Porphyrin‐Ryleneimide Hybrids: Low‐Bandgap Acceptors in Energy‐Transfer Cassettes

Abstract

Energy‐transfer cassettes consisting of naphthaleneimide‐fused metalloporphyrin acceptors (M=Zn and Pd) and BODIPY donors have been designed and synthesized. These systems have rigid pseudo‐tetrahedral structures with a donor‐acceptor separation of ca. 17.5 Å. Spectroscopic investigations, including femtosecond transient absorption measurements, showed efficient excitation energy transfer (EET) occurring according to the Förster mechanism. Strong fluorescence of the donor units and significant spectral overlap of the donor and acceptor subunits are prerequisites for the efficient EET in these systems.

Porphyrin–Ryleneimide Hybrids: Tuning of Visible and Near-Infrared Absorption by Chromophore Desymmetrization

“…Upon photoexcitation, 2b -Zn and 3b -Zn showed singlet state lifetimes of 460 and 230 ps followed by infinite residues contributed by the intersystem crossing processes to the triplet state (Figures S9 and S10). Thus, the excited singlet states of 2b -Zn and 3b -Zn are quenched 4 to 6 times faster than observed for 1b -Zn, indicating a faster deactivation of the excited singlet state in the asymmetrical structures.…”

“…In particular, we envisaged that the optical band gaps, absorption profiles, and redox properties of such mixed D–A porphyrins might be affected not only by the ratio of D and A subunits but also by the symmetry of the chromophore. − Systems containing imide functionalities are highly attractive as components for multichromophoric systems obtainable by covalent or supramolecular assembly. For instance, donor BODIPY dyes attached radially to A 4 -type porphyrins via N-imide substituents yield efficient energy transfer according to the Förster mechanism . The presence of four functionalization sites in the A 4 systems is however unsuitable for construction of unbranched architectures, notably linear and cyclic chromophore arrays.…”

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

“…NMI porphyrins were also incorporated into energy-transfer cassettes containing peripheral BODIPY units. 576 The free base porphyrin cassette 308.5a was obtained by condensing the octaacid 308.2d with the amino-functionalized BODIPY 308.7 , and was converted into metal complexes 308.5b and 308.5c ( Scheme 308 ). The Br-functionalized NMI metalloporphyrins 308.4a and 308.4b were subjected to Suzuki coupling with the catecholate-protected BODIPY 308.8 to afford the larger analogues 308.6a and 308.6b .…”

Acenaphthylene-fused ullazines: fluorescent π-extended monopyrroles with tunable electronic gaps

“…Here we demonstrate the synthesis of π-extended dibenzoullazines bearing acenaphthylene subunits fused to the β-β edge of the pyrrole ring (Scheme 1). This work was inspired by the chemistry of naphthalimide-fused (NMI) pyrroles, 29 which have been used as donor-acceptor units in diverse oligopyrrole motifs, [29][30][31][32][33][34][35][36][37] and their electron-rich congeners. [38][39][40][41][42][43][44][45] We show that the properties of ullazine can be controlled by introducing acenaphthylene units with variable acceptor strength.…”