Mechanochemical preparation of donor/acceptor adducts based on coronene and silver(i) pyrazolate metallacycles

The preparation of materials having optical properties is a fertile area of research because of their application in OLEDs, sensors, and semiconducting materials science field. Moreover, considering environmental concerns, there is an increasing need in the scientific community to enhance the preparative methods using eco-friendly approaches. In this work, the mechanochemical liquid assisted grinding (LAG) method is applied for the syntheses of hybrid organometallic/organic materials made of pi-acidic silver(i) or copper(i) metallacycles, with bridging ligands such as 3,5-bis(trifluoromethyl)pyrazolate or 3,5-dinitro-pyrazolate, and coronene, a highly symmetric polycyclic aromatic molecule (PAH). The LAG method was monitored by FT-IR spectroscopy and SEM; the former was applied to study the slight structural modification upon interactions, and the latter was used to depict the changes in the solid surface morphology upon CH2Cl2-assisted grinding. On the other hand, the dissolution of the materials reversibly yields the starting compounds. The stacked materials were characterized by elemental and TGA analyses, and photoluminescence (PL), and IR spectroscopies. The PL study highlights the room temperature quenching of the coronene emissions at 505 nm, indicating the occurrence of dispersive electrostatic interactions. Interestingly, the solid-state UV-Vis study allowed the calculations of direct (2.27 eV) and indirect (2.78 eV) band gaps for the D/A adduct {[3,5-(CF3)2pz]Ag}3@coronene, 1, with values featuring the materials in the semiconductor band gap range, useful for application in OFETs or OPVs.