Spectroscopy and Dynamics of a HOF and its Molecular Units: Remarkable Vapors Acid Sensing
Hexaazatriphenylene (HAT) derivatives are being used for the fabrication of hydrogen-bonded organic frameworks (HOFs). Here, we report on studies of two HAT derivatives: CBPHAT and its butylated partner, CBPHAT-C4H9, in N-N-dimethylformamide (DMF) solutions, and in solid state. CBPHAT displays no planar conformations, and different species when interacting with DMF. CBPHAT-C4H9 undergoes an intramolecular charge transfer (ICT) reaction in 50 ps, while in CBPHAT it is faster (~ 4.5 ps). Their emission lifetimes in DMF solution change from 50 ps to 2.3 ns. The slower relaxation of CBPHAT-C4H9 without oxygen quenching involves three long living states (~ 2, ~ 18 and ~ 100 µs). The CBPHAT-1a HOF (crystals) exhibit a proton and charge transfer reactions (60 ps), leading to different emitter of fluorescence lifetimes spanning from 100 ps to 2.66 ns. This HOF shows a remarkably strong responsive to HCl vapors in a reversible way at ambient conditions. This ability is reflected in its absorption and emission spectra, making it a new smart sensor of acid gas, and possibly in molecular memories vapor systems. The provided theoretical and experimental results will trigger more research in this family and related HOFs to further advance in its science.