Nicola Tasinato

Bio: Nicola Tasinato is an academic researcher from Ca' Foscari University of Venice. The author has contributed to research in topics: Rotational spectroscopy & Rotational–vibrational spectroscopy. The author has an hindex of 21, co-authored 70 publications receiving 1167 citations. Previous affiliations of Nicola Tasinato include Scuola Normale Superiore di Pisa.

Accuracy and Interpretability: The Devil and the Holy Grail. New Routes across Old Boundaries in Computational Spectroscopy.

Abstract: The past decade has witnessed an increasing interaction between experiment and theory in the field of molecular spectroscopy. On the computational side, ongoing developments of hardware and software have moved computational spectroscopy from a highly specialized research area to a general tool for researchers in different fields of chemical science. However, since its dawn, computational spectroscopy has been characterized by the dichotomies of qualitative and quantitative description, and of interpretation and accuracy. Indeed, the analysis of experiments is seldom straightforward because of the subtle interplay of several different effects, which are not easy to evaluate and isolate, and/or the complexity of the system under consideration. Often, the accuracy has to be set aside for a more qualitative analysis that will provide the means for a broad interpretation. In such a scenario, the most recent advances in theoretical treatments as well as computational tools have opened the way to the reconciliation of accuracy and interpretability, resulting in unequivocal analyses and assignments of experimental spectra and their unbiased interpretation. This Review aims at being a comprehensive, authoritative, critical, and readable account of general interest to the chemistry community because of the wealth of qualitative and quantitative information that can be obtained from spectroscopic investigations. Limiting ourselves to rotational and vibrational spectroscopy, emphasis will be put on accuracy and interpretability as well as on the routes toward their reconciliation and integration.

Anharmonic theoretical simulations of infrared spectra of halogenated organic compounds

Abstract: The recent implementation of the computation of infrared (IR) intensities beyond the double-harmonic approximation [J Bloino and V Barone, J Chem Phys 136, 124108 (2012)]101063/13695210 paved the route to routine calculations of infrared spectra for a wide set of molecular systems Halogenated organic compounds represent an interesting class of molecules, from both an atmospheric and computational point of view, due to the peculiar chemical features related to the halogen atoms In this work, we simulate the IR spectra of eight halogenated molecules (CH2F2, CHBrF2, CH2DBr, CF3Br, CH2CHF, CF2CFCl, cis-CHFCHBr, cis-CHFCHI), using two common hybrid and double-hybrid density functionals in conjunction with both double- and triple-ζ quality basis sets (SNSD and cc-pVTZ) as well as employing the coupled-cluster theory with basis sets of at least triple-ζ quality Finally, we compare our results with available experimental spectra, with the aim of checking the accuracy and the performances of the computat

Theory Meets Experiment for Noncovalent Complexes: The Puzzling Case of Pnicogen Interactions

Abstract: A gas-phase nitrogen-nitrogen noncovalent interaction has been unveiled in the nitroethane-trimethylamine complex in an environment free from solvent and matrix effects using rotational spectroscopy in supersonic expansion. Different quantum chemical models (NOCV/CD and NBO) agree in indicating that this interaction largely prevails over the C-H⋅⋅⋅O and C-H⋅⋅⋅N hydrogen bonds. Furthermore, a SAPT analysis shows that electrostatic and dispersion interactions play a comparable role in stabilizing the complex. The conformational landscape exploration and stationary points characterization have been performed using state-of-the-art quantum-chemical computations providing significant insights on structure determination.

Unveiling the Sulfur–Sulfur Bridge: Accurate Structural and Energetic Characterization of a Homochalcogen Intermolecular Bond

Abstract: By combining rotational spectroscopy in supersonic expansion with the capability of state-of-the-art quantum-chemical computations in accurately determining structural and energetic properties, the genuine nature of a sulfur-sulfur chalcogen bond between dimethyl sulfide and sulfur dioxide has been unveiled in a gas-jet environment free from collision, solvent and matrix perturbations. A SAPT analysis pointed out that electrostatic S⋅⋅⋅S interactions play the dominant role in determining the stability of the complex, largely overcoming dispersion and C-H⋅⋅⋅O hydrogen-bond contributions. Indeed, in agreement with the analysis of the quadrupole-coupling constants and of the methyl internal rotation barrier, the NBO and NOCV/CD approaches show a marked charge transfer between the sulfur atoms. Based on the assignment of the rotational spectra for 7 isotopologues, an accurate semi-experimental equilibrium structure for the heavy-atom backbone of the molecular complex has been determined, which is characterized by a S⋅⋅⋅S distance (2.947(3) A) well below the sum of van der Waals radii.

