Intermolecular Charge Transfer in H- and J-Aggregates of Donor–Acceptor–Donor Chromophores: The Curious Case of Bithiophene-DPP

Abstract

A vibronic exciton model is developed to describe low-energy electronic excitations in slip-stack aggregates of donor−acceptor−donor (DAD) chromophores with substantial overlap between the neighboring donor and acceptor fragments. In such stacks, J-and H-aggregate behavior is driven by intermolecular charge transfer (ICT) and not Coulomb coupling as is assumed in the Kasha model. In-phase (out-of-phase) intermolecular charge transfer integrals result in J-aggregate (H-aggregate) behavior, as unambiguously determined by the vibronic spectral signatures. Interestingly, both J-and H-aggregates are red-shifted, in contrast to the predictions of the Kasha model. Simulated spectral line shapes agree well with recent experiments on two derivatives of the bithiophene diketopyrrolopyrrole chromophore, 2T-DPP-2T, with different terminal groups.

Role of MCD and Mössbauer Spectroscopy in the Explanation of the Properties of a Highly Soluble (μ-Oxo)bis[tetra(tert-butyl)(phthalocyaninato)iron(III)] Complex, Its Pyridine Adduct, and Redox Forms Oxidized under Anaerobic Conditions in Non-Coordinating Solvents

“…If J C + J CT > 0, then an H-type behavior will be observed for the dimer, while if J C + J CT < 0, J-type behavior is expected. Taking into consideration that signs of J CT and J C are independent from each other, one might expect that each dimer could fall under HH, HJ, JH, and JJ categories (with the first letter identifying J CT and the second letter identifying J C contributions). − Indeed, the red-shifted H-aggregates have been observed and explained using this model.…”

“…An alternative explanation for the red-shifted Q-band in 1a is the presence of additional transition(s) with lower than Q-band energies that cause the charge-transfer-induced perturbation of H-aggregate energies. The charge-transfer-induced H-aggregate behavior in perturbative and resonance regimes was described in detail by Spano’s group. − Following Spano and co-workers, the energy shift of the allowed transition in J- and H-aggregates is reflective of the competition between the traditional Coulombic and CT-mediated intermolecular interactions that are simply quantified by J C and J CT , respectively ( J C is the Coulomb coupling and J CT is the coupling caused by the CT). If J C + J CT > 0, then an H-type behavior will be observed for the dimer, while if J C + J CT < 0, J-type behavior is expected.…”

Absorption and Photoluminescence in π-Stacks of Donor–Acceptor–Donor Chromophores: Effective Frenkel–Holstein Hamiltonian Approach

“…The multiparticle basis set containing up to 3-particle states is used to represent the FFCTH Hamiltonian. ,, Figure a shows two examples of one-particle states within a DAD monomer, where one fragment is electronically excited with any number of vibrational quanta in the shifted PES, while all other fragments are in their electronic ground states with no vibrational quanta in their unshifted PES. Figure b represents an example of a two-particle state, where two donor fragments are excited: one hosts a vibronic excitation on the first donor fragment, while the second hosts a pure vibrational excitation in the ground state of the second donor fragment.…”

Growth of Merocyanine Dye J‐Aggregate Nanosheets by Living Supramolecular Polymerization

“…The combined experimental data from AFM, WAXS and (polarized) UV‐vis measurements (Figure S9) allow us to propose a bilayer, membrane‐like packing model for Agg2 (Figure 4), where the hydrophilic OEG chains of amphiphile MC1 are oriented towards the outside of the nanosheet and the hydrophobic alkyl chains are concealed in the center of the sheet. In this model derived by BIOVIA Materials Studio 2017R2 , the MC chromophores are arranged in a slip‐stacked manner enabling both J‐type Coulomb and J‐type charge transfer couplings, where the latter originates from the close contacts of donor and acceptor heterocycles on top of each other (see Supporting Information for further information) [15,16] . As shown in Figure 4, the packing structure for each merocyanine layer leads to a huge macrodipole that is, however, compensated by the second layer in the bilayer nanosheet.…”