187,553 research outputs found
The Role of PSL(2, 7) in M‐theory: M2‐Branes, Englert Equation and the Septuples
No full textReconsidering the M2-brane solutions of (Formula presented.) supergravity with a transverse Englert flux introduced by one of us in 2016, we present a new purely group theoretical algorithm to solve Englert equation based on a specific embedding of the PSL(2, 7) group into (Formula presented.). The aforementioned embedding is singled out by the identification of PSL(2, 7) with the automorphism group of the Fano plane. Relying on the revealed intrinsic PSL(2, 7) symmetry of Englert equation and on the new algorithm we present an exhaustive classification of Englert fluxes. The residual supersymmetries of the corresponding M2-brane solutions associated with the first of the 8 classes into which we have partitioned Englert fluxes are exhaustively analyzed and we show that all residual (Formula presented.) supersymmetries with (Formula presented.) are available. Our constructions correspond to a particular case in the category of M2-brane solutions with transverse self-dual fluxes
Multinuclear and Dynamic NMR Study of trans-[Pt(Cl)(PHCy2)2(PCy2)], [Pt(Cl)(PHCy2)3][BF4], [Pt(Cl)(PHCy2)3][Cl], trans-[Pt(Cl)(PHCy2)2{P(S)Cy2}], and trans-[Pt(Cl)(PHCy2)2{P(O)Cy2}]. Influence of Intramolecular PO···H−P and Cl···H−P Interactions on Restricted Rotation about Pt−P Bond. X-ray Structure of trans-[Pt(Cl)(PHCy2)2{P(O)Cy2}]
No full textDynamic NMR experiments on trans-[Pt(Cl)(PHCy2)(2){P(X)Cy-2}](z) where X is a lone pair (1, z = 0), H (2, z = + 1), S (3, z = 0), or 0 (4, z = 0) show that the rotation around the P(X)-Pt bond is hindered for all molecules studied, with Delta(double dagger) ranging from 8.2 to 11.0 kcal/mol. The highest value of the series was calculated for trans-[Pt(Cl)(PHCy2){P(O)Cy-2}] (4) where intramolecular P=(OH)-H-...-P interactions act as a molecular brake at room temperature. Single-crystal X-ray diffraction confirms the presence of both intra and intermolecular P=(OH)-H-... interactions in solid 4. In the case of [Pt(Cl)(PHCy2)(3)]Cl, multinuclear NMR analysis indicates the presence of a P-(HCl-)-Cl-... interaction in aromatic or halogenated solvents which could have also a minor effect on the rotational barrier around the P(X)-Pt bond
Multinuclear and Dynamic NMR Study of trans-[Pt(Cl)(PHCy2)2(PCy2)], [Pt(Cl)(PHCy2)3][BF4], [Pt(Cl)(PHCy2)3][Cl], trans-[Pt(Cl)(PHCy2)2{P(S)Cy2}], and trans-[Pt(Cl)(PHCy2)2{P(O)Cy2}]. Influence of Intramolecular P=O···H-P and Cl···H-P Interactions on Restricted Rotation about Pt-P Bond. X-ray Structure of trans-[Pt(Cl)(PHCy2)2{P(O)Cy2}]
No full textDynamic NMR expts. on trans-[Pt(Cl)(PHCy2)2{P(X)Cy2}]z where X is a lone pair (1, z = 0), H (2, z = +1), S (3, z = 0), or O (4, z = 0) show that the rotation around the P(X)-Pt bond is hindered for all mols. studied, with G.thermod. ranging from 8.2 to 11.0 kcal/mol. The highest value of the series was calcd. for trans-[Pt(Cl)(PHCy2)2{P(O)Cy2}] (4) where intramol. P:OH-P interactions act as a mol. brake at room temp. Single-crystal x-ray diffraction confirms the presence of both intra and intermol. P:OH interactions in solid 4. In the case of [Pt(Cl)(PHCy2)3]Cl, multinuclear NMR anal. indicates a P-HCl- interaction in arom. or halogenated solvents which could have also a minor effect on the rotational barrier around the P(X)-Pt bond
Fermion masses for the Englert solution on the round seven-sphere
No full textUsing a mass formula for Englert-type solutions on arbitrary coset spaces, we have found that if the coset is the round S7, no massless fermions exist. For this purpose we develop a method to decompose SO(8) representations with respect to spin(7), which enables us to compute the eigenvalues of the spin(7)-invariant differential operators in the mass matrix by using algebraic identities satisfied by them
Self-consistent assessment of Englert-Schwinger model on atomic properties
No full textOur manuscript investigates a self-consistent solution of the statistical atom model proposed by Berthold-Georg Englert and Julian Schwinger (the ES model) and benchmarks it against atomic Kohn-Sham and two orbital-free models of the Thomas-Fermi-Dirac (TFD)-λvW family. Results show that the ES model generally offers the same accuracy as the well-known TFD-15vW model; however, the ES model corrects the failure in the Pauli potential near-nucleus region. We also point to the inability of describing low-Z atoms as the foremost concern in improving the present model.Peer reviewe
