Excimers in Multichromophoric Assemblies: Boon or Bane?

Abstract

Exciton dynamics in organic semiconductors is a subject of great significance from the standpoint of light emission, as well as light harvesting. As transient excited state species, excimers are expected to play a significant role in the dynamics and the fate of the excited state. Till recently, the discourse on excimers in organic systems revolved around their role in aggregation induced fluorescence quenching, or utilizing their characteristic red-shifted emission to report local interactions. But in the last decade, research in the area of organic multichromophoric systems has brought the spotlight back on this fascinating species. This review focuses on recent developments that highlight the importance of excimers in various processes involving multichromophoric systems, such as circularly polarized emission, exciton migration and singlet fission (SF). The review also attempts to address the question of whether excimers are useful or detrimental to various photophysical and photochemical processes of importance.

Bridged o-carborane–anthracene dyads as dual state emission luminogens: synthesis, characterization, and mechanochromic properties

“…Apart from being an additional example of the carborane excimer luminogens, compound 2 also belongs to the rare examples with excimer emission of supramolecular oligomers supported by weak interactions. 50…”

Excitonic Configuration Interaction: Going Beyond the Frenkel Exciton Model

“…In particular, the 1 nπ * 1 excitation makes the O atom a worse hydrogen bond acceptor, so the excitation energy of 1 nπ * 1 states should rise in the hydrogen-bonded full system. Indeed, ECIS+FDA captures this effect through the diagonal cross-fragment interaction terms in Equation (8). The FEM neglects those interaction terms and thus misses the change in hydrogen bond strength.…”

“…Of particular relevance are multichromophoric systems-systems having low-lying excited states localized on different moieties (typically called chromophores, fragments, or sites, which we use interchangeably in this article). Such systems are ubiquitously found in nature (e.g., light-harvesting complexes in chloroplasts 4,5 or DNA 6 ) and have also gained significant attention in the field of material design (e.g., photovoltaics 7 or organic semiconductors 8 ). Hence, the understanding of their photophysical and photochemical properties is one of the highest priorities in modern spectroscopy.…”

Excitonic Configuration Interaction: Going Beyond the Frenkel Exciton Model

“…The matrix elements of the full-system Hamiltonian in the FEM are given by the GFT expressions ( 8) to (10), but with the J and K terms in expressions ( 8) and ( 9) neglected. In other words, the diagonal matrix elements in the FEM are just the sums of site energies, and the diagonal cross-fragment interaction contribution is neglected.…”