Charge Transfer and Exciplex Emissions from a Naphthalenediimide-Entangled Coordination Framework Accommodating Various Aromatic Guests

A detailed photophysical study was performed on an entangled porous coordination polymer (PCP) containing N, N ′-dipyrid-4-yl-1,4,5,8-naphthalenediimide (dpNDI) as an electron acceptor moiety and different substituted benzene guests as electron donor units by time-resolved fluorescence spectroscopy. Emission from exciplex (A–D)* EX and charge transfer complex (A δ− –D δ+ )* CT states was identified thanks to the different conformations adopted by aromatic guests in the different adsorption sites of the PCP (denominated pore A and pore B). Fluorescence lifetime values of exciplexes and charge transfer complexes linearly correlate with the dipole moments and the ionization potentials of different substituted benzene guests, respectively. We have also identified other emissive species with much lower emission efficiency, that is, emission from the NDI pillar itself and from its interaction with the benzenedicarboxylate linker.