Predicting dipole orientations in spontelectric methyl formate

Capturing intermolecular interactions accurately is essential for describing, e.g., morphology of molecular matter on the nanoscale. When it reveals characteristics which are not directly accessible through experiments or ab initio theories, a model here becomes eminently beneficial. In laboratory astrochemistry, the intense study of ices has led i.a. to the exploration of the spontelectric state of nanofilms. Despite its success in biophysics or biochemistry and despite its predictive power, molecular modeling has however not yet been widely deployed for solid-state astrochemistry. In this article, therefore a pertinent hitherto unaddressed problem is tackled by means of the classical molecular-dynamics method, namely the unknown distribution of relative dipole orientations in spontelectric cis-methyl formate (MF). In doing so, from ab initio data, a molecular model is derived which confirms for the first time the anomalous temperature-dependent polarization of MF. These insights thus represent a further step toward understanding spontelectric behavior. Moreover, unprecedented first-principles predictions are reported regarding the ground-state geometry of the MF trimer and tetramer. In conjunction with the study of the binding to carbonaceous substrates, these additional findings can help to exemplarily elucidate molecular ice formation in astrochemical settings. Graphic Abstract

SÍNTESE, CARACTERIZAÇÃO E ESTUDO DOS PARÂMETROS DE JUDD-OFELT DE COMPOSTOS β-DICETONATOS DE Eu(III) OU Sm(III)

SYNTHESIS, CHARACTERIZATION AND JUDD-OFELT ANALYSIS OF Eu(III) OR Sm(III) β-DIKETONATE COMPLEXES. The lanthanide complexes [Ln(bmdm)3(L)] where Ln(III) = Eu and Sm were synthesized successfully using the diketone (1-(4-methoxyphenyl)-3-(4-tert-butylphenyl) propane-1,3-dione) (bmdm) and (L) = 1,10-phenanthroline (phen), 2,2’-bipyridine (bipy) ligands. The coordination modes were determined as bidentate chelate by the FT-IR. The ground state geometry was determined using the Sparkle/AM1 implemented in MOPAC2016 package. Europium complexes exhibit the characteristic emission bands that arise from 5 D0→7 FJ (J = 0-4); the presence of just one 5 D0→7 F0 line transition means that this site is without the center of inversion.Samarium complexes display transitions at 4 G5/2→6 HJ (J = 5/2; 7/2; 9/2 and 11/2), being the 4 G5/2→6 H9/2 the most intense, indicating that the forced electric dipole mechanism is predominant when compared with the magnetic dipole ones. The intensity parameters Ω2 and Ω4 were calculated according to the emission spectra for Eu(III) and absorption spectra for Sm(III). The high Ω2 values demonstrated that the lanthanide ion in bipy or phen complexes is in a highly polarizable chemical environment. The emission lifetime (τ) increases compared with that of precursor aquo complexes, confirming that the non-radiative quenching is minimized. The low quantum efficiency is a result of NIR emissions and non-radiative transitions of Sm(III).

Force-Modulated Reductive Elimination from Platinum(II) Diaryl Complexes

<div><p>Coupled mechanical forces are known to drive a range of covalent chemical reactions, but the interplay of mechanical force applied to a spectator ligand and transition metal reactivity is relatively unexplored. Here we report the effect of mechanical force on the rate of C(sp²)-C(sp²) reductive elimination from platinum(II) diaryl complexes containing macrocyclic bis(phosphine) force probe ligands. Compressive forces decreased the rate of reductive elimination whereas extension forces increased the rate of reductive elimination relative to the strain-free MeOBiphep complex with a 3.4-fold change in rate over a ~290 pN range of restoring forces. The natural bite angle of the free ligand changes with force, but ³¹P NMR analysis strongly suggests no significant force-induced perturbation of the ground state geometry of the (P–P)PtAr₂ complexes. Rather, the force/rate behavior observed across this range of forces (from ca. 65 pN in compression to >200 pN in extension) for reductive elimination is attributed to the coupling of force to the elongation of the O<b>^…</b>O distance in the transition state for reductive elimination. The results suggest opportunities to experimentally map geometry changes associated with reactions in transition metal complexes and potential strat-egies for force-modulated catalysis. </p></div><br>

Force-Modulated Reductive Elimination from Platinum(II) Diaryl Complexes

<div><p>Coupled mechanical forces are known to drive a range of covalent chemical reactions, but the interplay of mechanical force applied to a spectator ligand and transition metal reactivity is relatively unexplored. Here we report the effect of mechanical force on the rate of C(sp²)-C(sp²) reductive elimination from platinum(II) diaryl complexes containing macrocyclic bis(phosphine) force probe ligands. Compressive forces decreased the rate of reductive elimination whereas extension forces increased the rate of reductive elimination relative to the strain-free MeOBiphep complex with a 3.4-fold change in rate over a ~290 pN range of restoring forces. The natural bite angle of the free ligand changes with force, but ³¹P NMR analysis strongly suggests no significant force-induced perturbation of the ground state geometry of the (P–P)PtAr₂ complexes. Rather, the force/rate behavior observed across this range of forces (from ca. 65 pN in compression to >200 pN in extension) for reductive elimination is attributed to the coupling of force to the elongation of the O<b>^…</b>O distance in the transition state for reductive elimination. The results suggest opportunities to experimentally map geometry changes associated with reactions in transition metal complexes and potential strat-egies for force-modulated catalysis. </p></div><br>

