1. Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K.
2. Centre for Theoretical Chemistry and Physics, Institute of Advanced Studies, Massey University, Private Bag 102904, North Shore Mail Centre, Auckland 0632, New Zealand
3. Chemistry, School of Natural Sciences, Massey University, Palmerston North 4442, New Zealand
4. Chemistry, School of Natural Sciences, Massey University, Private Bag 102904, North Shore Mail Centre, Auckland 0632, New Zealand