Tuning Photoinduced Energy‐ and Electron‐Transfer Events in Subphthalocyanine–Phthalocyanine Dyads

Abstract

A series of subphthalocyanine-phthalocyanine dyads has been prepared by means of palladium-catalyzed cross-coupling reactions between a monoalkynylphthalocyanine and different monoiodosubphthalocyanines. Electronic coupling between the two photoactive units is ensured by a rigid and pi-conjugated alkynyl spacer. In addition, the electronic characteristics of the subphthalocyanine moiety were modulated by the introduction of different peripheral substituents. Cyclic and Osteryoung square-wave voltammetry experiments revealed that the reduction potential of this subunit can be decreased by about 400 mV on going from thioether or no substituents to nitro groups. As a consequence, the energy level of the charge-transfer state could be fine-tuned so as to gain control over the fate of the photoexcitation energy in each subunit. The diverse steady-state and time-resolved photophysical techniques employed demonstrated that, when the charge-transfer state lies high in energy, a quantitative singlet-singlet energy-transfer mechanism from the excited subphthalocyanine to the phthalocyanine takes place. On the contrary, stabilization of the radical pair by lowering the redox gap between electron donor and acceptor results in a highly efficient photoinduced electron-transfer process, even in solvents of low polarity such as toluene (Phi(ET) approximately 0.9). These features, together with the extraordinary absorptive cross section that these molecular ensembles display across the whole UV/Vis spectrum, make them model candidates for application in situations where broadband light sources are needed.

Non‐Centrosymmetric Homochiral Supramolecular Polymers of Tetrahedral Subphthalocyanine Molecules

“…[10] They are composed of three isoindole units condensed around a boron atom which also bears an axial ligand perpendicular to the macrocyclic core. [11] However, because of their intense absorption and emission in the visible region of the electromagnetic spectrum and their tunable electronic properties, [12] SubPcs have recently attracted significant technological interest in the fields of organic semiconductors and optoelectronics. This property, which stems from their nonplanar geometry, has proven beneficial for many applications in which dye aggregation needs to be prevented.…”

Synthesis, Photophysical Characterization, and Surface Photovoltage Spectra of Windmill‐Shaped Phthalocyanine–Porphyrin Heterodimers and Heteropentamers

“…The chemicals were purchased from Sigma-Aldrich and used without further purification. 3-Iodophthalonitrile, [11] 4-ethynylbenzaldehyde and SubPc [25] were synthesized as published. All solvents were dried by the standard methods prior to use.…”

Synthetic approaches to asymmetric phthalocyanines and their analogues

“…218,220,221,223,227,228,[236][237][238][239][240][241][242] This precursor can be used for the introduction of direct carboncarbon bonds as aryl, alkenyl, and alkynyl substituents. 217,219,220,226,234,235 In addition, the Buchwald reaction can be used for carbon-nitrogen bond formation. 218,220,223 Palladium-catalyzed coupling of the mono-iodo A 3 B phthalocyanine 62 with trimethylsilylacetylene forms an ethynyl-containing phthalocyanine, which can be deprotected under basic conditions to give the phthalocyanine 73 (Scheme 25) containing a highly reactive terminal C-H bond.…”