Theoretical Studies of Au3+/0/- Clusters Using Density Funtional Theory

In this study, the PW91PW91 method with LANL2DZ level was carried out to settle the dispute about the most stable structure of Au3+/0/-. Molecular orbital analyses and Walsh diagram were adopted to rationalize our computational result about the ground state geometry of Au3+/0/-. Our results show that the most stable geometry of Au3 is bent structure (C2v) with bond angle 146.0°. The less stable structure is equilateral triangle structure (D3h) with relative energies of 1.74 eV. The D3h structure possesses multiplicity 4 while the C2v structure 2. In addition, the most stable geometry of Au3+ and Au3- are equilateral triangle structure (D3h) and linear structure (D∞h), respectively. The preference of geometric change can be rationalized simply by using Walsh diagram. Besides, the linear structure of Au3 is found to be transition states (TS) of inversion of B-Au3. The inversion barrier is estimated to be 0.04 eV.

Dynamics and the emergence of geometry in an information mesh

The idea of a graph theoretical approach to modeling the emergence of a quantized geometry and consequently spacetime, has been proposed previously, but not well studied. In most approaches the focus has been upon how to generate a spacetime that possesses properties that would be desirable at the continuum limit, and the question of how to model matter and its dynamics has not been directly addressed. Recent advances in network science have yielded new approaches to the mechanism by which spacetime can emerge as the ground state of a simple Hamiltonian, based upon a multi-dimensional Ising model with one dimensionless coupling constant. Extensions to this model have been proposed that improve the ground state geometry, but they require additional coupling constants. In this paper we conduct an extensive exploration of the graph properties of the ground states of these models, and a simplification requiring only one coupling constant. We demonstrate that the simplification is effective at producing an acceptable ground state. Moreover we propose a scheme for the inclusion of matter and dynamics as excitations above the ground state of the simplified Hamiltonian. Intriguingly, enforcing locality has the consequence of reproducing the free non-relativistic dynamics of a quantum particle.

Theoretical Studies of Photophysical Properties of D−π−A−π−D-Type Diketopyrrolopyrrole-Based Molecules for Organic Light-Emitting Diodes and Organic Solar Cells

A series of D–π–A diketopyrrolopyrrole(DPP)-based small molecules were designed for organic light-emitting diode(OLEDs) and organic solar cell(OSCs) applications. Applying the PBE0/6-31G(d,p) method, the ground state geometry and relevant electronic properties were investigated. The first excited singlet state geometry and the absorption and fluorescent spectra were simulated at the TD-PBE0/6-31G(d,p) level. The calculated results revealed that the photophysical properties were affected through the introduction of different end groups. Furthermore, the electronic transitions corresponding to absorption and emission exhibited an intramolecular charge transfer feature. Our results suggest that the designed molecules acted not only as luminescent for OLEDs, but also as donor materials in OSCs. Moreover, they can also be used as potential electron transfer materials for OLEDs and OSCs.

Characterization of Photophysical Properties of D−π−A−π−D Type Diketopyrrolopyrrole Based Molecules for Organic Light-Emitting diodes and Organic Solar Cells

A series of D&ndash;&pi;&ndash;A diketopyrrolopyrrole (DPP)-based small molecules have been designed for organic light-emitting diodes (OLEDs) and organic solar cells (OSCs) applications. Appling the PBE0/6-31G(d,p) method, the ground state geometry and relevant electronic properties were investigated. The first excited singlet state geometry and the absorption and fluorescent spectra were simulated at the TD-PBE0/6-31G(d,p) level. The calculated results reveal that the photophysical properties are affected through the introduction of different end groups. Furthermore, the electronic transitions corresponding to absorption and emission exhibit intramolecular charge transfer feature. It was disclosed that the designed molecules act not only as luminescent for OLEDs, but also donor materials in OSCs. Moreover, they also can be used as potential electron transfer materials using for OLEDs and OSCs.

DFT Characteristics of Charge Transport in DBTP-Based Hole Transport Materials

To improve the hole-transport ability and photoelectric properties of perovskite solar cells, the ground-state geometry, frontier molecular orbital, and mobility of two organic molecules were investigated using density functional theory (DFT) with the Marcus hopping model. The absorption spectra were calculated using time-dependent DFT. The result indicated that the increase in the conjugated chain and change in the substituted group location from meta to para cause low mobility, which has a negative effect on the hole-transporting ability.