In this study, calix[4]arene derivatives (11 -14) bearing a single nucleobase (adenine, thymine, cytosine or guanine) were synthesised via click chemistry. The complexation ability of the synthesised derivatives with alkali metal ions was measured using MALDI-TOF mass spectrometry, and their molecular assembly in CDCl 3 was determined using 1 H NMR. Calix[4]arene derivatives (11 -14) formed 1:1 complexes with all alkali metal ions and the rank order for the complexation selectivity was Rb þ . Cs þ . K þ ø Na þ . Li þ . The attachment of nucleobase at the upper rim of calix[4]arene had little effect on its complexation selectivity for alkali metal ions. Thymine-, adenine-and guanine-calix[4]arenes formed selfassembled structures in CDCl 3 via base-base interactions. In addition, adenine-calix[4]arene (11) bound to thyminecalix[4]arene (12) to form a discrete species via Hoogsteen hydrogen bonding.