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The novel title furazan-containing macrocycle (systematic name: 6,9,14,17-tetraoxa-2,3,5,7,16,18-hexaazatricyclo[13.3.0.- 04.8]octadeca-4,7,15,18-tetraene), C8H10N6O4, (I), is the first macrocycle where the furazan rings are connected via a hydrazine group. In spite of the strain in the 12-membered macrocycle of (I), the geometry of the furazan fragment is the same in (I) and in its acyclic analogue 1,8-bis(5-aminofurazan-4-yloxy)-3,6-dioxaoctane, C10H16N6O6, (II). In both compounds, the participation of the furazan rings in intermolecular hydrogen bonding equalizes the N-O bonds within the furazan rings, in contrast with rings which do not participate in such interactions. [ABSTRACT FROM AUTHOR]

The low-temperature study of the title compound, (C36H30NP2)2[Cu2Br4], revealed the nature of rotational disorder which has been observed at room temperature for the [Cu2Br4]2− anion. The centrosymmetric anion has a planar structure with slightly distorted trigonal coordination of the Cu atoms. [ABSTRACT FROM AUTHOR]

Abstract: Novel radial tetra(ferrocenyl)- and tetra(cymantrenyl)cyclobutadienecobalt complexes were prepared by metal carbonyls free protocol of [2 + 2] cycloaddition reaction of 1,2-diferrocenyl- or 1,2-dicymantrenylethynes with chlorotris(triphenylphospine)cobalt(I) and carboethoxycyclopentadienide sodium with good yields. The molecular structure of these products was confirmed with X-ray analysis, and their electrochemical behavior was studied. [Copyright &y& Elsevier]

Abstract: The annular tautomeric equilibrium of two 4-cyano-3(5)-aminopyrazoles having hydrogen atom or methyl group in position 5(3) was studied by X-ray crystallography for the solid compounds and by DFT B3LYP/6-31G** and CBS-QB3 calculations for the free molecules. The 3-amino tautomer was found to be the more favorable form for the free molecules and the sole form in the solid state. [Copyright &y& Elsevier]

Abstract: (3E,5E)-3,5-Bis(benzylidene)-4-oxopiperidinium tetrafluoroborate [C19H18NO][BF4] (1), (3E,5E)-3,5-bis[4-(dimethylammonio)benzylidene]-4-oxopiperidinium bearing mixed tetrafluoroborate and bis(hexafluoro(μ-hydroxo)diborate) anions [C23H30N3O][B2F6OH] n [BF4] m ·xH2O (2), and (3E,5E)-3,5-bis[4-(diethylammonio)benzylidene]-4-oxopiperidinium tris(tetrafluoroborate) monohydrate [C27H38N3O][BF4]3·H2O (3) were obtained via mediated by the boron trifluoride etherate aldol-crotonic condensation of the corresponding aldehyde and piperidin-4-one hydrochloride monohydrate. Their structures were studied by IR and multinuclear NMR spectroscopy, and single crystal X-ray diffraction. The X-ray analysis revealed the presence of monoprotonated piperidinium cation in 1 and triprotonated cations in 2 and 3. The hexafluoro(μ-hydroxo)diborate anion was found in the mixed-anionic salts 2A and 2B which differ by the ratio of the anions. The extended hydrogen-bonded system is registered in all compounds. Static first order hyperpolarizabilities for the neutral (3E,5E)-3,5-bis[4-(dimethylamino)benzylidene]-piperidin-4-one and its positively charged derivatives along with their molecular geometries and binding energy of 1 were calculated using DFT approach. [Copyright &y& Elsevier]

Abstract: Phenanthro[4,5-abc]phenazine-18-crown-6 chromophore (1) was synthesized, and its two polymorphic modifications were obtained by recrystallization from dichloromethane/methanol and dichloromethane/hexane solvent mixtures. Both polymorphs 1a and 1b crystallize in the same monoclinic P21/c space group, and represent conformational polymorphs, which differ by the conformation of the macrocyclic cavity. The crystal structures obtained have been compared with molecular structures computed by density functional theory (DFT). As revealed by quantum chemical calculations, both polymorphs reach different minima on potential energy surface that supports our results that different solvents template distinctive conformational isomers found in crystals. [Copyright &y& Elsevier]

