Synthesis And Characterization Of Benzo[b]Disilole-based Fluorescent Small Molecules And D-A Type Conjugated Polymers

Siloles are considered as a new kind of ?*–?* conjugated material with low-lying LUMO energy levels,deriving from the effective interaction between the ?* orbital of the exocyclic silicon-carbon bond and the ?* orbital of the butadiene segment.Such a unique electronic structure imparts high electron affinity and fast electron mobility to siloles,and thus silole and its derivatives have special photo-electronic properties.In this dissertation,a novel monomer of benzo[b]disilole was successfully synthesized and characterized.Furthermore,through structural modification,a series of novel benzo[b]disilole based fluorescent small molecules and donor-acceptor(D-A) type conjugated polymers was designed and synthesized.Firstly,benzo[b]disilole was successfully synthesized with high yield and purity.Then by introducing substituents of thiophene or bithiophene units onto the ?-position of silole,a series of new thiophene-containing benzo[b]disilole small molecules was synthesized.UV-vis results show that the benzo[b]disilole derivatives have a broad absorption in the range of 320-510 nm,and strong fluorescence intensity in solution.Besides,with the increase of conjugation length,the UV-vis spectrum was red-shifted.DFT theoretical calculation results show that with increasing the conjugation length,the HOMO energy level was increased and benzo[b]disilole possesses weak electron-accepting ability compared with the thiophene units.Secondly,substituents with different steric hindrance were introduced to benzo[b]disilole,including trimethyl(prop-1-yn-1-yl)silyl,triethyl(prop-1-yn-1-yl)-silyl and triisopropyl(prop-1-yn-1-yl)silyl groups.The influence of steric hindrance on the photo-physical properties was investigated,which lays the foundation of structure-properties relationships.Thirdly,two copolymers with benzo[b]disilole as the weak electron donor and DPP or BT as the strong electron acceptor were designed.At first,the synthetic methods were systematically investigated and target polymers were successfully synthesized through Suzuki coupling.Polymer 4-1 has poor solubility in common solvents and thus the characterizations couldn't be carried out.For Polymer 4-2,its molecular weight is 14.9 kDa.and its PDI is 1.9.It has good absorption in the range of 300~700 nm.Besides,TGA results indicate the polymers have good thermal stability,which are qualified for device fabrication.