Facile Synthesis of New Spirothiadiazolopyridazines by 1,3‐Dipolar Cycloaddition

New derivatives of the spiro type of pyridazines have been synthesized by 1,3‐dipolar cycloaddition of N‐aryl‐C‐ethoxycarbonylnitrile imines with pyridazin‐3(2H)‐thiones. When the nitrile oxide was used, the corresponding pyridazin‐3(2H)‐one was obtained from the intermediate spirooxathiazole by elimination of isothiocyanate group. The peri‐ and regioselectivity of the reaction were ascertained by X‐ray analysis and ¹³C NMR spectroscopy of the cycloadducts 3–9.     

Crystal structure of 1,2‐[4‐butoxybenzoyloxy‐4′‐pentyl]diphenylethane

The crystal structure of 1,2‐[4‐butoxybenzoyloxy‐4′‐pentyl]diphenylethane (C₃₀H₃₆O₃) has been determined by direct methods using single crystal X‐ray diffraction data. It crystallizes in the monoclinic system with space group P2₁/a and Z?=?4. The unit cell parameters are: a?=?8.098(1), b?=?10.926(1), c?=?29.643(2)?Å and β?=?94.01(1)°. The final reliability factor is R?=?0.073 and the goodness of fit is equal to 1.027. The molecular arrangement is very typical, with molecules associated in dimers very closely parallel to the Oz axis. In a given dimer, the backbones of the two molecules run alongside each other; this association can be attributed to strong dipole–dipole interactions through the polar ester and ether groups. In addition these dimers are connected to neighbours via dipole–dipole interactions along the Oy direction. There are numerous very weak van der Waals interactions, particularly between the terminal aliphatic chains.     

A doubly folded spacer in a self-assembled hybrid material

The hydrolysis of a bridged alpha,omega-bis(trialkynylstannylated) compound leads to a hybrid material ordered by self-assembly where the spacer forms two six-membered [1,2]oxastanninane rings by intramolecular coordination.     

Conformational behaviour of laterally dialkoxy branched mesogens. Part one

The crystal structures of two mesogenic compounds having two neighbouring lateral alkoxy chains in the central part of the molecules have been solved. In both structures, the common four ring central core is extended and quite rigid with a total length close to 28.5 Å. All the molecules are strictly parallel because of the P1 space group; the molecular arrangement is characteristic of a nematogenic system. In these structures, the lateral alkoxy chains are folded back to the core; they exhibit slightly different conformations and are quite disordered. The ¹³C chemical shift of the first -OCH₂- within the lateral chains can probe the mean conformation of the chain in the nematic phase. This chemical shift is independent of the compound. Nevertheless, in the solid phase, this chemical shift is dependent on small geometrical changes due to the influence of the oxygen in the neighbouring lateral chain. In addition, temperature cycling of the sample leads to different crystalline solid forms as evidenced by DSC and NMR studies.     

Evidence for lateral chain conformation change in the solid phase of substituted nematogens

A new homologous series of 4-(4-chlorobenzoyloxy)-2-alkoxy-3-methyl-4'-(4-trans-pentyl-cyclohexanoyloxy) azobenzenes has been synthesized. These compounds contain four rings in the main core, a lateral alkoxy branch and an adjacent lateral methyl group on one inner ring. They present a large nematic range and a solid-solid phase transition for the first members of the series. The crystal structures of two similar compounds containing a lateral butoxy chain have been solved. The HM4 compound (C₃₁H₃₃N₂O₅Cl) is derived from the series, but does not have the terminal pentyl chain while the PM4 compound (C₃₆H₄₃N₂O₅Cl) possesses this terminal chain. HM4 and PM4 crystallize, respectively, in P2₁/c (Z = 4) and P1 (Z = 2) space groups. The final reliability factors are R = 0.138 for HM4 (the terminal cyclohexyl ring is largely disordered) and R = 0.041 for PM4, for 2204 and 1963 observed reflections, respectively. The four ring central core is linear and rigid for both compounds. The conformation of the butyloxy side chain branched on one of the central phenyl rings is very dependent on the terminal substituent, as it is found in a largely bent conformation in HM4 and in an extended conformation in PM4. To monitor the lateral chain conformation in the solid and nematic phase, we have used the -OCH₂- resonance in the ¹³C MAS NMR spectra. The temperature dependence of this resonance has indicated that the solid-solid transition encountered for the first members of the series is associated with a change of the lateral chain conformation within the solid phase. At the solid-nematic transition, the change of the chain conformation involving the first segment of the lateral chain is far less pronounced. When this solid-solid phase transition disappears for the last members of the series, this change in the conformation occurs at the solid-nematic transition.     

A generalized model for the molecular arrangement in the columnar mesophases of polycatenar mesogens. Crystal and molecular structure of two hexacatenar mesogens

The columnar mesophases of two series of hexacatenar palladium(II) mesogens have been studied in detail by a combination of X-ray diffraction on aligned and unaligned samples and dilatometry. The results of these studies, combined with the results of two single crystal structure determinations, have allowed a model of the molecular arrangement in the columnar phases to be proposed. This model differs in detail from that generally accepted for the arrangement of polycatenar mesogens in columnar phases, and a new model is proposed which accounts for both new and existing data.     

Dichlorobis(pyridine‐κN)bis(3,3,3‐trifluoropropyl‐κC1)tin(IV)

In the title compound, [Sn(C₃H₄F₃)₂Cl₂(C₅H₅N)₂], the Sn atom lies on an inversion centre and is octahedrally coordinated by two Cl atoms, two tri­fluoro­propyl groups and two N atoms in an all‐trans configuration. The electronegative tri­fluoro­propyl groups increase the electrophilic properties of the Sn atom, and the Sn—Cl and Sn—N bonds are shortened in comparison with those reported for analogous compounds.