On The Universality Class Of Little String Theories

We propose that Little String Theories in six dimensions are quasilocal quantum field theories. Such field theories obey a modification of Wightman axioms which allows Wightman functions (i.e. vacuum expectation values of products of fundamental fields) to grow exponentially in momentum space. Wightman functions of quasilocal fields in x-space violate microlocality at short distances. With additional assumptions about the ultraviolet behavior of quasilocal fields, one can define approximately local observables associated to big enough compact regions. The minimum size of such a region can be interpreted as the minimum distance which observables can probe. We argue that for Little String Theories this distance is of order {\sqrt N}/M_s.Comment: 25 pages, late

Intramolecular O -> Te and N -> Te coordination bonds in molecules of beta-tellurocyclohexenals and their nitrogen analogs

The structures of beta-tellurocyclohexenals and their nitrogen analogs, viz., beta-methyl-tellurocyclohexenal (6), beta-(4-ethoxyphenyltelluro)cyclohexenal (7), di(2-formylcyclohexen-1-yl) telluride (8), beta-(4-ethoxyphenyltelluro)cyclohexenylidene(4'-methylaniline) (9), beta-bromotellurenylcyclohexenylidene(4'-methylaniline) (10), and beta-bromotellurenylcyclohexenal (4-methylbenzoyl)hydrazone (11), were studied by X-ray diffraction analysis. Compounds 6-11 have a Z configuration at the double bond, which provides the formation of intramolecular O-->Te or N-->Te coordination bonds. The bonds about the Te atom have a T-shaped configuration. There is only one of two possible O-->Te coordination bonds in dialdehyde 8 and, consequently, this compound belongs to the 10-Te-3-tellurane structural type. Hydrazone 11 possesses both N-->Te and O-->Te intramolecular coordination bonds. Taking into account these interactions, the coordination polyhedron of the tellurium atom can be considered as a trigonal bipyramid. The intramolecular O-->Te or N-->Te coordination bond lengths in compounds 6 (2.692 Angstrom), 7 (2.657 Angstrom), 8 (2.657 Angstrom), and 9 (2.690 Angstrom) are 0.9-1.0 Angstrom smaller than the sums of the van der Waals radii of the corresponding atoms. These bond lengths in compounds 10 (2.170 Angstrom) and 11 (2.203 Angstrom) are almost equal to the standard covalent bond length

Synthesis and structure of N-arylimines of beta-tellurocyclohexenals with the intramolecular coordination N -> Te bonds

A series of N-arylimines of beta-tellurocyclohexenals 11 have been synthesized and the molecular and crystal structures of the compounds 11a-e and also beta-(dimethyltelluronium)cyclohexenal perchlorate 12 studied by X-ray crystallography. All the compounds contain strong intramolecular coordination N --> Te (O --> Te) bonds of the hypervalent type. In 11a-e, the lengths of the N --> Te bonds are within the range of 2.690-2.147 Angstrom and are 1.0-1.5 Angstrom shorter than the sum of the van der Waals radii of respective atoms. In the N-arylimines 11a-e with the electronegative groups attached to the tellurium center, the lengths of the N --> Te bonds are very close to that characteristic of a standard covalent N-Te bond. The experimental observed geometries are well reproduced by the DFT calculations performed at B3LYP/LanL2DZ level of approximation. The energies of the intramolecular coordination N --> Te bonds vary from 23 kJ mol(-1) for 11a to 119 kJ mol(-1) for 11e. The calculated energy of the O --> Te bond in 12 was found to be 50 kJ mol(-1). The Te-125 NMR chemical shifts of compounds 11 span the wide range of 734.3-1622.4 ppm. The largest downfield Te-125 NMR chemical shifts are observed in the case of the compounds 11e, f in which the most electronegative atoms are attached to the tellurim centers

Potentional photomagnetic materials based on cation photochromic mononitrosyl complex of ruthenium

The synthesis of a series of novel compounds containing the photochromic mononitrosyl cation [ Ru(NH$_{3})_{5}$NO] $^{3+}$ and metal complex paramagnetic anions : [ Ru(NH$_{3})_{5}$NO] [ M(CN)$_{6}$] (M= Cr (1), Fe (2)), [ Ru(NH$_{3})_{5}$NO] [ Cr(CN)$_{5}$NO] (3), [ Ru(NH$_{3})_{5}$NO] [ M(ox)$_{3}$] (M=Cr (4), Fe (5)) is reported. The crystal structure of salt 1 is discussed. The magnetic properties of 1 and 4 compounds studied by EPR and SQUID experimental techniques are presented. Key words. Photochromism, X-ray analysis, Mononitrosyl complexes, Hexacyanometallate, Magnetic properties