Abstract: Molecular structures of hexakis(amino)cyclotriphosphazene, N3P3(NH2)6, neutral and cationic forms of hexakis(ethylamino)cyclotriphosphazene, N3P3(NHC2H5)6, and dicationic form of octakis(ethylamino)cyclotetraphosphazene, N4P4(NHC2H5)8, were established through the X-ray diffraction experiments at 120(2), 165(2) and 110(2)K, respectively. Geometry of the six- and eight-membered cyclophosphazene rings of the molecules are discussed with the help of B3LYP/6-311G∗∗ method/basis DFT calculations of their methylamino analogs and topological analysis of the electron density distribution. In all cases P–N bonds show high polar nature with considerable P→N charge transfer. Change of the P–N bond lengths upon the cycle protonation well correlated with the net charge redistribution at the P and N centers but separately for the endocyclic and exocyclic bonds. Presence of the additional π-bonding covalent contribution, as it is evidenced from the analysis of the bonds ellipticity, has to be suggested to explain these separate correlations. In the cyclotriphosphazene cation the finer details of the endocyclic P–N bond lengths changes can be attributed to the interplay of the variable π-bonding contribution with the change in the bond ionicity. In the crystal all compounds demonstrate large variety of bridged hydrogen bond patterns though the N–H…N and N–H…Cl interactions. [Copyright &y& Elsevier]

The suitability of 1-borabicyclo[2.2.2]octane (1) as a structural element for liquid crystals was evaluated using computational methods and experimental studies of two complexes of its close analogue 1 -boraadamantane (2). The molecular and crystal structures for 1-pyridine-1-boraadamantane [2-P, C14H20BN, P21/m, a = 8.4404(13) Å, b = 6.8469(10) Å, c 10.5269(16) Å, β = 104.7 12(3)Å, Z = 2], 1-quinuclidine-l-boraadamantane [2-Q, C16H28BN, P211n, a = 6:6529(3) U, b = 10.6665(6) Å, c = 19.3817(10) Å, b = 94.689(3)Å, Z = 4], and 1-pyridine-trimethylborane [3P, C8H14BN, Ccma, a = 6.9875(10) Å, b 15.011(2) Å, c = 16.556(2) Å, Z 8] were determined by X-ray crystallography and compared with the results of DFT and MP2 calculations. Gas-phase thermodynamic stabilities of complexes 1-P, 1-Q, 2-P, and 2-Q were estimated using a correlation between theoretical (MP2/6-3 I +G(d)/IMP2/ 6-3lG(d) with B3LYP/6-31G(p) thermodynamic corrections) and experimental data for complexesof BMe3 (3) with amines lacking N-H bonds. The analysis showed the generally higher thermodynamic stability for the quinuclidine (Q) complexes compared to that of the pyridine (P) analogues in the gas phase and an overall order of stability of 1 > 2 > 3. This order is paralleled by high ring strain energy of 1 (SE = 27 kcal/mol) as compared to that of 1-boraadamantane (2, SE = 16.5 kcal/mol). The chemical stability of 2-P and 2-Q, with respect to hydrolytic and oxidative reagents, is high for the pyridine derivative and satisfactory for the quinuclidine complex at ambient temperature, which implies sufficiently high stability of l-borabicyclo[2.2.2]octane complexes for materials applications. Molecular dipole moments of 6.2 ± 0.1 and 6.0 ± 0.15 D were measured for 2-Q and 2-P, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A detailed analysis of monodentate and bidentate complexation of tris(pentafluorophenyl)silyl (TPFS) derivatives with neutral Lewis bases was performed. The NMR spectroscopy and X-ray diffraction analysis (11 structures) were the key methods to characterize tetra- or pentacoordinate silicon compounds, whereas the peculiarities of crystal packing were analyzed by means of DFT calculations. The interaction of TPFS-X (X=F, Cl, OTf) with strong Lewis bases (HMPA, N-methylpyrrolidinone) may afford three different species: neutral pentacoordinate TPFS(X)-L, cationic tetracoordinate TPFS-L+ X−, and cationic pentacoordinate TPFS-(L)+ 2X−, representatives of each type were characterized by X-ray diffraction. A variety of complexes with bidentate complexation, featuring the trigonal bipyramidal geometry with apical C6F5-group was prepared and structurally characterized. The extent of Si–Capical bond elongation depends on the donating ability of the coordinating ligand, with the longest Si–C bond of 1.981(1)Å observed for six-membered complex of TPFS-ether of N-(2-hydroxybenzoyl)pyrrolidine. [Copyright &y& Elsevier]

