We studied the chemical-physics and the nature of the interactions involved in the formation of adducts of two-dimensional black phosphorus (2D BP) with organoboron derivatives of a conjugated fluorescent molecule (pyrene). Time-resolved fluorescence spectroscopy showed a stabilization effect of 2D BP on all the organoboron derivatives, in particular for the adducts endowed with the boronic functionalities. Also, a stronger modulation of the fluorescence decay with oxygen was registered for one of the adducts compared to the corresponding organoboron derivative alone. NMR experiments in suspension and DFT simulations confirmed that only non-covalent interactions are involved in the formation of the adducts. The energetic gain in their formation arises from the interaction of P atoms with both C atoms of the pyrene core and with B atom of the boronic functionalities, with a stronger contribution from the ester with respect to the acid one. The interaction results in a lowering of the band gap of 2D BP by around 0.10 eV. Furthermore, we demonstrated through Raman spectroscopy an increased stability towards oxidation in air of 2D BP in the adducts in the solid state (more than six months). The modification of the electronic structure at the interface between 2D BP and a conjugated organic molecule through non-covalent stabilizing interactions mediated by the B atom is particularly appealing in view of creating heterojunctions for optoelectronic, photonic and chemical sensing applications.

In this work, we demonstrate the use of two-dimensional electronic spectroscopy (2DES) to study the mechanism and time scale of the femtosecond Stokes shift dynamics in molecules characterized by intramolecular charge transfer, such as distyryl-functionalized boron dipyrromethene (BODIPY) molecules. The obtained results demonstrate that 2DES allows clear and direct visualization of the phenomenon. The analysis of the 2D data in terms of 2D frequency–frequency decay associated maps provides indeed not only the time scale of the relaxation process but also the starting and the final point of the energy flow and the associated reorganization energy, identified by looking at the coordinates of a negative signature below the diagonal. The sensitivity of the 2DES technique to vibrational coherence dynamics also allowed the identification of a possible relaxation mechanism involving specific interaction between a vibrational mode of the dye and the solvent.

Vibronic spectra of two BODIPY derivatives were computed using both Time-Independent (TI) and Time-Dependent (TD) formalisms including solvent and temperature effects with several DFT functionals.