Search

The discovery of the $D^\ast_{s0}(2317)$ and $D_{s1}(2460)$ resonances in the charmed-strange meson spectra revealed that formerly successful constituent quark models lose predictability in the vicinity of two-meson thresholds. The emergence of non-negligible effects due to meson loops requires an explicit evaluation of the interplay between $Q\bar q$ and $(Q\bar q)(q\bar q)$ Fock components. In contrast to the $c\bar s$ sector, there is no experimental evidence of $J^P=0^+,1^+$ bottom-strange states yet. Motivated by recent lattice studies, in this work the heavy-quark partners of the $D_{s0}^\ast(2317)$ and $D_{s1}(2460)$ states are analyzed within a heavy meson chiral unitary scheme. As a novelty, the coupling between the constituent quark model P-wave $\bar B_s$ scalar and axial mesons and the $\bar B^{(\ast)}K$ channels is incorporated employing an effective interaction, consistent with heavy quark spin symmetry, constrained by the lattice energy levels., 9 pages, 2 figures, 1 table

Computational modeling of optical activity, circular dichroism (CD) and optical rotatory dispersion, is rapidly becoming a useful supplement to experimental studies of absolute configuration. Here, we investigate the predictions of two alternative formulations of the rotational strength based on time-dependent density functional theory (TD-DFT), for a series of high symmetry chiral systems. We employ the TD-DFT method as realized in Gaussian 03 suite with the hybrid functional B3LYP and as incorporated in the Amsterdam density functional (ADF) suite with PBE and SAOP functionals. The high-symmetry systems described here are somewhat larger than those used to evaluate the influence of basis sets and density functional choice, and for such large systems the very extensive basis sets recommended by most investigators may not be suitable for routine use. We observe that useful results for these systems can be obtained in modest bases, and in particular that diffuse functions may not be required for informative use of the ADF implementation. The statistical average of orbital potentials (SAOP) model developed by Baerends is essential to the success of the ADF implementation. In some cases chirality is defined by features of the molecular structure remote from the chromophore. This is a severe test of the TD-DFT theory, since high-lying excitations define the most prominent features of the CD spectra, and complicates the use of computations to guide the assignment of absolute configuration. Experimental investigation of the high symmetry systems described here is desirable.

Owing to the C2 symmetry structure of 1,1‘-diphenyl-3,3‘,4,4‘-tetramethyl-2,2‘-biphosphole, 1 (BIPHOS), we investigated the coordination of this chiral bidentate ligand to transition metals in order to explore the potential of these complexes in asymmetric catalysis. Nickel, palladium, and platinum complexes [M(BIPHOS)X2] (2 (M = Ni, X = Br), 3 (M = Pd, X = Cl), 4 (M = Pt, X = Cl) were synthesized and fully characterized. Their structures were determined by X-ray crystallography. The cationic palladium complexes [Pd(BIPHOS)(CH3CN)2](BF4)2, 6, and [Pd(BIPHOS)(η3-C3H5)]Cl, 7, were also synthesized. The π-allyl−palladium complex 7 reveals a potential interest for catalytic allylic substitution. The reaction of 1 with [Pd(CH3CN)4](BF4)2 leads to the formation of the meso diastereoisomer [Pd(BIPHOS)2] (BF4)2, 5, which was fully characterized. Its structure was determined by X-ray crystallography. A bis(BIPHOS) complex of Rh(I), 8, was also obtained by reaction of 1 with [Rh(COD)Cl]2 or [Rh(COD)2]BF4.

The aim of this work is the synthesis of some BINOL derivatives due to their catalytic, biological and medicinal activity. The rigid structure, thermal stability and the C2 symmetry of the binaphthyl molecules play an important rol in asymmetric induction. We report here a study on the radical addition of different triorganotin hydrides, R3SnH (R= n-Bu, Ph), to four (S)-BINOL unsaturated diesters (1,1'-binaphthyl-2-2´-diyl diacrylate; 1,1´-binaphthyl-2-2´-diyl dimethacrylate; 1,1´-binaphthyl-2-2´-diyl-(Z)-2-methyl-3-phenyl-2- propenoate and 1,1´-binaphthyl-2-2´-diyl di-(Z)-2,3-diphenyl-2-propenoate). The expected cyclohydrostannation products were not obtained in spite of the different conditions used for the reaction: sonication, irradiation and refluxing in toluene, with AIBN as radical initiator. This probably occurred due to the restricted conformational structure of the BINOL diesters. Rather than cyclization products, the corresponding mono- and diorganotin adducts were the mainly products obtained under radical addition of the tin hydrides. These organotin adducts can be easily derived in halotrialkyltin or halodialkylaryltin compounds, some of them with probable catalytic activity. For example, organotin halides are Lewis acids so they can be used as catalysts in different reactions, such as asymmetric Diels-Alder cycloaddition and alcohol acylations among others, where the metal catalytic centre is near the chiral binaphthyl moiety. Some authors have demonstrated that diorganotindihalides has higher catalytic effect compared to triorganotin halides and similar to geminal bis(haloorganostannanes). We studied the relation between mono and distannilated products and the diasteroselectivity in appropiate cases. These compounds were characterized with 1H, 13C and 119Sn-NMR.

A class of nanomaterials possessing the highest degree of chiral symmetry, the chiral icosahedral symmetry, is found by a combination of global optimization searches and first-principle calculations. These nanomaterials are core-shell nanoalloys with a Cu, Ni, or Co core and a chiral Ag or Au shell of monatomic thickness. The chiral shell is obtained by a transformation of an anti-Mackay icosahedral shell by a concerted rotation of triangular atomic islands which breaks all mirror symmetries. This transformation becomes energetically favorable as the cluster size increases. Other chiral nanoalloys, belonging to a different structural family of C(5) group symmetry, are found in the size range between 100 and 200 atoms. High-symmetry chiral nanoalloys associate strong energetic stability with potential for applications in optics, catalysis, and magnetism.

