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Complexes consisting of earth-abundant main group metals such as silicon with polypyridine ligands are of interest for a variety of optical and electronic applications including as electrochromic colorants. Previous spectroelectrochemical studies with tris(2,2′-bipyridyl)silicon(IV) hexafluorophosphate, [Si(bpy)3](PF6)4, demonstrated an ability to control the color saturation of the potential electrochromic dye, with the intensity of the dye’s green color increasing as the charge state sequentially reduces from 4+ to 1+. In this study, the synthesis of bis(4′-(4-tolyl)-2,2′:6′,2″-terpyridine)silicon(IV) hexafluorophosphate, [Si(ttpy)2](PF6)4, is reported along with electrochemical and spectroelectrochemical analyses. Computational modeling (density functional theory) is used to further elucidate the electrochromic properties of previously reported Si(bpy)3n+ species and the new Si(ttpy)2n+ species. While the homoleptic tris(bidentate)silicon(IV) complexes are attractive as electrochromic dyes for tunable color saturation, the bis(tridentate)silicon(IV) complexes are attractive as polychromatic electrochromic dyes.

 

Hexacoordinate silicon pincer complexes using 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy) ligands have been developed as a multifunctional, molecular electronic materials platform. We report the synthesis, characterization, and device application of a variety of Si(pincer) 2 complexes that exhibit tunable optoelectronic properties and excellent thermal stabilities. Promising, ambipolar charge carrier properties and excimeric electroluminescence were obtained from thermally deposited films using several device architectures. Incorporation of the complexes as a thin, interfacial contact and electron transport layer improved organic solar cell efficiencies by as much as 50%. The versatility and tailorability of this class of silicon complexes provides promising evidence for their future application in molecular electronic devices. 

A neutral hexacoordinate silicon complex containing two 2,6-bis(benzimidazol-2′-yl)pyridine (bzimpy) ligands has been synthesized and explored as a potential electron transport layer and electroluminescent layer in organic electronic devices. The air and water stable complex is fluorescent in solution with a λ max = 510 nm and a QY = 57%. Thin films grown via thermal evaporation also fluoresce and possess an average electron mobility of 6.3 × 10 −5 cm 2 V −1 s −1 . An ITO/Si(bzimpy) 2 /Al device exhibits electroluminescence with λ max = 560 nm.