Neutral diorganotin compounds of the 1,3-dithiole-2-thione-4,5-dithiolate ligand have been prepared. The syntheses of Me₂Sndmit, Et₂Sndmit, Bu₂Sndmit, (C₈H₁₇)₂Sndmit, (C₁₀H₂₁)₂Sndmit and (C₁₄H₂₉)₂Sndmit are described. For the purposes of indicating the formation of different structural phases, D.S.C. powder patterns are reported for initial and recrystallised samples of Me₂Sndmit, Et₂Sndmit and Bu₂Sndmit. Since Et₂Sndmitshowed different tin environments by solid phase state N.M.R. and clearly different powder patterns after recrystallisation, the compound was recrystallised from various solvents in an attempt to determine how many crystalline forms exist. To date, two forms have been identified: orthorhombic and monoclinic. The single crystal X-ray structure analyses of these are described. It has also been shown that upon heating a transition from the orthorhombic to the monoclinic form occurs at 140°C. The crystal strict of Me₂Sndmit has also been determined and is reported, along with Mossbauer parameters for Me₂Sndmit and Me₂Sndmio (dmio = 1,3-dithiole-2-one-4,5-dithiolate). Anionic organotin bis-dmit complexes of the form [RSn(dmit)₂][Q]⁺ have also been prepared, with a view to investigating their electrochemical properties. The syntheses of complexes with R chain length ranging from 4 to 18 carbons are described. The problem of formation of [Sn(dmit)₃][Q]₂ is also discussed. D.S.C. curves and cyclic voltammograms for [C₁₄H₂₉Sn(dmit)₂][C₁₄H₂₉NMe₃] and [NEt₄][(dmit)₂SnC₁₀H₂₀Sn(dmit)₂][NEt₄] are also described. Chiral macrocycles have potential uses as catalysts for asymmetric bond-forming reactions and as selective to metal ions. A chiral macrocyclic derivative of dmit was synthesised from methyl-4,6-<I>O</I>-benzylidene-2,3-bis-<I>O</I>-[(2-iodoethoxyethyl)-ethyl]-α-D-glucopyranoside. Since reaction of this with dmit proved to be unexpectedly problematic, attempted reactions of the sugar derivative with Na₂dmit<I> in situ</I>, isolated Na₂dmit, [Zn(dmit)₂][NEt₄]₂, [Ph₂Sn(dmit)I][NEt₄] and Cs₂dmit are described.

No / This paper reports on the growth of benzamide crystals in the presence of 2'-aminoacetophenone. The resulting self-replicating intergrowth of benzamide crystals gives rise to ordered crystal aggregates in which individuals share a common c*. This behavior is interpreted using the concept of a motif capper additive which is able to halt the extension of structural motifs at the surface of a growing crystal. In this case the additive was selected to terminate the hydrogen-bonding ribbons, which extend along the b axis of the benzamide structure.

Hydrocarbon chains are a basic component in a number of systems as diverse as biological membranes, phospholipids and polymers. A better understanding of the physical properties of n-alkane chains should provide a better understanding of these more complex systems. With this aim, vibrational spectroscopy has been extensively used. This technique, sensitive to molecular details, is the only one able to both identify and quantify conformational disorder present in paraffinic systems. To achieve this, methyl deformations have been widely used as "internal standards" for the normalisation of peak areas. However, in the case of n-alkanes with short chain length, such as n-C[44]H[90] for example, the infrared spectra recorded at liquid nitrogen temperature and reported here show the sensitivity of these latter peaks to the various crystal structures formed. Indeed, the main frequencies of the symmetric methyl bending mode were found between 1384 cm[-1] and 1368 cm[-1] as a function of the crystal form. Changes in the frequency of the first order of the L.A.M. present in the Raman spectra were also observed. At higher temperatures, non all-trans conformers, inferred from different infrared bands present in the wagging mode region, were found to be essentially placed at the end of the n-alkane chains. At the monoclinic phase transition, the concentration of end-gauche conformers, proportional to the area of the infrared band at 1342 cm[-1], increases abruptly. On the contrary, in the spectra recorded at liquid nitrogen temperature no such band is observed. We also studied the degree of disorder in two purely monodisperse long chain n-alkanes, namely n-C[198]H[398] and n-C[246]H[494]. The chain conformation as well as the tilt angle of the chains from the crystal surfaces were determined by means of low frequency Raman spectroscopy and S.A.X.S. measurements on solution-crystallised samples. The increase in the number of end-gauche conformers which was expected to occur with the increase of the tilt angle as a function of the temperature was not detected due to a perfecting of the crystals. Indeed, due to successive heating and cooling to -173&deg;C, the concentration of non all-trans conformers was found to decrease within the crystals. Their numbers were found to be up to six times higher in n-C[198]H[398] crystallised in once folded form than when crystallised in extended form. The C-C stretching mode region of the spectra was used to identify the chain conformation and to estimate the length of the all-trans stem passing through the crystal layers at -173&deg;C. The transition between once folded and extended form crystals was indicated by the presence of additional bands in this region at 1089 cm[-1], 1078 cm[-1] and 1064 cm[-1]. Some of those bands may be related to the fold itself. At the same time, a strong decrease of the intensity of the infrared bands present in the wagging mode region was observed. Finally, the triple layered structure proposed on the basis of X-ray measurements obtained from the crystals of a binary mixture of long chain n-alkanes, namely n-C[162]H[326] and n-C[246]H[494], was confirmed from the study of the C-C stretching mode region of the infrared spectra.

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