ChemInform Abstract: Calculations of Excited‐State Conformational Properties

Abstract

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Molecular Driving Forces for Z/E Isomerization Mediated by Heteroatoms: The Example Hemithioindigo

“…They constitute points of degeneracy between two (or more) PES and facilitate a rapid radiationless decay to the lower lying state. With the ongoing development of computational methods, the search in the degeneracy space, called the intersection space (IS), for energetically low lying crossings has become possible. ,− Studies by Bernardi, Garavelli, Olivucci, and Robb revealed that a number of minimum energy CoIn are characterized by common two-, three-, and four-center patterns. ,, The fundamental work of Michl and Bonačić-Koutecký shed light on the electronic structure of the IS , between GS and ES in linear conjugated systems. The torsional deformation about a double bond leads to the degeneracy of the π and π* orbitals and to the formation of an S 1 /S 0 avoided crossing (Figure a).…”

Signature of Nonadiabatic Coupling in Excited-State Vibrational Modes

“…The photoinduced electronic and vibrational energy redistribution and relaxation in extended conjugated molecules plays an important role in chemical physics, biology, and materials science . Following photoexcitation, nonradiative transitions involving internal conversion, and intersystem crossing can occur. , The photoinduced dynamics of extended conjugated molecules is often characterized by large nonadiabatic (NA) couplings between excited states. , Therefore, it is crucial to discover the state-specific nuclear motions that promote energy funneling to the lowest excited state thus reinforcing the celebrated Kasha’s rule, which is driven by NA couplings. Understanding the fundamental relationship between vibrational motions and the efficiency of NA nonradiative relaxation offers new routes toward materials-by-design approach for various applications and technologies.…”

From Ordinary to Blue Emission in Peralkylated n-Oligosilanes: The Calculated Structure of Delocalized and Localized Singlet Excitons

“…Concrete structures for the geometrical distortions that occur upon relaxation of the excited singlet state into a localized self-trapped exciton are of particular interest, and relate to previous proposals for the assignment of the nature of the blue emission. 1,5,22,51,52 For each chain length of seven or fewer silicon atoms, we find multiple S 1 minima that can be described as self-trapped exciton minima and are probably collectively responsible for the observed blue emission. As expected, the degree of excitation localization increases as the chain is shortened, and the geometrical differences relative to the ground state become more pronounced.…”

“…However, the calculations provide information that goes well beyond the classical model in that they predict the specific nature of the exciton–phonon coupling. Concrete structures for the geometrical distortions that occur upon relaxation of the excited singlet state into a localized self-trapped exciton are of particular interest, and relate to previous proposals for the assignment of the nature of the blue emission. ,,,, …”