Monomer, dimer, tetramer, polymer: Structural diversity in zinc and cadmium complexes of chelate-tethered nucleobases

A series of Zn-II and Cd-II complexes of adenine and guanine derivatives co ntaining a diamine tether have been isolated from aqueous solutions and cha racterised by single crystal X-ray analysis. These studies reveal a wide ra nge of structural types including monomeric, dimeric, tetrameric and polyme ric architectures. The extended structures arise from the ability of the li gands to bridge metal ions using the chelating tether in conjunction with N 7 of the nucleobase. Additional metal-nucleobase co-ordination is generally observed at the N3-site of the adenine derivatives. With Cd-II, ethylenedi amine-N9-ethylguanine forms an inverted G-tetrad type structure.