Investigation of excited states properties of donor-acceptor ruthenium(II)-perylene diimide dyads

Abstract

The design of organic-inorganic hybrid systems with near-infrared absorption and emission properties is attracting a great interest due to the variety of applications, including catalysis, medicine and luminescent sensing. An issue in planning organic-inorganic hybrid systems is the design of bridges to connect the different moieties and potentiate synergistic action. Following this strategy we have prepared a Ruthenium(II)-perylene diimide dyad, namely [Ru(phen)2(pPDIp)]2+, when pPDIp is a perylene functionalized at the imide positions with coordinating 1,10-phenanthroline (phen). This dyad has shown improved electronic coupling between the perylene and the Ru(II)-polypyridine moieties that triggers the population of the triplet excited state of the perylene group that decays with a lifetime of 1.8 µs. With the intent of designing new systems with improved optics properties we prepared the dyads [Ru(phen)2(PDI-Py)]2+ and [Ru(dmphen)2(PDI-Py)]2+, where dmphen is 5,6-Dimethyl-1,10-phenanthroline, and PDI-Py is a perylene functionalized at the 1,7 bay positions with pyrrolidine and at the imide positions with coordinating 1,10-phenanthroline. Both new dyads have excitation with light e 700 nm. The relevance of these results has intensified our interest in the dynamics of excited states of these dyads. A deeper insight into the mechanism of the excited-state processes allows to understand the photophysical processes. For example, it is expected that photoinduced charge separation (D+-A-) occurs rapidly and quantitatively and, at the same time, charge recombination is somehow impeded. We will also intent to investigate the photophysical properties of these dyads in polymeric films to be applied as an efficient and environmentally stable source of singlet oxygen (1O2). These studies are essential for practical applications of the proposed dyads i.e. wastewater treatment and photodynamic cancer therapy. In order to carry out these studies we are applying for the FAPESP-(BEPE-DR) program for a period of twelve months beginning in April 2021, at University of Bologna in Italy under Professor Paola Ceroni supervision. The laboratory of Professor Paola Ceroni is fully equipped for time-resolved photophysical measurements in the order of ps and fs time-scale, that allows the investigation not only of multicomponent systems in solution, but also to study their organization on solid supports and at the single-molecule level. (AU)