# Patricio F. Provasi's research while affiliated with National University of the Northeast and other places

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## Publications (58)

The solute polarization due to solvent is a an electrostatic quantum effect that impacts diverse molecular properties, including the nonlinear optical response of a material. An iterative procedure that allows updating the solute charge distribution in the presence of the solvent is combined with a sequential Monte Carlo/Quantum Mechanics methodolo...

Context:
Natural products and their biotransformation procedures are a powerful source of new chromophores with potential applications in fields like biology, pharmacology and materials science. Thus, this work discusses about the extraction procedure of 1-nitro-2-phenylethane (1N2PE) from Aniba canelilla, its biotransformation setup into 2-phenyl...

The diagonal components and the trace of two tensors which account for chiroptical response of the leucoindigo molecule C 16 H 12 N 2 O 2 $$ {\mathrm{C}}_{16}{\mathrm{H}}_{12}{\mathrm{N}}_2{\mathrm{O}}_2 $$ that is, static anapole magnetizability, and dynamic electric dipole-magnetic dipole polarisability depending on the frequency of impinging lig...

Within the framework of Density Functional Theory (DFT), the relevance of the term Hartree-Fock exchange (HFE) for a variety of molecular properties is a critical point. For this reason, we spend efforts to understand these relationships in nuclear magnetic resonance (NMR) parameters in a water solvent. This work takes advantage of the appropriate...

Intermolecular H-bonds play a fundamental role for macromolecules in biochemistry. In this sense, the analysis of NMR scalar couplings across H-bonded chains has emerged as an important method to unveil the quasi-covalent character of the so-called intermolecular self-assembly. To investigate relationships between these couplings and molecular prop...

Glycine in its neutral form can exist in the gas phase while its zwitterion form is more stable in water solution, but how many waters are actually necessary to stabilize the zwitterionic structure in the gas phase? Are the intramolecular isotropic spin spin coupling constants sensitive enough to accuse the change in the environment? or the conform...

Glycine in its neutral form can exist in the gas phase while its zwitterion form is more stable in water solution.But how many waters are actually necessary to stabilize the zwitterionic structure in the gas phase? Are the intramolecular isotropic spin spin coupling constants sensitive enough to accuse the change in the environment? or the conforme...

The diagonal components and the trace of tensors which account for chiroptical response of the hydrazine molecule N2H4, that is, static anapole magnetizability and frequency‐dependent electric dipole‐magnetic dipole polarisability, are a function of the H─N─N─H dihedral angle. They vanish for symmetry reasons at ϕ = 0° and ϕ = 180°, corresponding r...

We have investigated the spin‐spin coupling constants (SSCC's) of diborane(4) and diborane(6), their Li‐doped counterparts, and the dimerization of diborane(6), using the second order polarization propagator approximation with coupled cluster singled and double [SOPPA(CCSD)] substitutions. We employed an adapted basis set to perform the calculation...

We present time-dependent density functional theory (TDDFT) calculations of the electronic optical rotation (ORP) for seven oxirane and two aziridine derivatives in the gas phase and in solution and compare the results with the available experimental values. For seven of the studied molecules it is the first time that their optical rotation was stu...

We combined different models of solvation and density functional theory calculations to study the magnetic properties of uracil in the liquid dimethyl sulfoxide environment. Special attention was paid to the effect of weak hydrogen bonds formation. In uracil, C=O groups act as hydrogen acceptors while N–H is hydrogen donor. The influence in the int...

The second‐order noniterative doubles‐corrected random phase approximation (RPA) method has been extended to triplet excitation energies and the doubles‐corrected higher RPA method as well as a shifted version for calculating singlet and triplet excitation energies are presented here for the first time. A benchmark set consisting of 20 molecules wi...

It is shown that the anapolar interaction of the electrons of a molecule with an external uniform magnetic field B and a uniform curl C determines different thermodynamical stabilization of the ground state for the enantiomers and diastereoisomers of a chiral molecule. A series of potential candidates for enantioselective syntheses has been investi...

In this article, the RPA(D) and HRPA(D) models for the calculation of linear response functions are presented. The performance of the new RPA(D) and HRPA(D) models is compared to the performance of the established RPA, HRPA, and SOPPA models in calculations of indirect nuclear spin–spin coupling constants using the CCSD model as a reference. The do...