Based on l,l'-binaphthalene-2,2'-diol 1. that is considered the prototype of the class of "man-made" chiral auxiliaries possessing C2 symmetry, a variety of other chiral molecules containing the binaphthyl or biphenyl skeleton has been developed. Among them, 1 ,l'-binaphthalene- 2,2'-dithiol 2 is the one that has experienced the largest assortment of applications. "Man made" chiral auxiliaries are becoming increasingly popular over the classic auxiliaries directly derived from the natural chiral pool. Especially popular are those based on the binaphthyl skeleton (1) not only because of the high degree of optical induction that they provide, but also because these molecules incorporate a number of features that "natural" chiral auxiliaries rarely possess. For example, the high-symmetry chirality (C2-symmetry), the direct attachment of the functional groups to an aromatic system, the high crystallinity, the simple spectra, the possibility to access both enantiomers and the versatility to attach almost any functional group make them suitable for any occasion. Well known representative examples of this class of molecules are l.l'-binaphthalene-2,2'- diol 1 (2) and the dithiol2 (3).

The utility of high-symmetry, doubly substituted organosulfur compounds as chiral auxiliaries in asymmetric reactions is described.

The generalized hidden local symmetry (GHLS) model is the chiral model of pseudoscalar, vector, and axial vector mesons and their interactions. It contains also the couplings of strongly interacting particles with electroweak gauge bosons. Here, GHLS model is confronted with the ALEPH data on the decay ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\nu}}_{\ensuremath{\tau}}$. It is shown that the invariant mass spectrum of final pions in this decay calculated in GHLS framework with the single ${a}_{1}(1260)$ resonance disagrees with the experimental data at any reasonable number of free GHLS parameters. Two modifications of GHLS model based on inclusion of two additional heavier axial vector mesons are studied. One of them, which gives a good description of the ALEPH data with all the parameters kept free, is shown to result in very large ${\ensuremath{\Gamma}}_{{a}_{1}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\gamma}}$ partial width. The other scheme with the GHLS parameters fixed in a way that the universality is preserved and the observed central value of ${\ensuremath{\Gamma}}_{{a}_{1}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\gamma}}$ is reached, which results in a good description of the three pion spectrum in ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ decay.

Based on l,l'-binaphthalene-2,2'-diol 1. that is considered the prototype of the class of "man-made" chiral auxiliaries possessing C2 symmetry, a variety of other chiral molecules containing the binaphthyl or biphenyl skeleton has been developed. Among them, 1 ,l'-binaphthalene- 2,2'-dithiol 2 is the one that has experienced the largest assortment of applications. "Man made" chiral auxiliaries are becoming increasingly popular over the classic auxiliaries directly derived from the natural chiral pool. Especially popular are those based on the binaphthyl skeleton (1) not only because of the high degree of optical induction that they provide, but also because these molecules incorporate a number of features that "natural" chiral auxiliaries rarely possess. For example, the high-symmetry chirality (C2-symmetry), the direct attachment of the functional groups to an aromatic system, the high crystallinity, the simple spectra, the possibility to access both enantiomers and the versatility to attach almost any functional group make them suitable for any occasion. Well known representative examples of this class of molecules are l.l'-binaphthalene-2,2'- diol 1 (2) and the dithiol2 (3).

The title organosulfur compounds 1 and 2 were prepared via Newman-Kwart rearrangment of the tetrathiocarbamate of 2,2′,6,6′-tetrahydroxybiphenyl. The 2,2′,6,6′-tetramercaptobiphenyl 3a, hitherto unknown, is not stable and it oxidizes easily to the bisdisulfide 1. An X-ray crystallographic analysis of 1 is reported.

It is shown that there must exist degenerate parity doublets of heavy mesons with arbitrary spin if QCD possesses both heavy quark and chiral symmetries. The chiral symmetric pahase and chiral broken phase can be dynamically turned in the Bethe-Salpeter approach. In the chiral broken phase the mass splittings of the parity doublets can be calculated and they are proportional to the constituent mass [ital m] of the light quark to order [ital m]/[Lambda][sub [chi]].

Physical review letters 130(7), 071602 (2023). doi:10.1103/PhysRevLett.130.071602, We study coupled unitary Virasoro minimal models in the large rank (m→∞) limit. In large m perturbation theory, we find two nontrivial IR fixed points which exhibit irrational coefficients in several anomalous dimensions and the central charge. For N>4 copies, we show that the IR theory breaks all possible currents that would otherwise enhance the Virasoro algebra, up to spin 10. This provides strong evidence that the IR fixed points are examples of compact, unitary, irrational conformal field theories with the minimal amount of chiral symmetry. We also analyze anomalous dimension matrices for a family of degenerate operators with increasing spin. These display further evidence of irrationality and begin to reveal the form of the leading quantum Regge trajectory., Published by APS, College Park, Md.

We study coupled unitary Virasoro minimal models in the large rank ($m \rightarrow \infty$) limit. In large $m$ perturbation theory, we find two non-trivial IR fixed points which exhibit irrational coefficients in several anomalous dimensions and the central charge. For $N>4$ copies, we show that the IR theory breaks all possible currents that would otherwise enhance the Virasoro algebra, up to spin 10. This provides strong evidence that the IR fixed points are examples of compact, unitary, irrational CFTs with the minimal amount of chiral symmetry. We also analyze anomalous dimension matrices for a family of degenerate operators with increasing spin. These display further evidence of irrationality and begin to reveal the form of the leading quantum Regge trajectory.