absorption under solid state became wide between 200nm-800nm and the three characteristic peaks from perylene core completely disappeared by comparision with that of single molecular at 10-5 mol/L concentration between 400nm～550nm.Compared to low-ordered powder,the perfectly ordered crystal had higher fluorescence quantum yield and shorter emission wavelength,and it might be caused by discontinuous π-πinteraction in crystal that was constructed by using dimers as motif.