Theoretical modeling of UV-Vis absorption and emission spectra in liquid state systems including vibrational and conformational effects: the vertical transition approximation

In this paper we describe in detail a general and efficient methodology, based on the perturbed matrix method and molecular dynamics simulations, to model UV-Vis absorption and emission spectra including vibrational and conformational effects. The basic approximation used is to consider all the chromophore atomic coordinates as semiclassical degrees of freedom, hence allowing the calculation of the complete spectral signal by using the electronic vertical transitions as obtained at each possible chromophore configuration, thus including the contributions of vibrations and conformational transitions into the spectrum. As shown for the model system utilized in this paper, solvated 1-phenyl-naphthalene, such an approximation can be rather accurate to reproduce the absorption and emission spectral line shape and properties when, as it often occurs, the vertical vibronic transition largely overlaps the other non-negligible vibronic transitions

The ionization potential of NF 3 : a G3 computational study on the thermochemical properties of NF x and NF ϩ x x 1-3

Abstract The adiabatic ionization potential (IP) of NF x x 1-3 and the enthalpies of formation of NF x and NF ϩ x have been computed using the Gaussian-3 (G3) theory. The obtained values are generally found in very good agreement with the experimental ones. However, the G3 enthalpy of formation of N

The Conformational Dynamics of the Ligands Determines the Electronic Circular Dichroism of the Chiral Au38(SC2H4Ph)24 Cluster

Effects of the conformational dynamics of 2-PET protective ligands on the electronic circular dichroism (ECD) of the chiral Au-38(SC2H4Ph)(24) cluster are investigated. We adopt a computational protocol in which ECD spectra are calculated via the first principle polTDDFT approach on a series of conformations extracted from MD simulations by using Essential Dynamics (ED) analysis, and then properly weighted to predict the final spectrum. We find that the experimental spectral features are well reproduced, whereas significant discrepancies arise when the spectrum is calculated using the experimental X-ray structure. This result unambiguously demonstrates the need to account for the conformational effects in the ECD modeling of chiral nanoclusters. The present procedure proved to be able of capturing the essential conformational features of the dynamic Au-38(SC2H4Ph)(24) system, opening the possibility to model the ECD of soluble chiral nanoclusters in a realistic way

Calculation of the optical rotatory dispersion of solvated alanine by means of the perturbed matrix method

Abstract The zwitterionic form of aqueous L L-alanine is chosen as a benchmark for the theoretical evaluation of the optical rotatory dispersion (ORD) in solution, as provided by a simple application of the perturbed matrix method (PMM). Results show the applicability of this procedure, suggesting that its use might provide a general theoretical-computational tool for describing, at atomic-molecular level, the optical activity of a molecule in a complex environment

Effect of quantitative feed restriction on the performance of broiler chickens in Tunisia

The study was conducted to investigate the effect of a quantitative feed restriction phase on the live weight of broilers and assess their compensatory growth performance. Four hundred day-old chicks (Arbor Acres) were reared in four units of 100 chicks. These units were randomized into a control group (T) fed ad libitum and three restricted groups (A, B and C). Chickens of groups A, B and C were limited to 90, 80 and 70%, respectively, of the ad libitum feed intake between 16 and 23 days of age. After the 23rd day of age, all chickens were fed ad libitum until the end of the experiment (42 days of age). Results showed that during the restriction phase the body weight and average daily gain were significantly different (p < 0.01) between the four groups, and higher in chicks fed ad libitum than in those in the restricted groups. Delayed growth was more pronounced in chicks restricted at 70% of ad libitum consumption. After returning to ad libitum feeding, compensatory growth, characterized by rapid growth, was observed just after refeeding in chicks restricted at 70%, at 35 days of age in those assigned the least severe restriction (90%), and in the last week of rearing in the group assigned an intermediate level of restriction (80%). Feed efficiency improved in the restricted groups but the final body weights remained lower than those in the group fed ad libitum. Thus, with an intermediate reduction of the amount of feed consumed (20% for eight days), a final acceptable body weight was obtained