Tunable\nFluorescence in Two-Component Hydrogen-Bonded\nOrganic Frameworks Based on Energy Transfer

Abstract

A dumbbell-shaped compound (TPAD)\nwith four 2,4-diaminotriazine\nmoieties as H-bond units and a benzene ring as a bridge group was\nfound to form hydrogen-bonded organic frameworks (HOFs) with strong\ncyan fluorescence. An energy acceptor, 6,6′,6″,6‴-(((benzo­[<i>c</i>]­[1,2,5]­thiadiazole-4,7-diylbis-(4,1-phenylene))­bis­(azanetriyl))­tetrakis­(benzene-4,1-diyl))­tetrakis­(1,3,5-triazine-2,4-diamine)\n(BTAD), with the same molecular skeleton as TPAD and a longer emission\nwavelength could homogeneously distribute within the framework of\nTPAD through occupying the locations of TPAD. As a result, two-component\nHOFs (TC-HOFs) were formed. The nonradiative energy transfer from\nTPAD as the donor to BTAD as the acceptor happens within frameworks\nowing to the efficient spectral overlap between the emission of TPAD\nand the absorption of BTAD. Moreover, the emission wavelengths and\ncolors of TC-HOFs could be easily and continuously modulated by the\ncontent of the acceptor. The fluorescence color changed from cyan\nto orange when the content of BTAD gradually increased. This finding\naffirms that TC-HOFs with continuously adjustable composition can\nbe constructed from two molecules with the same molecular skeleton,\nand highly efficient nonradiative energy transfer may happen in porous\nTC-HOFs. To the best of our knowledge, these TC-HOFs are the first\nexample of TC-HOFs involved in energy transfer.