Development and Implementation of Advanced Fitting Methods for the Calculation of Accurate Molecular Structures.

Abstract: The determination of accurate equilibrium molecular structures plays a fundamental role for understanding many physical-chemical properties of molecules, ranging from the precise evaluation of the electronic structure to the analysis of dynamical and environmental effects in tuning their overall behavior. For this purpose the so-called semiexperimental approach, based on a nonlinear least-squares fit of the moments of inertia associated with a set of available isotopologues, allows one to obtain very accurate results, without the unfavorable computational cost characterizing high-level quantum chemical methods. In the present work the MSR (Molecular Structure Refinement) software for the determination of equilibrium structures by means of the semiexperimental approach is presented, and its implementation is discussed in some detail. The software, which is interfaced with a powerful graphical user interface, includes different optimization algorithms, an extended error analysis, and a number of advanced fe...

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Global warming potentials and radiative efficiencies of halocarbons and related compounds: a comprehensive review

Abstract: [1] In the mid-1970s, it was recognized that chlorofluorocarbons (CFCs) were strong greenhouse gases that could have substantial impacts on radiative forcing of climate change, as well as being substances that deplete stratospheric ozone. Around a decade later, this group of radiatively active compounds was expanded to include a large number of replacements for ozone-depleting substances such as chlorocarbons, hydrochlorocarbons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), bromofluorocarbons, and bromochlorofluorocarbons. This paper systematically reviews the published literature concerning the radiative efficiencies (REs) of CFCs, bromofluorocarbons and bromochlorofluorocarbons (halons), HCFCs, HFCs, PFCs, sulfur hexafluoride, nitrogen trifluoride, and related halogen containing compounds. In addition, we provide a comprehensive and self-consistent set of new calculations of REs and global warming potentials (GWPs) for these compounds, mostly employing atmospheric lifetimes taken from the available literature. We also present global temperature change potentials for selected gases. Infrared absorption spectra used in the RE calculations were taken from databases and individual studies and from experimental and ab initio computational studies. Evaluations of REs and GWPs are presented for more than 200 compounds. Our calculations yield REs significantly (> 5%) different from those in the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) for 49 compounds. We present new RE values for more than 100 gases which were not included in AR4. A widely used simple method to calculate REs and GWPs from absorption spectra and atmospheric lifetimes is assessed and updated. This is the most comprehensive review of the radiative efficiencies and global warming potentials of halogenated compounds performed to date.

Fully anharmonic IR and Raman spectra of medium-size molecular systems: accuracy and interpretation

Abstract: Computation of full infrared (IR) and Raman spectra (including absolute intensities and transition energies) for medium- and large-sized molecular systems beyond the harmonic approximation is one of the most interesting challenges of contemporary computational chemistry. Contrary to common beliefs, low-order perturbation theory is able to deliver results of high accuracy (actually often better than those issuing from current direct dynamics approaches) provided that anharmonic resonances are properly managed. This perspective sketches the recent developments in our research group toward the development of a robust and user-friendly virtual spectrometer rooted in second-order vibrational perturbation theory (VPT2) and usable also by non-specialists essentially as a black-box procedure. Several examples are explicitly worked out in order to illustrate the features of our computational tool together with the most important ongoing developments.

Applications in stereochemical analysis of synthetic compounds, natural products, and biomolecules

Abstract: This book provides an introduction to the important methods of chiroptical spectroscopy in general, and circular dichroism (CD) in particular, which are increasingly important in all areas of chemistry, biochemistry, and structural biology. The book can be used as a text for undergraduate and graduate students and as a reference for researchers in academia and industry. Experimental methods and instrumentation are described with topics ranging from the most widely used methods (electronic and vibrational CD) to frontier areas such as nonlinear spectroscopy and photoelectron CD, as well as the theory of chiroptical methods and techniques for simulating chiroptical properties. Applications of chiroptical spectroscopy to problems in organic stereochemistry, inorganic stereochemistry, and biochemistry and structural biology are also discussed, and each chapter is written by one or more leading authorities with extensive experience in the field.