A theoretical study of FCCF:(H2O)n complexes, with n = 1 and 2, has been carried out by means of ab initio computational methods. Three kinds of interactions are observed in the complexes: H···π and H···F hydrogen bonds and O···FC tetrel bonds. The indirect spin–spin coupling constants have been calculated at the CCSD/aug-cc-pVTZ-J computational le...

We present the results of a computational study of the NMR properties of glycine in water solution at the level of density functional theory employing the B3LYP functional and the 6-31G(d,p) and pcSseg-2 basis sets, describing the solvent either via the PCM continuous solvation model or PCM with additional explicit water molecules hydrogen-bonded t...

The influence of the hydrogen bond formation on the NMR spin–spin coupling constants (SSCC), including the Fermi contact (FC), the diamagnetic spin-orbit, the paramagnetic spin-orbit, and the spin dipole term, has been investigated systematically for the homogeneous glycine cluster, in gas phase, containing up to three monomers. The one-bond and tw...

The trace of tensors which account for chiroptical response of the hydrogen peroxide molecule is a function of the HO-OH dihedral angle. It vanishes at 0 and 180 degrees, due to the presence of molecular symmetry planes, but also for values in the range 90-100 degree of this angle, in which the molecule is unquestionably chiral. Such an atypical ef...

The experimental (1) H nuclear magnetic resonance (NMR) spectrum of 1H-pyrazole was recorded in thermotropic nematic liquid crystal N-(p-ethoxybenzylidene)-p-butylaniline (EBBA) within the temperature range of 299-308 K. Two of three observable dipolar DHH -couplings appeared to be equal at each temperature because of fast prototropic tautomerism....

In the presence of a static, nonhomogeneous magnetic field, represented by the axial vector B at the origin of the coordinate system and by the polar vector C=∇×B, assumed to be spatially uniform, the chiral molecules investigated in this paper carry an orbital electronic anapole, described by the polar vector A. The electronic interaction energy o...

It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to a...

We discuss the effect of electron correlation on the unexpected differential sensitivity (UDS) in the (1)J(C-H) coupling constant of CH4 using a decomposition into contributions from localized molecular orbitals and compare with the (1)J(N-H) coupling constant in NH3. In particular, we discuss the well known fact that uncorrelated coupled Hartree-F...

A combination of 13 C and 15 N CPMAS NMR spectroscopy and theoretical methods (DFT and DFT-D) was used to discuss the observation of large splittings affecting some atoms in 3(5)-phenyl-5(3)-methylpy-razolium chloride and bromide. Conventional calculations using fully optimized structures with C 2 sym-metry reproduce solution spectra, but the large...

Calculations have been carried out for C4H4X2 cyclic molecules, with X=O, S, Se, and Te, characterized by the presence of magnetic-field induced toroidal electron currents and associated orbital anapole moments. The orbital anapole induced by a static nonuniform magnetic field B, with uniform curl C=∇×B, is rationalized via a second-rank anapole ma...

A theoretical study of magnetic properties of hydrogen peroxide in water has been carried out by means of Monte Carlo simulation and quantum mechanics calculations. The solvent effects are evaluated in supermolecular structures generated by simulations in the NPT ensemble. The solute-solvent structure was analyzed in terms of radial distribution fu...

Dalton is a powerful general‐purpose program system for the study of molecular electronic structure at the H artree– F ock, K ohn– S ham, multiconfigurational self‐consistent‐field, M øller– P lesset, configuration‐interaction, and coupled‐cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculate...

The theory of response of a molecule in the presence of a static non-uniform magnetic field with uniform gradient is reviewed and extended. Induced magnetic dipole, quadrupole and anapole moments are expressed via multipole magnetic susceptibilities. Dependence of response properties on the origin of the coordinate system with respect to which they...

We have calculated the vicinal indirect nuclear spin-spin coupling constants (3)J(1H1H) in the series of molecules H3C-CH2X with X=H, F, Cl, Br, and I at the self-consistent field level and using the second order polarization propagator approximation (SOPPA). We have studied the effect of electron correlation and of the substituents (X=F, Cl, Br, a...