A novel anion-radical salt (N-Et-2.5-di-Me-Pz)(TCNQ)₂ (Pz is pyrazine)

Synthesis, structure and properties of the new tetracyanoquinodimethane anion-radical salt (ARS) having the composition (N-Et-2.5-di-Me-Pz)(TCNQ)₂ (Pz is pyrazine) are reported. The compound has a layered structure where conducting anion-radical layers formed by TCNQ alternate with non-conducting cation layers along the a axis. The charges of TCNQ particles in the stack alternate, i.e. are localized appreciably, which can account for a rather unusual temperature dependence of electric resistance. Such a peculiarity of structure renders to the ARS electronic system a somewhat two-dimensional character that is unusual for TCNQ ARS and agrees with the electrophysical measurements.Описаны синтез и свойства новой анион-радикальной соли (АРС) тетрацианохинодиметана состава (N-Et-2,5-di-Me-Pz)(TCNQ)₂ (Pz - пиразин). Соединение имеет слоистую структуру, в которой проводящие анион-радикальные слои, образованные TCNQ, чередуются с непроводящими катионными слоями вдоль оси a. 3аряды частиц TCNQ в стопках альтернируют, то есть, заметно локализованы, что может быть причиной необычной температурной зависимости электросопротивления. Такая особенность структуры придает электронной системе АРС определенную двумерность, необычную для АРС TCNQ, и согласуется с результатами электрофизических измерений.Описано синтез та властивостi нової анiон-радикальної солi (АРС) тетрацiанохiнодiметану складу (N-Et-2,5-дi-Me-Pz)(TCNQ)₂ (Pz - пiразин). Сполука має шарувату структуру, в якiй провiднi анiон-радикальнi шари, утворенi TCNQ, чередуються з непровiдними катiонними шарами уздовж осi a. 3аряди часток TCNQ в стопках альтернують, тобто, суттєво локалiзованi, що може бути причиною незвичайної температурної залежностi електроопору. Така особливiсть структури додає електроннiй системi АРС певну двомiрнiсть, незвичайну для АРС TCNQ, i добре узгоджується з результатами електрофiзичних вимiрiв

Synthesis, Structure and Magnetic Properties of Mn<inf>2</inf>Tb<inf>2</inf> Tetranuclear Complex with p-tert-Butylthiacalix[4]arene

© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A new tert-buthylthiacalix[4]arene-based tetranuclear 3d-4f metal complex with the Mn2Tb2 core has been synthesized and its molecular and crystal structures have been studied by X-ray diffraction. The complex geometry is similar to that of the earlier synthesized tert-buthylthiacalix[4]arene-based M2Ln2 complexes with M=Mn(II), Co(II), and Ln=Gd, Pr, Eu, but unlike those systems, it exhibits intricated cooperative low-temperature magnetic properties arising from the presence of intercluster interactions. At T<8.5 K the complex shows weak spin-canted ferromagnetism and field induced metamagnetic phase transition. The paramagnetic behavior observed at temperatures higher than 8.5 K is similar to that previously reported for the Mn2Gd2 complex, this being indicative of the existence of competitive ferro- and antiferromagnetic intracluster interactions

Experimental and theoretical study of the influence of peripheral environment on magnetic properties of tetranuclear manganese skeleton in new representatives of calix[4]arene-containing [MnII2 MnIII2] clusters

A new representative of calix[4]arene-containing tetranuclear manganese complexes of [Mn2IIIMn2II] type with 2,2′-dipyridyl bidentate ligand coordinated in the equatorial plane of the complex (II) has been obtained. The complex is crystallized in monoclinic space group P21/c (a = 14.9402(7) Å, b = 32.816(1) Å, c = 21.595(1) Å, β = 106.888(4)). Its magnetic properties have been studied by the method of SQUID magnetometry. The substitution of a peripheral ligand was shown to influence substantially on the structure of the central fragment of the metal complex, and, hence, on the magnetic properties. Quantum-chemical calculations were performed for this complex and for the similar calix[4]arene-containing manganese complex with pyridine ligand (I). The influence of peripheral environment on the magnetic properties of tetranuclear manganese skeleton was elucidated for both complexes