Ladder Conjugated Photo-Electric Functional Materials Building By Tetraamino Fluorene

Conjugated polymers,as typical organic semiconductors,play very important roles in the fields of OLED,solar cells,OFET,and organic solid lasers.Among the vast conjugated polymer classes,most are linear,single strand polymers,but ladder-type conjugated polymers only take a very small portion.The rigid and planar frameworks of ladder conjugated polymers facilitate electron delocalization and enhance conductivity,compared with linear polymers.Another advantage of ladder polymers is the high resistance to mechanical,thermal, and chemical degradation.In present work,a novel teraamino structure——2,3,6,7-tetraamino-9,9-bis(2-ethylhexyl) fluorene(TABEF)as the multifuntional monomer for ladder conjugated polymers/molecules has been designed.TABEF is successfully synthesized via a six-step method(actually 8 synthetic reactions,because both step 3 and 6 contain two continuous reaction operations). After optimizing the reaction condition and operation,this six-step synthetic method from fluorene to TABEF·4HCl is efficient with a total yield of 30%.Two series of new model ladder compounds are designed with TABEF as the building block.A pair of ladder isomers BPTF-1 and BPTF-2 have been synthesized,which connet two naphthalene diimide structures through fluorine.Fluorescence quenching experiment and the electrochemical properties suggest that these two isomers are electron affinity and have strong electron accepting ability(low LUMO),compared with NDI-C8.Preliminary tests show that BPTF-1 and BPTF-2 will be promising N-type materials for polymer solar cells.Two novel ladder molecules DF-1 and DF-2,containing quinoxaline structure have also been designed.DF-1 and DF-2 exhibit intriguing optical properties because of their ladder structure and intramolecular D-A system.They have show strong solid/solution fluorescence, high quantum yield(as high as 0.5),perfect mirror symmetry in optical spectrum,narrow spectra band,and blue fluorescence in solution,which makes DF-1 and DF-2 promising candidates for novel blue light emitting materials.