The angular dependence of the vicinal fluorine-fluorine coupling constant, (3)J(FF), for 1,2-difluoroethane has been investigated with several polarization propagator methods. (3)J(FF) and its four Ramsey contributions were calculated using the random phase approximation (RPA), its multiconfigurational generalization, and both second-order polariza...

Effects of lone pairs and electronegativity on indirect nuclear spin-spin coupling constants in CH2X (X=CH2, NH, O, S) using optimized calculations with contracted basis sets were studied. Second order polarization propagator approximation (SOPPA) and SOPPA with coupled cluster singles and doubles amplitude (CCSD) were used. The coupling changes du...

A theoretical study of FCCF:(HF)n complexes, with n = 1 and 2, has been carried out by means of ab initio
computational methods. Two types of complexes are formed: those with FH� � �p interactions and those
with FH� � �FC hydrogen bonds. The indirect spin–spin coupling constants have been calculated at the
CCSD/aug-cc-pVTZ-J computational level. Sp...

Electronic polarization induced by the interaction of a reference molecule with a liquid environment is expected to affect the magnetic shielding constants. Understanding this effect using realistic theoretical models is important for proper use of nuclear magnetic resonance in molecular characterization. In this work, we consider the pyridine mole...

The set of 1:1 and 2:1 complexes of XOOX' (X, X' = H, CH(3)) with lithium cation has been studied to determine if they are suitable candidates for chiral discrimination in an isotropic medium via nuclear magnetic resonance spectroscopy. Conventional nuclear magnetic resonance is unable to distinguish between enantiomers in the absence of a chiral s...

A theoretical study of the 1:1 and 2:1 complexes of XOOX' (X, X' = H, CH(3)) with the lithium cation has been carried out by means of ab initio computational methods up to the MP2/aug-cc-pVTZ level. The optical rotatory power and NMR parameters (absolute chemical shielding and indirect coupling constants) have been calculated. In addition, the race...

We present a theoretical study of the structures of silver silicon clusters, AgSin, n = 1–15, using density functional tight binding methods. We discuss in detail the search for silicon clusters stabilized by silver dopage, their dissociation paths, and electronic properties. We also investigate the properties of silver encapsulated structures and...

The aug-cc-pVTZ-J series of basis sets for indirect nuclear spin-spin coupling constants has been extended to the atoms B, Al, Si, P, and Cl. The basis sets were obtained according to the scheme previously described by Provasi et al. [J. Chem. Phys. 115, 1324 (2001)]. First, the completely uncontracted correlation consistent aug-cc-pVTZ basis sets...

We recently showed, by analyzing contributions from localized molecular orbitals, that the anomalous deuterium isotope effect in the one-bond indirect nuclear spin-spin coupling constant of methane, also called the unexpected differential sensitivity, can be explained by the transfer of s-orbital character from the stretched bond to the other uncha...

The NMR spin coupling parameters, (1)J(N,H) and (2)J(H,H), and the chemical shielding, sigma((15)N), of liquid ammonia are studied from a combined and sequential QM/MM methodology. Monte Carlo simulations are performed to generate statistically uncorrelated configurations that are submitted to density functional theory calculations. Two different L...

In this work it was sought to explore the versatility of geminal spin-spin coupling constants, (2)J(XY) SSCCs, as probes for stereochemical studies. A set of compounds, where their experimental (2)J(XY) SSCCs through the X-C-Y molecular fragment are predicted to be sensitive to hyperconjugative interactions involving either bonding or antibonding o...

Ab initio equation of motion coupled cluster singles and doubles (EOM-CCSD) and second-order polarization propagator approximation (SOPPA) calculations have been performed to evaluate spin-spin coupling constants for FCCF (difluoroethyne). The computed EOM-CCSD value of (3)J(F-F) obtained at the experimental geometry of this molecule supports the p...

Anomaly explained: The secondary isotope effect on the carbon-hydrogen indirect nuclear spin-spin coupling constant in methane, which is larger than the primary isotope effect, is explained in terms of contributions to the coupling constant from localized molecular orbitals. (Graph Presented)

Several theoretical methods have been used to compute ²JHH in neutral, anionic and cationic HXH hydrides, X being the 14 nuclei from Li to Cl (28 molecules). Since the calculations also provide ¹JXH spin–spin coupling constants (SSCC), these have also been analyzed. The best results were obtained using Second-order polarization propagator approxima...