We report the first structural data for bis(diarylamine) "bipolarons": we have isolated and crystallographically characterized salts of the dications obtained by two-electron oxidation of E-4,4'-bis- [di(p-anisyl)amino]stilbene and E, E-2,5-bis{4-[di(p-anisyl)amino]styryl}-3,4-di(n-butoxy)thiophene, [1 ]2+ and [2]2+ respectively. ESR, NMR, and magnetometry suggest both species have singlet ground states. X-ray structures, together with ¹H NMR coupling constants for [2]2+, indicate geometries in which the bond lengths are shifted toward a quinoidal pattern relative to that in the neutral species, but not to a fully quinoidal extent. In particular, the bond-length alternations across the vinylene bridging groups approach zero. DFT calculations with closed-shell singlet configurations reproduce the observed structures well. Our results indicate that singlet species for which one might expect quinoidal geometries (with differences of ca. 0.1 Å between formally single and double bonds) on the basis of a limiting valence-bond representation of the structure can, in fact, show structures with significantly different patterns of bond lengths. [ABSTRACT FROM AUTHOR]

Synthesis of the title compounds, viz. [RN(CH2CHR'O)2]2Ge (1, R = Me, R' = H; 2, R = Me, R' = Ph; 3, R = Ph, R' = H), by the reaction of 2 equiv of corresponding dialkanolamines RN(CH2CHR'OH)2 (4, R = Me, R' = H; 5, R = Me, R' = Ph; 6, R = Ph, R' = H) with (AIkO)4Ge is reported. Composition and structures of all novel compounds were established by ¹H and 13C NMR spectroscopy and mass spectrometry as well as elemental analysis data. The single-crystal X-ray diffraction of 2 has clearly indicated the presence of two transannular interactions Ge←N in the compound. N atoms are cis-orientated. The compound 3 possesses long Ge…N distances. The structural data obtained from geometry optimizations by DFT calculations on 1-3 reproduces experimental results. Both cis- and trans-isomers were studied, and cis-configuration was found to be more thermodynamically stable for all three compounds. The transition states for possible tis ↔ trans rearrangement processes in 1-3 were calculated. The properties of the Ge-O and Ge←N bonds in 1-3 were analyzed by the AIM approach. The interactions between the Ge atom and N atoms as well as O atoms possess predominantly ionic character. [ABSTRACT FROM AUTHOR]

A novel half-sandwich Zr(IV) complex [η5:η1-N-C5(CH3)4CH2CH2N(CH3)2]ZrCl3 (6) together with zirconocene dichlorides [η5-C5(CH3)4CH2CH2N(CH3)2][η5-C5(CH3)5]ZrCl2 (4) and [η5-C5(CH3)4CH2CH2N(CH3)2]2ZrCl2 (5) have been prepared. Complex 6 has been isolated and characterized in three different forms, namely, as an adduct with THF 6a, an adduct with tetrahydrothiophene 6b, and a solvent-free form 6c. Molecular structures of complexes 4, 6b, and 6c have been established by X-ray diffraction analysis. Complex 6c has been shown to be a monomeric solvent-free half sandwich Zr(IV) complex. The dynamic behavior of complex 6a in a non-solvating medium (an equilibrium between 6a and 6c along with a degenerate interconversion of the Zr–Ccp–CH2–CH2–N(CH3)2–(Zr) pseudo-five-member metallacycle) have been studied by the variable-temperature 1H and 13C{1H} NMR spectroscopy. The activation parameters for the degenerate five-member cycle interconversion have been elucidated. [Copyright &y& Elsevier]

Crystalline polymorphism is quite common for non-linear optical (NLO) compounds. During our studies of NLO materials we found several compounds that crystallize in two or more forms. We present a short review of our recent data on the crystalline polymorphism of NLO compounds. Among the compounds studied, we found examples of concomitant polymorphism, induced conformational polymorphism, and organic polytypism. For several compounds, X-ray data are discussed along with computational data on molecular and crystal structure energy. [Copyright &y& Elsevier]

The crystal structure and spectral properties of new Zn(ii) chelate complex with bis(2,4,7,8,9-pentamethyldipyrrolylmethen-3-yl)methane were determined by single-crystal X-ray diffraction, 1H NMR, UV and IR spectroscopy; a sufficiently high quantum yield of fluorescence in nonpolar solvents, a long-wavelength emission maximum and good photostability of the complex were demonstrated. [ABSTRACT FROM AUTHOR]