The formation of either dinuclear double-stranded or pentanuclear circular helicates from a ligand containing two tridentate domains separated by a phenylene unit can be controlled by inter-ligand steric interactions which themselves are governed by the size of the metal ion.Controlling the structure of multi-component assemblies is one of the leading challenges for the supramolecular chemist. One of the simplest assemblies is the dinuclear doublestranded helicate, and the rules that govern the formation of this species are largely established. [1][2][3][4][5][6][7] The formation of the helicates' higher nuclearity cousin, the cyclic helicate, is conversely less well understood. One of the major problems in the formation of these higher nuclearity assemblies is that the design principles that apply to helicate formation, i.e. using a ligand that contains two binding domains that coordinate different metal ions, equally apply to the formation of cyclic helicates. For the larger cyclic species to preside in solution, the formation of the entropically favoured dimer has to be prevented and this can be achieved by intermolecular interactions (e.g. templation by anions) 8 or by intramolecular interactions which stabilise the formation of the cyclic species relative to its double-stranded alternative. As an example of the first of these approaches, in the work carried out by Ward et al., a ligand with two bidentate domains separated by a 1,8-naphthalenediyl spacer was reported to form a simple mononuclear species with Cu(CF 3 SO 3 ), but in the presence of tetrafluoroborate, a tetranuclear cyclic helicate [Cu 4 L 4 ] 4+ was observed. 9 Hannon et al., on the other hand, demonstrated that a metal ion's preference for different coordination geometries could affect the self-assembly outcome. In this case a bis-bidentate ligand containing a 1,3-bis(aminomethyl)phenyl spacer formed linear dimers with tetrahedral metal ions and trinuclear circular helicates with octahedral metal ions. 10 Other reports have cited inter-strand CHÁ Á Áp interactions as the principal driving force for the preferential formation of high complexity cyclic assemblies over their dimeric In this communication we describe how the formation of either dinuclear double-stranded or pentanuclear circular helicates can be controlled by inter-ligand steric interactions which, in turn, are governed by the size of the metal ion. This approach allows for the specific formation of either of the two structures and gives valuable insight into some of the factors which control the formation of cyclic helicates.The ligand L 1 , which was prepared by the reaction of 2,2 0 -bipyridine-6-thioamide with 1,3-di(a-bromoacetyl)benzene, contains two tridentate binding domains separated by a phenylene ring (Fig. 1) was confirmed by a single crystal X-ray diffraction study (Fig. 2).z In the solid-state the ligand partitions into two tridentate domains, each comprising a thiazole-pyridyl-pyridyl

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A systematic investigation has been carried out into the effect of different reaction parameters on the oxidation of oct-1-ene by manganese(iii) acetate in acetic acid and acetic anhydride. The most important factor in dictating the ratio of products is the composition of the solvent. In the absence of anhydride y-decanolactone is virtually the sole product. Even small quantitites of anhydridy lead to the lactone being replaced b y other products derived from cationic intermediates C, H, ,CHCH,COX (X = OH or OAc). Further increases in the amount of anhydride encourage the formation of decanoic acid until, in 90% anhydride, this becomes the predominant product. The results cannot be interpreted simply in terms of competition for the alkene by the radicals *CH,CO,H and *CH,COOCOCH,. Decanoic acid formation is also favoured by low temperatures, low concentration of oxidants, and by the addition of acetate ions. A comparision is made of the efficiency of addition when the initiating species is manganese( 111) or a peroxide.

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There is a requirement for reliable real-time analytical tools for reaction monitoring to optimise chemical syntheses. We have developed a new technique which combines thermal analysis, digital microscopy and chemical identification using ambient ionisation mass spectrometry. We term this hot-stage microscopy-Direct Analysis in Real-Time mass spectrometry (HDM). The technique provides optical data as a function of temperature coupled with chemical characterisation of evolved species, including reactants, intermediates and products throughout the course of a reaction.In addition, only a few milligrams of sample are required with analyte detection down to the nanogram range. We demonstrate the benefits of HDM using a series of solventfree reactions. Our results confirm the suitability of the technique as the reactions studied follow the same pathways as published previously. The accurate temperature control achieved with HDM could also be used to assess the optimum temperature at which thermally-driven reactions can proceed efficiently.