A theoretical study of the complexes formed by the N2F cation (fluorodiazonium ion) and a series of small molecules containing nitrogen atoms have been carried out at the MP2 computational level. In addition, fluorine transfer has been studied. The electron density, NMR shielding and indirect coupling constants of the complexes have been evaluated....

Locally dense basis sets (< DBSs) were developed for correlated ab initio calculations of vicinal fluorine-fluorine indirect nuclear spin-spin couplings in several saturated and unsaturated fluorinated hydrocarbons. We find that the choice of the basis set for each atom belonging to our studied model compounds depends on its location with respect t...

A theoretical study of linear and cyclic clusters of (HCN)n and (HNC)n (up to n = 10) has been carried out by means of DFT and MP2 ab initio methods. The transition states linking the cyclic clusters show high energetic barriers that prevent the spontaneous transformation of the high-energy clusters, (HNC)n, into the low-energy ones, (HCN)n. The ef...

The cooperativity effects on both the electronic energy and NMR indirect nuclear spin-spin coupling constants J of the linear complexes (HCN)n and (HNC)n (n = 1-6) are discussed. The geometries of the complexes were optimized at the MP2 level by using the cc-pVTZ basis sets. The spin-spin coupling constants were calculated at the level of the secon...

Numerical calculations of relativistic effects on nuclear magnetic shielding constants sigma corresponding to all one-body operators obtained within a formalism developed in previous work were carried out. In this formalism, the elimination of small component scheme is applied to evaluate all quantities entering a four-component RSPT(2) expression...

The electronic origin of the Karplus-type behavior of vicinal NMR J couplings for H3X−C2H4−XH3, X = C, Sn model compound is analyzed within the framework of the polarization propagator formalism. It is shown that its whole pattern can be understood by generalizing previous hyperconjugative mechanisms, in such a way that the hyperconjugative delocal...

Large long-range indirect nuclear spin coupling constants are of great interest for quantum computers. But they are rarely observed and are usually considered very small, unless the coupled nuclear spins are proximate in space. Looking for counterexamples, we have calculated F-F couplings in four different series of acyclic hydrocarbons (alkanes, c...

Substituent effects for (2)J(F,F) couplings in aliphatic and olefinic CF2 moieties and (3)J(F,F) couplings in fluorinated derivatives of ethylene were studied using both high level ab initio and DFT/B3LYP calculations. Where possible, J variations have been compared with experimental values. In general, the SOPPA (second-order polarization propagat...

Abstract: Ab initio calculations of the spin-spin coupling constants have been carried out for methan- and ethanimine, methanal- and ethanaloxime at the level of the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes (SOPPA(CCSD)) using the aug-cc-pVTZ-J basis sets. Previously we have shown that t...

Some non-singlet quasi-instabilities (QIs) cases that arise in the calculation of NMR-J parameters are analyzed within response theory. The relationship between ‘very close to zero’ eigenvalues of the principal propagator and the rate of convergency for specific coupling pathways is shown by a power series implemented to calculate the principal pro...

The implementation and calculation of the principal propagator matrix elements as a power's series are presented. The scheme is applied to singlet- and triplet-type properties at random phase approach (RPA) level of approximation. Its application to both the polarizability and the J-NMR spectroscopic parameter by using localized molecular orbitals...

## Citations

... 0.01, and 3.40 eV, respectively. The lower HOMO-LUMO gaps indicate that these complexes may have enhanced NLO response as observed by Fonseca et al. in their work on NLO response of chromophores[62]. ...

... They are the simplest objects among short oligopeptides, thus, are very attractive for investigation by experimental and computer simulation methods. The tautomerization and the pH dependence of glycine and glycine containing oligopeptides were widely investigated by various theoretical [16][17][18][19][20][21][22] and experimental (capillary electrophoresis, potentiometry, IR and UV spectroscopy, THz spectroscopy, EPR spectroscopy, etc.) methods [23,24], including NMR spectroscopy [25][26][27][28][29][30][31]. Previously, it was shown that chemical shifts [32] and 1 J CαH one bond spin-spin coupling constants (SSCC) [33] of amino acid residues in various (backbone, C-or N-terminal) positions in peptides are different. ...

