Covalent organic frameworks (COFs) are commonly synthetized under harsh conditions yielding unprocessable powders. Control in their crystallization process and growth has been limited to studies conducted in hazardous organic solvents. Herein, we report a one-pot synthetic method that yields stable aqueous colloidal solutions of sub-20 nm crystalline imine-based COF particles at room temperature and ambient pressure. Additionally, through the combination of experimental and computational studies, we investigated the mechanisms and forces underlying the formation of such imine-based COF colloids in water. Further, we show that our method can be used to process the colloidal solution into 2D and 3D COF shapes, as well as to generate a COF ink that can be directly printed onto surfaces. These findings should open new vistas in COF chemistry enabling new application areas.

Novel pi-conjugated donor-acceptor chromophores, based on the strong electron-donating tetrathiafulvalene moiety and different electron-withdrawing acceptors, exhibit large second-order optical nonlinearities. The effect of increasing the length of the polyenic spacer and the influence of the nature of the acceptor moiety on the NLO properties have been studied by using the electric field-induced second-harmonic generation (EFISH) technique as well as by semiempirical and ab initio theoretical calculations. A charge-transfer band has been observed in the absorption spectra of these D-pi-A compounds that undergoes an hypsochromic shift when increasing the number of vinylenic spacer units connecting both donor and acceptor moieties. The degree of the intramolecular charge transfer from the donor to the acceptor has also been analyzed by means of Raman spectroscopy.

We have synthesised new conjugated donor-π-acceptor (D-π-A) chromophores 7, 9, and 12−15 in which monosubstituted tetrathiafulvalene (TTF) and trimethyl-TTF units are the donor moieties, connected by ethylenic bridges to electrondeficient benzene derivatives as the acceptor moieties. These compounds display a broad intramolecular charge transfer (ICT) band in their solution UV/Vis spectra at λ max = ca.

No abstract

No abstract