The Paraquat dication forms a 1 : 1 molecular inclusion complex both in acetone solution and in the solid state with the bisparaphenylene-34-crown-I 0 derivative (BPP34ClO) as a result of intra-complex stabilisation from charge transfer interactions as well as from hydrogen and electrostatic bonding. In the previous communication,l 1H n.m.r. spectroscopy in CD3COCD3 solution established that BPP34ClO-l is capable of complexing with [Paraquat][PF&,-t as well as with [Diquat][PF&.t In common with BMP32C10,T we noted that free BPP34C10, as revealed by the conformations (I and 11) it adopts in the solid state, has a preformed receptor cavity for substrates such as these bipyridinium dications. Not discouraged by our initial failure2 t o isolate a crystalline complex t The structural formulae for BMP32C10, BPP34C10, [Paraquat][PF612, and [Diquat][PF612 are illustrated in the three preceding communications (refs. 1-3).

U.V. and 1H n.m.r. spectroscopic studies in solution on the 1 : 1 complexes both [Paraquat][PF6I2 and [Diquat][PF612 form with the bismetaphenylene-32-crown-I 0 derivative (BMP32C10), supported by X-ray crystal structures on the free BMP32C10 and [ D ~~U ~~. B M P ~~C I O ] [ P F ~] ~. M ~~C O ,provide further fundamental understanding of the electronic and steric nature of the intermolecular noncovalent interactions that are essential to the successful design and synthesis of a molecular receptor for optimal binding of the [Paraquat]2+ dication.

X-Ray structural investigations of a bisparaphenylene-34-crown-10 derivative (BPP34C10) and its 1 : 1 : 1 complex with [Diquat][PF& and H20 reveal that, of two crystallographically independent conformations (I and II) both supporting large molecular cavities, one (11) retains its gross shape on complexation and interacts with the [Diquat]2+ dication by means of hydrogen and electrostatic bonds whilst accommodating weak charge transfer interactions and a hydrogen bonded H 2 0 molecule within the docking constraints and microcavity, respectively, imposed by the more dominant non-covalent forces.Greatly encouraged by the observation1 that BMP32ClO-t is capable of complexing with [Paraquat][PF&,t as well as with [Diquat][PF6I2,1-by virtue of a combination2 of electrostatic t The structural formulae for BMP32C10 and for [Paraquat][PF& and [Diquat][PF& are illustrated in the two preceding communications (refs. 1 and 2). The structural formula for the bisparaphenylene-34-crown-10 derivative (BPP34C10) is numbered with reference to its systematic name,

Enantioselective reductions of prochiral aromatic ketones with adducts formed between ammonia-borane and (2Rr3R,1 1 R,12R)-and (2S,3Sr1 1 Sr12S)-tetraphenyl-1 ,4,7,10r13,16-hexaoxacyclo-octadecane, (RRRR)-( 3) and (SSSSI-(3), have afforded the corresponding (S) and ( R ) aromatic secondary alcohols with enantiomeric excesses of 2 0 -6 7 ' / o.

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