... A time-independent magnetic field induces toroidal electron flow in chiral molecules [1][2][3][4][5][6][7][8], giving rise to a static toroidal moment, which can be represented by a vector odd under charge conjugation C, parity P and time reversal T. The optical fields associated with a beam of monochromatic light, oscillating with frequency ω, also induce the anapolar response, which can be rationalized in terms of dynamic anapole polarizabilities and magnetizabilities [9]. ...

... Since the first implementation of ASEC, a variety of molecular properties have been studied and, according to the results, parameters such as the nuclear magnetic constants, [21][22][23][24][25] as well as the convergence of electronics excitation spectra of chromophore [26,27] are strongly affected by solvent polarization. However, despite these advances, a discussion on how the NLO parameters can be affected by the redistribution of electronic charges in the solute molecule is lacking. ...

... Most recently, Eriksen et al. [22,23] presented the PCM-SOPPA/RPA solvent model (described in Section 2.2) and applied it to the calculation of excitation energies in a water environment. The results showed that the PCM-SOPPA/RPA calculations had a tendency to underestimate the excitation energies compared with experimental values, as is also observed in gas phase SOPPA calculations [24,25]. Different solvent models have also been combined with density functional theory (DFT) for calculations of spin-spin coupling constants. ...

... I. As the constitutive molecular properties that account for the manifestation of magnetic anapoles are dipole-quadrupole and quadrupole-quadrupole magnetizabilities, [73][74][75]81 in the first place, we review the theoretical state-of-the-art, outlining and extending the results of previous investigations [82][83][84][85] into the anapolar response of a molecule to time-independent magnetic fields, based on time-independent Rayleigh-Schrödinger perturbation theory (RSPT) 86,87 and alternative powerful procedures, allowing for a nonperturbative approach and basis sets of London orbitals, [88][89][90][91] which have also been applied to evaluate the relevant tensors. 68,70,92 To enquire into the more general case of optical anapoles 64,93,94 for molecules in the presence of optical fields, time-dependent perturbation theory 95 has been applied to determine a set of dynamic anapole susceptibilities in Sec. ...

... Our benchmark set was chosen based on the availability of good experimental data and keeping the size of the selected molecules small to reduce the computational effort. For the SSCC calculations, five different methods were used: SOPPA [28][29][30][31], HRPA(D) [32] and DFT with the functionals B3LYP [33,34], BHandH [34,35], and PBE0 [36,37]. ...

... The PBE0/pcJ-1 level had satisfactory agreement with the obtained experimental J FH SSCC, being used in the remaining SSCCs calculations. The calculation of through-space SSCC involving fluorine was also recently studied by Sauer et al., [39][40][41] and the authors reported that PBE0 was the functional of best performance, which is in agreement with what we observed in this paper. The calculated SSCC reproduces the behavior of the experimental SSCC: as the solvent polarity increases, the trans-TFT conformer becomes more populated (Table S5, ESI †). ...

... DFT) [83,104,105]. For DFT approaches, the factors that significantly affect the accuracy of predicted 13 C and/or 1 H NMR chemical shifts are the optimization level of molecular geometry [106][107][108], the use of different DFT theories [109][110][111][112], implicit and explicit solvation models [113][114][115], unique molecular properties of metabolites [116][117][118][119][120][121], etc. Agreement between predicted and experimental chemical shifts can be improved when (i) the basis set is enlarged [104,122], (ii) the quality of the method is improved for geometry optimization [123,124], (iii) a scaling procedure is employed [125,126], (iv) conformational sampling is applied [127], and (v) solvation is taken into account appropriately [128,129]. However, the question of what level of accuracy is required for calculated NMR chemical shifts when using these as reference spectra for molecular identification remains largely unexplored. ...

... Hence, the proton transfer of the neutral glycine, stable in the gas phase, to zwitterionic conformer, stable in aqueous solution, has an estimated free energy barrier of about 7.3 kcal mol [1][2][3]5,6,8,[10][11][12][13][14]. Some other recent works aim to study small clusters of Glycine: (H 2 O) n complexes in order to elucidate structures and binding energies [15][16][17][18], or the stabilization of Z-Glycine in water and its NMR signature [19] and the election of a method for fast accurate of 1 J(C, H) for application in proteins [20]. ...