Caffeine is a xanthine alkaloid and a stimulant drug. It is found in tea leaves, cocoa beans, coffee beans, and kola nuts. Caffeine is a weak base with Kb value of 4.1 x 10-4.   It is an aromatic molecule. The five membered ring of the caffeine molecule has ten pi electrons and sp2 hybridized carbons and nitrogens. It is essentially a planar molecule as well. Caffeine has a profound effect as an inhibitor neurotransmitter. At high doses about 500 mg caffeine inhibits the GABA neurotransmission initiating anxiety, rapid heart rate and rapid respiration rate.  Caffeine molecule has four nitrogen atoms. Non-bonding electron pair on the nitrogen atom in the five membered ring participate in the aromaticity.  Therefore those electrons do not contribute to the basicity of the molecule. In this study, we are using divalence ions such as Cu2+, Ni2+, Fe2+, Pb2+, and Hg2+ to demonstrate the coordinating ability of caffeine to make organo-metallic complexes. Metal ions are good Lewis acids whereas caffeine can act as a good Lewis base to form Lewis-acid base complexes. The complex formation is monitored using spectroscopy techniques. The purpose of this study is to demonstrate the metal coordinating ability of caffeine molecule.

Caffeine-divalent metal Lewis acid-base complexes: [M(caffeine)<sub>n</sub>]<sup>2+</sup>

247th National Meeting (2014)

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Caffeine-divalent metal Lewis acid-base complexes: [M(caffeine)n]2+

Caffeine-divalent metal Lewis acid-base complexes: [M(caffeine)_n]²⁺