* Corresponding authors

^a Framework Solids Laboratory, Solid State Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India
E-mail: snatarajan@sscu.iisc.ernet.in
Fax: +91-80-2360-1310

^b The Davy-Faraday Research Laboratory, The Royal Institution of Great Britain, 21 Albemarle Street, London, UK

^c Department of Chemical Engineering, Indian Institute of Science, Bangalore 560 012, India
E-mail: giridhar@chemeng.iisc.ernet.in