Engaging Copper(III) Corrole as an Electron Acceptor: Photoinduced Charge Separation in Zinc Porphyrin–Copper Corrole Donor–Acceptor Conjugates

Abstract

An electron-deficient copper(III) corrole was utilized for the construction of donor-acceptor conjugates with zinc(II) porphyrin (ZnP) as a singlet excited state electron donor, and the occurrence of photoinduced charge separation was demonstrated by using transient pump-probe spectroscopic techniques. In these conjugates, the number of copper corrole units was varied from 1 to 2 or 4 units while maintaining a single ZnP entity to observe the effect of corrole multiplicity in facilitating the charge-separation process. The conjugates and control compounds were electrochemically and spectroelectrochemically characterized. Computational studies revealed ground state geometries of the compounds and the electron-deficient nature of the copper(III) corrole. An energy level diagram was established to predict the photochemical events by using optical, emission, electrochemical, and computational data. The occurrence of charge separation from singlet excited zinc porphyrin and charge recombination to yield directly the ground state species were evident from the diagram. Femtosecond transient absorption spectroscopy studies provided spectral evidence of charge separation in the form of the zinc porphyrin radical cation and copper(II) corrole species as products. Rates of charge separation in the conjugates were found to be of the order of 10(10) s(-1) and increased with increasing multiplicity of copper(III) corrole entities. The present study demonstrates the importance of copper(III) corrole as an electron acceptor in building model photosynthetic systems.

Porphyrinoid rotaxanes: building a mechanical picket fence

“…Here we demonstrate the utility of the AT-CuAAC reaction in the synthesis of mechanically interlocked analogues of previously studied triazole-linked porphyrin–corrole conjugates, 21 and that, because the covalent structure of the chromophores is not altered, photo-induced electron transfer between the tetrapyrrole chromophores is unaffected by mechanical bond formation. 22 Conversely, the threaded macrocycles significantly modify the steric properties of the system, creating a “mechanical picket fence” motif that suppresses aggregation and ligand driven self-assembly.…”

Azides and Porphyrinoids: Synthetic Approaches and Applications. Part 1—Azides, Porphyrins and Corroles

“…Among the different strategies used in the functionalization/post-functionalization of easily available corroles to obtain target molecules, the CuAAC approach is being successfully used. New corrole derivatives linked to other corroles [124], to porphyrins [125,126] and to BODIPYs [127] were successfully obtained, as recently reviewed by some of us [123]. In this section, only a few publications are being considered to illustrate the impact of the CuAAC approach in the functionalization of corroles.…”

Synthesis and spectroscopic properties of β-meso directly linked porphyrin–corrole hybrid compounds

“…The first studies on the synthesis of multichromophores were based on obtaining multiporphyrin arrays [ 7 – 9 ] that could stabilize only metal ions in a bivalent state. To overcome this limitation, porphyrin conjugates with different chromophore groups such as fullerene [ 10 – 12 ], BODIPY [ 13 – 15 ], corrole [ 16 – 23 ], phthalocyanine [ 24 – 26 ], subporphyrin [ 27 ] and expanded porphyrins [ 28 – 30 ] were prepared and their photophysical and electrochemical properties were characterized. Among these compounds, corroles, contracted porphyrin analogues [ 31 – 33 ], assumed an important place in porphyrin chemistry due to their small cavities, trianionic characters, high fluorescence quantum yields and favorable electronic properties.…”

“…Porphyrin–corrole conjugates have been successfully used as donor–acceptor systems in photoinduced charge separation processes. It was shown that derivatives of these conjugates could be potentially used in photovoltaic applications [ 21 – 23 ]. In order to achieve rapid energy and electron transfer between macrocycles, the short distance between subunits keeps an important place.…”

“…Therefore, two important factors affect the physical and electronic properties of porphyrin–corrole conjugates: (i) type of linkers and (ii) position of substitution ( meso or β). So far, corrole macrocyles have been integrated into porphyrin conjugates via anthracene, biphenylene, xanthene, dibenzofuran [ 16 – 20 ], amide [ 21 ] and triazole [ 22 – 23 ] linkers. Despite the large number of studies on the synthesis of porphyrin–corrole conjugates, systematic studies on directly linked porphyrin–corrole hybrid structures are limited and there is no report on β-porphyrin, meso -corrole linked hybrids of these conjugates.…”