title: Synthesis and photophysics of silicon phthalocyanine-perylenebisimide triads connected through rigid and flexible bridges.
abstract: Three new bisperylenebisimide-silicon phthalocyanine triads [(PBI)(2)-SiPcs 1, 2, and 3] connected with either rigid or flexible bridges were synthesized and characterized. A new synthetic approach to connect SiPc and PBI moieties through click chemistry produced triad 3 with an 80% yield. In (PBI)(2)-SiPc 1, PBI and SiPc are orthogonal and were connected with a rigid connector; triads 2 and 3 bear flexible aliphatic bridges, resulting in a tilted (2) or nearly parallel arrangement (3) of PBI and SiPc. Photoinduced intramolecular processes in these (PBI)(2)-SiPcs were studied and the results are compared with those of the reference compounds SiPc-ref and PBI-ref. The occurrence of electron-transfer processes between the SiPc and PBI units was confirmed by time-resolved emission and transient absorption techniques. Charge-separated (CS) states with lifetimes of 0.91, 1.3 and 2.0 ns for triads 1, 2, and 3, respectively, were detected using femtosecond laser flash photolysis. Upon the addition of Mg(ClO(4))(2), an increase in the lifetime of the CS states to 59, 110 and 200 μs was observed for triads (PBI)(2)-SiPcs 1, 2, and 3, respectively. The energy of the CS state (SiPc(·+)-PDI(·-)/Mg(2+)) is lower than the energy of both silicon phthalocyanine ((3)SiPc*-PDI) and perylenebisimide (SiPc-(3)PDI*) triplet excited states, which decelerates the metal ion-decoupled electron-transfer process for charge recombination to the ground state, thus increasing the lifetime of the CS state. The photophysics of the three triads demonstrate the importance of the rigidity of the spacer and the orientation between donor and acceptor units.
authors.affiliation: División de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Elche 03202, Spain.
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Céspedes-Guirao
authors.forename: Luis
authors.initials: L
authors.lastname: Martín-Gomis
authors.forename: Kei
authors.initials: K
authors.lastname: Ohkubo
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
authors.forename: Fernando
authors.initials: F
authors.lastname: Fernández-Lázaro
authors.forename: Angela
authors.initials: A
authors.lastname: Sastre-Santos
mesh_terms: D057930:Click Chemistry; D007094:Imides / Q000138:chemical synthesis* / Q000737:chemistry; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D017646:Organosilicon Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010569:Perylene / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D055668:Photochemical Processes
chemical_list: D007094:Imides; D007211:Indoles; D017646:Organosilicon Compounds; C510697:perylene bisimide; C082854:silicon phthalocyanine; D010569:Perylene