The analysis of the photoabsorption spectra of molecules shows that the band maximum is usually redshifted in comparison to the vertical excitation. We conducted a throughout analysis of this shift based on low-dimensional analytical and numerical model systems, showing that its origin is rooted in the frequency change between the ground and the excited states in multidimensional systems. Moreover, we deliver a benchmark of ab initio results for the shift based on a comparison of vertical excitations and band maxima calculated with the nuclear ensemble approach for the 28 organic molecules in the Mülheim molecular dataset. The mean value of the shift calculated over 60 transitions is 0.11 ± 0.08 eV. The mean value of the band width is 0.32 ± 0.14 eV.

We implemented a version of the decoherence-corrected fewest switches surface hopping based on linear-response time-dependent density functional tight binding (TD-DFTB), enhanced by transition density analysis. The method has been tested for the gas-phase relaxation dynamics of two cycloparaphenylene molecules, [8]CPP and [10]CPP, explaining some important features of their nonadiabatic dynamics, such as the origin of their long fluorescence lifetimes (related to the slow radiative emission from the S state) and the trend of increasing the fluorescence rate with the molecular size (related to an increase in the S-S energy gaps and oscillator strengths in the larger molecule). The quality of the TD-DFTB electronic structure information was assessed through four quantities: excitation energies; charge-transfer (CT) numbers, which estimate the charge transfer character of states; participation ratio (PR), which describes delocalization of electronic density; and participation ratio of natural transition orbitals (PRNTO), which describes the multiconfigurational character of states. These quantities were computed during dynamics and recomputed for the same geometries with the higher-level long-range-corrected TD-LC-DFTB and a lower-level single-determinant approximation for the excited states, SD-(LC)-DFTB. Taking TD-LC-DFTB as the standard, TD-DFTB underestimates the excitation energies by ∼0.5 eV and overestimates CT and PR. SD-DFTB underestimates excitation energies and overestimates CT to the same extent that TD-DFTB does, but it predicts reasonable PR distributions. SD-LC-DFTB leads to an extreme overestimation of the excitation energies by ∼3 eV, overestimates the charge transfer character of the state, but predicts the PR values very close to those obtained with TD-LC-DFTB.

After UV excitation, gas phase thymine returns to a ground state in 5 to 7 ps, showing multiple time constants. There is no consensus on the assignment of these processes, with a dispute between models claiming that thymine is trapped either in the first (S 1 ) or in the second (S 2 ) excited states. In the present study, a nonadiabatic dynamics simulation of thymine is performed on the basis of ADC(2) surfaces, to understand the role of dynamic electron correlation on the deactivation pathways. The results show that trapping in S 2 is strongly reduced in comparison to previous simulations considering only non-dynamic electron correlation on CASSCF surfaces. The reason for the difference is traced back to the energetic cost for formation of a CO π bond in S 2 .

SLE and RA are associated with severe autonomic dysfunction and the presence of significant risk predictors related to the onset of sudden cardiac death.

Newton-X is an open-source computational platform to perform nonadiabatic molecular dynamics based on surface hopping and spectrum simulations using the nuclear ensemble approach. Both are among the most common methodologies in computational chemistry for photophysical and photochemical investigations. This paper describes the main features of these methods and how they are implemented in Newton-X. It emphasizes the newest developments, including zero-point-energy leakage correction, dynamics on complex-valued potential energy surfaces, dynamics induced by incoherent light, dynamics based on machine-learning potentials, exciton dynamics of multiple chromophores, and supervised and unsupervised machine learning techniques. Newton-X is interfaced with several third-party quantum-chemistry programs, spanning a broad spectrum of electronic structure methods.

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Organic fluorophores with an enhanced emission in the condensed phase have great potential for the design of optoelectronic materials. Several propeller-shaped molecules show aggregation-induced emission (AIE), in particular, silole derivatives have attracted wide attention because of their significant quantum yields in the solid state. In this contribution, we investigate the mechanism of AIE of a propeller-shaped blue emitter: 1,2,3,4-tetraphenyl-1,3-cyclopentadiene (TPC). We explore the excited state mechanism in the light of models most commonly used to explain it: restriction of intramolecular motions (RIM) and restricted access to the conical intersection (RACI). Our interpretation is supported by excited state dynamics simulations and the analysis of Huang-Rhys factors and reorganisation energies. We quantify the effects of intermolecular interactions and exciton couplings. The mechanism for TPC is compared with previous investigations of analogue silole compounds. Our systematic investigation highlights the role of conical intersections on the nonradiative decay mechanisms and complementary descriptions provided by the RIM and RACI models.[a] Dr.

Development of purely organic materials displaying room-temperature phosphorescence (RTP) will expand the toolbox of inorganic phosphors for imaging, sensing or display applications. While molecular solids were found to suppress non-radiative...