Accurate Prediction of the Excited States in the Fully Conjugated Porphyrin Tapes across the Full Spectral Range: A Story of the Interplay between π–π* and Intramolecular Charge-Transfer Transitions in Soft Chromophores

Abstract

The ability of density functional theory (DFT) and time-dependent DFT (TDDFT) methods for the accurate prediction of the energies and oscillator strengths of the excited states in a series of fully conjugated meso–meso β–β β–β triple-linked porphyrin oligomers (porphyrin tapes 2–12) was probed in the gas phase and solution using several exchange-correlation functionals. It was demonstrated that the use of the hybrid B3LYP functional provides a good compromise for the accurate prediction of the localized π–π* and intramolecular charge-transfer transitions, thus allowing confident interpretation of the UV–vis–NIR spectra of porphyrin oligomers. The TDDFT-based sum-over-state (SOS) calculations for the porphyrin tape dimer 2 and trimer 3 as well as parent monomer 1 correctly predicted the signs and shapes of the magnetic circular dichroism (MCD) signals in the low-energy region of the spectra.

Global Aromaticity in Neutral Porphyrin Nanobelts

“…At small r12, OX-B3LYP (EE0 = 19%) is virtually identical to B3LYP (EE = 19%), which is a suitable DFA for modelling the optical properties of edge-fused porphyrin nanoribbons (Figure 1a). [30] In the long-range limit, OX-B3LYP recovers the correct form of the Columbic decay (EE∞ = 100%).…”

Global Aromaticity in Neutral Porphyrin Nanobelts

“…At small r12, OX-B3LYP (EE0 = 19%) is virtually identical to B3LYP (EE = 19%), which is a suitable DFA for modelling the optical properties of edge-fused porphyrin nanoribbons l-PN (Figure 1a; see SI Section B). [31] In the long-range limit, OX-B3LYP recovers the correct form of the Columbic decay (EE∞ = 100%).…”

Metal Complexes of Singly, Doubly and Triply Linked Porphyrins and Corroles: An Insight into the Physicochemical Properties

“…Directly linked ( meso ‐ meso / meso ‐β/β‐β) porphyrin dimers usually exhibit splitting of the Soret bands due to the large excitonic coupling among the individual porphyrin units, while spectral changes pertaining to Q‐band display slightly broadened features (Figure 5). [35a,49] The origin of the splitting of Soret bands in case of meso ‐ meso linked porphyrin can be ascribed to the coulombic interactions between the transition dipole moment indicating disruption of the electron delocalization across the π‐conjugated system which can be qualitatively accounted for by the orthogonal conformation of the neighboring porphyrins. Fused porphyrin dimers on the other hand display significantly altered absorption profile as compared to the directly linked and monomeric counterparts.…”