Alkali and Alkaline Earth Metal Compounds: Core-Valence Basis Sets and Importance of Subvalence Correlation

Core-valence basis sets for the alkali and alkaline earth metals Li, Be, Na, Mg, K, and Ca are proposed. The basis sets are validated by calculating spectroscopic constants of a variety of diatomic molecules involving these elements. Neglect of $(3s,3p)$ correlation in K and Ca compounds will lead to erratic results at best, and chemically nonsensical ones if chalcogens or halogens are present. The addition of low-exponent $p$ functions to the K and Ca basis sets is essential for smooth convergence of molecular properties. Inclusion of inner-shell correlation is important for accurate spectroscopic constants and binding energies of all the compounds. In basis set extrapolation/convergence calculations, the explicit inclusion of alkali and alkaline earth metal subvalence correlation at all steps is essential for K and Ca, strongly recommended for Na, and optional for Li and Mg, while in Be compounds, an additive treatment in a separate `core correlation' step is probably sufficient. Consideration of $(1s)$ inner-shell correlation energy in first-row elements requires inclusion of $(2s,2p)$ `deep core' correlation energy in K and Ca for consistency. The latter requires special CCV$n$Z `deep core correlation' basis sets. For compounds involving Ca bound to electronegative elements, additional $d$ functions in the basis set are strongly recommended. For optimal basis set convergence in such cases, we suggest the sequence CV(D+3d)Z, CV(T+2d)Z, CV(Q+$d$)Z, and CV5Z on calcium.Comment: Molecular Physics, in press (W. G. Richards issue); supplementary material (basis sets in G98 and MOLPRO formats) available at http://theochem.weizmann.ac.il/web/papers/group12.htm

Overcoming artificial broadening in Gd³⁺–Gd³⁺ distance distributions arising from dipolar pseudo-secular terms in DEER experiments

By providing accurate distance measurements between spin labels site-specifically attached to bio-macromolecules, double electron–electron resonance (DEER) spectroscopy provides a unique tool to probe the structural and conformational changes in these molecules. Gd3+-tags present an important family of spin-labels for such purposes, as they feature high chemical stability and high sensitivity in high-field DEER measurements. The high sensitivity of the Gd3+ ion is associated with its high spin (S = 7/2) and small zero field splitting (ZFS), resulting in a narrow spectral width of its central transition at high fields. However, under the conditions of short distances and exceptionally small ZFS, the weak coupling approximation, which is essential for straightforward DEER data analysis, becomes invalid and the pseudo-secular terms of the dipolar Hamiltonian can no longer be ignored. This work further explores the effects of pseudo-secular terms on Gd3+–Gd3+ DEER measurements using a specifically designed ruler molecule; a rigid bis-Gd3+-DOTA model compound with an expected Gd3+–Gd3+ distance of 2.35 nm and a very narrow central transition at the W-band (95 GHz). We show that the DEER dipolar modulations are damped under the standard W-band DEER measurement conditions with a frequency separation, Δν, of 100 MHz between the pump and observe pulses. Consequently, the DEER spectrum deviates considerably from the expected Pake pattern. We show that the Pake pattern and the associated dipolar modulations can be restored with the aid of a dual mode cavity by increasing Δν from 100 MHz to 1.09 GHz, allowing for a straightforward measurement of a Gd3+–Gd3+ distance of 2.35 nm. The increase in Δν increases the contribution of the |−5/2〉 → |−3/2〉 and |−7/2〉 → |−5/2〉 transitions to the signal at the expense of the |−3/2 〉 → |−1/2〉 transition, thus minimizing the effect of dipolar pseudo-secular terms and restoring the validity of the weak coupling approximation. We apply this approach to the A93C/N140C mutant of T4 lysozyme labeled with two different Gd3+ tags that have narrow central transitions and show that even for a distance of 4 nm there is still a significant (about two-fold) broadening that is removed by increasing Δν to 636 MHz and 898 MHz.This research was supported by the Israeli Science Foundation (grant 334/14) and made possible in part by the historic generosity of the Harold Perlman Family. D. G. holds the Erich Klieger professorial chair in Chemical Physic

Nuevos datos acerca de los repertorios teatrales en el primer catálogo de «El peregrino en su patria»

En este artículo se muestra cómo los títulos que contienen los repertorios de los autores de comedias presentes en El peregrino en su patria de 1604 están dispuestos según un orden cronológico, aunque con algunos matices y no pocas excepciones. Además, se amplían los repertorios descubiertos por Thornton Wilder y se afina la fecha de composición de varias obras, prestando especial atención a textos que se han perdido, como La perdición de España, La gobernadora, La gran pintora, La bella gitana o La toma de Álora. Finalmente, el presente artículo pretende mostrar de un modo práctico cómo una base de datos digital como el Diccionario biográfico de actores del teatro clásico español (DICAT) puede resultar de gran ayuda a la hora de resolver algunos de los problemas clásicos de la filología en general y del teatro del Siglo de Oro en particular.This paper shows that the plays contained in the repertoire of the autores de comedias which appear in El peregrino en su patria (1604) are organised chronologically, although there are some nuances and exceptions. The article also expands the repertoire discovered by Thornton Wilder and sets the date of composition for some plays, paying special attention to lost texts such as La perdición de España, La gobernadora, La gran pintora, La bella gitana or La toma de Álora. Finally, this paper attempts to show in a practical way that a database such as the Diccionario biográfico de actores del teatro clásico español (DICAT) can be extremely helpful when it comes to dealing with some of the philology's classical problems in general and those of the theatre of the Golden Age in particular

Evaluation of the Factors Impacting the Accuracy of ¹³C NMR Chemical Shift Predictions using Density Functional TheoryThe Advantage of Long-Range Corrected Functionals

The various factors influencing the accuracy of ¹³C NMR calculations using density functional theory (DFT), including the basis set, exchange-correlation (XC) functional, and isotropic shielding calculation method, are evaluated. A wide selection of XC functionals (over 70) were considered, and it was found that long-range corrected functionals offer a significant improvement over the other classes of functionals. Based on a thorough study, it is recommended that for calculating NMR chemical shifts (δ) one should use the CSGT method, the COSMO solvation model, and the LC-TPSSTPSS exchange-correlation functional in conjunction with the cc-pVTZ basis set. A selection of problems in natural product identification are considered in light of the newly recommended level of theory

Enolonium Species-Umpoled Enolates

Enolonium species/iodo(III) enolates of carbonyl compounds have been suggested to be intermediates in a wide variety of hypervalent iodine induced chemical transformations of ketones, including α-C-O, α-C-N, α-C-C, and alpha-carbon- halide bond formation, but they have never been characterized. We report that these elusive umpoled enolates may be made as discrete species that are stable for several minutes at-78 degrees C, and report the first spectroscopic identification of such species. It is shown that enolonium species are direct intermediates in C-O, C-N, C-Cl, and C-C bond forming reactions. Our results open up chemical space for designing a variety of new transformations. We showcase the ability of enolonium species to react with prenyl, crotyl, cinnamyl, and allyl silanes with absolute regioselectivity in up to 92% yield

Authorizing Multiple Chemical Passwords by a Combinatorial Molecular Keypad Lock

A combinatorial fluorescent molecular sensor operates as a highly efficient molecular security system. The ability of a pattern-generating molecule to process diverse sets of chemical inputs, discriminate among their concentrations, and form multivalent and kinetically stable complexes is demonstrated as a powerful tool for processing a wide range of chemical “passwords” of different lengths. This system thus indicates the potential for obtaining unbreakable combination locks at the molecular scale