Niobium(I) and tantalum(I) tetracarbonyl derivatives containing nitrogen ligands
No full textDiamino derivatives of niobium(l) and tantalum(l) of general formula MX(CO)4(NN), MNb, Ta; XCl, 1; NNethylendiamine
(en), N,N%dimethylethylendiamine (dmen), N,N,N%,N%-tetramethylethylendiamine (tmen), 2,2-dipyridyl (2,2%-dipy), 4,4%-
dipyridyl (4,4%-dipy), have been prepared by oxidation of the [M(CO)6] anions with either 1,1%-dimethyl-4,4%-dipyridilium
diiodide (methylviologen, mvI2) in the presence of the diamine or the diprotonated salt of the corresponding diamine,
[(NN)H2]Cl2. Alternatively, these derivatives have been obtained by amine exchange reactions on [MCl(CO)4(4,4-dipy)]n or by
chloride substitution on the dinuclear anion [Nb2(m-Cl)3(CO)8]. The MX(CO)4(NN) derivatives have been characterized by
analytical, spectroscopic and, in the case of TaI(CO)4 (tmen), also by single crystal diffractometry. Crystal data. TaI(CO)4(tmen),
monoclinic, space group P21:c (No. 14); a16.222 (5); b12.855 (3); c16.452 (6) A°
, b117.67 (2)°, M536.10 g mol1;
V3038.4 (1) A°
3; Z8; Dc2.344 g cm3; l0.7107 A°
; T203 K; m91.71 cm1; F(000)1984; R0.045; Rw0.048
Synthesis and Carbonylation of Platinum(II) Organometallic Complexes with Bis(phosphanyl) Monosulfides − Crystal Structures of [κ2P,S-{Ph2CH2P(S)Ph2}Pt(CH3)(Cl)] and [κP,μ-κS-{Ph2CH2CH2P(S)Ph2}Pt-(CH3)]2[BF4]2
No full textThe neutral complexes of formula [kappa(2)P,S-(dppmS)Pt(CH3)(Cl)] (1) and [kappa(2)P,S-(dppeS)Pt(CH3)(Cl)] (2) [dppmS = Ph2PCH2P(S)Ph-2, dppeS = Ph2P(CH2)(2)P(S)Ph-2] have been synthesised and characterised. Reaction of 1 and 2 with AgBF4 carried out in CH3CN or CH3CN/CH2Cl2 affords the corresponding monomeric cationic complexes [kappa(2)P,S-(dppmS)Pt(CH3CN)(CH3)][BF4] (3) and [kappa(2)P,S-(dppeS)Pt(CH3CN)(CH3)][BF4] (4). Complexes 3 and 4 partially dissociate in CD2Cl2, giving, in the case of 3, the asymmetric dimer {[kappa(2)P,S-(dppmS)](CH3)Pt{kappaP,mu-kappaS-(dppmS)}Pt(CH3)(CH3CN)][BF4](2) (5), and, in the case of 4, the symmetrical sulfur-bridged dimer [kappaP,mu-kappaS-(dppeS)Pt(CH3)](2)[BF4](2) (6). Pure 6 can be obtained by heating 4 under vacuum. Exposing CD2Cl2 solutions of the cationic complexes 3 and 4 to CO at ambient conditions brings about the formation of the monomeric methyl carbonyl complexes [kappa(2)P,S-(dppmS)Pt(CO)(CH3)][BF4] (CO trans to P, 7a) and [kappa(2)P,S-(dppeS)Pt(CO)(CH3)][BF4] (CO trans to P, 8a), which slowly transform into their CO cis to P isomers 7b and 8b, respectively. The single-crystal X-ray diffraction studies of 1(.)CD(2)Cl(2) and 6(.)2CD(2)Cl(2) are reported. Mass spectrometric analyses with APCI and ESI interfaces were also performed for all new complexes
Synthesis and characterization of homologous nickel(II) and palladium(II) complexes with biphosphine monoxide ligands Ph2P(CH2)nP(O)Ph2 (n = 1–3) and pTol2P(CH2)P(O)pTol2
No full textA series of cationic nickel complexes [(η3-methally)Ni(P∧P(O))]SbF6 (1–4) [P∧P(O) = Ph2P(CH2)P(O)Ph2 (dppmO) (1), Ph2P(CH2)2P(O)Ph2 (dppeO) (2), Ph2P(CH2)3P(O)Ph2 (dpppO) (3), pTol2P(CH2)P(O)pTol2 (dtolpmO) (4)] has been synthesized in good yields by treatment of [(η3-methally)NiBr]2 with biphosphine monoxides and AgSbF6. The ligands are coordinated in a bidentate way. Starting from [(η3-all)PdI]2 the cationic complexes [(η3-all)P∧P(O))]Y (8–14). [P∧P(O) = dppmO, dppeO, dpppO, dtolpmO;Y = BF4, SbF6, CF3SO3, pTolSO3] were synthesized in good yields. The coordination mode of the ligand is dependent on the backbone and the anion, revealing a monodentate coordination with dppmO for stronger coordinating anions. The intermediates [(η3-all)Pd(I)(P∧P(O)-κ1-P)] (5–7) [P∧P(O) = dppmO (5), dppeO (6), dtolpmO (7)] were isolated and characterized. Neutral methyl complexes [(Cl)(Me)Pd(P∧P(O))] (15–18). [P∧P(O) = dppmO (15), dppeO (16), dpppO (17), dtolpmO (18)] can easily be obtained in high yields starting from [(cod)PdCl2]. For dppmO two different routes are presented. The structure of [(Me)(Cl)Pd{;Ph2P(CH2-P(O)Ph2-κ2-P,O};] · CH2Cl2 (15) with the chlorine atom trans to phosphorus was determined by X-ray diffraction
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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