Bithiophenesilane Dendrimers: Synthesis and Thermal and Optical Properties

For the first time the synthesis and thermal and optical properties of a number of first-generation bithiophenesilane dendrimers with alkyl end groups, namely, tris{5‘-[methylbis(5‘-hexyl-2,2‘-bithienyl-5-yl)silyl]-2,2‘-bithienyl-5-yl}methylsilane (1), tris{5‘-[methylbis(5-hexyl-2-thienyl)silyl]-2,2‘-bithienyl-5-yl}methylsilane (2), and tris{5‘-[methylbis(5-ethyl-2-thienyl)silyl]-2,2‘-bithienyl-5-yl}methylsilane (3), are described. The influence of the dendritic architecture on the thermal and optical properties was investigated and compared to those of the linear and branched bithiophenesilanes. The results obtained showed a significant increase of the fluorescence quantum yield Q with an increasing number of bithiophenesilane fragments being a constituent part of the dendritic molecule. It reaches 30% for dendrimer 1 with nine such fragments as compared to Q = 6% for 5,5‘-bis(trimethylsilyl)-2,2‘-bithiophene and Q = 1.8% for 5-hexyl-2,2‘-bithiophene. This effect was explained by the impact of the specif...