The absorption of one photon by a semiconductor material usually creates electron–hole pair. However, this general rule breaks down in few organic semiconductors, such as pentacene and tetracene, where may result two pairs. This process, singlet exciton transforms to triplet excitons, can have quantum yields high 200%. Singlet fission be useful solar cell technologies increase the power conversion efficiency beyond so-called Shockley-Queisser limit. Through time-resolved two-photon...

Real‐time time‐dependent functional theory (RT‐TDDFT) directly propagates the electron density in time domain by integrating Kohn–Sham equations. This is contrast to popular linear response TDDFT matrix formulation that computes transition frequencies from a ground state reference. RT‐TDDFT is, therefore, potentially powerful technique for modeling atto‐ picosecond dynamics, including charge transfer pathways, specific applied field, and frequency dependent nonlinear properties. However,...

ConspectusMolecular mechanical force fields have been successfully used to model condensed-phase and biological systems for a half century. By means of careful parametrization, such classical can be provide useful interpretations experimental findings predictions certain properties. Yet, there is need further improve computational accuracy the quantitative prediction biomolecular interactions properties that depend on wave functions not just energy terms. A new strategy called explicit...

Multistate density functional theory (MSDFT) is presented to estimate the effective transfer integral associated with electron and hole reactions. In this approach, charge-localized diabatic states are defined by block localization of Kohn–Sham orbitals, which constrain for each state in orbital space. This differs from procedure used constrained that partitions within specific spatial regions. For a series model systems, computed integrals consistent experimental data show expected...

For reliable condensed phase simulations, an accurate model that includes both short- and long-range interactions is required. Short- can be particularly strong in aqueous solution, where hydrogen-bonding may play a large role at short range polarization long range. Although short-range solute–solvent such as charge transfer, hydrogen bonding, taken into account with quantum mechanical (QM) treatment of the solvent, it unclear how much QM solvent necessary to accurately different solutes. In...

Time-dependent density functional theory (TDDFT) calculations are employed to examine the optical absorption and circular dichroism (CD) spectra of undecagold Au(11)L(4)X(2)(+) (X = Cl, Br) complexes their Au(2)X(2)L precursors, where L is either 2,2'-bis(diphenylphosphino)-1,1'-binaphtyl (BINAP) or 1,4-diphosphino-1,3-butadiene (dpb). These systems exhibit intense mirror-image Cotton effects in CD spectra. Experimental peak positions well reproduced calculations. The low energy peaks arise...

In recent years, the development and application of real-time time-dependent density functional theory (RT-TDDFT) has gained momentum as a computationally efficient method for modeling electron dynamics properties that require going beyond linear response density. However, RT-TDDFT within adiabatic approximation can unphysically shift absorption peaks throughout dynamics. Here, we investigate origin these resonances observed in spectra. Using both exact exchange hybrid exchange-correlation...

Mixed quantum mechanical (QM)/classical methods provide a computationally efficient approach to modeling both ground and excited states in the condensed phase. To accurately model short-range interactions, some amount of environment can be included QM region, whereas classical treat long-range interactions maintain computational affordability. The best protocol for these mixed QM/classical determined by examining convergence molecular properties. Here, we compare (MM) fixed point charges...

Meteoric material injected into the atmosphere of Titan, Saturn's moon, can react with nitriles and other organic compounds that constitute Titan's atmosphere. However, specific chemical outcomes have not been fully explored. To understand fates meteoric metal ions in Titan environment, reactions Mg+ Al+ CH3CN (acetonitrile) C2H5CN (propionitrile) were carried out using a drift cell ion reactor at room temperatures (300 K) reduced (∼193 modeled density functional theory coupled-cluster...

A promising approach for accurately modeling both short-range and long-range solvation effects is to combine explicit quantum mechanical (QM) solvent with a classical polarizable continuum model (PCM), but the best PCM these combined QM/classical calculations relatively unexplored. We find that choice of cavity very important obtaining physically correct results since unphysical double counting from QM dielectric can occur poor cavity. investigate dependence electronic excitation energies on...

Classical molecular dynamics simulations reveal size-dependent trends of alkaline earth metal ions binding to DNA are due ion size and hydration behavior.

A critical element in theoretical characterization of the mechanism proton-coupled electron transfer (PCET) reactions, including hydrogen atom (HAT), is formulation and proton localized diabatic states, based on which a More O'Ferrall-Jencks diagram can be represented to determine step-wise concerted nature reaction. Although states have often been used empirically develop models for PCET potential energy surfaces these never determined directly first principles calculations using electronic...

The citrate reduction method is one of the simplest and most common methods used in synthesis gold nanoparticles. It has been thought that acts as both a reducing agent for salt capping agent. However, it recently reported using density functional theory (DFT) electron builds up on uncomplexed apex atoms binding formate (the carboxylate model citrate) becomes unfavorable after two additions, limiting citrate's utility In this study, Au20-formyloxyl radical interactions are investigated DFT...

To investigate the ability of alkaline earth metal ions to tune ion-mediated DNA adsorption, hydrated Mg2+, Ca2+, Sr2+, and Ba2+ bound a carboxylate anion, phosphate guanine nucleobase were modeled using density functional theory (DFT) combined explicit continuum solvent model. The large first solvation shell requires larger solute cavity defined by solvent-accessible surface, which is used model all ions. Alkaline bind indirectly or directly each binding site. DFT energies decrease with...

The optical, structural, and magnetic properties of iron(II,III) sandwich complexes, Fe(Tp')2n+ (Tp' = bis(3,5-dimethylpyrazolyl)benzotriazolylborate), are described. intensely colored FeII(Tp')2 (orange) FeIII(Tp')2+ (purple) show strong MLCT bands. Geometric isomerism for M(Tp')2 is established crystallographically in the racemate chiral cis-Fe(Tp')2. For first time, paramagnetic 11B NMR describes solution-phase low-spin (LS, S 0) to high-spin (HS, 2) crossover behavior Fe(Tp')2....

Anionic polyelectrolytes, such as DNA, are attracted to anionic surfaces in the presence of multivalent cations. A major barrier toward molecular-level understanding these attractive interactions is paucity measurements binding strength. Here, atomic force microscopy-based single molecule spectroscopy was used quantify free energy double-stranded DNA an surface, with complementary density functional theory calculations energies metal ion-ligand complexes. The results support both...

Anionic polyelectrolytes, such as DNA, are attracted to anionic surfaces in the presence of multivalent cations. A major barrier toward molecular-level understanding these attractive interactions is paucity measurements binding strength. Here, atomic force microscopy-based single molecule spectroscopy was used quantify free energy double-stranded DNA an surface, with complementary density functional theory calculations energies metal ion-ligand complexes. The results support both...

Reactions of Au+(1S,3D) and AuX+ with CH3X (X = I Br) were performed in the gas phase by utilizing a selected-ion drift cell reactor. These experiments done at room temperature as well reduced (∼200 K) total pressure 3.5 Torr helium. Rate coefficients, product sequencing, branching fractions obtained for all reactions to evaluate reaction efficiencies higher-order processes. both Au+ states proceed moderate compared average dipole orientation model these neutral substrates. Results from this...