[1] Univ Leicester, Dept Chem, Leicester LE1 7RH, Leics, England
[2] Univ Birmingham, Sch Chem Sci, Birmingham B15 2TT, W Midlands, England
[3] Syngenta Ltd, Jealotts Hill Int Res Ctr, Bracknell RG42 6EY, Berks, England
[4] Univ Southampton, Dept Chem, EPSRC, Natl Xray Crystallog Serv, Southampton SO17 1BJ, Hants, England